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Hydrogen fuel is a non-toxic and source-abundant energetic system, but for its applications in the industry, several issues related to its storage must be resolved. Compounds like NaBH 4 appear as promising hydrogen sources, while can release the latter rapidly under controllable conditions with the use of heterogeneous catalyst systems. In this work, we synthesized a Ni–CoP catalyst by electrodeposition in a three-step process on carbon paper as support. The materials were characterized via SEM-EDS, XRD, and XPS techniques, while the hydrogen evolution reaction (HER) from alkaline NaBH 4 solutions was tested as a batch experiment. Ni–CoP catalyst showed a high amount of H 2 generated in a short time (∼550 mL in 1 min) and remained at 78 and 54% of its initial performance after respectively 100 and 300 h of a continuous hydrolysis process. Our catalyst revealed exceptional performance and stability at higher temperatures and a long process time, which have been a rare subject of investigation in other reports for NaBH 4 hydrolysis in the past. This work paves a new perspective in studying catalysts for hydrogen generation from borohydrides. [Display omitted] • Ni–CoP catalyst was electrodeposited on a carbon support. • Material characterization proved the formation of desired active layers. • High efficiency and stability of the catalyst for a long-term NaBH 4 hydrolysis was revealed. [ABSTRACT FROM AUTHOR]

In recent years, the catalyst efficiency of hydrogen evolution reaction (HER) has been extensively studied. However, the stability of catalysts at high current densities is still a challenge. Herein, layered Ni−Co−P was electrodeposited on carbon fiber paper (CFP) via cyclic voltammetry (CV). This low‐cost electrode exhibits high efficiency and excellent durability for HER in 1 M KOH. To achieve current densities of 10, 100, 500, and 1000 mA cm−2, Ni−Co−P/CFP required overpotentials of 49, 95, 170, and 295 mV, respectively. The layered structure allows the catalyst to fall off layer by layer. After the outer layer of catalyst falls off, the inner layer of catalyst will be exposed to continue working. After 300 h of HER at 1000 mA cm−2, Ni−Co−P/CFP still has a regular morphology and high efficiency. Our work shows that layered Ni−Co−P/CFP has excellent prospects for practical applications. [ABSTRACT FROM AUTHOR]

Hydrogen, as a clean, safe, and efficient energy carrier, is one of the hot energy sources that have attracted much attention. Mo2C, due to the introduction of C atoms, makes the atomic spacing of the Mo lattice decrease and changes the width of the d-band, which makes the electronic properties of Mo2C similar to that of Pt noble metals, exhibiting excellent electrochemical hydrogen precipitation performance. MoS2, due to its special crystal structure and tunable electronic structure, has been widely studied. In this paper, Mo2C nanoparticles were prepared by high-temperature carbonization, and then two-dimensional layered MoS2 were be loaded on Mo2C nanoparticles by the hydrothermal method to synthesize Mo2C/MoS2 composite catalysts. Their electrochemical hydrogen precipitation (HER) performance under acidic conditions was tested. The above catalysts were also characterized by modern material testing methods such as XRD, SEM, TEM, and XPS. The results showed that the composite catalysts exhibited the most excellent electrochemical hydrogen precipitation performance at Mo2C/MoS2-3, with the lowest overpotential at a current density of 10 mA cm−2, Tafel slope, and electrochemical impedance. At the same time, the electrochemically active area was dramatically enhanced, with good stability under prolonged testing. The catalytic activity was significantly improved compared with that of Mo2C and MoS2. The characterization and experimental results indicate that the heterogeneous structure of Mo2C and MoS2 formed a built-in electric field between the two, which accelerated the electron transfer efficiency and provided more active sites. The Mo2C/MoS2 composite catalyst is a low-cost, easy-to-prepare, and high-efficiency electrochemical hydrogen precipitation catalyst, providing a new idea for developing green and clean energy. [ABSTRACT FROM AUTHOR]

Transition metal phosphates with hollow structure have attracted substantial attentions as high-performance electrocatalyst for oxygen evolution reaction (OER). However, these electrocatalytic materials need conductive carrier to realize efficient charge transfer and further improve the OER activity. In this work, ZIF-67 derived hollow NiCo phosphate nanocages supported by waste paper-based carbon aerogel (NCP@WPCA) was prepared as high-efficiency and stable electrocatalyst. Benefited from the enhanced electrochemical active surface area and fast gas emission, the NCP@WPCA catalyst exhibits superior OER activity with low overpotential of 351 mV at current density of 10 mA cm−2, along with good stability in alkaline solution. Additionally, the waste paper-based carbon aerogel as the carrier for electrocatalysts achieves low-cost waste reuse. [Display omitted] [ABSTRACT FROM AUTHOR]

It is important to consider the synergy of heterostructures to improve the slow kinetics of water dissociation in the alkaline hydrogen evolution reaction (HER). Herein, we report a simple method to design a heterohierarchical CoMo catalyst. The CoMo catalyst was prepared by simple one-pot electrodeposition on carbon paper (CP). The CoMo/CP catalyst was optimized for the alkaline HER by controlling the electrodeposition bath conditions, potential, and time. The optimized catalyst shows the heterohierarchical structure containing the electrically conductive metallic Co in the bulk and Mo-incorporated Co containing Mo4+ at the surface. It exhibited a lower HER overpotential of 0.11 V at −20 mA/cm2 compared to those of the others owing to the synergetic effect of the between the Co and Mo incorporated Co. The results highlight the advantages of the simple method developed herein for the design of heterohierarchical catalysts. [Display omitted] • A heterohierarchical CoMo catalyst is fabricated on carbon paper. • The optimized CoMo/CP shows a low HER overpotential of 0.11 V at −20 mA/cm2. • A facile method is proposed to design the heterostructured catalyst. [ABSTRACT FROM AUTHOR]

Fe/N-doped carbon (Fe-NC) is an excellent base-metal catalyst for use in an electrocatalytic oxygen reduction reaction (ORR) with high activity. In this paper, graphite phase carbon nitride (g-C3N4) was first obtained from the pyrolyzing of melamine, and then different proportions of FeCl3 were separately doped into g-C3N4 to further prepare the Fe-NC catalyst. The Fe-NC catalyst was applied in an ORR reaction, and the results show that the Fe-NC catalyst doped with 0.5 mmol FeCl3 possesses exceptional electrocatalytic performance, with an onset potential of 0.96 V and a half-wave potential of 0.81 V, which approaches that of a Pt/C catalyst. Meanwhile, the Fe-NC catalyst displays high stability and methanol resistance. The results supply a new way to prepare efficient ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Molybdenum based phosphides have gradually become the investigation frontier of hydrogen evolution catalysts due to the platinum like electronic structure. In this paper, N, P double-doped graphite carbon layers wrapped with MoP nanoparticles (P–MoP@NPC), is directly compounded by one-step high-temperature carboning PMo 12 -APP@ZIF-8 precursor. P–MoP@NPC possesses splendid hydrogen production reactive, in two kinds of electrolytes, when the overpotentials of P–MoP@NPC are 132 mV and 161 mV, the slope of current density reaching 10 mA cm−2, Tafel slope are 67 and 79 mV dec−1, respectively. In the bargain, P–MoP@NPC displays satisfactory durability in acid and alkaline mediums and can continue to work for more than 24 h. The wonderful hydrogen production ability of P–MoP@NPC is ascribed to the synergistic effect of MoP nanoparticles, hierarchical porous structure as well as N, P double-doped carbon layers. The confinement effect of ZIF-8 makes most of the synthesized MoP nanoparticles evenly distributed. The hierarchical porous structure caused by the volatilization of Zn atoms with high temperature can expose more active centers. The N, P double-doped graphitic carbon layers not only protect the catalyst but also adjust the electronic structure of MoP, promoting the hydrogen production capacity. This work may provide a general way to study molybdenum phosphide catalysts synthesized by APP as a green phosphorus source for energy conversion. Molybdenum phosphide catalyst (P–MoP@NPC) was synthesized by simple solution mixing and high temperature calcination. The synthesized P–MoP@NPC has good catalytic activity and stability at 0.5 M H 2 SO 4 and 1 M KOH. [Display omitted] • APP is used as a green phosphorus source for phosphatization. • N, P dual-doped catalyst (P–MoP@NPC) was constructed with high efficiency hydrogen evolution activity; • Zn ions volatilization in ZIF-8 causes multistage pores to expose more active sites; • The confinement effect of ZIF-8 makes MoP nanoparticles evenly distributed. [ABSTRACT FROM AUTHOR]

