•Pt nanocrystals with concave nanocubes structure are deposited on rGO.•Pt nanocrystals supported on rGO present high catalytic performance.•Square-wave potential method can rapidly prepare gas diffusion electrode.Carbon fiber paper (CFP) wrapped with reduced graphene oxide (rGO) film as the composite support (rGO/CFP) of Pt catalysts was studied. It was found that rGO could affect the size and morphology of Pt nanocrystals (NCs). Concave nanocubes (CNC) Pt NCs ~ 20 nm were uniformly electrodeposited on high reduced HrGO/CFP while irregular Pt NCs ~ 62 nm were loaded on low reduced LrGO. Compared with Pt-LrGO/CFP and Pt-MrGO/CFP, the CNC Pt-HrGO/CFP exhibited a higher electrochemically active surface area (121.7 m2 g−1), as well as enhanced electrooxidation activity of methanol (499 mA mg−1) and formic acid (950 mA mg−1). The results further demonstrated that the CNC Pt-HrGO/CFP could serve as the gas diffusion electrode in fuel cells and yielded a satisfactory performance (1855 mW mg−1). The work can provide an attractive perspective on the convenient preparation of the novel gas diffusion electrode for proton exchange membrane fuel cells.

•Mesoporous sulfated zirconia is introduced in Nafion as proton exchange membranes.•The mesopores increase the material surface area for high protonic group contents.•Continuous ion pathways are constructed on the interface of mesopores and Nafion.•The hybrid membranes are assembled in fuel cells that achieve high performance.•Mesopores as water reservoirs allow fuel cells to adjust different humidity.Proton exchange membranes (PEMs) are a vital component in fuel cells (FCs) that attract significant research interest for the present hydrogen energy use. High proton conductivity of PEMs under various operation conditions highly influences the integrated performance of FCs that determines their commercial applications. Hence mesoporous superacidic sulfated zirconia (S-ZrO2) is fabricated and introduced into Nafion matrix to construct hybrid PEMs. The mesoporosity of S-ZrO2 is demonstrated highly controllable. High mesoporosity leads to increased amount of sulfonic groups (SO3H) aggregating on S-ZrO2 surface. When introduced in PEMs, the highly mesoporous S-ZrO2 chemically enhances the amount of proton-containing groups, structurally improves the density of ion channels, and reserves water as effective reservoirs, which resultantly maintains high proton conductivity under variable conditions, and thus the performance of assembled FCs. The S-ZrO2 exhibits the highest surface area of 181 m2 g−1. The hybrid PEMs loaded with 10 wt% such S-ZrO2 achieve a highest proton conductivity of 0.83 S cm−1 that is ∼7 time of that for pristine Nafion® membranes. The power density at 0.6 V of FCs with the hybrid PEMs is 786 mW cm−2, much higher than that for commercial Nafion 211.Download high-res image (219KB)Download full-size image

Here, we report a two-step dealloying method using ferric chloride to synthesize nanoporous gold (NPG), instead of the traditional corrosive nitric acid method. In the new method, the pore size can be easily controlled by using various solutions and additives. For example, when using ethylene glycol (EG) as a solvent, the NPG (NPG-EG) pore size can be made as small as 8 nm, thus increasing the electrochemical specific surface area of the NPG to seven times higher than that of traditional NPG with a pore size of 25 nm. NPG-EG showed an enhanced capacitance of 1340 F g−1 at a current density of 2.0 A g−1 when electrodeposited with Ni3S2.

Pyrolyzed Fe/N/C, a promising nonprecious-metal catalyst for oxygen reduction reaction (ORR), usually relies on abundant micropores, which can host a large amount of active sites. However, microporous structure suffers from severe water flooding to break the triple-phase interface where ORR occurs, especially in a direct methanol fuel cell (DMFC) fed with liquid fuel. Current studies about the fabrication of a triple-phase interface are mainly limited on a Pt/C catalyst layer, where mesopores and macropores are concerned. Here, we successfully constructed a triple-phase interface in micropores of Fe/N/C catalysts by controlling the distribution of a hydrophobic additive, dimethyl silicon oil (DMS), just partially penetrating into the micropores. The elaborately constructed Fe/N/C-based DMFC can deliver high power density (102 and 130 mW cm–2 at 60 and 80 °C, respectively) and durability comparable to that of Pt/C-based DMFC. This study presents a new avenue to engineer catalyst microporous channels to boost the performance of nonprecious-metal catalysts for fuel cells.

