•Co3O4 with a urchin-like sphere structure was directly grown on Ni foam.•Co3O4 exhibits an advanced bifunctional catalytic activity for the HER and OER.•Co3O4 functioned as a catalyst for H2 and O2 generation in a two-electrode system.Electrochemical water splitting has attracted great interest because of the growing demand for sustainable energy and increasing concerns for the environment. We present a facile strategy to design the three-dimensional (3D) urchin-like sphere arrays Co3O4 as an effective bifunctional catalyst for electrochemical water splitting. The 3D urchin-like Co3O4 was directly grown on Ni foam by a hydrothermal reaction and annealing treatment at a low temperature. This process offers several advantages including facile synthesis, binder-free, and low cost. The 3D urchin-like Co3O4 as a catalyst for hydrogen evolution reaction exhibits a low onset potential (−130 mV vs. RHE) and good cycling stability in an alkaline electrolyte. When urchin-like Co3O4 is used as a catalyst for oxygen evolution reaction, the onset potential is at 1.46 V (vs. RHE) with a low overpotential of only 230 mV. The good catalytic activity can be attributed to the unique urchin-like nanostructure, abundant mesopores, and low charge-transfer resistance (compared with Co3O4 NPs). In addition, H2 and O2 generation was performed using Co3O4 as both cathode and anode catalysts with a potential of 1.64 V to reach a current density of 10 mA cm−2.

•A Fe-P/CNFs electrocatalyst had been successfully synthesized.•Fe-P/CNFs possessed a 3D porous network structure and large surface area.•Fe-P/CNFs for ORR exhibited good electrocatalytic activity.•Fe-P/CNFs were considered as a potential candidate for replacing Pt-based catalysts.Heteroatom-doped carbon materials as efficient electrocatalysts for oxygen reduction reaction have been attracted a lot of research interest. For its low cost, high selectivity and excellent stability, heteroatoms-doped carbon materials have been considered as the candidate for replacing Pt-based catalysts. We had designed an iron and phosphorus co-doped carbon nanofibers (Fe-P/CNFs) derived from bacterial cellulose for oxygen reduction reaction, which not only showed a three-dimensional (3D) porous network structure, but also possessed large surface area. The unique 3D porous network could accelerate oxygen diffusion and electron transfer, and meanwhile enlarge specific surface area. Accordingly, the obtained material had more active sites for electrocatalysis. More importantly, the unusual synergistic effects between the doped Fe and P atoms could efficiently improve the electrocatalytic performance of oxygen reduction reaction. As expected, the Fe-P/CNFs showed a high ORR electrocatalytic activity with a more positive onset potential of 1.01 V, similar with 1.03 V at 20 wt% Pt/C, and a good long-term stability (94% retention of current density after chronoamperometry 20,000s).

A flexible asymmetric supercapacitor (ASC) based on a CoAl-layered double hydroxide (CoAl-LDH) electrode and a reduced graphene oxide (rGO) electrode was successfully fabricated. The CoAl-LDH electrode as a positive electrode was synthesized by directly growing CoAl-LDH nanosheet arrays on a carbon cloth (CC) through a facile hydrothermal method, and it delivered a specific capacitance of 616.9 F g−1 at a current density of 1 A g−1. The rGO electrode as a negative electrode was synthesized by coating rGO on the CC via a simple dip-coating method and revealed a specific capacitance of 110.0 F g−1 at a current density of 2 A g−1. Ultimately, the advanced ASC offered a broad voltage window (1.7 V) and exhibited a high superficial capacitance of 1.77 F cm−2 at 2 mA cm−2 and a high energy density of 0.71 mWh cm−2 at a power density of 17.05 mW cm−2, along with an excellent cycle stability (92.9% capacitance retention over 8000 charge–discharge cycles).

