Improving the long-term stability of metal catalysts is crucial to developing polymer electrolyte fuel cells (PEFCs). In this work, we first report an inorganic (TiO2)–organic (perfluorosulfonic acid, PFSA) costabilized Pt catalyst supported on graphene nanosheets (GNS) (Pt-PFSA-TiO2/GNS). Herein, TiO2, as a robust wall, impedes the collision between the metal nanoparticles (NPs) in plane along the horizontal x and y axes, while PFSA mainly anchors the metal NPs to constrain detachment along the vertical z axis. The resulting catalyst displays higher oxygen reduction reaction (ORR) activity in comparison to that of commercial Pt/C. Significantly, the stability is particularly better than that of only PFSA- or TiO2-decorated catalysts (Pt-PFSA/GNS or Pt-TiO2/GNS) and far better than that of Pt/C. After 6000 potential cycles, the half-wave potential (E1/2) of Pt-PFSA-TiO2/GNS decreases by only 16 mV, far less than that of Pt/C (56 mV). The excellent electrochemical property of Pt-PFSA-TiO2/GNS is predominantly attributed to the synergistic effect of PFSA and TiO2 in costabilizing the Pt NP by anchoring and blocking Pt NPs in all three spatial directions. The structural dynamics and mechanism of enhanced properties are also discussed.

Developing facile and low-cost porous graphene-based catalysts for highly efficient oxygen reduction reaction (ORR) remains an important matter for fuel cells. Here, a defect-enriched and dual heteroatom (S and N) doped hierarchically porous graphene-like carbon nanomaterial (D-S/N-GLC) was prepared by a simple and scalable strategy, and exhibits an outperformed ORR activity and stability as compared to commercial Pt/C catalyst in an alkaline condition (its half-wave potential is nearly 24 mV more positive than Pt/C). The excellent ORR performance of the catalyst can be attributed to the synergistic effect, which integrates the novel graphene-like architectures, 3D hierarchically porous structure, superhigh surface area, high content of active dopants, and abundant defective sites in D-S/N-GLC. As a result, the developed catalysts are used as the air electrode for primary and all-solid-state Zn–air batteries. The primary batteries demonstrate a higher peak power density of 252 mW cm–2 and high voltage of 1.32 and 1.24 V at discharge current densities of 5 and 20 mA cm–2, respectively. Remarkably, the all-solid-state battery also exhibits a high peak power density of 81 mW cm–2 with good discharge performance. Moreover, such catalyst possesses a comparable ORR activity and higher stability than Pt/C in acidic condition. The present work not only provides a facile but cost-efficient strategy toward preparation of graphene-based materials, but also inspires an idea for promoting the electrocatalytic activity of carbon-based materials.Keywords: electrocatalyst; fuel cell; graphene-like; oxygen reduction; Zn−air battery;

Exploring efficient and earth-abundant electrocatalysts for water splitting is crucial for various renewable energy technologies. In this work, iron (Fe)-doped nickel phosphide (Ni2P) nanosheet arrays supported on nickel foam (Ni1.85Fe0.15P NSAs/NF) are fabricated through a facile hydrothermal method, followed by phosphorization. The electrochemical analysis demonstrates that the Ni1.85Fe0.15P NSAs/NF electrode possesses high electrocatalytic activity for water splitting. In 1.0 M KOH, the Ni1.85Fe0.15P NSAs/NF electrode only needs overpotentials of 106 mV at 10 mA cm–2 and 270 mV at 20 mA cm–2 to drive the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Furthermore, the assembled two-electrode (Ni1.85Fe0.15P NSAs/NF∥Ni1.85Fe0.15P NSAs/NF) alkaline water electrolyzer can produce a current density of 10 mA cm–2 at 1.61 V. Remarkably, it can maintain stable electrolysis over 20 h. Thus, this work undoubtedly offers a promising electrocatalyst for water splitting.Keywords: electrocatalysts; hydrogen evolution reaction; Ni1.85Fe0.15P nanosheet arrays; oxygen evolution reaction; water splitting;

To overcome inferior rate capability and cycle stability of MnO-based materials as a lithium-ion battery anode associated with the pulverization and gradual aggregation during the conversion process, we constructed robust mesoporous N-doped carbon (N–C) protected MnO nanoparticles on reduced graphene oxide (rGO) (MnO@N–C/rGO) by a simple top-down incorporation strategy. Such dual carbon protection endows MnO@N–C/rGO with excellent structural stability and enhanced charge transfer kinetics. At 100 mA g–1, it exhibits superior rate capability as high as 864.7 mAh g–1, undergoing the deep charge/discharge for 70 cycles and outstanding cyclic stability (after 1300 cyclic tests at 2000 mA g–1; 425.0 mAh g–1 remains, accompanying merely 0.004% capacity decay per cycle). This facile method provides a novel strategy for synthesis of porous electrodes by making use of highly insulating materials.Keywords: anode; graphene oxide; lithium-ion battery; manganese monoxide; nitrogen doping;

We report a rationally designed electrocatalyst with high activity for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) based on a nanocarbon-intercalated graphene (CIG) material doped with nitrogen (N) and iron (Fe) (Fe–N-CIG). This easily made novel 3D Fe–N-CIG catalyst exhibits a surprisingly high ORR and OER activity and stability, making it a new noble-metal-free bifunctional catalyst for future applications in regenerative energy conversion systems.

In this work, we propose a one-step process to realize the in situ evolution of molybdenum carbide (Mo2C) nanoflakes into ordered mesoporous carbon with few-layered graphene walls (OMG) by chloridization and self-organization, and simultaneously the Cl-doping of OMG (OMG-Cl) by modulating chloridization and annealing processes is fulfilled. Benefiting from the improvement of electroconductivity induced by Cl-doping, together with large specific surface area (1882 cm2 g–1) and homogeneous pore structures, as anode of lithium ion batteries, OMG-Cl shows remarkable charge capacity of 1305 mA h g–1 at current rate of 50 mA g–1 and fast charge–discharge rate within dozens of seconds (a charge time of 46 s), as well as retains a charge capacity of 733 mA h g–1 at a current rate of 0.5 mA g–1 after 100 cycles. Furthermore, as a promising electrode material for supercapacitors, OMG-Cl holds the specific capacitances of 250 F g–1 in 1 M H2SO4 solution and 220 F g–1 at a current density of 0.5 A g–1 in 6 M KOH solution, which are ∼40% and 20% higher than those of undoped OMG electrode, respectively. The high capacitive performance of OMG-Cl material can be due to the additional fast Faradaic reactions induced from Cl-doping species.Keywords: chlorine-doped ordered mesoporous carbon; few-layered graphene wall; Li ion battery; molybdenum carbide; supercapacitor;

To construct a suitable structure for both electronic conduction and ionic transport towards supercapacitors, peanut-like hierarchical manganese carbonate (MnCO3) microcrystals assembled with floss-like nanowires are synthesized via a hydrothermal process and primarily used as an active material for supercapacitors. The formation mechanism is illustrated by means of a dissolution–recrystallization process and magnetically driven self-assembly. The electrode with peanut-like hierarchical MnCO3 microcrystals exhibits a high specific capacitance of 293.7 F g−1 and a superior cycle stability of 71.5% retention after 6000 cycles, which are higher than those of the reported Mn-based active materials in alkaline electrolytes. The asymmetric supercapacitor, assembled with the peanut-like MnCO3 electrode as the positive electrode and a home-made porous carbon electrode as the negative electrode, exhibits an energy density of 14.7 W h kg−1 at a power density of 90.2 W kg−1 and an energy density of up to 11.0 W h kg−1 at 3.3 kW kg−1. An as-assembled all-solid-state supercapacitor series can light up a LED indicator for 10 min, indicating a promising practical application of peanut-like MnCO3 microcrystals.

The changeable structure of 2D graphene nanosheets makes the Pt-based nanoparticles (NPs) possess a low efficiency toward oxygen reduction reaction (ORR) and a short lifetime for proton exchange membrane fuel cells. Thus, a unique TiC@graphene core-shell structure material with low surface energy is designed and prepared by an in situ forming strategy, and firstly applied as a stable support of Pt NPs. The as-prepared Pt/GNS@TiC catalyst presents a high activity. Especially, its ORR stability is remarkably improved. Even after 15000 potential cycles, the half-wave potential and mass activity toward ORR have almost no change. This can be attributed to that the graphene nanosheet existing in a sphere shape effectively avoids the restacking or folding caused by the giant surface tension in 2D graphene nanosheets, impeding the decrease of the triple-phase boundary on Pt NPs. Significantly, the power density of fuel cells with our novel catalyst reaches 853 mV cm–2 under a low Pt loading (0.25 mgPt cm–2) and H2/Air conditions. These indicate the new ceramic@graphene core-shell nanocomposite is a promising application in fuel cells and other fields.Download high-res image (197KB)Download full-size imageWe designed and prepared a TiC–GNS core-shell structure nanocomposite material (TiC@GNS) by a novel in situ forming strategy and for the first time used it as a durable support of metal catalysts for PEM fuel cells.