It is highly attractive to develop a photoelectrochemical (PEC) sensing platform based on a non-noble-metal nano array architecture. In this paper, a PEC hydrogen peroxide (H2O2) biosensor based on Ni/WS2/WC heterostructures was synthesized by a facile hydrothermal synthesis method and melamine carbonization process. The morphology, structural and composition and light absorption properties of the Ni/WS2/WC catalyst were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–visible spectrophotometer. The average size of the Ni/WS2/WC nanosheets was about 200 nm. Additionally, the electrochemical properties toward H2O2 were studied using an electrochemical workstation. Benefiting from the Ni and C atoms, the optimized Ni/WS2/WC catalyst showed superior H2O2 sensing performance and a large photocurrent response. It was found that the detection sensitivity of the Ni/WS2/WC catalyst was 25.7 μA/cm2/mM, and the detection limit was 0.3 mmol/L in the linear range of 1−10 mM. Simultaneously, the synthesized Ni/WS2/WC electrode displayed excellent electrocatalytic properties in hydrogen evolution reaction (HER), with a relatively small overpotential of 126 mV at 10 mA/cm2 in 0.5 M H2SO4. This novel Ni/WS2/WC electrode may provide new insights into preparing other efficient hybrid photoelectrodes for PEC applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bifunctional catalyst Fe[ Pc (I) 4 ] + Ni[ Pc (I) 4 ]@NC PDI for ORR and OER is synthesized. • The NC PDI with 2D structure and superior stability was used as support. • Iodine groups in TM[ Pc (I) 4 ] creates a built-in electric field to enhance catalysis. • The synergistic effect of Fe[ Pc (I) 4 ]/Ni[ Pc (I) 4 ] enhances the catalytic performance. • The catalyst has superior performance for ORR/OER in rechargeable Zn-air batteries. In this paper, we report on the preparation and catalysis of a bifunctional molecular catalyst (Fe[ Pc (I) 4 ]+Ni[ Pc (I) 4 ]@NC PDI) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Zn-air batteries. This catalyst is prepared by self-assembling tetraiodo metal phthalocyanines (Fe[ Pc (I) 4 ] and Ni[ Pc (I) 4 ]) on a 2D N -doped carbon material (NC PDI) through π-π interactions. The introduction of iodine groups in the edge of phthalocyanines controls the density of electron cloud and electrostatic potential around Fe-N/Ni-N sites and constructs a built-in electric field that facilitates directional transport of charges, enhancing the catalytic activity of the catalyst. Density functional theory (DFT) calculations support this mechanism by showing a reduced energy barrier for the ORR rate-determining step (RDS). The Fe[ Pc (I) 4 ]+Ni[ Pc (I) 4 ]@NC PDI exhibits excellent performance outperforming 20 wt% Pt/C and single-molecule self-assembled Fe[ Pc (I) 4 ]@NC PDI and Ni[ Pc (I) 4 ]@NC PDI , with a half-wave potential of E 1/2 = 0.940 V in the ORR process under alkaline condition. During the OER process, Fe[ Pc (I) 4 ]+Ni[ Pc (I) 4 ]@NC PDI exhibited a low overpotential of 298 mV at 10 mA cm−2 under the alkaline condition, which is much better than RuO 2 , Fe[ Pc (I) 4 ]@NC PDI and Ni[ Pc (I) 4 ]@NC PDI. The catalyst also demonstrates excellent catalysis and durability in rechargeable Zn-air batteries. This work provides a simple and specific method to develop efficient multifunctional molecular electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple three-step approach for h-FeP showed excellent HER activity. • Existence of SDS and removal of Al lead to hollow urchin-like FeP. • 100 h@100 mA cm-2 testing demonstrates the excellent durability. A novel self-supported hollow urchin-like iron phosphide (h-FeP) on carbon paper (h-FeP/CP) is synthesized by phosphating hollow Fe 3 O(OH) derived from selective etching treatment of FeAlOOH precursor. The as-obtained h-FeP/CP catalyst exhibits larger surface areas due to its specific hollow urchin-like structure, and thus endows more accessible active sites. The h-FeP/CP catalyst manifests the most prominent catalytic activity for hydrogen evolution reaction (HER). The current density of 10 mA cm−2 and 100 mA cm−2 are from the overpotentials of 90 mV and 258 mV in 0.5 mol/L H 2 SO 4 , respectively. And the current density of 10 mA cm−2 and 100 mA cm−2 are from the overpotential of 146 mV and 376 mV in 1.0 mol/L KOH, respectively. In addition, h-FeP/CP catalyst also exhibited excellent stability and durability at a large current density of 100 mA cm−2 in both acidic and alkaline solutions. The improved HER performance of h-FeP/CP is decided by the large amount of exposed activated sites and collective effects of large surface area, providing the faster interfacial charge transfer kinetic in the process of HER. [ABSTRACT FROM AUTHOR]

At present, energy shortage and environmental pollution are becoming more and more serious. If environmental governance and energy supply can be combined, it will be more consistent with the long-term concept of sustainable development. Urea electrooxidation may achieve the degradation of pollutants and the conversion of energy supply, urea oxidation occurs at the anode and hydrogen evolution occurs at the cathode. However, the electrochemical oxidation process of urea requires the transfer of six electrons, and the reaction rate is slow. The electrocatalyst is a key factor in improving the reaction kinetics. In this context, catalysts used in urea electrocatalytic oxidation in recent years are reviewed in this paper. The application of the electrocatalyst in electrolytic hydrogen production, urea wastewater treatment, urea fuel cells and urea sensors are described in detail. In addition, the future research directions, research emphases and areas needing improvement of these catalysts are discussed. [Display omitted] • Urea electrooxidation has double benefits of environmental protection and energy supply. • Electrocatalysts for urea electrooxidation in alkaline electrolytes are reviewed. • The applications of electrocatalyst in the electrooxidation of urea are demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, N-doped Ni 2 P (N-Ni 2 P) as a catalyst for hydrogen evolution was proposed. Firstly, the feasibility of N atom doping was calculated by density functional theory (DFT). Ni top site, Ni bridge site, Ni hollow site and P top site were calculated for Ni 2 P (001) and N-Ni 2 P (001). The results confirm that N atom doping can make the Gibbs free energy (ΔG H∗) closer to thermal neutrality (ΔG H∗ = 0) and move the d -band center away from Fermi level. Besides, charge density difference pattern and bader charge indicate N atom doping regulate the charge structure of the catalyst surface. Based on the guidance of DFT calculation results, Ni 2 P and N-Ni 2 P catalysts were also experimentally synthesized. It is revealed that the N-Ni 2 P can achieve cathodic current densities of 10 mA cm−2 and 100 mA cm−2 at overpotentials of 110 mV and 302 mV in 1.0 M KOH and 82 mV and 235 mV in 0.5 M H 2 SO 4 , respectively. This work shows that it is feasible to increase HER performance by modifying Ni 2 P catalyst with N doping. [Display omitted] • N-Ni 2 P exhibits an ideal hydrogen evolution performance in acidic and alkali media. • The introduction of N atoms modifies the electronic structure of Ni 2 P. • N-Ni 2 P has a Gibbs free energy closer to thermal neutrality than Ni 2 P. • N-Ni 2 P with unique scale structure is conducive to the increase of active site. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction reaction (CO2RR) presents a promising approach for producing valuable chemicals and fuels, offering a dual benefit in terms of environmental preservation and the efficient utilization of carbon resources. In this work, we proposed a stepwise electrodeposition method to prepare Cu−Pb bimetallic heterojunction catalyst on polyaniline‐modified carbon paper (PANI‐CuPb‐x), where x is the electrodeposition times(min). Among the studied catalysts, the electrode electrodeposited for 2 min (PANI‐CuPb‐2) exhibited a remarkable performance during the electrocatalysis CO2 to multicarbon (C2+) products process, achieving a Faraday efficiency (FE) of 81.46 % and a partial current density of 15.41 mA cm−2 at −1.2 V (vs. RHE) in an H‐type cell. The detailed study demonstrated that introducing Pb could effectively improve the formation of COOH*inhibit hydrogen evolution reaction (HER). Furthermore, the heterojunction structure in the catalysts facilitated C−C coupling of the generated C1 intermediate species, which enhanced the CO2 to C2+ reaction. [ABSTRACT FROM AUTHOR]