The oxygen evolution reaction (OER), as a key half-reaction in water splitting for clean hydrogen energy, is kinetically sluggish and usually requires efficient electrocatalysts to reduce the overpotential. Herein, we report a simple method to synthesize novel two-dimensional Ni76Co24 layered double hydroxides (Ni76Co24–LDHs) nanosheets as an effective OER catalyst. The obtained Ni76Co24–LDHs display a low onset overpotential of 242 mV, along with an excellent cycling stability. The Tafel slope of Ni76Co24–LDHs is only 57 mV dec−1 which demonstrates an active kinetics for OER. The high catalytic activity of Ni76Co24–LDHs may be attributed to the porous tremella-like structure with large surface area, synergistic effect of Ni and Co, and a pinning of the Co3+/4+ and Ni3+/4+. More importantly, the high catalytic property and simple synthetic method of Ni76Co24–LDHs may have a promising potential for practical application.

Recently, nitrogen-doped carbon materials have attracted immense interest because of their great potential in various applications. In this work, FeN-doped carbon microspheres are large-scale synthesized using basic magnesium carbonate as the template and glycine as the carbon and nitrogen precursor by a simple liquid impregnation method under a relatively low pyrolysis temperature. Iron is introduced into the carbon microspheres to enhance the graphitic degree and improve the electrocatalytic performance. This carbon material with high specific area, high nitrogen content and part-graphitization shows high activity and four-electron selectivity for the oxygen reduction reaction in an alkaline medium. Compared to a commercial Pt/C catalyst, this material presents exceeding stability and durability, which can be a candidate for potential applications in the fuel cell and electrochemical industries of oxygen reduction.

Flake-like Co/Al layered double hydroxides (Co/Al LDHs) were synthesized by using a facile and free-template hydrothermal method. Reduced graphene oxide (rGO) is obtained by a simple, clean and controlled hydrothermal reduction route to convert graphene oxide (GO) to stable graphene solution which avoided reductant. Because of their unique structure, both materials exhibit excellent electrochemical performances, which the maximum specific capacitance of Co/Al LDHs is 1158F/g and rGO is 223.2F/g. An asymmetric capacitor incorporating the LDHs as the positive electrode and the rGO as the negative electrode was fabricated. The experimental results indicate that the optimized asymmetric supercapacitor shows intriguing performances with a maximum specific capacitance of 97.5 F/g and high energy density of 34.7Wh/kg at a cell voltage of 1.6 V. A good electrochemical stability with 93% specific capacitance retained was demonstrated after consecutive 2000 cycle numbers. Because of the large mass loading and high energy density, this device after 2000 cycles still drives a red light-emitting-diode (LED). This impressive result presented here may have outstanding potential in commercial applications.

Nitrogen-doped carbon nanomaterials have been attracted increasing research interests in lithium-O2 and Zinc-O2 batteries, ultracapacitors and fuel cells. Herein, nitrogen-doped graphitic carboncages (N-GCs) have been prepared by mesoporous Fe2O3 as a catalyst and lysine as a nitrogen doped carbon source. Due to the catalysis of Fe2O3, the N-GCs have a high graphitization degree at a low temperature, which is detected by X-ray diffraction and Raman spectrometer. Simultaneously, the heteroatom nitrogen is in-situ doped into carbon network. Therefore, the excellent electrocatalysis performance for oxygen reduction reaction is expected. The electrochemical measurement indicates that The N-GCs for oxygen reduction reaction in O2-saturated 0.1 mol L−1 KOH show a four-electron transfer process and exhibit excellent electrocatalytic activity (EORR = -0.05 V vs. Ag/AgCl) and good stability (i/i0 = 90% at -0.35 V after 4000 s with a rotation rate of 1600 rpm).