AbstractHighly active, stable, and cheap Pt-free catalysts for the hydrogen evolution reaction (HER) are under increasing demand for future energy conversion systems. However, developing HER electrocatalysts with Pt-like activity that can function at all pH values still remains as a great challenge. Herein, based on our theoretical predictions, we design and synthesize a novel N,P dual-doped carbon-encapsulated ruthenium diphosphide (RuP2@NPC) nanoparticle electrocatalyst for HER. Electrochemical tests reveal that, compared with the Pt/C catalyst, RuP2@NPC not only has Pt-like HER activity with small overpotentials at 10 mA cm−2 (38 mV in 0.5 m H2SO4, 57 mV in 1.0 m PBS and 52 mV in 1.0 m KOH), but demonstrates superior stability at all pH values, as well as 100 % Faradaic yields. Therefore, this work adds to the growing family of transition-metal phosphides/heteroatom-doped carbon heterostructures with advanced performance in HER.

•High index (222) faceted TaC nanocrystals are first created.•A subtle micro-cutting-fragmentation technique is newly developed.•The novel catalyst exhibits much higher HER activity than that of bulk TaC.•It has become one of the most competitive transition metal carbides-based HER catalyst.•DFT calculations are used to clarify the role of (222) facet.The electrocatalysis of nanoscale group V metal carbides (e.g. TaC) has almost received far less attentions owing to lack of active sites. Our theoretical calculations show that high-index (222) facets of TaC are dramatically more active than its other facets towards hydrogen evolution reaction (HER). However, the easy evolution of exposed high-index (222) facets causes a big challenge in fabrication. Here, to obtain the carbon-cohered high-index (222) faceted tantalum carbide nanocrystals (TaC NCs@C), we first develop a novel chlorine-assisted “micro-cutting-fragmentation” technique by incomplete chlorination towards bulk TaC. Interestingly, benefiting from transition zones between in situ formed carbon layers and (222) facets, the evolution of high-index (222) facets with high surface energy can be prevented during the preparation and electrochemical reaction. When evaluated as a HER catalyst, TaC NCs@C presents a low overpotential of ~146 mV at 10 mA cm-2, a large exchange current density of 9.69×10-2 mA cm-2 and outstanding long-term cycling performance. To the best of our knowledge, this HER performance is far preferable to that of the reported group V metal carbides-based catalysts. In the light of the highly generic nature, the methodology developed in this study can be widely applied to produce other in situ carbon armored high-index faceted metal carbide nanocrystals.High-index (222) faceted tantalum carbide nanocrystals cohered by in situ amorphous carbon are one-step fabricated based on a novel “micro-cutting-fragmentation” technique by incomplete chlorination towards bulk TaC. Consistent with theoretical calculations, the new produced catalyst presents extraordinary HER activity which surpasses all reported group V metal carbides-based catalysts. That can be attributed to abundant active sites on the exposed high-index (222) facets.Download high-res image (178KB)Download full-size image

Fe–N–C series catalysts are always attractive for their high catalytic activity towards the oxygen reduction reaction (ORR). However, they usually consist of various components such as iron nitrides, metallic iron, iron carbides, N-doped carbon and Fe–N4 moieties, leading to controversial contributions of these components to the catalysis of the ORR, especially iron nitrides. In this work, to investigate the function of iron nitrides, FexN nanoparticles (NPs) embedded in mesoporous N-doped carbon without Fe–N4 moieties are designed and constructed by a simple histidine-assisted method. Herein, the use of histidine can increase the N and Fe contents in the product. The obtained catalyst exhibits excellent ORR catalytic activity which is very close to that of the commercial Pt/C catalyst in alkaline electrolytes. Combining the catalytic activity, structural characterization (especially from Mössbauer spectroscopy), and the results of DFT calculations for adsorption energies of oxygen on the main surfaces of Fe2N including ε-Fe2N and ζ-Fe2N, it can be deduced that Fe2N NPs as active species make a contribution to the ORR catalysis, of which ε-FexN (x ≤ 2.1) is more active than ζ-Fe2N. In addition, we find that there exists an obvious synergistic effect between Fe2N NPs and N-doped carbon, leading to the greatly enhanced ORR catalytic activity.

A considerable amount of intensive research has been made towards efficient energy storage, particularly regarding rechargeable lithium-ion batteries (LIBs). However, there are still huge limitations to the applications of state-of-the-art LIBs, including their inadequate durability, safety concerns and high costs, and so they cannot meet the ever-growing demand for portable electronic devices and power batteries. Therefore, designing viable LIBs with high cost efficiency and performance through integration of new alternative electrode materials possessing well-controlled nanostructures is critical. Herein, we rationally design a facile and effective method to construct Na0.55Mn2O4·1.5H2O@C (SMOH@C) yolk–shell nanorods which integrate a one side internal void with the outer carbon shell framework. By virtue of such a yolk–shell structure and composition, as an anode material, the as-built electrode endows LIBs with attractive electrochemical performances including a high specific reversible capacity (750 mA h g−1 at 0.1 A g−1), an excellent rate and superior long term cycling capability (448 mA h g−1 capacity retention after 3000 cycles at 4.0 A g−1). This unique structure design strategy paves the way to produce new anode materials with superior performances for next-generation LIBs.

Developing non-platinum catalysts for the oxygen reduction reaction (ORR) has become urgent for electrochemical energy devices. Herein, we synthesize N-doped hollow carbon nanospheres (N-HCNs) which only contain active pyridinic-N and graphitic-N by using polystyrene spheres and aniline as the corresponding template and precursor. The electrochemical measurements show that N-HCNs possess superior ORR electrocatalytic activity (half-wave potential is 15 mV higher than that of the precious Pt/C electrocatalyst), durability and anti-toxicity to Pt/C in alkaline media. Simultaneously, N-HCNs also reveal comparable ORR activity and superior stability to Pt/C in acidic media. Such high ORR performance can be ascribed to their hierarchical porous structure, ultra-high specific surface area, plenty of edge defects and high contents of active N atoms. It is noteworthy that when used as the catalyst for the air electrode of zinc–air batteries, N-HCNs present a higher power density and a larger operating voltage than Pt/C at the same discharge current density.

Engineered graphene materials (EGMs) with unique structures and properties have been incorporated into various components of polymer electrolyte membrane fuel cells (PEMFCs) such as electrode, membrane, and bipolar plates to achieve enhanced performances in terms of electrical conductivity, mechanical durability, corrosion resistance, and electrochemical surface area. This research news article provides an overview of the recent development in EGMs and EGM-based PEMFCs with a focus on the effects of EGMs on PEMFC performance when they are incorporated into different components of PEMFCs. The challenges of EGMs for practical PEMFC applications in terms of production scale, stability, conductivity, and coupling capability with other materials are also discussed and the corresponding measures and future research trends to overcome such challenges are proposed.

Designing a non-noble-metal catalyst with high efficiency toward oxygen evolution reactions (OERs) is critical for renewable energy storage and conversion devices (e.g., water-splitting and metal–air batteries). In the current study, a flexible electrode of nickel diphosphide nanosheet arrays on carbon cloth (NiP2/CC) is synthesized through phosphidation of Ni(OH)2 nanosheet arrays as a precursor on the carbon cloth. The resultant three-dimensional (3D) porous nanosheet array architecture enhances the exposure of surface active sites and the release of gaseous products. When used as an OER catalyst, such an integrated 3D array electrode affords a current density of 4 mA cm−2 at an OER overpotential of 570 mV with good stability in neutral solution. Moreover, the NiP2/CC electrode also exhibits good OER performance (j = 20 mA cm−2 at η = 310 mV) under alkaline conditions. Notably, this electrode also shows high activity and stability under both neutral and alkaline media toward the HER. More importantly, when assembled as a symmetric full water splitting device with NiP2/CC as both the cathode and anode, a current density of 10 mA cm−2 at a voltage of 1.65 V is achieved in 1.0 M KOH solution. Owing to its low cost and high activity, NiP2/CC presents potential applications toward overall water splitting electrolysis and other electrochemical devices.

Applications of highly-efficient and durable non-precious metal electrocatalysts for hydrogen evolution reaction (HER) have great potential to relieve the energy crisis. Here, we demonstrate a green method for fabrication of a number of transition metal phosphides (TMPs) by pyrolyzing melamine and self-assembled phytic acid (PA) cross-linked metal complexes. The obtained materials consisting of TMP nanoparticles (NPs) are encapsulated in N,P-codoped carbon (NPC). Among TMPs, the resultant FeP NPs encapsulated in the NPC matrix (FeP NPs@NPC) show the highest HER activity at all pH values. At a current density of 10 mA cm−2, FeP NPs@NPC displays overpotentials of 130, 386 and 214 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution (PBS) and 1.0 M KOH, respectively. Additionally, the encapsulation by NPC effectively prevents FeP NPs from corrosion, exhibiting almost unfading catalytic activity after 10 h testing in acidic, neutral and basic electrolytes. More importantly, other TMPs wrapped in NPC (CoP NPs@NPC and Ni2P NPs@NPC) can be easily obtained by this method, which also exhibit relatively high activity toward HER. Therefore, this generic synthesis strategy opens a door for unprecedented design and fabrication of novel low-cost TMP based electrocatalysts for HER and other electrochemical applications.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm2 g−1). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of −0.075 V and a half-wave potential of −0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures.