Developing high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) is of great importance. In this paper, dendrite-free Ni–Cu catalysts were synthesised via one-step pulse electrodeposition under a weak magnetic field (0.5 T). Regardless of the direction of the magnetic field, the ions were affected by the magnetohydrodynamic (MHD) effect, which greatly promoted the mass transfer and dispersion uniformity, and suppressed the uncontrollable agglomeration by electrodeposition. It was found that the nucleation mechanism changed from progressive nucleation under a 0 T magnetic field to instantaneous nucleation under a 0.5 T magnetic field. Large-scale (325 nm, 0 T) dendrite growth on the single-sided plane was successfully suppressed, and replaced by smaller (90 nm, 0.5 T) and uniformly distributed cluster growth around the carbon paper. In addition, the (111) plane was strengthened by the magnetic field. Electrochemical analysis showed that the Ni–Cu catalysts exposed more surface area and exhibited greatly enhanced catalytic activity, which only needed −57.3 mV to deliver the current density of 10 mA cm−2 with a small Tafel slope of 99.4 mV dec−1 in 1 M KOH. Overall, magneto-electrodeposition, especially under weak magnetic field conditions, provides great promise for the preparation of HER catalysts. [ABSTRACT FROM AUTHOR]

In this paper, an island-like Re-containing phytate bimetal nanocluster catalyst was uniformly prepared on nickel foam by the chemical induced deposition@self-assembly method. The existence of valence-enriched Re and hydrophilic phytate molecules will improve the active area, charge transfer rate, and wetting ability of the intrinsic NiP catalyst. The bifunctional NiRe-IP6 catalyst can drive 100 mA/cm2 glucose oxidation reaction (GOR) and hydrogen evolution reaction (HER) processes by only 1.28 V [vs reversible hydrogen electrode (RHE)] and −0.115 V (vs RHE) in alkaline glucose electrolyte, respectively, outperforming almost all the as-reported GOR/HER bifunctional catalysts, especially at high current density. [ABSTRACT FROM AUTHOR]

MXene‐supported noble metal alloy catalysts exhibit remarkable electrocatalytic activity in various applications. However, there is no facile one‐step method for synthesizing these catalysts, because the synthesis of MXenes requires a strongly oxidizing environment and the preparation of platinum nanoalloys requires a strongly reducing environment and high temperatures. Hence, achieving coupling in one step is extremely challenging. In this paper, a straightforward one‐step molten salt method for preparing MXene‐supported platinum nanoalloy catalysts is proposed. The molten salt acts as the reaction medium to dissolve the transition metals and platinum ions at high temperatures. Transition metal ions oxidize the A‐site element from its MAX precursor at high temperatures, and the resulting transition metals further reduce platinum ions to form alloys. By coupling Al oxidation and platinum ion reduction using a molten salt solvent, this method directly converts Ti3AlC2 to a Pt‐M@Ti3C2Tx catalyst (where M denotes the transition metal). It further offers the possibility of extending the Pt‐M phase to binary, ternary, or quaternary platinum‐containing nanoalloys and converting the Al‐containing MAX phase to Ti2AlC and Ti3AlCN. Due to the strong interfacial interaction, the as‐prepared Pt‐Co@Ti3C2Tx is superior to commercial Pt/C (20 wt.%) in the hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Catalytic hydrolysis of ammonia borane (AB) can be applied as an on-demand hydrogen production system. Low-cost and highly active catalysts towards AB hydrolysis are highly desirable for the industrial application of this technology. In this paper, we have reported the synthesis of Cu3P-Co2P nanoplatelets by a simple method and the formation process of the final products. It is revealed that Cu2O–Co(OH)2 composite nanoplatelets are obtained after hydrothermal reaction, which are transformed into Cu3P-Co2P nanoplatelets during the phosphorization process. In AB hydrolysis, the Cu3P-Co2P nanoplatelets exhibit high catalytic activity with the hydrogen generation rate of 4.03 LH2 gcat.−1 min−1, which is much higher than those for many noble-metal-free catalysts in the documents. It is discovered that AB hydrolysis follows the pseudo-first-order kinetics with respect to the catalyst dosage and pseudo-zero-order kinetics with respect to the AB amount. In view of the cheapness and high performance, the Cu3P-Co2P nanoplatelets can be a promising catalyst candidate to AB hydrolysis for hydrogen production. [ABSTRACT FROM AUTHOR]

• Flexible film of Ag decorated WSe 2 on a paper substrate for visible light (390–780 nm) photodetection and electrocatalysis for hydrogen evolution reaction (HER) • A facile handprint technique, and drop cast methods were used to fabrication of flexible electrode without the use of binders and toxic liquids. • The pave of WSe 2 crystals on paper was followed facial, cost-effective, non-toxic, environmentally friendly handprint technique. • The performance of the photodetector was tested under bending, folding, and twisting state to determine the flexibility of photodetector. • The photodetector advocates the photoresponsivity (0.43 mA/W) and a specific detectivity (2.9 × 108 Jones) at 780 nm at low bias of 1.0 V. • The HER performance of the fabricated paper-based WSe 2 /Ag electrode were carried out by linear sweep voltammetry (LSV), cyclic-voltammetry, Tafel slope, chronopotentiometry, and electrochemical impedance spectroscopy (EIS) • The WSe 2 /Ag catalyst film require an overpotential of −341 mV for HER at a current density of −10 mA/cm2, which is significantly lower than pristine WSe 2. • This study opens new opportunities for the application of the paper-based flexible devices, and convenient electrodes for electrocatalysis. Modern life is gravitating toward the light harvesting and clean energy production route because fossil fuels are becoming obsolete, which propels the researcher and scientific community to requirements of future photo-sensing and energy inventive devices based on two dimensional (2D) nanomaterials. Herein, we present the fabrication of a flexible film of Ag decorated WSe 2 on a paper substrate for visible light (390–780 nm) photodetection and electrocatalysis for hydrogen evolution reaction (HER). A facile handprint technique, and drop cast methods were used without the use of binders and toxic liquids. The photodetector advocates the photoresponsivity (0.43 mA/W) and a specific detectivity (2.9 × 108 Jones) at 780 nm at a low bias of 1.0 V. The WSe 2 /Ag catalyst film requires an overpotential of −341 mV for HER at a current density of −10 mA/cm2, which is significantly lower than pristine WSe 2. The stability of the WSe 2 /Ag electrode for a long time interval of 15 h indicates chemical robust behavior towards HER reaction. This research opens up the versatile possibility of energy harvesting, and photoconductive devices based on heterostructures. [ABSTRACT FROM AUTHOR]