•A kind of microporous metal-free catalyst is synthesized based on the ribose.•The materials have high surface area and a large amount of micropores.•The catalyst has better stability compared to other metal-free catalysts.Nitrogen-doped carbon materials are known to be promising candidates as oxygen reduction reaction electrocatalysts used in fuel cells. However, developing metal-free catalysts with high performance and stability still remains a big challenge. Herein we report a new route by using the Maillard reaction, to caramelize ribose in a dispersing salt matrix, followed by carbonization of this caramel to synthesize metal-free catalysts. This catalytic material has the morphology of microporous nitrogen doped graphene-like carbon, and a highest surface area of 1261 m2 g−1 with a large amount of micropores. Such microporous structure offers numerous defects that generate a large number of reactive sites. As a result, when used as the cathode materials in fuel cells, the fuel cell shows a high power density of 547 mW cm−2 under 1.0 atm back pressure with good stability with only 12.5% loss after 250 h. Such catalyst has good performance in the class of metal-free oxygen reduction reaction catalysts, and is possible for commercial use.In this work the report is about a new route by using the Maillard reaction, to caramelize ribose in a dispersing salt matrix, followed by carbonization of this caramel. And the obtained metal-free catalysts for oxygen reduction reaction (ORR) is with high activity and stability.Download high-res image (161KB)Download full-size image

3D CoNi2S4 and cross-linked NiCo2S4 arrays have been grown on carbon paper (CP) using a one-step hydrothermal method. The 3D cross-linked structure provides a convenient channel for electron and lithium-ion (Li+) transport and performs a facile strain relaxation during cycling, exhibits high capacity, excellent rate capability and superior cycle performance.

Tuna is one of the most rapid and distant swimmers. Its unique gill structure with the porous lamellae promotes fast oxygen exchange that guarantees tuna’s high metabolic and athletic demands. Inspired by this specific structure, we designed and fabricated microporous graphene nanoplatelets (GNPs)-based Fe/N/C electrocatalysts for oxygen reduction reaction (ORR). Careful control of GNP structure leads to the increment of microporosity, which influences the O2 adsorption positively and desorption oppositely, resulting in enhanced O2 diffusion, while experiencing reduced ORR kinetics. Working in the cathode of proton-exchange membrane fuel cells, the GNP catalysts require a compromise between adsorption/desorption for effective O2 exchange, and as a result, appropriate microporosity is needed. In this work, the highest power density, 521 mW·cm–2, at zero back pressure is achieved.Keywords: graphene nanoplatelets; microporosity; nonprecious metal catalyst; oxygen reduction reaction; proton-exchange membrane fuel cells

•Fe/N/C catalyst for ORR is synthesized based on the inexpensive melamine resin.•Carbon will enhance ORR activity due to the abundant micropores in Fe/N/C catalyst.•Addition of Tween 80 during synthesis can significantly improve the performance.The aim of non-precious metal catalysts (NPMCs) is to replace expensive Pt-based catalysts for fuel cells. NPMCs require not only high oxygen reduction reaction (ORR) catalytic activity but also cheap ingredients, and the facile synthetic method of the catalyst is amendable to mass production. We describe a potential catalyst for catalyzing the cathodic ORR, which is synthesized by a facile method: uses porous carbon-supported melamine-formaldehyde resin as a precursor to a carbon–nitrogen template for high-temperature synthesis of catalysts incorporating iron. In the synthesis process of porous carbon-supported melamine-formaldehyde resin, the uses of surfactant (Tween 80), making the activity of catalysts have been improved significantly. As a result, the catalyst demonstrates remarkable ORR activity in both acid and alkaline electrolytes, thus making it a promising alternative as an ORR catalyst for application in fuel cells.In this work the study of the inexpensive melamine resin synthesized to obtain Fe/N/C catalyst with high activity for oxygen reduction reaction (ORR) is reported. And with the use of surfactant (Tween 80) modified carbon black, ORR activity of Fe-MF-C catalyst has been significantly improved.

The prohibitive cost and scarcity of the precious metals used for oxygen reduction reaction (ORR) catalysts limit the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs). Great efforts have been made to improve the ORR activity of non-precious metal catalysts. Herein, we describe a one-pot synthesis process of preparing triazine-polymer–Fe–C catalysts using polyimide (PI), ferric chloride and melamine as the precursors with a pronounced electrocatalytic activity towards ORR in acid media. The ORR activity of catalysts and the performance of single cells strongly depend on the properties of the carbon supports, which affect the surface areas and microporosities of the final catalysts. The optimized PI–Fe–C catalyst exhibits an excellent performance (onset potential of 0.92 V and the half-wave potential 0.78 V) towards ORR activity in acid medium. A maximum power density of 310 mW cm−2 is obtained with a loading of 2 mg cm−2 in a single cell.