Developing efficient non-precious metal hydrogen evolution reaction (HER) electrocatalysts is a great challenge for sustainable hydrogen production from water. In this communication, for the first time, semimetallic MoP2 nanoparticle films on a metal Mo plate (MoP2 NPs/Mo) are fabricated through a facile two-step strategy. When used as a binder-free hydrogen evolution cathode, the as-prepared MoP2 NPs/Mo electrode exhibits superior HER catalytic activity at all pH values. At a current density of 10 mA cm−2, the catalyst displays overpotentials of 143, 211 and 194 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution and 1.0 M KOH, respectively. Furthermore, it exhibits excellent stability over a wide pH range. Thus, this in situ route opens up a new avenue for the fabrication of highly efficient, cost-effective and binder-free non-precious catalysts for water splitting and other electrochemical devices.

3D graphene-based materials offer immense potentials to overcome the challenges related to the functionality, performance, cost, and stability of fuel cell electrocatalysts. Herein, a nitrogen (N) and sulfur (S) dual-doped 3D porous graphene catalyst is synthesized via a single-row pyrolysis using biomass as solitary source for both N and S, and structure directing agent. The thermochemical reaction of biomass functional groups with graphene oxide facilitates in situ generation of reactive N and S species, stimulating the graphene layers to reorganize into a trimodal 3D porous assembly. The resultant catalyst exhibits high ORR and OER performance superior to similar materials obtained through toxic chemicals and multistep routes. Its stability and tolerance to CO and methanol oxidation molecules are far superior to commercial Pt/C. The dynamics governing the structural transformation and the enhanced catalytic activity in both alkaline and acidic media are discussed. This work offers a unique approach for rapid synthesis of a dual-heteroatom doped 3D porous-graphene-architecture for wider applications.Keywords: 3D porous graphene; biomass; heteroatoms; OER; ORR

The radical degradation of Pt-based catalysts toward oxygen reduction reaction (ORR), predominantly caused by the oxidation of carbon supports, heavily blocks the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). As reported, the electrochemical oxidation of carbon could be accelerated by Pt catalysts; however, hitherto no direct evidence is present for the promotion of Pt catalysts. Herein, a unique ultrathin carbon layer (approximately 2.9 nm in thickness) covered Pt catalyst (Pt/C-GC) is designed and synthesized by a chemical vapor deposition (CVD) method. This magnifies the catalysis effect of Pt to carbon oxidation due to the greatly increased contact sites between the metal–support, making it easy to investigate the carbon oxidation process by observing the thinning of the carbon layer on Pt nanoparticles from TEM observations. Undoubtedly, this finding can better guide the structural design of the durable metal catalysts for PEMFCs and other applications.Keywords: carbon; electrochemical oxidation; metal catalyst; observation; stability

•A graphene doped PAN/PVDF electrospun nanofiber membrane electrode is developed.•This novel electrode has high electrical conductivity and porosity.•This electrode does not require microporous layers widely used in conventional electrodes.•The fuel cell performance is improved using this electrode under low Pt loading.A rational electrode structure can allow proton exchange membrane (PEM) fuel cells own high performance with a low noble metal loading and an optimal transport pathway for reaction species. In this study, we develop a graphene doped polyacrylonitile (PAN)/polyvinylident fluoride (PVDF) (GPP) electrospun nanofiber electrode with improved electrical conductivity and high porosity, which could enhance the triple reaction boundary and promote gas and water transport throughout the porous electrode. Thus the increased electrochemical active surface area (ECSA) of Pt catalysts and fuel cell performance can be expected. As results, the ECSA of hot-pressed electrospun electrodes with 2 wt% graphene oxide (GO) is up to 84.3 m2/g, which is greatly larger than that of the conventional electrode (59.5 m2/g). Significantly, the GPP nanofiber electrospun electrode with Pt loading of 0.2 mg/cm2 exhibits higher fuel cell voltage output and stability than the conventional electrode.

The low utilization and stability of noble-metal catalysts is always a big barrier to commercialize proton exchange membrane (PEM) fuel cells. Here we report a positive progress on stabilizing the catalyst by modulating 2D graphene as an advanced support of Pt nanoparticles, where the interlayer of graphene is near perfectly intercalated by nano-B4C ceramics. The strong restriction effect of nano-ceramics in graphene interlayers, can greatly improves the usage and electrochemical stability of Pt catalysts. As results, our new graphene/B4C supported Pt catalyst (Pt-RGO/B4C) shows greatly enhanced electrochemical surface area (121 m2 g−1) and mass activity (185 A g−1 Pt) towards oxygen reduction reaction (ORR), which is remarkably higher than the reduced graphene oxide (RGO) supported Pt (Pt/RGO) catalyst and the commercial Pt/C catalyst. In addition, the Pt-RGO/B4C electrode also possesses higher fuel cell performance than the Pt/RGO electrode. Especially, after the electrochemical acceleration test for 10000 cycles, our new catalyst presents an excellent stability, even retains 45.2% initial electrochemical surface area, while the Pt/RGO and Pt/C are only 29.7 and 23.4%, respectively. These indicate our unique catalyst is promising to allow the PEM fuel cell have high ORR activity and stability.

Porous nitrogen-doped graphene with a very high surface area (1152 m2 g−1) is synthesized by a novel strategy using intrinsically porous biomass (soybean shells) as a carbon and nitrogen source via calcination and KOH activation. To redouble the oxygen reduction reaction (ORR) activity by tuning the doped-nitrogen content and type, ammonia (NH3) is injected during thermal treatment. Interestingly, this biomass-derived graphene catalyst exhibits the unique properties of mesoporosity and high pyridine-nitrogen content, which contribute to the excellent oxygen reduction performance. As a result, the onset and half-wave potentials of the new metal-free non-platinum catalyst reach −0.009 V and −0.202 V (vs. SCE), respectively, which is very close to the catalytic activity of the commercial Pt/C catalyst in alkaline media. Moreover, our catalyst has a higher ORR stability and stronger CO and CH3OH tolerance than Pt/C in alkaline media. Importantly, in acidic media, the catalyst also exhibits good ORR performance and higher ORR stability compared to Pt/C.

Developing high-efficiency and stable catalysts from earth-abundant elements for the hydrogen evolution reaction (HER) is essential for renewable energy conversion. In this work, Se-promoted molybdenum sulfide nanosheet arrays supported on flexible carbon cloth (Se–MoS2/CC) have been successfully synthesized and explored for the first time as a 3D hydrogen evolution cathode. Without any active process, the Se–MoS2/CC electrode exhibits greatly enhanced activity with a smaller Tafel slope (63 mV dec−1) and a higher exchange current density (0.16 mA cm−2) than the pristine MoS2/CC one (79 mV dec−1 and 0.1 mA cm−2). The overpotentials needed to attain the current densities of 10 and 100 mA cm−2 are merely 127 and 218 mV, respectively. In addition, Se–MoS2/CC maintains its high electrocatalytic activity for at least 25 h in acidic media.

We report a general approach to NiAu alloy nanoparticles (NPs) by co-reduction of Ni(acac)2 (acac = acetylacetonate) and HAuCl4·3H2O at 220 °C in the presence of oleylamine and oleic acid. Subject to potential cycling between 0.6 and 1.0 V (vs reversible hydrogen electrode) in 0.5 M H2SO4, the NiAu NPs are transformed into core/shell NiAu/Au NPs that show much enhanced catalysis for hydrogen evolution reaction (HER) with Pt-like activity and much robust durability. The first-principles calculations suggest that the high activity arises from the formation of Au sites with low coordination numbers around the shell. Our synthesis is not limited to NiAu but can be extended to FeAu and CoAu as well, providing a general approach to MAu/Au NPs as a class of new catalyst superior to Pt for water splitting and hydrogen generation.

We synthesized a novel 2D hybrid material composed of Li2FeSiO4 nanorods (LFSNRs) anchored on graphene. Such a chemically bonded interface leads to electron coupling at the interface between the nano-LFS and graphene, creating effective charge transport for LFSNR@graphene hybrid cathodes. Used as a cathode material, it possesses a high capacity (300 mA h g−1 at 1.5–4.8 V), high charging–discharging rate (134 mA h g−1 @ 12 C) and long-life performance (maintaining 95% capacity over 240 cycles), which is mainly attributed to the effective depolarization introduced by the synergistic effects of LFSNRs bonded with graphene, which improves the electrochemical activity of the LFSNRs. Thus, a hybrid cathode modified with an interfacial chemical structure with nanoparticles bonded with an electrical conduction network such as graphene or CNTs can significantly enhance the electrochemical performance, and this novel type of material is very promising for commercial applications that require high energy, a long operating life, and excellent abuse tolerance, such as electric vehicles.