•The origin of the ORR activity of nitrogen-doped graphene is studied.•Valley-N is found to improve the ORR activity.•The nitrogen content does not influence the ORR activity.Nitrogen-doped graphene is studied as a kind of non-noble metal catalyst for the oxygen reduction reaction in the cathode of fuel cells. Graphene is synthesized by pyrolyzing ion exchange resin and nitrogen doping is realized by a second pyrolysis step with nitrogen precursor. High resolution transmission electron microscopy proves the graphene is composed by 8–10 graphitic layers. The defect of graphene caused by nitrogen doping is detected by Raman spectra. The nitrogen group of the doped graphene is studied in detail with X-ray photoelectron spectroscopy spectra and a special type of nitrogen: valley-N is distinguished. The valley-N is proved to play an important role in the oxygen reduction reaction. Nitrogen content is found not directly related with the activity of the oxygen reduction reaction.Nitrogen-doped graphene was synthesized and showed effective activity as electrocatalyst for the oxygen reduction reaction (ORR) in alkaline solution. Valley-N (N4) could improve the ORR activity and the nitrogen content did not influence the ORR activity.

A graphitic ordered mesoporous carbon (G-OMC) has been synthesized for the first time using mesoporous nickel oxide as a template and catalyst and dopamine as a carbon source. The probable formation mechanism for the preparation of G-OMC is also proposed. Characterization by X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy indicate that the as-prepared mesoporous carbon has a high degree of graphitization. The electrochemical performance of G-OMC is visibly superior to typical CMK-3D in alkalic media, involving fast kinetic transfer, anti-corrosion, a capacitance of 68 μF cm−2 at 0.1 A g−1 and a light increase of the 6000th-cycle capacitance compared to the initial capacitance. In organic electrolyte, a wider potential window of 2.5 V is presented. The fast charge transfer, quick response and anti-corrosion properties promise that G-OMC will have a great prospect as a supercapacitor for energy storage applications.

Graphitic mesoporous carbon (GMC) has been prepared with non-toxic and economical sucrose as the carbon precursor and mesoporous iron oxide as a catalyst at a relatively low carbonization temperature. XRD patterns suggest that GMC is formed by a carbide intermediate. The data of nitrogen sorption exhibit that the GMC possesses a mesoporous structure. Pt nanoparticles are uniformly loaded on the graphitic mesoporous carbon by a facile and effective microwave assisted ethylene glycol process. All the results show that the graphitic mesoporous carbon-supported Pt nanoparticles have superior electrocatalytic properties compared to Vulcan XC-72 and CMK-3 catalyst supports, suggesting this novel and general method will have a bright future in fuel cell applications.

Nitrogen-doped carbon nanorods (N-CNRs) are prepared by a direct carbonization method using polyaniline nanorods as the carbon precursor. The electrochemical behavior of the N-CNRs-Nafion modified electrode is evaluated in connection with dopamine and ascorbic acid by cyclic voltammetry and differential pulse voltammetry. Experimental results indicate that the N-CNRs modified electrode has improved current response and fast electron transfer kinetics. The linear response for the selective determination of dopamine in the presence of ascorbic acid is obtained in the range of 0.008 μM to 15.0 μM with a detection limit of 8.9 × 10−9 M (S/N = 3) by differential pulse voltammetry under optimum conditions. The N-CNRs-Nafion modified electrode exhibits a wide linear range, very low detection limit and anti-interference ability. Meanwhile, a kinetic reaction process and a reaction mechanism for the N-CNRs are also proposed.

A series of hierarchical porous carbons are synthesized from metal-organic frameworks as a precursor and glycerol as a carbon source. N2 adsorption–desorption measurement indicates that glycerol has a pronounced effect on the specific surface area of the synthesized porous carbons. And the pore size distribution and BET can be modulated by adding different amounts of Bi(NO3)3·5H2O. The amount of Bi(NO3)3·5H2O is changed from 0 to 0.4 mmol, resulting in the increase of surface area from 1796 m2 g−1 to 2857 m2 g−1. Due to its unique hierarchical pore structure, the synthesized porous carbons exhibit a high specific capacitance and show potential application in electrochemical capacitor.Highlights► Hierarchical porous carbons have been synthesized via direct carbonization of MOFs. ► The synthesis process is free for the removal of template. ► BET surface area of HPCs corresponds to the amount of Bi(NO3)3 and glycerol volume. ► The hierarchical porous carbons exhibit a high specific capacitance.