A Ni3S2 coated indium tin oxide (ITO) core–shell structure on flexible carbon fabrics (CF@ITO@Ni3S2) was prepared by electrodepositing Ni3S2 nanosheets on ITO nanowire arrays grown on flexible carbon fabrics by chemical vapor deposition. The ITO nanowires on carbon fabrics formed a conductive support which offered a large contact surface with the electrolyte and hence was accessible for ion diffusion. Ni3S2 nanosheets were uniformly deposited on the ITO nanowire. The maximum mass loading of Ni3S2 on ITO nanowire array coated carbon fabrics could reach about a quadruple higher amount than that on the bare carbon fabrics. The prepared CF@ITO@Ni3S2 electrodes exhibited excellent capacitive performance compared with Ni3S2 coated bare carbon fabric electrodes (CF@Ni3S2). High areal capacitance of 3.85 F cm−2 and gravimetric capacitance of 1865 F g−1 were achieved when the mass loadings of Ni3S2 on the ITO nanowire arrays were around 4.12 mg cm−2 and 0.96 mg cm−2, respectively. The sample with 0.96 mg cm−2 of Ni3S2 could also deliver 1372 F g−1 when charge–discharge current density reached 50 mA cm−2, indicating the excellent rate capability of the structure. The assembled all-solid-state full cell based on symmetric electrodes obtained a relatively high areal capacitance of 736 mF cm−2 at 8 mA cm−2, which delivered a maximum energy density of 1.02 mW h cm−3 at a power density of 39.9 W cm−3. The outstanding capacitive performance suggests that the CF@ITO@Ni3S2 device was promising for application in an inexpensive energy storage system.

•Methanol oxidization on well-ordered Ru@Pt catalysts is systematically studied.•Its electrochemical performance significantly depends on shell thicknesses.•It shows a perfect stability in half and single cell by suppressing Ru-dissolution.•A maximum power density of 185 mW/cm2 can be obtained in DMFC.Platinum-based alloy nanocatalysts are highly attractive for both heterogeneous catalysis and electrocatalysis. However, their stability remains a major concern for their application under realistic operating conditions. We herein report a microwave-assisted synthesis of atomically ordered Ru-core Pt-shell (Ru@Pt) nanoparticles that show superior catalytic properties for methanol electrooxidation. The Ru@Pt catalysts are found to display higher methanol oxidation activity and CO-deactivation resistance than the commercial Pt–Ru catalysts. Shell-thickness variation induced properties is of great importance for core–shell catalysis. Above all, well-ordered Ru@Pt with sub-nm Pt shell exhibit superior durability in long-term and extreme operation condition in direct methanol fuel cell (DMFC). This type of core–shell catalysts thus hold great potential to be applied as high performance anode catalysts in DMFCs.Well-ordered Ru@Pt catalysts with sub-nm Pt-shell exhibit enhanced activity and durability towards methanol oxidation for DMFCs.

•Ultralong CaV6O16·3H2O nanoribbons were successfully fabricated.•It shows long-term cyclability and high-rate kinetics as Li-intercalated material.•The alkaline-earth metals in V–O may induce a better electrochemical response.The applications of vanadium oxide bronzes as cathode materials for rechargeable lithium-ion batteries are hindered by inferior cyclability and insufficient rate capability, which arised from weak structural stability and sluggish electrochemical kinetics. To address this issue, we incorporate alkaline-earth metals as interlayer materials within the vanadium oxide layered framework, leading to a whole new family of potential Li+ intercalated materials with a general formula MV6O16·nH2O (M=Mg, Ca, Sr, Ba). In these bronze-hydrated compounds, interlayer water can serve as pillars pinning the V–O layers together, coupled with the enhanced divalent cation pillars, maintaining substantial structure stability and leading to excellent long-term stability. Additionally, the interlayer spacing can be further expanded by intercalation of water molecules, offering enhanced Li+ diffusion channel and leading to high rate capability. In this family, we fabricate and study the first such candidate, ultralong metahewettite CaV6O16·3H2O nanoribbons. When evaluated as cathode materials, for the first time, they exhibit high-rate kinetics (103, 78 mA h g−1 at 6 and 10 A g−1, respectively) and excellent long-term cyclability (83.6%, 89.5% capacity retention after 1000 cycles at 2 and 6 A g−1, respectively). The electrode shows optimal cycling stability for vanadate-based cathode materials for LIBs ever reported.Ultralong Metahewettite CaV6O16·3H2O Nanoribbons exhibit excellent long-term cyclability integrated with high-rate kinetics afforded by a synergistic effect between ultralong 1D nanostructures and intercalated Ca ions along with water molecules within the vanadium oxide layered framework.

Solid phase polymerization of phenylenediamine with a template toward a self-supported FeNx/C catalyst was introduced. Using ZnO nanoparticles as the hard template could increase the surface area of the catalyst, thus the oxygen reduction activity was radically enhanced, to 21.9 A g−1 at 0.80 V (vs. RHE) in acid medium.