A novel ultrathin carbon layer (UTCL) stabilized Pt catalyst (Pt-UTCL/C) with an open framework is synthesized to significantly enhance the stability of the catalyst in proton exchange membrane fuel cells. Herein, a cheap and widely available polymer, soluble starch (SS), as a precursor, is employed to wrap Pt nanoparticles (NPs) and is then carbonized into a UTCL with a thickness of few molecular-layers (0.58 nm on average) at a mild temperature. Significantly, it possesses extremely high stabilities of both electrochemical surface area and ORR compared to the commercial Pt/C catalyst even after 10000 potential cycles. Such excellent stability can be ascribed to the anchoring effect of the UTCL towards Pt NPs to the inhibited migration, agglomeration and detachment of Pt NPs from the supports as well as to the possibly mitigated dissolution-growth process of Pt NPs in light of the UTCL.

Development of a cathode material with safety, low cost, high energy and power densities, long life and excellent abuse tolerance for Li-ion batteries is critical for hybrid electric vehicles (HEVs) and electric vehicles (EVs). Here, we developed graphene activated 3D-hierarchical flower-like Li2FeSiO4 with secondary nanopetals (G@3D-HFLFS), which exhibited a discharge capacity of 327.2 mA h g−1 (specific energy of 879 W h kg−1) approaching the full theoretical capacity with large-current and long-life performance. The electrochemical reaction mechanism of G@3D-HFLFS was investigated by Mössbauer spectroscopy and parallel model X-band ESR. The high performance can be attributed to the secondary petal-like structures having an ultra-rapid Li-ion diffusion along the minimum length, the graphene coating layers facilitating double transport of electrons and Li-ions, and the special hierarchical structure with an optimal petal thickness possessing excellent structural stability. These results clearly demonstrate that our novel material is a promising cathode for commercial applications that require high energy and power densities, long operating life and excellent abuse tolerance.

(1 − x)Li2FeSiO4·xLiFeBO3/C (x = 0, 0.02, 0.05, 0.08, 0.12, and 1.00) hetero-grains are successfully synthesized via an in situ citric acid-based sol–gel method and evaluated as cathode materials for lithium ion batteries. As a result, 0.92Li2FeSiO4·0.08LiFeBO3/C delivers an optimum discharge capacity of 251 mA h g−1 which corresponds to nearly 1.51 Li+ intercalation per molecule. Furthermore, a capacity retention of 104.5% after 5 cycles at 0.1 C is attained, and a value of 188.3 mA h g−1 (approaching 1.13 Li+ intercalation per molecule) remains even after one hundred cycles at 1 C. In particular, at a high-rate of 10 C, there is almost no capacity decline even after 500 cycles, indicating an excellent cycling stability. The greatly improved electrochemical lithium storage properties of the novel in situ hybridized materials can be attributed to the enhanced kinetics towards Li+ diffusion and electron transport compared with that of pure Li2FeSiO4/C electrodes.

A non-noble metal nitrogen (N)-doped carbon catalyst, with a porous graphene-like structure, is prepared by pyrolyzing polyaniline with addition of urea. Herein, urea not only serves as a N source similar to polyaniline by incorporating N atoms into the carbon matrix, but plays a key role in forming the porous graphene-like structured carbon nanosheet. The electrochemical characterization shows that the prepared catalyst with a unique graphene-like structure exhibits an oxygen reduction reaction (ORR) activity that outperforms that of the commercial Pt/C catalyst in alkaline media, its half-wave potential nearly 30 mV more positive than Pt/C, and both superior stability and fuel (methanol and CO) tolerance to Pt/C. Significantly, such a catalyst also exhibits a good ORR activity which is comparable to Pt/C, as well as a higher stability than Pt/C in acidic media.

•Cobalt nickel sulfide dendrite/quasi-spherical nanocomposite is synthesized.•Co1.5Ni1.5S4 electrode exhibits the highest areal specific capacitance.•Co1.5Ni1.5S4-AC asymmetric supercapacitor exhibits high energy density.In this study, a spinel binary transition metal sulphide Co1.5Ni1.5S4 dendrite/quasi-spherical nanocomposite with high electronic conductivity and a suitable porous structure was synthesized via a facile hydrothermal process. The morphology and structure of the Co1.5Ni1.5S4 nanocomposite were easily manipulated by tuning the hydrothermal reaction time. To the best of our knowledge, due to its good electronic conductivity and suitable structure for the electrochemical redox reaction, the Co1.5Ni1.5S4 electrode exhibited the highest areal specific capacitance of 41.0 F cm−2. The electrochemical impedance spectroscopy (EIS) results demonstrate that Co1.5Ni1.5S4 possesses a higher electronic conductivity and faster charge transfer than single-component sulphides (CoS and NiS) or cobalt-nickel hydroxides and oxides. These characteristics contribute to the high specific capacitance of the Co1.5Ni1.5S4 electrode even at high material loading, corresponding to an ultrahigh areal specific capacitance. An asymmetric supercapacitor, which was assembled with Co1.5Ni1.5S4 as the positive electrode active material and HNO3-treated activated carbon as the negative electrode active material, exhibited a superior energy density of 32.4 Wh kg−1 at a power density of 103.4 W kg−1 and 25.0 Wh kg−1 at a high power density of 5.5 kW kg−1.

•N-doped nano porous carbon is prepared by a simple but template–free method.•Such N-doped carbon owns a porous structure with a high surface area.•It possesses the same onset potential compared to the commercial Pt/C catalyst in alkaline media.•It also exhibits impressive durability and excellent fuel resistance over Pt/C.A novel nitrogen (N)-doped carbon catalyst has been prepared using a simple but effective method by pyrolyzing polyvinylpyrrolidone (PVP) as the precursor and urea as a promoter. The physicochemical measurements results show that the sample upon adding urea not only has a porous structure with high surface area, but possesses more active N content and edge defects than the sample without adding urea. The electrochemical characterizations show that the catalyst owns a good oxygen reduction reaction (ORR) activity and a nearly 4-electron pathway selectivity in alkaline media. Notably, the onset potential of the catalyst is equal to the commercial Pt/C catalyst, and its half-wave potential is only 30 mV lower than that of Pt/C. Moreover, our catalyst exhibits impressive durability and excellent resistance to methanol crossover and CO poisoning in comparison with Pt/C catalyst.

The P21/n structured nanocrystalline-Li2FeSiO4 is prepared by a confinement effect of three-dimensional conductive carbon frameworks, which are formed through a chelating reaction and subsequent pyrolysis. As a benefit of enhanced electronic conductivity by carbon frameworks and Li-ion diffusion kinetics by nanocrystalline-Li2FeSiO4 architectures, the novel nanocomposite shows a 1.28 Li-ion storage capacity (211.3 mA h g−1) at 0.1 C, corresponding to two successive steps of oxidation and reduction of Fe2+/Fe3+/Fe4+. Furthermore, the discharge capacity is 189.8, 175.6, 148.9, 125.7 and 106.6 mA h g−1 at a variable rate of 0.5, 1, 2, 5 and 10 C, respectively, and then easily returns to 175 mA h g−1 at 1 C. It is a surprise that the initial capacity is 90.9 mA h g−1 at 10 C, and 97.7% is retained after 1000 cycles. Thus, we believe that the nanocrystalline-Li2FeSiO4 with carbon frameworks, possessing high-capacity and high-rate performance, is a promising next-generation cathode material for high-power lithium-ion batteries.

Low temperature fuel cells (LTFCs) have received broad attention due to their low operating temperature, virtually zero emissions, high power density and efficiency. However, the limited stability of the catalysts is a critical limitation to the large scale commercialization of LTFCs. State of the art carbon supports undergo corrosion under harsh chemical and electrochemical oxidation conditions, which results in performance degradation of catalysts. Therefore, non-carbon materials which are highly oxidation resistant under strongly oxidizing conditions of LTFCs are ideal alternative supports. This minireview highlights the advances and scenarios in using nano-ceramics as supports to enhance the stability of catalysts, the solutions to improve electrical conductivity of nano-ceramic materials, and the synergistic effects between metal catalyst and support to help improve the catalytic activity and CO/SO2 tolerance of catalysts.

A non-precious metal catalyst (NPMC), with nano-porous structure and high BET surface area, is prepared by pyrolyzing the polyaniline on carbon nanospheres using ferric chloride both as an oxidant and iron source. Electrochemical test results show that the catalyst has a high activity and much better stability than that of commercial Pt/C in acid medium.