[Display omitted] Developing efficient and durable bifunctional air–cathode catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the key efforts promoting the practical rechargeable zinc-air batteries (ZABs). In this paper, high-performance bifunctional air–cathode catalysts by a two-step strategy: atomically dispersed Ni on N -doped carbon is first derived from MOF to form uniformly dispersed NiNC, which are pyrolyzed together with Fe source at different high-temperatures to form FeNi@NC-T (T = 800, 900, and 1000 °C) catalysts. The as-synthesized non-noble metal FeNi@NC-900 catalyst exhibits a considerably small potential gap (ΔE) of 0.72 V between ORR and OER, which is as the same as commercial noble metal Pt/C + Ir black mixed catalyst. The performance of the ZABs using FeNi@NC-900 as the air–cathode catalyst displays a power density of 119 mW·cm−2 and a specific capacity of 830.1 mAh·g−1, which is superior to that of Pt/C + Ir black mixed catalyst. This work provides a guideline for designing alloy electrocatalysts with uniform size and nanoparticle distribution for metal-air batteries with bifunctional air-cathodes. [ABSTRACT FROM AUTHOR]

Carbon-based single-atom catalysts (SACs) for electrochemical nitrogen reduction reaction (NRR) have received increasing attention due to their sustainable, efficient, and green advantages. However, at present, the research on carbon nanotubes (CNTs)-based NRR catalysts is very limited. In this paper, using FeN3@(n, 0) CNTs (n = 3 ~ 10) as the representative catalysts, we demonstrate that the CNT curvatures will affect the spin polarization of the catalytic active centers, the activation of the adsorbed N2 molecules and the Gibbs free energy barriers for the formation of the critical intermediates in the NRR processes, thus changing the catalytic performance of CNT-based catalysts. Zigzag (8, 0) CNT was taken as the optimal substrate, and twenty transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Tc, Ru, Rh, Pd, W, Re, Ir, and Pt) were embedded into (8, 0) CNT via N3 group to construct the NRR catalysts. Their electrocatalytic performance for NRR were examined using DFT calculations, and TcN3@(8, 0) CNT was screened out as the best candidate with a low onset potential of − 0.53 V via the distal mechanism, which is superior to the molecules- or graphene-support Tc catalysts. Further electronic properties analysis shows that the high NRR performance of TcN3@(8, 0) CNT originates from the strong d-2π* interaction between the N2 molecule and Tc atom. TcN3@(8, 0) CNT also exhibits higher selectivity for NRR than the competing hydrogen evolution reaction (HER) process. The present work not only provides a promising catalyst for NRR, but also open up opportunities for further exploring of low-dimensional carbon-based high efficiency electrochemical NRR catalysts. [ABSTRACT FROM AUTHOR]

Solar energy is an inexhaustible clean energy providing a key solution to the dual challenges of energy and environmental crises. Graphite-like layered molybdenum disulfide (MoS2) is a promising photocatalytic material with three different crystal structures, 1T, 2H and 3R, each with distinct photoelectric properties. In this paper, 1T-MoS2 and 2H-MoS2, which are widely used in photocatalytic hydrogen evolution, were combined with MoO2 to form composite catalysts using a bottom-up one-step hydrothermal method. The microstructure and morphology of the composite catalysts were studied by XRD, SEM, BET, XPS and EIS. The prepared catalysts were used in the photocatalytic hydrogen evolution of formic acid. The results show that MoS2/MoO2 composite catalysts have an excellent catalytic effect on hydrogen evolution from formic acid. By analyzing the photocatalytic hydrogen production performance of composite catalysts, it suggests that the properties of MoS2 composite catalysts with different polymorphs are distinct, and different content of MoO2 also bring differences. Among the composite catalysts, 2H-MoS2/MoO2 composite catalysts with 48% MoO2 content show the best performance. The hydrogen yield is 960 µmol/h, which is 1.2 times pure 2H-MoS2 and two times pure MoO2. The hydrogen selectivity reaches 75%, which is 22% times higher than that of pure 2H-MoS2 and 30% higher than that of MoO2. The excellent performance of the 2H-MoS2/MoO2 composite catalyst is mainly due to the formation of the heterogeneous structure between MoS2 and MoO2, which improves the migration of photogenerated carriers and reduces the possibilities of recombination through the internal electric field. MoS2/MoO2 composite catalyst provides a cheap and efficient solution for photocatalytic hydrogen production from formic acid. [ABSTRACT FROM AUTHOR]

In this paper, a waxberry‐like MnS/Ni3S4 composite catalyst was designed and synthesized. In this coating structure, MnS is located inside and Ni3S4 is wrapped on the surface to form a spherical structure. This structure makes the material show excellent stability in the electrocatalytic process. The diffusion staggered region structure formed at the two‐phase interface greatly enhances the synergistic interaction between MnS and Ni3S4. At the same time, the defects and vacancies formed by the diffusion mechanism at the interface of the two phases increase the active site and improve the interfacial electron transfer kinetics. Therefore, MnS/Ni3S4 composites showed good catalytic performance for ORR/OER. At 10 mA cm−2, the overpotential of it is only 320 mV, and the half‐wave potential can reach 0.81 V. The catalyst also exhibited extraordinary cycle stability and small voltage gap when used as cathode of Zn‐air batteries. When the current density is 3 mA cm−2, the cyclic discharge can be stable for 400 h and the voltage difference between the front and back does not increase more than. When the current density increases to 5 mA cm−2, the cyclic charge and discharge can be stable for more than 300 h. [ABSTRACT FROM AUTHOR]

Accelerating the charge transfer (CT) capability of photocatalysts is an efficient way to improve the overall photocatalytic performance, yet the precise regulation of CT in photocatalyst systems is still lacking. In this paper, a series of hybrid photocatalysts composed of graphitic carbon nitride (CN) and various viologens (V) were prepared for the photocatalytic hydrogen evolution (PHE) from water splitting under visible-light irradiation. Considering the fixed energy structure of CN , the different electron-withdrawing substituents were introduced to engineer the band structure of V delicately and modulate the CT process between CN and V. It was shown that all the hybrid photocatalysts CN-x%V y exhibited higher photocatalytic performance, of which CN–1%V 3 , possessing the strongest electron withdrawing group (-NO 2), demonstrated the best PHE performance (3572.3 μmol g−1 h−1), exceeding 29 times over the unmodified CN. It was proposed that the introduction of V can optimize the interfacial photogenerated electron transfer (CN → V →Pt) of the whole photocatalytic system effectively. We highlighted the V as an efficient chemical segment to modify semiconductors toward enhanced activity due to the following unique characteristics: (i) the unique redox ability, (ii) the easy synthetic methods for controlling the band structures precisely, and (iii) the inherent positively charged feature. This work provides a deep understanding of CT for the rational design of high-performance photocatalysts through band engineering. [Display omitted] • Hybrid photocatalysts CN-x%V y composed of g -C 3 N 4 (CN) and viologens (V) were prepared. • The photocatalytic performance of CN-x%V y catalysts was dependent on the band engineering of V. • Charge transfer of CN-x%V y catalysts was precisely regulated. • CN–1%V 3 exhibited a 29 times higher photocatalytic H 2 evolution rate than the unmodified CN. [ABSTRACT FROM AUTHOR]

Hydrogen production by photocatalysis will be an important means of obtaining hydrogen energy in the future. In this paper, a novel single‐atom catalysts structure was designed to improve the conversion efficiency of the reaction. A novel single‐atom catalysts was designed by using two‐dimensional crystalline and amorphous ZrO2 and Graphitic Carbon Nitride g‐C3N4 to form a sandwich single‐atom structure. Rh single‐atoms load was carried on the interlayer ZrO2 surface. The electronic structure and catalytic performance of the catalyst were calculated and analyzed by density functional theory. It has been shown that the electron concentration induced by the unsaturated coordination bond on the surface of the amorphous state has an excellent effect on the photocatalytic hydrogen evolution reaction. The local surface plasmon resonance effect of noble metal reduces the work function of catalyst and improves the electron transition ability. This paper proves that amorphous interlayer photocatalyst has a wide research prospect. It provides new ideas for the design of new catalysts and green energy in the future. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