•The degradation of three composite membranes with various thicknesses under OCV was investigated.•A high hydrogen crossover would accelerate the thinning of the composite membranes.•Pt particle growth can be enhanced due to the hot point generated by permeable hydrogen and oxygen.Membrane chemical degradation and platinum catalyst agglomeration under long-term open circuit voltage (OCV) conditions were investigated using three types of composite membranes with various membrane thicknesses. Hydrogen permeation increases as membrane thickness decreases, which has a significant influence on proton exchange membrane and platinum catalysts. Higher Hydrogen permeation accelerated the membrane degradation, resulting in the thinning of membrane which can be verified by fluoride emission rates (FERs). Carbon-supported platinum catalysts also experienced agglomeration under OCV conditions. The statistics of platinum size distribution demonstrated catalysts size growth, ranging from 3.83 to 6.02 nm in diameter along with the increasing hydrogen crossover

•The cell performance was optimized in a simulated condition for open-cathode PEMFCs.•A thick electrode helps to maintain water in a high temperature operation.•A best cell performance was obtained with a 17 μm-thick composite Nafion/PTFE membrane.•Performance improvement can be attributed to better water retention in the MEA.The oxidant supply coupled with the cooling task in open-cathode proton exchange membrane fuel cells (PEMFCs) creates a simple system configuration. Based on a simulated condition which was previously established for evaluating cell performance of different membrane electrode assemblies, this work has conducted performance optimization by altering electrocatalysts, thickness of micro-porous layer (MPL) and membranes. The thickness of the catalyst layers was around ∼35 μm with 20 wt% Pt/C, and reduced to only 12 μm with 60 wt% Pt/C. Although a thick catalyst layer resulted in a stable performance at various air stiochiometric ratios, especially under high temperatures where cell performance decreased due to a low Pt utilization and poor mass transport of proton and reactants in the cathode. The cathode with 2 mg cm−2 carbon loading in the MPL gave the best performance and the cell voltage varied between 0.71 and 0.62 V at 800 mA cm−2 in the temperature range from 50 °C to 60 °C. Finally, different membranes were investigated, and a thin composite Nafion/PTFE membrane around 17 μm showed better performance comparing to Nafion 211, which can be attributed to a good water retention capacity owing to easy crossover of hydrogen and water through the membrane.

Due to breathing O2 from the air, vertebrates can suffer from diseases originating from oxidative stress. These, however, can be relieved by various antioxidants. Similarly, proton exchange membrane fuel cells (PEMFCs) suffer from the major problem of limited lifetimes, caused by chemical attacks by reactive oxygen species (ROS). Inspired by vertebrates, we herein show that the incorporation of a natural antioxidant, α-tocopherol (α-TOH), the most abundant component of vitamin E, which acts as a free radical scavenger, enables a maintenance of performance for PEMFCs which is impossible to achieve for fuel cells in the absence of α-TOH. It is notable that oxidized α-TOH can in turn be reduced by permeated H2 during fuel cell operation, resulting in its regeneration. Such reversibility leads to a chemical circulation system, which not only ensures the effective recycling of α-TOH, but also permits efficient protection of proton exchange membranes (PEMs) and thus allows their long-term operation.

Direct formic acid fuel cells (DFAFCs) are promising portable energy conversion devices for supplying our off-grid energy demands. However, traditional Pt-based catalysts suffer from poor performance; consequently the precious metal loading in an actual fuel cell has to be maintained at a very high value, typically orders of magnitude higher than the acceptable level. Through a molecular self-assembly/electro-deposition process, Pt atoms are effectively dispersed onto the surface of a nanoporous gold substrate, and the resulting nanocomposites demonstrate superior electrocatalytic performance toward formic acid electro-oxidation, which can be attributed to a nearly ideal catalyst configuration where all the Pt atoms are involved in a highly desired direct reaction path. In both half-cell electrochemical testing and actual DFAFCs, these rationally designed electrodes show over two orders of magnitude improvement in Pt efficiency, as compared with the state-of-the-art Pt/C catalyst. This design strategy allows customized development of new generation electrocatalysts for high performance energy saving technologies.

Functional design was conducted for ionic liquid (IL) by introducing –SO3H to the cation, and an IL of N,N,N-trimethyl butylsulphonate ammonium hydrosulfate ([N1114SO3H]HSO4) was synthesized as the electrolyte in a proton exchange membrane fuel cell (PEMFC). Subsequently, a series of single cell tests was carried out, and the results show high cell performance for the PEMFC with the designed IL as the electrolyte. A maximum power density (MPD) of 90 mW cm−2 was obtained with the functionalized IL of [N1114SO3H]HSO4, while the MPD for the fuel cell with a similar but not functionalized IL can only provide an MPD of approximately 60 mW cm−2. Possible mechanisms behind the elevation of the fuel cell performance were investigated and discussed. The results show that the proton diffusion coefficient elevation of the functionalized IL is one important explanation for the increased fuel cell performance. Finally, theoretical calculation for the potential barrier for proton transportation in the two ILs was conducted. The results show that the potential barrier for the functionalized IL was lowered. All of these results imply that introducing a functional group to the cation is a promising way for a high proton conductive IL to function as the electrolyte in a PEMFC.