The sulfonated reduced graphene oxide (S-rGO) as supports and size-controlled Pt nanoparticles (NPs) for proton exchange membrane fuel cell (PEMFC) catalysts was investigated. The S-rGO was fabricated by a lyophilization-assisted method from a liquid mixture of GO and (NH4)2SO4 with a subsequent thermal treatment in inert gas. Sulfonic acid groups were grafted on GO and a reduction of GO was achieved simultaneously. Transmission electron microscope (TEM) results showed a uniform deposition of Pt NPs on S-rGO (Pt/S-rGO) with a narrow particle size distribution ranging from 2 to 5 nm in diameter. A higher catalytic activity of this novel Pt/S-rGO catalyst was revealed in comparison with that of Pt/GO, Pt/rGO and conventional Pt/C catalysts by cyclic voltammetry and oxygen reduction reaction measurements due to an enhanced triphase boundary. Significantly, the Pt/S-rGO catalyst also presented an excellent electrochemical stability. This new catalyst thus holds a great potential application in PEMFCs in terms of enhanced activity and durability.

Currently, nitrogen (N) doped carbon materials, as the most promising non-precious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) for low temperature fuel cells, have become a research hotspot. However, most of the N sources are derived from expensive organic monomers or ammonia, which are either expensive or harmful to human health. Here we demonstrate a facile and green strategy to synthesize a novel N-self-doped carbon nanoporous material with high surface area using pork liver (PL) both as N and carbon source; the prepared catalyst possesses an outstanding electrocatalytic activity towards ORR, and both superior stability and fuel (methanol and CO) tolerance compared to the conventional Pt/C catalyst. This work supplies a new paradigm for taking advantage of the abundant animal waste resources in energy conversion materials.

A new strategy to synthesize novel nano-sandwiched graphene/carbon/graphene (GCG) composites is described, employing the aqueous dispersion of low cost carbon nanospheres (CNS) in graphene oxide layers with subsequent thermal reduction. This 3D GCG sandwich shows a particular exfoliated graphene morphology, with CNS regularly embedded into the graphene nanosheets (GNS), from SEM and high-resolution TEM observations. The incorporation of CNS not only increases the Brunauer–Emmett–Teller (BET) surface area due to the effective expansion of the graphene interlayer, but also enhances the electrochemically accessible surface area and the charge transfer speed at the GCG–electrolyte interfaces due to a high density of between-plane electrolyte diffusion channels, that facilitate the reaction species transport and electron transport at high rates. As a result, this unique GCG nanoarchitecture with highly dispersed Pt particles exhibits a very high electrocatalytic activity for the oxygen reduction reaction (ORR). The half cell ORR mass activity of the Pt/GCG catalyst (17.7 A g−1) is 2.2 times of that of Pt/GNS (8.2 A g−1), and 3.8 times that of commercial Pt/C catalysts (4.6 A g−1). Moreover, the Pt/GCG catalyst also shows excellent electrochemical stability. Therefore our new catalyst holds tremendous promise for potential applications in proton exchange membrane (PEM) fuel cells.

•A hierarchical shuttle-like Li2FeSiO4 was synthesized using hydrothermal method.•The growth mechanism of the shuttle-like Li2FeSiO4 was discussed.•The shuttle-like Li2FeSiO4 possessed excellent electrochemical performance.We successfully synthesized the novel hierarchical shuttle-like Li2FeSiO4 using one step hydrothermal method with ethylene glycol assisted. The growth mechanism of the shuttle-like Li2FeSiO4 constructed of nanosingle crystals was discussed and its electrochemical performance as a cathode material for lithium ion battery was investigated. Astonishingly, the 1st discharge specific capacity of the new material without carbon coating was 180.6 mA h g−1 at 0.1 C with a remarkably high Coulombic efficiency of 97.5%, and an improved high-rate capability (71.0 mA h g−1 at 2 C) was offered which is comparable to the commonly carbon-coated Li2FeSiO4. Moreover, it exhibited a very stable discharge specific capacity at current densities from 0.1 to 2 C. Its excellent electrochemical performance can be ascribed to the significantly improved diffusion coefficient of lithium ions (5.6421 * 10−11 cm2 s−1), which was greatly larger than the reported carbon-coated Li2FeSiO4 nanocomposites and diatomic metallic ions (Ni2+, Cu2+, Zn2+) doped Li2FeSiO4. These indicate the shuttle-like Li2FeSiO4 is a very promising cathode material for lithium-ion batteries.

•SO2 tolerance is better at lower content of CeO2 presenting in catalyst.•CO tolerance increases as increasing content of CeO2 presenting in catalyst.•The amount of oxygen supplied by CeO2 is important to the CO and SO2 oxidation.SO2 and CO are detrimental agents to Pt based catalysts applied in proton exchange membrane (PEM) fuel cells. We introduce low-content (2, 4, and 6 wt%) amorphous cerium oxide (CeO2) to modify Pt catalysts for enhancing the SO2 and CO tolerance. The structure and morphology of the catalysts are studied by XRD, TEM and XPS analyses. Electrochemical results show that 2 wt% of CeO2 in the Pt/C catalyst exhibits the best SO2 poisoning resistance, while CO tolerance is enhanced as increasing content of CeO2. The promotional effect of Pt–CeO2/C catalysts on SO2 and CO poisoning resistance is also discussed.

Sulfur adsorption and poisoning of Pt-based catalysts cause an undesired, detrimental effect on performance of proton exchange membrane fuel cells. Here, WOx is adopted for the first time to modify such noble metal catalysts with an aim of acquiring excellent sulfur tolerance, due to its unique nature with hydrophilicity, redox couple in lower valence, as well as proton spillover effect. A series of WOx–Pt/C catalysts with various contents of tungsten oxide from 1 to 50 wt% were synthesized and compared to conventional Pt/C catalysts toward sulfur resistance using cyclic voltammetry (CV), as well as rotating ring-disk electrode (RRDE) methods. The results show that the catalyst with 5 wt% WOx has excellent sulfur tolerance, which might be ascribed to the synergistic effect between WOx and Pt. The OH groups generated on hydrophilic surfaces of WOx would accelerate the oxidation of sulfur and lead to rapidly recovering the performance of poisoned WOx–Pt/C electrodes. The loss of SOx at the first potential cycling for poisoned WOx–Pt/C is as high as 51.2% of the total SOx coverage. Moreover, the higher catalytic activity of WOx–Pt/C toward oxygen reduction reaction (ORR) is revealed in comparison with Pt/C after both were poisoned by SOx where the electron transfer number of the former is closer to four-electron than that of the latter. The electronic interaction between Pt and WOx is evidently confirmed by X-ray photoelectron spectroscopy analysis and strongly suggested as the crucial factor for the ORR enhancement.

A nano-ZrO2 shell was decorated successfully on the surface of carbon to improve the stability of an electrocatalyst. Pt nanoparticles (NPs) were formed on the support by an isothermal hydrolysis procedure. This composite was characterized by X-ray powder diffraction, thermogravimetric analysis, high-resolution transmission electron microscopy (HRTEM) with EDS and cyclic voltammogram techniques. HRTEM images show that the nano-ZrO2 shell has been decorated on the surface of carbon and 2–3 nm Pt NPs are dispersed on the carbon surface homogeneously, including the edge of the nano-ZrO2 shell. The electrochemical stability of the prepared Pt/ZrO2–C is enhanced considerably in comparison with a conventional Pt/C catalyst, which can be attributed to the inhibition of the migration and aggregation of Pt NPs on the support and the increase of the oxidation resistance of carbon with the nano-ZrO2 shell.

Platinum (Pt) nanoparticles were successfully deposited on the surface of nano-B4C with fragmentary nanostructured carbon thin film through a polyol process in an ethylene glycol solution. The electrochemical surface area of the Pt/B4C was investigated and showed remarkable enhancement compared with conventional Pt/C catalysts, which could be attributed to fast hydroxyl adsorption and high OHad coverage occurring during the hydrogen desorption process. It was also found that the novel Pt/B4C catalysts presented much enhanced methanol oxidation activity and CO tolerance by a negative shift in the onset potential and an increase of the peak current density in comparison to Pt/C catalysts. Meanwhile, the Pt/B4C showed an improved oxygen reduction reaction activity compared to the Pt/C catalyst.

Highly active and stable Pt/reduced graphene oxide (RGO) electrocatalysts for the application of proton exchange membrane fuel cells were developed by tuning the O/C atom ratio of RGO supports. The results showed that Pt nanoparticles with a narrow distribution of particle sizes were well dispersed on RGO, and an increased conductivity and stability of RGO were achieved when the Pt/RGO was deoxidized with an increased graphitization degree of RGO during hydrogen reduction. The highest activity of oxygen reduction reaction (ORR) and stability of Pt/RGO was obtained by hydrogen heat treatment Pt/RGO for 1 hour, in which the O/C atom ratio was 0.14. However, with increment of the reaction time, the atom ratio of O/C decreased to 0.11, the performance dropped sharply due to the further removal of the oxygenated groups on RGO, resulting in a serious aggregation of Pt nanoparticles. This study strongly suggested a bifunctional effect of both graphitization and the oxygenated groups on the catalytic activity and stabilization of metal (such as Pt) nanoparticles on RGO. This will open a door to apply graphene in fuel cells and other fields.