Non-noble metal-based bifunctional electrocatalysts may be a promising new resource for electrocatalytic water-splitting devices. In this work, transition metal (cobalt)-incorporated graphitic carbon nitride was synthesized and fabricated in electrodes for use as bifunctional catalysts. The optimum catalytic activity of this bifunctional material for the hydrogen evolution reaction (HER), which benefitted at a cobalt content of 10.6 wt%, was promoted by the highest surface area and conductivity. The activity achieved a minimum overpotential of ~85 mV at 10 mA/cm2 and a Tafel slope of 44.2 mV/dec in an acidic electrolyte. These values of the HER were close to those of a benchmark catalyst (platinum on carbon paper electrode). Moreover, the kinetics evaluation at the optimum catalyst ensured the catalyst flows (Volmer–Heyrovsky mechanism), indicating that the adsorption step is rate-determining for the HER. The activity for the oxygen evolution reaction (OER) indicated an overpotential of ~530 mV at 10 mAcm−2 and a Tafel slope of 193.3 mV/dec, which were slightly less or nearly the same as those of the benchmark catalyst. Stability tests using long-term potential cycles confirmed the high durability of the catalyst for both HER and OER. Moreover, the optimal bifunctional catalyst achieved a current density of 10 mAcm−2 at a cell voltage of 1.84 V, which was slightly less than that of the benchmark catalyst (1.98 V). Thus, this research reveals that the present bifunctional, non-noble metallic electrocatalyst is adequate for use as a water-splitting technology in acidic media. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting represents a promising alternative to conventional carbon-based energy sources. The hydrogen evolution reaction (HER) is a key process, still if conducted in alkaline media, its kinetics is slow thus requiring high amount of Pt based catalysts. Extensive research has been focused on reducing Pt utilization by pursuing careful electrode investigation. Here, a low-cost chemical methodology is reported to obtain large amount of microflowers made of interconnected NiO nanowalls (20 nm thick) wisely decorated with ultralow amounts of Pt nanoparticles. These decorated microflowers, dispersed onto graphene paper by drop casting, build a high performance HER electrode exhibiting an overpotential of only 66 mV at current density of 10 mA cm−2 under alkaline conditions. Intrinsic activity of catalyst was evaluated by measuring the Tafel plot (as low as 82 mV/dec) and turnover frequencies (2.07 s−1 for a Pt loading of 11.2 μg cm−2). The effect of Pt decoration has been modelled through energy band bending supported by electrochemical analyses. A full cell for alkaline electrochemical water splitting has been built, composed of Pt decorated NiO microflowers as cathode and bare NiO microflowers as anode, showing a low potential of 1.57 V to afford a current density of 10 mA cm−2 and a good long-term stability. The reported results pave the way towards an extensive utilization of Ni based nanostructures with ultralow Pt content for efficient electrochemical water splitting. • Pt nanoparticles decoration of NiO microflowers. • Effect of decoration on Hydrogen Evolution Reaction mechanism and on energy band modification of NiO. • Overall water splitting with NiO and Pt–NiO electrodes in alkaline conditions. [ABSTRACT FROM AUTHOR]

The rational design of high-efficiency electrocatalysts for application in water oxidation in alkaline media remains a great challenge. In this paper, Ni3+-rich nanograss-like Mo-doped Ni3S2/NiS/VS arrays grown on nickel foam (denoted as Mo-NiVS@NF) have been successfully constructed through a hydro/solvothermal method. Interestingly, Mo-NiVS@NF exhibits superior catalytic OER performance, needing an overpotential of 217 mV to drive a current density of 10 mA cm−2, outperforming most previously reported NiS-based electrocatalysts. The result indicates that the Ni3+-rich active sites caused by the modulation of the electronic structure environment via the introduction of V and high-valency Mo play an important role in the high activity for the OER. Moreover, this catalyst shows high long-term electrochemical durability. [ABSTRACT FROM AUTHOR]

The development of highly efficient and low-cost bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is the key to the industrialization of large-scale hydrogen production, while the development of non-precious-metal catalysts that can be substituted for precious-metal materials is the current trend of research. In this paper, nickel foam (NF) self-supported CoFe layered bimetallic hydroxide (LDH)-CuCo 2 S 4 electrocatalysts were prepared using a simple hydrothermal and electrodeposition method. The prepared CuCo 2 S 4 @CoFe-LDH/NF catalysts showed good performance in alkaline water oxidation, proton reduction and overall water decomposition with an overpotential of 293 mV for the oxygen evolution reaction (OER) at a current density of 50 mA cm−2 and 63 mV for the hydrogen evolution reaction (HER) at a current density of 10 mA cm−2. When CuCo 2 S 4 @CoFe-LDH/NF was used as a bifunctional electrocatalyst for the decomposition of water, the voltage of the 10 mA cm−2 electrolyzer was only 1.54 V, and the stability of the electrolyzer reached 60 h, which was superior to other bifunctional catalysts. [Display omitted] • CoCu-LDH grows firmly on nickel foam by a hydrothermal method. • Vulcanization at room temperature makes the experimental conditions milder and simpler. • An electrodeposition method was used to grow nanosheets on nanowires. [ABSTRACT FROM AUTHOR]

The potential of converting traditional biomass into low-cost HER catalysts has broad application prospects. In this paper, fungus is used as a carbon-based carrier. The bimetallic catalyst RuM-C (M = V, Mo, W, Zn, Cu) was synthesized under inert gas protection at high temperature. The order of electrocatalytic activity is RuV-C > RuZn-C > RuW-C > RuMo-C > Ru-C > RuCu-C > BF-C, which indicates that RuV-C exhibits excellent HER activity. Due to its irregular sheet structure, the specific surface area of the catalyst is increased. Impressively, it exhibits extremely high catalytic activity for HER in 1 M KOH due to favorable kinetics and excellent specific activity. Consequently, the prepared RuV-C exhibited excellent and stable HER activity compared Ru-C with a low overpotential of 65.78 mV at the current densities of 10 mA cmâˆ'2 and Tafel slope of 45.26 mV decâˆ'1. The potential only decreased by 88 mV after 24 h of continuous testing, which indicates that the catalyst has outstanding stability. This work will provide positive inspiration for the promotion of a new Ru-based biomass HER electrocatalyst. [ABSTRACT FROM AUTHOR]

Schematic diagram of fabricating process of NixSey/MoSe2/NF hollow rod arrays. [Display omitted] Alkaline water electrocatalysis is considered as one of the most reliable method to prepare the stable, inexpensive, and sustainable water splitting catalyst in large-scale. Recently, MoSe 2 attracted great attention as a promising catalyst because of its high electrochemical activity and earth-abundant nature. In this paper, bionic Ni x Se y /MoSe 2 coralline-liked heterogeneous structures were successfully prepared on 3D nickel foam (NF) via a simple solvothermal process complemented by hydrothermal strategy with selenization and alkali treatment. Furthermore, to overcome the less active sites and poor electrical conductivity of MoSe 2 , we learned from the coral structure for the inspiration, and reported a novel hollow rod-like structure with increased active sites. Also, 1 T-2H MoSe 2 improved the electrical conductivity of single phase MoSe 2. We first confirmed the multi-phase of catalyst by XPS analysis with Mo 3d 5/2 splited into two independent regions with the 2H and 1 T phase transition. The optimal ratio of Ni x Se y/ MoSe 2 /NF-5 exhibited excellent electrocatalytic activity towards HER in 1 M KOH, driving current densities of 10, 100 and 200 mA cm−2 at only 76, 165 and 194 mV with stability over 24 h. The work provides new ideas for the construction of transition metal selenides hollow rod array structures of efficient HER electrocatalysts. [ABSTRACT FROM AUTHOR]

The stability of functional carriers single-atom catalysts can be effectively guaranteed by using stable mineral materials to support low dimensional catalytic materials. In this paper, the theoretical calculation of electrochemical hydrogen evolution reaction (HER) of the composite functional single-atom catalysts supported by single-atom Ni was carried out using first-principles method. And the original structure of MoS2, amorphous structure and S-vacancy structure are studied. Through the analysis and discussion of electronic properties, adsorption energy and active sites, it is found that Ni@Amorphous MoS2-FeS has excellent effect of hydrogen evolution in acidic environment, Î" G H is 0.312 eV, and the other two structures supporting Ni single-atom also have excellent HER properties in a wide range of pH. This design broadens the research idea of single-atom catalysts carriers and provides a new direction for the research and development of electrocatalytic materials. [ABSTRACT FROM AUTHOR]