•Impact of cation selection on PEM fuel cell performance was studied.•The results shed more light on the influence of organic cations on the Pt/C catalyst.•The results show that the influence of ILs on the Pt/C should be considered.•The work provides helpful information in applying ILs as electrolyte for PEMFC.The cation impact of trimethylethyl amide ([N1114]+), ethyl pyridinium ([Epdy]) and ethylmethyl imidazolium ([Emim]+) on the performance of proton exchange membrane fuel cell (PEMFC) is studied. The cell performance with ionic liquid (IL) as the electrolyte is dramatically improved by replacing [Emim] cation with [N1114]. A maximum power density (MPD) of 65 mW cm−2 is obtained with [N1114]HSO4 as the electrolyte in PEMFC while the one with imidazolium ILs can only provide around 1 mW cm−2. Subsequently, the influence of cations of ILs on Pt/C catalyst is investigated by cyclic voltammogram, and it can be found that the imidazolium cation result in smaller electrochemical active surface areas (EAS) of Pt/C than those of [N1114]+ and pyridinium. In addition, theoretical calculation with the Gaussian 03 program implies that the adsorption energy of the [Emim]+ on the Pt catalyst surface is much higher than [N1114]+, thus decreasing EAS of Pt catalyst in fuel cells. Therefore, it indicates that the cation should be carefully selected when applying ILs as an electrolyte for fuel cells.

•Pt/C in CCM-based MEA under potential cycling and potential holding was studied.•In-situ electrochemical tests and ex-situ SEM/TEM/XPS characterization were conducted.•“Pt band” occurred in the membrane and Pt particles can reach hundreds of nanometers.•Carbon surface oxidation current appeared as well as different carbon surface groups.The stability of platinum and carbon support in catalyst-coated membrane (CCM) was investigated by a potential cycling between 0.7 and 0.9 V and a potential-static holding at 1.2 V, 1.3 V and 1.5 V in single cells. Clear cell performance deterioration can be observed by polarization curves during accelerated stress tests, along with electrochemical surface area (ESA) loss of Pt catalysts by cyclic voltammogram (CV). The X-ray diffraction (XRD) results of CCM before and after tests show that a distinct Pt agglomeration occurred from approximate 3 nm–8 nm in diameter, which is in accord with the observation of Pt/C by transmission electron microscopy (TEM). It is also interesting to note that, redeposited Pt particles in the membrane could be as large as hundreds of nanometers from TEM images of CCM microtomy. X-ray photoelectron spectroscopy (XPS) of carbon 1S indicates that the corrosion of carbon support is highly dependent on the holding potential, and enormous surface groups, such as carboxyl, lactones and ether were generated after tests. Meanwhile, a severer ESA loss of Pt after carbon corrosion under high potential holdings happens than that of potential cycling. The results indicate that both Pt and carbon support in the catalyst are important to maintain a long-term stable operation for fuel cells.

•Nafion/PTFE composite membrane in PEMFC was studied in accelerated stress tests.•An edge protection should be adopted to avoid immediate mechanical failure.•OCV under H2/N2 was confirmed to be a rapid diagnose tool to membrane condition.•Hot-pressing process performed a long accelerated lifetime for a low H2 crossover.Accelerated stress tests (ASTs) were performed to study the degradation mechanism of Nafion/PTFE composite membrane in PEM fuel cell with intensive RH cycling and load cycling. It was recognized that the edge of membrane electrode assembly (MEA) should be carefully treated to prevent the immediate failure for excessive or non-uniform mechanical stress mainly caused by RH cycling in the early period of ASTs. A long accelerated life (over 1000 h) was obtained for MEA with an edge protection and a hot-pressing process along with a low hydrogen permeation current. In addition, the decay of open circuit voltage, the fluoride emission rate (FER) from cathode side and the polarization curves were also monitored during the test. It was verified that the chemical degradation of membrane occurred inevitably caused by radical attack (HO, HO2 and H2O2) due to the intensification of gas mutual permeation. Membrane thinning, Pt particles gathering along the interfaces, even ionomer disappearing at cathode side could be observed from TEM and SEM results. Besides, open circuit voltage under H2/N2 atmosphere of MEA was confirmed to be a rapid diagnose tool of membrane physical condition.