N-doped carbon nanowires are synthesized by a simple impregnation method under low carbonization temperature. l-Arginine is adopted as carbon sources and nitrogen sources and SBA-15 is employed as hard template. The obtained carbon nanowires possess uniform and ultrafine diameter of around 6.5 nm, in good accord with the pore size of the SBA-15 silica template. The probable mechanism is proposed that l-arginine is elongated to form long chains in the pore of SBA-15 through dehydration–condensation reaction. The as-synthesized carbon nanowires contain heteroatoms such as nitrogen and oxygen, which are very helpful to the pseudo-capacitance and the wettability of carbon materials. The experimental results demonstrate that N-doped carbon nanowires exhibit superior performance in supercapacitance properties.Ultrafine N-doped carbon nanowires are synthesized by SBA-15 template from l-arginine at low carbonization temperature. The obtained carbon nanowires possess uniform diameter of around 6.5 nm, meanwhile, a wormlike microporous structure can also be observed (an insert image). These nanowires exhibit good electrochemical performance for electrochemical energy storage.Research highlights► 6.5 nm N-doped carbon nanowires were synthesized by SBA-15 template. ► Ultrafine carbon nanowires were obtained from the carbonization of l-arginine. ► These nanowires exhibit good electrochemical energy storage.

Nitrogen-enriched carbon nanowires have been prepared with the direct carbonization method using polyaniline nanowires as a carbon precursor at different temperatures. The structure and morphology of as-prepared materials are characterized by X-ray diffraction, N2 sorption, scanning electron microscopy, transmission electron microscopy and FT-IR spectrometer. The electrochemical measurements are conducted by cyclic voltammetry and galvanostatic charge/discharge, and the results demonstrate that the specific capacitance of electrode material reaches 327 F g− 1 at a current density of 0.1 A g−1.

2-D hexagonal mesoporous carbon is combined with polyaniline by a simple chemical oxidation polymerization. As-prepared samples are characterized via Fourier transform infrared spectrum, nitrogen sorption analysis and transmission electron microscopy. The experimental results demonstrate that polyaniline is linked with the functional groups on the surface of mesoporous carbon via the chemical bonds. The electrochemical tests reveal mesoporous carbon and polyaniline have a strong synergetic effect, which not only enhances the stability of polyaniline, but also increases the capacitance and energy density of the composite materials. A wide potential window of 1.1 V for the composite is obtained in aqueous electrolyte. The specific capacitance and specific energy density are as high as 470 F/g and 76.4 Wh/kg, respectively.Highlights► Polyaniline is linked with the functional groups on the surface of 2-D hexagonal mesoporous carbon via the chemical bonds. ► Between mesoporous carbon and polyaniline have a strong synergetic effect, enhancing the stability of polyaniline and increasing the capacitance and the energy density of the composite materials. ► A wide potential window of 1.1 V and a high specific capacitance up to 470 F/g for the composite are obtained in aqueous electrolyte.

A quick and facile microwave method has been employed to prepare Mn3O4/worm-like mesoporous carbon (Mn3O4–MC) composites. Structural and morphological characterizations of worm-like mesoporous carbon and Mn3O4–MC composites have been carried out using X-ray diffraction, transmission electron microscopy, N2 adsorption–desorption, and electrochemical measurement. Cyclic voltammograms demonstrate that the Mn3O4–MC composites perform improved capacitive behavior at the range of −0.8~0.2 V (vs. Hg/HgO electrode) with reversibility. The Mn3O4–MC composite electrode possesses an enhanced specific capacitance of 266 F g−1 at a sweep rate of 1 mV s−1.