Summary: Obstacles to the efficient operation of rechargeable aluminum‐air batteries include slow oxygen reduction reaction (ORR), slow kinetics, and large overpotential of oxygen evolution reactions (OER). An effective solution is to develop a new bifunctional electrocatalyst that is effective for both the ORR/OER processes. In this study, we prepared the α‐MnO2/Co3O4 bifunctional composite catalyst by the in situ generation of Co3O4 nanoparticles on α‐MnO2 nanorods. ORR/OER catalytic activity and structures of the prepared catalysts have been investigated systematically. Compared with single‐component α‐MnO2 nanorods and Co3O4 particles catalyst, the α‐MnO2/Co3O4 composite catalyst possesses the smallest average pore diameter (11.84 nm), and the largest specific surface area (41.34 m2 g−1), which is due to the restriction of the growth of Co3O4 particles by α‐MnO2 nanorods. Besides, during the ORR process, the α‐MnO2/Co3O4 composite catalyst shows the most positive onset potential of 0.833 V, the most positive half‐wave potential of 0.760 V, and the biggest limiting current density of 3.881 mA cm−2. Meanwhile, during the OER process, the composite catalyst exhibits the lowest onset potential of 1.630 V, the lowest overpotential of 554 mV, and the biggest limiting current density of 24.590 mA cm−2. Furthermore, the α‐MnO2/Co3O4‐assembled aluminum‐air battery (AAB) delivers the best cycling performance. Our work provides an idea for optimizing the bifunctional catalyst with high ORR/OER activity and low cost used in secondary AAB. Highlights: A novel α‐MnO2/Co3O4 bifunctional composite catalyst was prepared successfully.The α‐MnO2/Co3O4 composite catalyst was applied in a rechargeable Al‐air battery.The α‐MnO2/Co3O4 exhibited better ORR/OER catalytic activity than α‐MnO2 and Co3O4.The Al‐air battery using α‐MnO2/Co3O4 catalyst showed excellent cycling performances. Novelty Statement: This is our original work. Neither the entire paper nor any part of its content has been published or has been accepted elsewhere. It is not being submitted to any other journal. [ABSTRACT FROM AUTHOR]

[Display omitted] As a promising dopant, electron deficient B atom not only tunes the electronic structure of electrocatalysts for improving their intrinsic catalytic activities, but also combines with hydroxy radical as strong adsorption sites for accelerating the water dissociation during the hydrogen evolution reaction (HER). In this paper, we report an electrocatalyst based on boron-modified Ru anchored on carbon nanotubes (B-Ru@CNT) that shows impressive HER activity in acidic and alkaline media. The boron-rich closo -[B 12 H 12 ]2- borane was selected as a moderately strong reductant for the in situ reduction of a Ru salt, which yielded B-doped Ru nanoparticles. The experimental and theoretical results indicate that the incorporation of B not only weakens the Ru-H bond and downshifts the d-bond centre of Ru from the Fermi level by reducing the electron density at Ru but also accelerates the water dissociation reaction by providing B sites, which strongly adsorb OH* intermediates, and nearby Ru sites, which act as sites for the adsorption of the H* intermediate, thus boosting the HER performance and enhancing the HER kinetics. As a result of the tuning of the electronic structure via B doping, B-Ru@CNT showed excellent HER performance, yielding overpotentials of 17 and 62 mV at a current density of 10 mA cm−2 in alkaline and acidic solutions, respectively. These results indicate that our synthetic method is a promising route to B-doped metallic Ru with enhanced pH-independent HER performance. [ABSTRACT FROM AUTHOR]

Summary: Catalysts with cobalt (Co) and graphitic carbon hybrid structure are receiving significant attention in various electrocatalysis applications because of their stability and high activities. In addition, the size and the well dispersed distribution of metal active site are some of the most important factors for electrocatalyst. In this paper, we successfully synthesized ultra‐small and well dispersed Co nanoparticle on nitrogen‐doped carbon structure (Co/NC) adding and evaporating a Zinc (Zn) and found the optimized ratio of Co and Zn. We used a bottom‐up method to synthesize catalysts with Co on carbon substrate structure from zeolitic imidazolate frameworks (ZIF). Zinc (Zn) was also added and evaporated by pyrolysis. By addition and evaporation of Zn, Co nanoparticle became smaller and more evenly dispersed. As a result, the OER performance was significantly improved than the catalyst without Zn. Also, an optimized catalyst with abundant uniformly dispersed Co was successfully synthesized by appropriately controlling the ratio of Co and Zn comprising the ZIFs. As the ratio of Zn increased, the size and the amount of Co nanoparticles were decreased, and Co nanoparticles were more evenly dispersed. Furthermore, carbon substrate has more porous structure due to the evaporation of Zn atoms. When the Co:Zn ratio was 1:3, Co/NC showed the best electrocatalytic performance due to optimized active sites and large surface area. The optimized Co/NC showed an overpotential of 1.56 V (vs RHE) to acquire a current density of 10 mA cm−2, which is higher activity than commercial RuO2. We also analyzed the material characterization occurred as the ratio of Zn in ZIF increased, revealing the factors enhancing the OER activity. Optimized Co/NC (Co:Zn = 1:3) exhibited improved OER activity and long‐term and cycle stability in the OER. [ABSTRACT FROM AUTHOR]

In order to obtain platinum-group-metal-free catalysts for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in alkaline electrolyzers, nitrogen-doped mesoporous carbons were prepared from pyrolysis of two cobalt metal organic frameworks (MOFs), one linear coordination polymer and one complex. The catalyst derived from cobalt 2,3-pyrazinedicarboxylate polymer (700 °C) had a Tafel slope of 90 mV dec−1 and 130 mV dec−1 for the HER and OER respectively, a current density of 10 mA cm−2 was reached at − 0.23 V and 1.56 V vs RHE for the HER and OER respectively. In order to prove the bifunctional catalytic activity towards the overall water splitting, a two electrode electrolyzer was constructed depositing the catalyst on carbon paper. H2 and O2 evolved volumes followed the Faraday law, showing efficiency very close to 100%. The same materials also showed catalytic activity towards the oxygen reduction reaction (ORR), reaching an electron transfer number close to 4 and low H2O2 yields. The acid leached catalyst derived from Cobalt 2,3-pyrazinedicarboxylate polymer (700 °C) reached a ∆E = Ej = 10(OER) −E½(ORR) = 0.80 V, making it an useful oxygen catalyst for metal-air batteries. [ABSTRACT FROM AUTHOR]

Single atom catalysts (SACs) can improve the efficiency of oxygen evolution reaction (OER). However, metal SACs anchored on carbon materials are relatively uncommon for the OER. In this paper, using carbon black as carrier, NiFe SACs are fabricated by one step pyrolysis method. When the weight ratio of Ni/Fe is lower than 5:3, NiFe@C exibits highly-dispersed SACs over carbon in addition to some Ni 3 Fe alloy. The prepared NiFe@C 5:3 SACs showed excellent OER performance with an overpotential of 322 mV and 438 mV for current density of 10 mA/cm2 and 100 mA/cm2, respectively. The Tafel slope of NiFe@C 5:3 was as small as 87.6 mV/dec, indicating fast charge transfer of NiFe@C 5:3 during OER process, which was also confirmed by electrochemical impedance spectra with R ct = 18.07 Ωcm2. Meanwhile, NiFe@C 5:3 had the highest specific capacitance of 5 mF/cm2 with good stability. This work provides a reference for designing electocatalyst material for efficient, stable and economical OER process. • NiFe SACs are fabricated by pyrolysis method. • NiFe@C 5:3 exibits highly dispersed SACs on carbon. • The required over potential of NiFe@C 5:3 for current density 10 mA/cm2 is only 322 mV. • This work provides a reference for designing electocatalyst material. [ABSTRACT FROM AUTHOR]