•TiN–G was prepared by the microwave-assisted synthesis method.•Pt/TiN–G shows improved methanol oxidation activity and enhanced CO tolerance.•The improvement effect should be ascribed to the presence of TiN.•Pt/TiN–G could decompose water to form OH groups which is similar to Pt–Ru.A one-step and fast microwave technique was developed to synthesize graphene-supported TiN nanoparticles (TiN–G) directly from graphene and dihydroxybis (ammonium lactato) titanium (IV). During the synthesis graphene served as a reductant and template to reduce the Ti-precursor into TiN and then uniformly disperse TiN nanoparticles on it. Pt/TiN–G catalyst was also successfully prepared with the portion of Pt nanoparticles was anchored at the interface of TiN and graphene. Electrochemical measurements showed that the Pt/TiN–G catalyst exhibited improved catalytic activity for methanol oxidation and enhanced CO tolerance than those of Pt/G catalyst, attributed to the formation of –OH groups on the surface of TiN. And the –OH attached TiN assisted the conversion of CO into CO2.

The perovskite-structured La2CuO4 nanocrystals with a fiber-like morphology were fabricated with bacterial cellulose nanofibers as the templates at a hydrothermal temperature of 120 °C. The La2CuO4 nanofibers were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), N2 adsorption (BET). The catalytic performance of the La2CuO4 nanofiber was evaluated for steam reforming of methanol (SRM). At the low temperature of 200 °C methanol was completely converted into hydrogen and CO2, without the generation of CO. Compared with La2CuO4 bulk powder, La2CuO4 nanofibers showed better catalytic activity for the SRM reaction. It is concluded that the special structure and unique morphology of the La2CuO4 nanofibers with larger specific area, are responsible for their excellent performance in catalyzing the SRM.Highlights► A novel metathesis route for the synthesis of La2CuO4 was described. ► Shape-Controlled Synthesis of La2CuO4 Nanostructures was investigated. ► The excellent performance of the novel La2CuO4 nanofibers in catalyzing SRM was studied in detail.

Low humidification, large air stoichiometry, dry hydrogen and low operational temperature makes open-cathode proton exchange membrane fuel cells (PEMFCs) with forced-air convection, which is designed for portable applications, quite different from that used in automobile vehicles. In this paper, PEMFCs humidified at 30 °C using Nafion 212 and Nafion 211 as electrolytes were systematically investigated under simulating conditions. These conditions included air stoichiometry from 3 to 100 and cell temperature from 30 °C to 60 °C. The results indicate that the thinner membrane (Nafion 211) had better performance and more stable voltage output under air dual-function configuration than Nafion 212. Furthermore, the dynamic response of the voltage with cell temperature was also studied during rising and cooling procedure between 30 °C and 60 °C.Highlights►Evaluation of single cell in a simulated condition of open-cathode stack. ►The conditions include low humidification and temperature and large air stoichiometry. ►The thinner Nafion 211 membrane shows better polarization curves than Nafion 212. ►The voltage variation under dynamic discharging is also smaller for Nafion 211.

Pt nanoparticles are deposited onto graphene sheets via synchronous reduction of H2PtCl6 and graphene oxide (GO) suspension using NaBH4. Lyophilization is introduced to avoid irreversible aggregation of graphene (G) sheets, which happens during conventional drying process. Pt/G catalysts reveal a high catalytic activity for both methanol oxidation and oxygen reduction reaction compared to Pt supported on carbon black (Pt/C). The performance of Pt/G catalysts is further improved after heat treatment in N2 atmosphere at 300 °C for 2 h, and the peak current density of methanol oxidation for Pt/G after heat treatment is almost 3.5 times higher than Pt/C. Transmission electron microscope (TEM) images show that the Pt particles are uniformly distributed on graphene sheets. X-ray photoelectron spectroscopy (XPS) results demonstrate that the interaction between Pt and graphene is enhanced during annealing. It suggests that graphene has provided a new way to improve electrocatalytic activity of catalyst for fuel cell.

Nanoporous gold (NPG) fabricated by dealloying Au–Ag film was investigated for the non-enzymatic detection of H2O2. The apparent activation energy of H2O2 electrochemical reduction on NPG was found to be as low as ∼30 kJ mol−1. The reduction currents at −0.4 V vs. SCE demonstrated a strict linear dependence in a wide H2O2 concentration region from 10 μM to 8 mM with a detection limit 3.26 μM. Furthermore, the biosensor based on NPG exhibited high selectivity, good reproducibility, and long-term stability. These results indicate that NPG could be a promising electrochemical material for H2O2 detection.Highlights► Nanoporous gold electrode as non-enzymatic H2O2 sensor. ► A low activation energy ∼30 kJ mol−1 for H2O2 electrochemical reduction. ► A wide H2O2 detection concentration region with a low detection limit. ► High selectivity, good reproducibility and long-term stability.