In this work an efficient functionalizing method of carbon nanotubes (CNTs) by intermittent microwave heating (IMH) KOH media is reported. The performance of such modified CNTs as Pt electrocatalysts supports is demonstrated. FTIR spectrum and Raman spectrum are used to investigate the surface state of the CNTs. TEM technology is employed to study the dispersion of Pt particles for the prepared electrocatalysts. Meanwhile, cyclic voltammetry and chronopotentiometry measurements are adopted to investigate the corresponding activity and stability of the electrocatalysts. The results indicate that the CNTs functionalized by the IMH method in the form of 15s-ON/10s-OFF for pulse 20 repetitions used as electrocatalysts supports shows significantly higher activity and stability towards methanol electrooxidation in comparison with the CNTs decorated in other forms in the present study. The present method is simple and economic and displays a probability of mass production for supporting materials and electrocatalysts as well.Highlights► CNTs are modified by intermittent microwave heating (IMH) in KOH in a few minutes. ► The modified CNTs supported catalysts show higher performance for methanol oxidation. ► The IMH method is simple and can be applied to mass production of nanomaterials.

The lyophilization was used to enhance platinum (Pt) nanoparticle distribution on carbon nanotube (CNTs). The results indicate that this method is very available to uniformly disperse nanotubes and effectively prevent Pt metal particles from agglomeration. The Pt nanoparticles ranging from 2 to 5 nm in diameter are uniformly deposited on CNTs characterized by both transmission electron microscopy (TEM) and X-ray diffraction (XRD). Instead, Pt/CNT catalysts fabricated by conventional drying method present a lower dispersion degree compared with that by lyophilization. The as-prepared catalysts have higher electrochemical active surface area and higher oxygen reduction reaction (ORR) activity as compared to that by drying method characterized through cyclic voltammetry (CV) and ORR.Highlights► The lyophilization is used to improve the dispersion of Pt nanoparticles on carbon nanotubes (CNTs). ► The results show Pt nanoparticles are well dispersed on CNTs and uniform in particle size. ► The prepared catalyst possess a higher catalytic activity than that by drying method. ► The lyophilization has potential for enhancing metal nanoparticle dispersion on inert supports.

Graphene nanosheets (GNS) supporting Pt nanoparticles (PNs) are prepared using perfluorosulfonic acid (PFSA) as a functionalization and anchoring agent. Transmission electron microscope (TEM) results indicate that the prepared Pt NPs are uniformly deposited on GNS with a narrow particle size ranging from 1 to 4 nm in diameter. A high catalytic activity of this novel catalyst is observed by both cyclic voltammetry and oxygen reduction reaction (ORR) measurements due to the increasing of proton (H+) transmission channels. Significantly, this novel PFSA-functionalized Pt/GNS (PFSA-Pt/GNS) catalyst reveals a better CO oxidation and lower loss rate of electrochemical active area in comparison with that of the plain Pt/GNS and conventional Pt/C catalysts, indicating our PFSA-Pt/GNS catalysts hold much higher stability and CO tolerance by virtue of introduction of PFSA.

The Pt@Au catalysts demonstrate remarkably high oxygen reduction reaction (ORR) activity compared with Pt/C catalysts. The ORR of Pt2@Au1/C and Pt1@Au2/C is 9.5 and 6.6 times that of Pt/C, respectively. This improvement is attributed to the electronic structure effect of the Au core on the Pt shell and introduction of PFSA.

In order to protect the perfluorosulfonic acid (PFSA) ionomer from an attack of contaminant metal ions as well as to enhance the mechanical stability of catalyst layers, palygorskite (PGS) is introduced into the catalyst layer of polymer electrolyte membrane fuel cells. PGS is a widely used natural nano-sized silicate mineral fiber with unique nano-sized channel structure, has a strong absorption capacity for heavy metal ions. We identify a negative influence of Fe2+ on PFSA membranes to make a comparative study. Subsequently catalyst coated membranes (CCMs) prepared with a PGS-Pt/C composite catalyst show a great effect in reducing Fe2+ ion crossover. Results display that PGS absorbs Fe2+ in nano-structure channels, and effectively protect PFSA ionomer in both the catalyst layer and membrane from hydroxyl radicals (OH) attack. Thus, the chemical stability of PFSA ionomer in both the catalyst layer and membrane is greatly improved. Furthermore, the enhancement of the mechanical performance of catalyst layers is discussed.Highlights► Palygorskite (PGS) is introduced to the catalyst layer of polymer electrolyte membrane fuel cells. ► PGS as a widely used natural nano-sized silicate mineral fiber with unique nano-sized channel structure and a strong absorption capacity for heavy metal ions. ► The introduction of PGS shows a great improvement in reducing Fe2+ ion crossover and effectively protect PFSA ionomers in both the catalyst layer and membrane from OH attack. ► The mechanical enhancement of catalyst coated membranes is achieved by the reinforcing function of PGS.

Pt nanoparticles supported on TiB2 conductive ceramics (Pt/TiB2) have been prepared through a liquid reduction method, where the TiB2 surfaces are stabilized with perfluorosulfonic acid. The prepared Pt/TiB2 catalyst is characterized with X-ray diffraction (XRD) and TEM techniques, and a rotating disk electrode (RDE) apparatus. The Pt nanoparticles are found to uniformly disperse on the surface of the TiB2 particles with narrow size distribution. The electrochemical stability of Pt/TiB2 is evaluated and found highly electrochemically stable compared to a commercial Pt/C catalyst. Meanwhile, the catalyst also shows comparable performance for oxygen reduction reaction (ORR) to the Pt/C. The mechanism of the remarkable stability and comparable activity for ORR on Pt/TiB2 is also proposed and discussed.Highlights► Titanium diboride (TiB2) has unique properties such as excellent thermal and electrochemical stability, and good electrical conductivity, perfectly for the catalyst support of polymer electrolyte membrane fuel cells. ► Perfluorosulfonic acid polymer stabilized TiB2 particles are available to enhance the interactions between Pt particles and TiB2 support as well as significantly improve the dispersion of Pt nanoparticles on such inert ceramic supports. ► Especially, our own Pt/TiB2 catalysts also show a comparable oxygen reduction reaction (ORR) activity to commercial Pt/C catalysts.

To further improve lifetime and performance of carbon nanotube (CNT) supported Pt catalysts for proton exchange membrane fuel cells, perfluorosulfonic acid (PFSA) was introduced by a simple colloid route to functionalize Pt (PFSA-Pt/CNT) catalysts. Here the PFSA is available as a binder to tightly anchor Pt nano-particles onto the CNT surfaces, and as a proton conductor to increase the triple phase boundary zone of the catalysts. The prepared Pt nano-particles ranging from 2 to 5 nm in diameter are uniformly deposited on CNTs. A high catalytic activity of this novel composite catalyst was observed by both cyclic voltammetry and oxygen reduction reaction (ORR) measurements. The loss rate of the electrochemically active area of the PFSA-Pt/CNT catalyst decreases by a factor of two in comparison with that of the plain Pt/CNT catalyst. Meanwhile, a lower loss rate for the new catalyst was also observed by electrochemically-accelerated durability testing for the ORR activity. These results indicate that the stability of the new catalyst is significantly improved over that of the plain Pt/CNT catalyst by introduction of PFSA.Graphical abstractThe perfluorosulfonic acid (PFSA) polymer was introduced to improve the lifetime and performance of CNT-supported Pt catalysts. We demonstrated that Pt nano-particles can be produced well-dispersed on the CNT surfaces, and the catalytic activity and stability of the resulting composite catalyst was greatly enhanced with additional PFSA.Research highlights► Compared to carbon black, the carbon nanotube (CNT) has high chemical stability and unique mechanical property, which could effectively decrease the support degradation. ► The introduction of perfluorosulfonic acid (PFSA) polymer greatly improves dispersion of metal particles on inert CNT surfaces by enhancing metal-support interaction. ► The PFSA polymer can enhance the catalytic activity of Pt catalysts by increasing the triple phase boundary reaction zone. Most significantly, the PFSA offers a strong metal-support interaction as both a binder and a stabilizer for Pt nano-particles, which further improves the CNT supported catalyst lifetime.

We report a new and simple solution to increase life of Pt/C catalysts using the proton-conducting polymer (perfluorosulfonic acid, PFSA) stabilized carbon support (denoted these catalysts as Pt/NFC catalysts) as compared to conventional Pt/C catalysts commonly used in PEM fuel cells. A high catalytic activity of the catalyst is observed by both CV (cyclic voltammetry) and ORR (oxygen reduction reaction) measurements. Especially, our own catalysts have a 60% better life as compared to Pt/C under electrochemically accelerated durability test conditions. The loss rate of electrochemical active area (ECA) for Pt/NFC catalysts is only 0.007 m2 g−1 cycle−1, compared to a value of 0.011 m2 g−1 cycle−1 for Pt/C.