[Display omitted] • WN nanosheets were prepared by sol–gel method. • CdS/WN was prepared by one pot solvothermal method. • Intimate interfacial contact between CdS NPs and WN engenders Schottk junction. • The evolution rate of optimal CdS/WN H 2 was 9.28 times that of CdS NPS. Based on the strategy that electrocatalysts can be used as additives to improve the performance of photocatalysts, and the unique metalloid properties of tungsten nitride (WN), it can form a Schottky junction with the semiconductor at the heterogeneous interface to improve the photocatalytic performance of semiconductor catalysts. In this paper, WN with excellent electrical conductivity was selected as a new noble-metal-free co-catalyst to improve the photoreduction hydrogen (H 2) evolution performance of CdS nanoparticles (NPs). Firstly, WN nanosheets were prepared by sol–gel method; then, a novel and noble-metal-free heterojunction photocatalyst, which is CdS NPs deposited on the surface of WN, was successfully fabricated via one-pot solvothermal method. Under visible light irradiation, the H 2 production rate of the WN/CdS composite catalyst is 24.13 mmol/g/h, which is 9.28 times that of pure CdS NPs. The observably boosted H 2 generation activity could be ascribed to the broadened visible-light absorption and intimate interfacial contact between CdS NPs and WN engenders Schottky junction. This study provides a novel and cost-effective approach for designing efficient noble-metal-free photocatalysts and improving H 2 evolution activity of CdS under visible-light-driven photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

Hydrogen energy as a significant part of clean energy in the future has been widely studied. Hydrogen production from electric cracking water is the most effective and mature development method at present. Heterostructured electrocatalysts are favored due to their low overpotential, excellent assembly structure and good electron transfer ability. Consequently this paper reviews the development of heterogeneous electrocatalysts, the measurement parameters of electrocatalytic hydrogen evolution reaction (HER), and related research progress, and gives the hydrogen evolution mechanism in acidic, alkaline and neutral environments. Finally, we explain the essential development direction and severe challenges in this field. [ABSTRACT FROM AUTHOR]

Hydrogen, the most abundant element in the universe, holds a great promise as an alternative to conventional fuels. Among various approaches, the renewable energy-driven electro- and photocatalytic generations have lately gained prominence owing to the plethora of advantages that they offer. It is evident that when employing these methods for the H 2 production, catalyst is one of the significant components of the reaction, determining how much H 2 could be evolved by the proposed system. This has led to a rise in the number of scientific papers devoted to the development of novel and active catalysts as potential candidates for catalyzing the hydrogen evolution reaction. In this regard, phthalocyanine (Pc)-based catalysts offer powerful pathway due to the particular properties, including the ease of large-scale manufacturing, unique redox behavior, high efficiency, ease of separation, and recyclable nature. In this review, we have provided a comprehensive overview of publications on the generation of hydrogen by electrolysis and photolysis of various substrates, both of which are accomplished through the use of a variety of Pc-based catalysts. A number of critical variables were discovered to be consequential for the ultimate H 2 generation rate in the catalytic H 2 evolution systems such as the effects of metal center, substitution, support, size, and crystallinity of Pc. • The renewable energy-driven electro(photo) catalytic hydrogen production. • Phthalocyanine-based electro(photo) catalysts for green hydrogen generation. • Water splitting towards hydrogen evolution. • Phthalocyanines as photosensitizer, semiconductor, and catalysts in hydrogen evolution. [ABSTRACT FROM AUTHOR]

The development of economical, efficient and stable non-noble metal catalysts plays a key role in electrocatalytic hydrogen evolution. NiCo 2 S 4 has been proved to be an efficient non-noble catalyst, to further improve its electrocatalytic performance is a meaningful work. In this paper, the effects of Fe doping on electrochemical performance of NiCo 2 S 4 is investigated. The Fe-doped NiCo 2 S 4 catalyst is prepared by a facile solvothermal method with metal-organic-framework (MOF, ZIF-67) as template, and it exhibits an improved hydrogen evolution reaction (HER) performance with an overpotential of 181 mV at 10 mA cm−2, a Tafel slope of 125 mV dec−1 compared with that of NiCo 2 S 4 (252 mV overpotential and 149 mV dec−1 Tafel slope). The combination of improved conductivity, mesopores architecture retained with the ZIF-67 template, which result the reduced internal resistance, enhanced charge transportation as well as large electrochemical double-layer capacitance. This work provides an effective and synergistic strategy for fabricating NiCo 2 S 4 -based catalysts toward electrochemical water splitting. • Fe-doped NiCo 2 S 4 catalyst was synthesized by using ZIF-67 as a template. • The conductivity of NiCo 2 S 4 is increased by Fe doping. • Mesopores architecture of the Fe-doped NiCo 2 S 4 is retained with the template. • The Fe-doped NiCo 2 S 4 catalyst presents an improved HER activity and stability. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) catalyzed by non-precious metals and their compounds in alkaline environments are regarded as a key research topic for the use of water for hydrogen production to alleviate the global energy crisis. Cobalt-iron layered double hydroxide (CoFe-LDH) has attracted much attention as a potential high-performance oxygen evolution reaction catalyst. In this paper, we report a strategy to introduce metal elements M (M = Cu, K, Al, Cr and Zn) into CoFe-LDH to further enhance the OER performance. The experimental results show that CoFeK-15 exhibits the lowest overpotential (203 mV to reach 10 mA cm−2) and Tafel slope (77.1 mV dec−1) and maintains excellent catalytic activity after 50 h i-t test. Through the introduction of potassium ions, the electronic structure inside the catalyst underwent lattice distortion, resulting in a larger active surface area and exposure of more oxygen vacancies, which in turn accelerated the OER reaction. This study reveals the important influence of potassium doping on the electronic structure modification strategy to enhance the performance of OER and provides new ideas for the development of more efficient catalysts in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

• An efficient Co 9 S 8 /Ni 3 S 2 bifunctional electrocatalyst is synthesized by hydrothermal method. • Co 9 S 8 /Ni 3 S 2 possesses a large specific surface area because of the flocculated structure. • Overpotentials of 53.6 and 107.6 mV were obtained to achieve current density of 10 mA/cm2 for HER and OER. • A cell potential of 1.55 V was required to drive the overall water splitting at a current density of 10 mA/cm2. Modern industrial hydrogen production is a crucial solution to address the energy crisis. Therefore, the development of a cost-effective and highly efficient hydrolytic hydrogen production catalyst holds significant practical importance. In this study, we propose to synthesize an efficient bifunctional electrocatalyst of Co 9 S 8 /Ni 3 S 2 grown on nickel foam (NF) by a one-step hydrothermal method, which has a large specific surface area due to its flocculated structure. Through electrochemical testing, the Co 9 S 8 /Ni 3 S 2 /NF electrode exhibits remarkable performance in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, low overpotentials of 53.6, 90.2, and 209.2 mV are required to achieve current densities of 10, 20, and 100 mA/cm2 during HER, respectively. Similarly, for OER, the overpotentials are only 107.6, 150.6, and 350.4 mV. Additionally, the Co 9 S 8 /Ni 3 S 2 /NF electrode demonstrates a small Tafel slope of 68.7 mV/dec for HER and 91.8 mV/dec for OER, indicating efficient reaction kinetics. Notably, the electrode exhibits exceptional long-term stability. Moreover, in a self-assembled monolithic water splitting device with Co 9 S 8 /Ni 3 S 2 /NF electrodes as cathode and anode, a cell potential of 1.55 V is required to drive the overall water splitting process at a current density of 10 mA/cm2, and the reaction shows excellent stability with a loss of voltage of only 16.5 mV over a 10-hour period. This paper presents a simple and innovative approach for constructing bimetallic sulfides electrocatalysts. [ABSTRACT FROM AUTHOR]