This paper discusses the electrochemical behaviors of worm-like mesoporous carbon obtained in 1.0 mol L−1 LiClO4/ethylene carbonate + dimethyl carbonate solution. The capacitance for nanoporous carbon system advances up to 147 F g−1 and a wide voltage window (2.5 V) for three electrode system was achieved. The specific energy and specific power reach as high as 127.6 Wh kg−1 and 5.0 kW kg−1. These results show that worm-like mesoporous carbon can be used for high energy density and power density non-aqueous electrolyte supercapacitors.

Copper-supported ordered mesoporous carbon (Cu/CMK-3) was prepared by impregnating ordered mesoporous carbon (CMK-3) with CuCl2 aqueous solution. CMK-3 was served as a carrier for the continuous immobilization of Cu. The supported copper was observed to be the bivalence state, indicating that the Cu2+ ion was not reduced into cuprous species or metallic copper in the CMK-3. The BET surface area and pore volume of Cu/CMK-3 were 728 m2/g and 0.95 cm3/g, respectively. The antibacterial activities of Cu/CMK-3 were tested by means of minimal inhibitory concentration (MIC) and viable cell counting method. The results show that Cu/CMK-3 presents a good antibacterial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which indicates its potential applications as antibacterial material for microbiocides.

Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO3 and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and electrochemical methods. Hexagonal closepacked WC was successfully synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic ability for the oxygen reduction reaction.

Novel carbon tubes with a diameter of 200–500 nm and a length of 3–5 μm have been synthesized via decomposing magnesium acetate. Novel carbon tubes have been analyzed and characterized using by X-ray diffraction, scanning electron microscope, transmission electron microscope, selected area electron diffraction (SAED) and Raman spectrum. The analysis results indicate that the graphitic degree of novel carbon tubes is low under our synthesis condition. Interestingly, inside these tubes, smaller Z-shaped carbon nanotubes (CNTs) are formed. The unusual morphologies have not been reported before. A tentative formation mechanism is proposed.

The coin-like hollow carbon (CHC) has been synthesized by only using ethanol as the carbon source with a novel Mg/NiCl2 catalytic system via a facile solvothermal method for the first time. The CHC synthesized at optimized conditions shows an average thickness of less than 154 nm and the coin diameter of 1–3 μm. The CHC is characterized by SEM, TEM, XRD and electrochemical techniques. Pd on CHC (denotes as Pd/CHC) electrocatalysts are prepared for methanol oxidation in alkaline media. The Pd/CHC electrocatalyst gives a mass activity of 2930 A g−1 Pd for methanol oxidation against 870 A g−1 Pd on Pd/C electrocatalyst. One main reason for the higher mass activity of the Pd/CHC is the higher electrochemical active surface area (EASA) of the Pd/CHC.

The electrochemical behavior of La3+ ion is investigated on a Pt electrode in the 2.5 × 10−3 mol L−1 La(ClO4)3–7.5 × 10−2 mol L−1 LiClO4–dimethylsulfoxide (DMSO) system. The experimental results indicate that the reduction of La3+ ion is irreversible. Some electrochemical parameters are measured. The pulse deposition technique is used to prepare La–Co alloy films. The surfaces of La–Co alloy films are uniform, compact and showed a metallic luster. The grain sizes of La–Co alloy observed by scanning electron microscope (SEM) are about 100 nm. La–Co alloy film is amorphous as proven by the X-ray diffraction (XRD). The magnetic properties of the amorphous La–Co alloy film are measured.

Graphitic mesoporous carbon (GMC) has been prepared with non-toxic and economical sucrose as the carbon precursor and mesoporous iron oxide as a catalyst at a relatively low carbonization temperature. XRD patterns suggest that GMC is formed by a carbide intermediate. The data of nitrogen sorption exhibit that the GMC possesses a mesoporous structure. Pt nanoparticles are uniformly loaded on the graphitic mesoporous carbon by a facile and effective microwave assisted ethylene glycol process. All the results show that the graphitic mesoporous carbon-supported Pt nanoparticles have superior electrocatalytic properties compared to Vulcan XC-72 and CMK-3 catalyst supports, suggesting this novel and general method will have a bright future in fuel cell applications.