Electrocatalytically active platinum (Pt) nanoparticles on a carbon nanotube (CNT) with enhanced nucleation and stability have been demonstrated through introduction of electron-conducting polyaniline (PANI) to bridge the Pt nanoparticles and CNT walls with the presence of platinum−nitride (Pt−N) bonding and π−π bonding. The Pt colloids were prepared through ethanol reduction under the protection of aniline, the CNT was dispersed well with the existence of aniline in the solution, and aniline was polymerized in the presence of a protonic acid (HCl) and an oxidant (NH4S2O8). The synthesized PANI is found to wrap around the CNT as a result of π−π bonding, and highly dispersed Pt nanoparticles are loaded onto the CNT with narrowly distributed particle sizes ranging from 2.0 to 4.0 nm due to the polymer stabilization and existence of Pt−N bonding. The Pt−PANI/CNT catalysts are electroactive and exhibit excellent electrochemical stability and therefore promise potential applications in proton exchange membrane fuel cells.

An experimentally simple process is reported in aqueous solution and under ambient conditions to prepare highly dispersed and active Pd/C catalyst without the use of a stabilizing agent. The [Pd(NH3)4]2+ ion is synthesized with gentle heating in aqueous ammonia solution without formation of Pd(OH)x complex intermediates. The adsorbed [Pd(NH3)4]2+ on the surface of carbon (Vulcan XC-72) is reduced in situ to Pd nanoparticles by NaBH4. The Pd/C catalyst obtained is characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that highly dispersed Pd/C catalyst with 20 wt.% Pd content and with an average Pd nanoparticle diameter of 4.3–4.7 nm could be obtained. The electrochemical measurements show that the Pd/C catalyst without stabilizer has a higher electro-oxidation activity for formic acid compared to that of a Pd/C catalyst prepared in a traditional high temperature polyol process in ethylene glycol.

The effect of pore volume on the catalyst layer durability of PEM fuel cell was simulated by soaking the catalyst coated membrane (CCM) into H2O2/Fe2+ solution. Before this simulation, the CCM with various pore volumes in catalyst layer was fabricated. The structure of catalyst layers was optimized with an increase in pore volume, leading to an improvement of fuel cell performance. However, this treatment causes a negative effect on the lifetime of CCM especially when H2O2/Fe2+ introduced. As a result, the catalyst layer with high pore volume has a higher detaching rate than that with low pore volume. The detaching of catalyst layers could be attributed to degradation of both the recast Nafion in catalyst layers and the Nafion membrane. The catalyst layer with high pore volume accelerates the recast Nafion degradation. Thus, the durability of membrane electrode assembly should be considered when the catalyst layer is optimized.

A simple, high efficient and environmentally friendly approach was investigated to recycle the key materials of membrane electrode assembly (MEA) applied in proton exchange membrane fuel cell (PEMFC). The catalyst coated membranes (CCMs) was dipped into sulfuric acid until the formation of transparent solution composed of Pt and perfluorosulfonic acid resin. Wherein, the membrane was dissolved, and the amorphous carbon nanoparticles as catalyst supports in catalyst layers were oxidized. Subsequently, both metal Pt and perfluorosulfonic acid resin were separated by centrifugal separation. Then the resin was recast into a membrane and the single fuel cell performance was tested. As a result, the solution to recycle the key materials of MEAs is promising for recycling MEA materials used in PEMFC.

A novel approach to increase lifetime of Pt/C catalysts was demonstrated and shown that Nafion-stabilized Pt catalyst (denoted here as Nafion-Pt/C) synthesized by a colloid route gives rise to an enhanced durability as compared to a conventional Pt/C catalysts commonly used in PEM fuel cell. A high catalytic activity of the catalyst is also observed by both CV (cyclic voltammetry) and ORR (oxygen reduction reaction) measurements. This catalyst durability in comparison with conventional Pt/C is increased directly by electrochemically-accelerated durability test (ADT). The loss rate of electrochemical active area (ECA) for Nafion-Pt/C catalysts is only 0.004 m2 g−1 cycle−1, compared to a value of 0.012 m2 g−1 cycle−1 for Pt/C. This indicates the catalyst is three times higher durability than Pt/C.

The Pt@Au catalysts demonstrate remarkably high oxygen reduction reaction (ORR) activity compared with Pt/C catalysts. The ORR of Pt2@Au1/C and Pt1@Au2/C is 9.5 and 6.6 times that of Pt/C, respectively. This improvement is attributed to the electronic structure effect of the Au core on the Pt shell and introduction of PFSA.

A nano-ZrO2 shell was decorated successfully on the surface of carbon to improve the stability of an electrocatalyst. Pt nanoparticles (NPs) were formed on the support by an isothermal hydrolysis procedure. This composite was characterized by X-ray powder diffraction, thermogravimetric analysis, high-resolution transmission electron microscopy (HRTEM) with EDS and cyclic voltammogram techniques. HRTEM images show that the nano-ZrO2 shell has been decorated on the surface of carbon and 2–3 nm Pt NPs are dispersed on the carbon surface homogeneously, including the edge of the nano-ZrO2 shell. The electrochemical stability of the prepared Pt/ZrO2–C is enhanced considerably in comparison with a conventional Pt/C catalyst, which can be attributed to the inhibition of the migration and aggregation of Pt NPs on the support and the increase of the oxidation resistance of carbon with the nano-ZrO2 shell.

To construct a suitable structure for both electronic conduction and ionic transport towards supercapacitors, peanut-like hierarchical manganese carbonate (MnCO3) microcrystals assembled with floss-like nanowires are synthesized via a hydrothermal process and primarily used as an active material for supercapacitors. The formation mechanism is illustrated by means of a dissolution–recrystallization process and magnetically driven self-assembly. The electrode with peanut-like hierarchical MnCO3 microcrystals exhibits a high specific capacitance of 293.7 F g−1 and a superior cycle stability of 71.5% retention after 6000 cycles, which are higher than those of the reported Mn-based active materials in alkaline electrolytes. The asymmetric supercapacitor, assembled with the peanut-like MnCO3 electrode as the positive electrode and a home-made porous carbon electrode as the negative electrode, exhibits an energy density of 14.7 W h kg−1 at a power density of 90.2 W kg−1 and an energy density of up to 11.0 W h kg−1 at 3.3 kW kg−1. An as-assembled all-solid-state supercapacitor series can light up a LED indicator for 10 min, indicating a promising practical application of peanut-like MnCO3 microcrystals.

MnO anode materials with high energy densities for lithium-ion batteries (LIBs) face significant challenges in avoiding inferior reversible capacity and fast capacity fading. Here we demonstrate a facile and scalable approach to realizing excellent performance, overcoming such disadvantages. A well-connected three-dimensional (3D) hierarchical porous-conducting framework, consisting of MnO nanorods conformally encapsulated by a nitrogen-doped carbon network, was synthesized via an in situ polymerization of polyaniline into manganese dioxide along with thermal calcination. Such a structure possesses a continuous electrically conductive carbon network with porous spaces for volume expansion of MnO rods, and the carbon coating on the nanorods further alleviates pulverization and self-aggregation of the active materials. As an anode, it demonstrates a reversible capacity as high as 798.6 mA h g−1 after 5 cycles at 50 mA g−1, beyond the theoretical capacity of MnO, and an extremely stable cycle life of 3000 cycles with ∼95% capacity retention, even at a high current density of 4000 mA g−1. Significantly, the electrochemical behavior of this novel material was also probed by an in situ XRD technique.

We synthesized a novel 2D hybrid material composed of Li2FeSiO4 nanorods (LFSNRs) anchored on graphene. Such a chemically bonded interface leads to electron coupling at the interface between the nano-LFS and graphene, creating effective charge transport for LFSNR@graphene hybrid cathodes. Used as a cathode material, it possesses a high capacity (300 mA h g−1 at 1.5–4.8 V), high charging–discharging rate (134 mA h g−1 @ 12 C) and long-life performance (maintaining 95% capacity over 240 cycles), which is mainly attributed to the effective depolarization introduced by the synergistic effects of LFSNRs bonded with graphene, which improves the electrochemical activity of the LFSNRs. Thus, a hybrid cathode modified with an interfacial chemical structure with nanoparticles bonded with an electrical conduction network such as graphene or CNTs can significantly enhance the electrochemical performance, and this novel type of material is very promising for commercial applications that require high energy, a long operating life, and excellent abuse tolerance, such as electric vehicles.