Nanoporous gold (NPG) membranes prepared by dealloying AgAu alloys in concentrated nitric acid towards hydrazine electrochemical oxidation were studied. Compared with bulk gold, NPG shows not only the enhanced current but also the lower overpotential of hydrazine oxidation. The diffusion coefficient of hydrazine was examined to be 1.65 × 10−5 cm2 s−1 using chronoamperometry. In addition, it can be found that the behavior of hydrazine oxidation on NPG depends strongly on the pH value of the solution. A detection limit of 16.7 nM hydrazine can be determined by high sensitive NPG. These results indicate that NPG can be employed to be as an efficient electrode material of electrochemical sensors for hydrazine detection in solution.Highlights► Nanoporous gold (NPG) membrane was fabricated by a quick and simple way. ► NPG showed superior catalytic activity toward hydrazine oxidation. ► A low detection limit of 16.7 nM and promising reproducibility can be reached.

The WO3–C hybrid materials are prepared by intermittently microwave-pyrolysis using ammonium tungstate as the precursor, and then Pt nano-particles are deposited by microwave-assited polyol process on WO3–C. The TEM images show the dispersion of ∼10 nm WO3 particles size supported on carbon and ∼3 nm Pt metal crystallites supported on WO3–C. XRD results illustrate that WO3 presented as monoclinic phase and the content of WO3 in WO3/C and Pt/WO3–C catalysts is further characterized by EDAX. Furthermore, XPS characterizations indicate that the interaction between Pt and WO3 is dramatically enhanced after heat treatment at 200 °C. The activities of Pt/WO3–C for the electrochemical oxidation of methanol are compared with Pt/C in acid solution by cyclic voltammetry, CO-stripping and chronoaperometry. Pt/WO3–C catalyst calcined at 200 °C exhibits the highest activity per electrochemical active surface area for methanol oxidation and is 60 mV more negative for CO electro-oxidation than that of Pt/C and Pt/WO3–C without heat treatment. The great enhancement of electrochemical performance may be due to the improvement of the synergistic effect between Pt and WO3 in Pt/WO3–C catalyst after heat treatment.

Palladium catalyst poisoned in the anode of direct formic acid fuel cell (DFAFC) during constant current discharging can be fully regenerated by a non-electrochemical method, i.e. just switching pure water to DFAFC for 1 h. Electrochemical impedance spectrum of DFAFC during the discharging and regeneration were recorded and analyzed. No much difference could be found for the high-frequency resistance of DFAFC after discharging while the charge transfer resistance in the mediate-frequency region increased significantly. The voltage variation during the regeneration showed that one platform of 0.35 V was formed by the intermediate species of formic acid oxidation, which is proven to be critical for cell performance regeneration. The results indicated that the absorption of poisoning species on Pd was the main reason for the decaying of cell performance.

Carbon (Vulcan XC-72, Cobat Corp.) is pretreated using acetic acid (HAC) before the Pt deposition by microwave assisted glycol method. TEM and XRD results indicate that 3 nm Pt nano-particles are uniformly dispersed on the surface of modified XC-72. In order to examine the interaction between Pt nano-particles and carbon, Pt/C-HAC and commercial Pt/C (Johnson Matthey Corp.) are calcined at 500 °C for 2 h under nitrogen atmosphere. The average Pt particle size of Pt/C-HAC after calcination is only 10–12 nm in diameter while commercial Pt particles grow up to 25–35 nm with a broad size distribution. Meanwhile, electrochemical studies of Pt/C-HAC reveal higher activity and stability for both methanol oxidation and oxygen reduction than that of Pt/C-JM. The pore structure and surface composition are investigated by BET and XPS, which implies that much microporous structure and carbonyl functional groups on carbon surface are obtained after HAC treatment. The high catalytic performance and stability might mainly be due to the strong interaction between Pt nano-particles and carbon by carbonyl functional groups. Therefore, HAC treatment is proved to be a facile and effective method for carbon as the support for Pt as fuel cell catalyst.

In situ deposition of platinum (Pt) nanoparticles on bacterial cellulose membranes (BC) for a fuel cell application was studied. The platinum/bacterial cellulose (Pt/BC) membranes under different experimental conditions were characterized by using SEM (scanning electron microscopy), TEM (transmission electron microscopy), EDS (energy dispersive spectroscopy), XRD (X-ray diffractometry) and TG (thermo-gravimetric analysis) techniques. TEM images and XRD patterns both lead to the observation of spherical metallic platinum nanoparticles with mean diameter of 3–4 nm well impregnated into the BC fibrils. TG curves revealed these Pt/BC composite materials had the high thermal stability. The electrosorption of hydrogen was investigated by CV (cyclic voltammetry). It was found that Pt/BC catalysts have high electrocatalytic activity in the hydrogen oxidation reaction. The single cell performance of Pt/BC was tested at 20 °C, 30 °C, and 40 °C under non-humidified conditions. Preliminary tests on a single cell indicate that renewable BC is a good prospect to be explored as membrane in fuel cell field [B.R. Evans, H.M. O’Neill, V.P. Malyvanh, I. Lee, J. Woodward, Biosens. Bioelectron. 18 (2003) 917].