Highly active and stable Pt/reduced graphene oxide (RGO) electrocatalysts for the application of proton exchange membrane fuel cells were developed by tuning the O/C atom ratio of RGO supports. The results showed that Pt nanoparticles with a narrow distribution of particle sizes were well dispersed on RGO, and an increased conductivity and stability of RGO were achieved when the Pt/RGO was deoxidized with an increased graphitization degree of RGO during hydrogen reduction. The highest activity of oxygen reduction reaction (ORR) and stability of Pt/RGO was obtained by hydrogen heat treatment Pt/RGO for 1 hour, in which the O/C atom ratio was 0.14. However, with increment of the reaction time, the atom ratio of O/C decreased to 0.11, the performance dropped sharply due to the further removal of the oxygenated groups on RGO, resulting in a serious aggregation of Pt nanoparticles. This study strongly suggested a bifunctional effect of both graphitization and the oxygenated groups on the catalytic activity and stabilization of metal (such as Pt) nanoparticles on RGO. This will open a door to apply graphene in fuel cells and other fields.

A new strategy to synthesize novel nano-sandwiched graphene/carbon/graphene (GCG) composites is described, employing the aqueous dispersion of low cost carbon nanospheres (CNS) in graphene oxide layers with subsequent thermal reduction. This 3D GCG sandwich shows a particular exfoliated graphene morphology, with CNS regularly embedded into the graphene nanosheets (GNS), from SEM and high-resolution TEM observations. The incorporation of CNS not only increases the Brunauer–Emmett–Teller (BET) surface area due to the effective expansion of the graphene interlayer, but also enhances the electrochemically accessible surface area and the charge transfer speed at the GCG–electrolyte interfaces due to a high density of between-plane electrolyte diffusion channels, that facilitate the reaction species transport and electron transport at high rates. As a result, this unique GCG nanoarchitecture with highly dispersed Pt particles exhibits a very high electrocatalytic activity for the oxygen reduction reaction (ORR). The half cell ORR mass activity of the Pt/GCG catalyst (17.7 A g−1) is 2.2 times of that of Pt/GNS (8.2 A g−1), and 3.8 times that of commercial Pt/C catalysts (4.6 A g−1). Moreover, the Pt/GCG catalyst also shows excellent electrochemical stability. Therefore our new catalyst holds tremendous promise for potential applications in proton exchange membrane (PEM) fuel cells.

We report a rationally designed electrocatalyst with high activity for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) based on a nanocarbon-intercalated graphene (CIG) material doped with nitrogen (N) and iron (Fe) (Fe–N-CIG). This easily made novel 3D Fe–N-CIG catalyst exhibits a surprisingly high ORR and OER activity and stability, making it a new noble-metal-free bifunctional catalyst for future applications in regenerative energy conversion systems.

A Mo2C quantum dot (averagely 2 nm) embedded N-doped graphitic carbon layer (Mo2C QD/NGCL) is prepared through a simple, green and scalable solid-state reaction. This material exhibits remarkable hydrogen evolution reaction (HER) catalytic activity and durability at all pH values owing to the synergistic effect between Mo2C QDs and NGCLs.

A non-precious metal catalyst (NPMC), with nano-porous structure and high BET surface area, is prepared by pyrolyzing the polyaniline on carbon nanospheres using ferric chloride both as an oxidant and iron source. Electrochemical test results show that the catalyst has a high activity and much better stability than that of commercial Pt/C in acid medium.

A non-noble metal nitrogen (N)-doped carbon catalyst, with a porous graphene-like structure, is prepared by pyrolyzing polyaniline with addition of urea. Herein, urea not only serves as a N source similar to polyaniline by incorporating N atoms into the carbon matrix, but plays a key role in forming the porous graphene-like structured carbon nanosheet. The electrochemical characterization shows that the prepared catalyst with a unique graphene-like structure exhibits an oxygen reduction reaction (ORR) activity that outperforms that of the commercial Pt/C catalyst in alkaline media, its half-wave potential nearly 30 mV more positive than Pt/C, and both superior stability and fuel (methanol and CO) tolerance to Pt/C. Significantly, such a catalyst also exhibits a good ORR activity which is comparable to Pt/C, as well as a higher stability than Pt/C in acidic media.

The P21/n structured nanocrystalline-Li2FeSiO4 is prepared by a confinement effect of three-dimensional conductive carbon frameworks, which are formed through a chelating reaction and subsequent pyrolysis. As a benefit of enhanced electronic conductivity by carbon frameworks and Li-ion diffusion kinetics by nanocrystalline-Li2FeSiO4 architectures, the novel nanocomposite shows a 1.28 Li-ion storage capacity (211.3 mA h g−1) at 0.1 C, corresponding to two successive steps of oxidation and reduction of Fe2+/Fe3+/Fe4+. Furthermore, the discharge capacity is 189.8, 175.6, 148.9, 125.7 and 106.6 mA h g−1 at a variable rate of 0.5, 1, 2, 5 and 10 C, respectively, and then easily returns to 175 mA h g−1 at 1 C. It is a surprise that the initial capacity is 90.9 mA h g−1 at 10 C, and 97.7% is retained after 1000 cycles. Thus, we believe that the nanocrystalline-Li2FeSiO4 with carbon frameworks, possessing high-capacity and high-rate performance, is a promising next-generation cathode material for high-power lithium-ion batteries.

A novel ultrathin carbon layer (UTCL) stabilized Pt catalyst (Pt-UTCL/C) with an open framework is synthesized to significantly enhance the stability of the catalyst in proton exchange membrane fuel cells. Herein, a cheap and widely available polymer, soluble starch (SS), as a precursor, is employed to wrap Pt nanoparticles (NPs) and is then carbonized into a UTCL with a thickness of few molecular-layers (0.58 nm on average) at a mild temperature. Significantly, it possesses extremely high stabilities of both electrochemical surface area and ORR compared to the commercial Pt/C catalyst even after 10000 potential cycles. Such excellent stability can be ascribed to the anchoring effect of the UTCL towards Pt NPs to the inhibited migration, agglomeration and detachment of Pt NPs from the supports as well as to the possibly mitigated dissolution-growth process of Pt NPs in light of the UTCL.

(1 − x)Li2FeSiO4·xLiFeBO3/C (x = 0, 0.02, 0.05, 0.08, 0.12, and 1.00) hetero-grains are successfully synthesized via an in situ citric acid-based sol–gel method and evaluated as cathode materials for lithium ion batteries. As a result, 0.92Li2FeSiO4·0.08LiFeBO3/C delivers an optimum discharge capacity of 251 mA h g−1 which corresponds to nearly 1.51 Li+ intercalation per molecule. Furthermore, a capacity retention of 104.5% after 5 cycles at 0.1 C is attained, and a value of 188.3 mA h g−1 (approaching 1.13 Li+ intercalation per molecule) remains even after one hundred cycles at 1 C. In particular, at a high-rate of 10 C, there is almost no capacity decline even after 500 cycles, indicating an excellent cycling stability. The greatly improved electrochemical lithium storage properties of the novel in situ hybridized materials can be attributed to the enhanced kinetics towards Li+ diffusion and electron transport compared with that of pure Li2FeSiO4/C electrodes.

Development of a cathode material with safety, low cost, high energy and power densities, long life and excellent abuse tolerance for Li-ion batteries is critical for hybrid electric vehicles (HEVs) and electric vehicles (EVs). Here, we developed graphene activated 3D-hierarchical flower-like Li2FeSiO4 with secondary nanopetals (G@3D-HFLFS), which exhibited a discharge capacity of 327.2 mA h g−1 (specific energy of 879 W h kg−1) approaching the full theoretical capacity with large-current and long-life performance. The electrochemical reaction mechanism of G@3D-HFLFS was investigated by Mössbauer spectroscopy and parallel model X-band ESR. The high performance can be attributed to the secondary petal-like structures having an ultra-rapid Li-ion diffusion along the minimum length, the graphene coating layers facilitating double transport of electrons and Li-ions, and the special hierarchical structure with an optimal petal thickness possessing excellent structural stability. These results clearly demonstrate that our novel material is a promising cathode for commercial applications that require high energy and power densities, long operating life and excellent abuse tolerance.

Porous nitrogen-doped graphene with a very high surface area (1152 m2 g−1) is synthesized by a novel strategy using intrinsically porous biomass (soybean shells) as a carbon and nitrogen source via calcination and KOH activation. To redouble the oxygen reduction reaction (ORR) activity by tuning the doped-nitrogen content and type, ammonia (NH3) is injected during thermal treatment. Interestingly, this biomass-derived graphene catalyst exhibits the unique properties of mesoporosity and high pyridine-nitrogen content, which contribute to the excellent oxygen reduction performance. As a result, the onset and half-wave potentials of the new metal-free non-platinum catalyst reach −0.009 V and −0.202 V (vs. SCE), respectively, which is very close to the catalytic activity of the commercial Pt/C catalyst in alkaline media. Moreover, our catalyst has a higher ORR stability and stronger CO and CH3OH tolerance than Pt/C in alkaline media. Importantly, in acidic media, the catalyst also exhibits good ORR performance and higher ORR stability compared to Pt/C.