•Ultrathin LFP-NS were prepared through ultrasonic exfoliation approach.•LFP-NS were self-assembled with GO to enhance the electron conduction.•LFP-NS were monodispersed after freeze drying and it is benefit to Li+ diffusion.•LFP-NS/rGO reveal excellent rate performance, e.g. up to 102 mA h g−1 at 30 C.•Discharge capacity retention of LFP-NS/rGO can up to 93.4% after 500 cycles.Liquid-phase ultrasonic exfoliation approach was applied to acquire ultrathin lithium iron (II) phosphate (LiFePO4) nanosheets (LFP-NS) with the thickness of only ∼15 nm. The LFP-NS were then self-assembly with graphene oxide (GO) with amido bonds. Ultrashort diffusion pathways to lithium ions (Li+) could be achieved with high percentage of (0 1 0) facets exposed to LFP-NS, which reduced the diffusion distance for Li+ along the [0 1 0] direction effectively. In addition, the reduced graphene oxide (rGO) firmly adhered to the surface of LFP-NS by self-assemble method after sintering, which formed an excellent conductive network and facilitate electron transportation. The ultrathin diffusion channels into Li+ and tight conductive network resulting in an excellent high rate discharging performance, e.g. up to 102 mA h g−1 at 30 C, while discharge capacity retention can reach to 93.4% at 20 C after 500 cycles. This kind of composite was an ideal cathode material used in high rate lithium ion batteries.Download high-res image (150KB)Download full-size image

Functional design was conducted for ionic liquid (IL) by introducing –SO3H to the cation, and an IL of N,N,N-trimethyl butylsulphonate ammonium hydrosulfate ([N1114SO3H]HSO4) was synthesized as the electrolyte in a proton exchange membrane fuel cell (PEMFC). Subsequently, a series of single cell tests was carried out, and the results show high cell performance for the PEMFC with the designed IL as the electrolyte. A maximum power density (MPD) of 90 mW cm−2 was obtained with the functionalized IL of [N1114SO3H]HSO4, while the MPD for the fuel cell with a similar but not functionalized IL can only provide an MPD of approximately 60 mW cm−2. Possible mechanisms behind the elevation of the fuel cell performance were investigated and discussed. The results show that the proton diffusion coefficient elevation of the functionalized IL is one important explanation for the increased fuel cell performance. Finally, theoretical calculation for the potential barrier for proton transportation in the two ILs was conducted. The results show that the potential barrier for the functionalized IL was lowered. All of these results imply that introducing a functional group to the cation is a promising way for a high proton conductive IL to function as the electrolyte in a PEMFC.

3D CoNi2S4 and cross-linked NiCo2S4 arrays have been grown on carbon paper (CP) using a one-step hydrothermal method. The 3D cross-linked structure provides a convenient channel for electron and lithium-ion (Li+) transport and performs a facile strain relaxation during cycling, exhibits high capacity, excellent rate capability and superior cycle performance.

Solid phase polymerization of phenylenediamine with a template toward a self-supported FeNx/C catalyst was introduced. Using ZnO nanoparticles as the hard template could increase the surface area of the catalyst, thus the oxygen reduction activity was radically enhanced, to 21.9 A g−1 at 0.80 V (vs. RHE) in acid medium.

Direct formic acid fuel cells (DFAFCs) are promising portable energy conversion devices for supplying our off-grid energy demands. However, traditional Pt-based catalysts suffer from poor performance; consequently the precious metal loading in an actual fuel cell has to be maintained at a very high value, typically orders of magnitude higher than the acceptable level. Through a molecular self-assembly/electro-deposition process, Pt atoms are effectively dispersed onto the surface of a nanoporous gold substrate, and the resulting nanocomposites demonstrate superior electrocatalytic performance toward formic acid electro-oxidation, which can be attributed to a nearly ideal catalyst configuration where all the Pt atoms are involved in a highly desired direct reaction path. In both half-cell electrochemical testing and actual DFAFCs, these rationally designed electrodes show over two orders of magnitude improvement in Pt efficiency, as compared with the state-of-the-art Pt/C catalyst. This design strategy allows customized development of new generation electrocatalysts for high performance energy saving technologies.