The development of renewable clean energy is imminent as global warming and environmental pollution become more serious issues today. Hydrogen energy has been widely studied as an ideal green energy source. Among several common hydrogen production methods, hydrogen production by electrolysis of water is considered an efficient, environmentally friendly, and sustainable hydrogen production strategy. Transition metal phosphates have outstanding electrocatalytic conductivity and high catalytic efficiency, thus exhibiting catalytic effects similar to noble metals. To further enhance the catalytic activity of the transition metal phosphates, in this paper, the cauliflower-like Co-W-P-O 4 /NF catalyst based on three-dimensional nickel foam was prepared by the method of element doping. The catalyst exhibited good bifunctional catalytic activity in alkaline solution. The prepared Co-W-P-O 4 /NF has a unique crystalline-amorphous phase structure with abundant active sites at the interface. In addition, W atoms can interact with Co atoms to co-optimise the electronic structure, enabling the Gibbs free energy of hydrogen adsorption (ΔG H*) to be close to 0, which is conducive to improving the performance of water electrolysis. To achieve a current density of 10 mA·cm−2, the Co-W-P-O 4 /NF required overpotentials of 42.1 mV for HER and 348.2 mV for OER in 1 M KOH solution, with the Tafel slopes being 48.0 and 83.6 mV·dec−1, respectively. When Co-W-P-O 4 /NF was used as both cathode and anode for water splitting, the two-electrode electrolyzer could achieve 10 mA·cm−2 with only 1.62 V, along with good stability. [Display omitted] • The cauliflower-like Co-W-P-O 4 /NF with crystalline-amorphous phase structure is prepared. • Co-W-P-O 4 /NF catalyst shows good bifunctional catalytic activity in alkaline solution. • The electron rearrangement and the rough surface structure can improve the performance of catalyst. [ABSTRACT FROM AUTHOR]

• Alkaline Water Electrolysis functions best between 65 and 100 °C at 2–10 bar pressure. • Solid Oxide Electrolysis Cells operate at higher temperatures of 600–1200 °C. • Proton exchange membrane electrolyzers work at current densities >2 A cm−2. • Transition metal-based catalysts demonstrate high performance for HER and OER. • Photocatalysts such as Zn 0.5 Cd 0.5 S/Ti 2 C/TiO 2 have excellent catalytic activity. Hydrogen energy is essential to building a sustainable society with net zero carbon emissions in the face of global climate change and the energy revolution. Hydrogen generation begins with most Power-to-X methods that shape the future energy market. Electrolysis systems that use water/steam to make hydrogen have their own benefits and downsides. Electrolysis and photocatalysis are the main water-splitting methods employed to produce hydrogen. This study outlines these technologies and their future problems and potential. The literature suggests that Alkaline Water Electrolysis (AWE) is a commercial technology that can produce hydrogen on a large scale, whereas Proton Exchange Membrane Electrolysis (PEME) and Solid Oxide Electrolysis Cells (SOEC) are very efficient. Energy-efficient and economically feasible water electrolysis face several challenges. It requires effective, long-lasting catalysts to boost Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) efficiency. This publication includes a table of electrocatalyst groups. Transition metal catalysts are cheaper and as efficient as noble metal catalysts such as IrO 2 , RuO 2 , Pt, and Pd. It also highlights the challenges of electrocatalyst industrialization and commercialization and suggests solutions. The latter half of the paper reviews photocatalysis as an efficient method to produce hydrogen. It also discusses photocatalysts developed to increase H 2 production efficiency. The photocatalytic water splitting activity of pure photocatalysts is enhanced by manipulating morphology, cationic/anionic doping, heterojunction/nanocomposite constructions, and defect formation. The report also covers other alternative renewable energy sources for hydrogen generation. [ABSTRACT FROM AUTHOR]

• Structure-activity relationship of high entropy oxides (HEOs) catalysts for oxygen evolution reaction (OER) were studied. • Band gap of TM 3d-O 2p is a decisive descriptor of the intrinsic OER activity of HEOs. • Band gap of TM 3d-O 2p exhibited a volcano relationship with the intrinsic OER activity of HEOs. High entropy oxides (HEOs) are promising catalysts of oxygen evolution reactions (OER) in water splitting. However, multi-components, complicated phases and numbers of defects make a lack of deep understanding to the structure–activity relationship of HEOs catalysts. In this paper, different transition metal elements of Fe, Cr, Mn, Mg and Al were doped into (CoNiCuZn)O to form five quinary HEOs. To explore the structure–activity relationship of OER catalysts of HEOs, the phase structure, element valence, oxygen vacancies and electronic structure were characterized and their OER performance was tested. The results show that among all the HEOs, (FeCoNiCuZn)O has the optimal OER catalytic performance: an overpotential of 323 mV at a current density of 10 mA cm−2 in 1 M KOH solution, a Tafel slope of 64.5 mV dec-1, maintaining a high stability for at least 50 h. Its superior OER performance can be attributed to a combination of three main factors: an appropriate band gap of transition metal (TM) 3d and oxygen (O) 2p, a high concentration of oxygen vacancies and a spinel phase precipitation. Among them, the band gap of TM 3d and O 2p showing a volcano relationship with the intrinsic OER activity can be the most decisive descriptor of the intrinsic OER activity of HEOs. A moderate band gap of TM 3d and O 2p being tuned by various cations will lead to more reasonable intermediate adsorption and desorption abilities of HEOs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomically dispersed Ru/Mg-CeO 2 catalyst was prepared and possessed excellent catalytic performance for photo-thermal catalytic CO 2 methanation reaction. • The photo-electron excitation/migration path and the surface structure changes induced by light were systematically characterized by operando experiments. • All potential micro-reaction steps and light intensification steps were determined by in situ DRIFTs experiments. • The reversible dynamic structural evolution between Ru-O-Ce structure and Ru-O v -Ce structure could be induced by light. It is a promising green technology to reduce CO 2 to CH 4 by using renewable solar energy driving photo-thermal catalysis route. However, the efficiency of photo-thermal catalytic CO2 methanation remained to be improved, and the mechanism of this reaction still required further investigation. In this paper, a Ru/Mg-CeO 2 catalyst was designed based on the concepts of single atom catalyst and photo-thermal catalysis concept. The catalyst achieved the CH 4 formation rate of 469 mmol·gcat−1·h−1 at 400 °C under photo-thermal conditions with good catalytic stability. Besides, the superiority of the single-atom of Ru, Ru-O-Ce structure and doping of alkaline metals in catalytic process was proved by a series of physicochemical and optical characterization, and electron migration direction from Ce and Mg elements to Ru sites through Ru-O-Ce and Ru-O-Mg path under photo-thermal catalysis was determined by ISI-XPS experiment. Finally, the comprehensive reaction mechanism and reversible dynamic structural evolution process between Ru-O-Ce and Ru-O v -Ce structures were investigated by in situ DRIFTs experiments, and the source of the excellent performance and structure-function relationship of the catalyst was explored, which provided the theoretical and practical basis for the development of catalyst and industrial application of the reaction. [ABSTRACT FROM AUTHOR]

A facile and efficient electrocatalyst for hydrogen evolution reaction (HER) to produce hydrogen is very important for future energy. In this paper, amorphous manganese–cobalt nanosheets are successfully prepared by electrospinning on a foamed nickel substrate. It is found that the manganese (Mn) introduction in manganese–cobalt composites can simultaneously enhance their electrocatalytic performances. As a result, benefitting from the 3D structure, the self-supported Mn–Co hydroxides exhibits unprecedented HER activity with a relatively low overpotential of 100 mV at 10 mA cm−2 and has a possibility for the large-scale production of hydrogen. Amorphous PVP/Mn4Co nanofibers formed by electrospinning on Ni foam (NF) has remarkable catalytic activity and stability for HER after operation for 6 h in 1 M KOH, with a low overpotential of 0.1 V at 100 mA cm−2, a low Tafel slope of 65.4 mV dec−1. [ABSTRACT FROM AUTHOR]

Exploring effective bi-functional catalysts is of great significance to enhance the electrochemical activity for overall water splitting. To date, Fe 7 S 8 has been rarely reported to realize electrochemical overall water splitting because of its intrinsic poor conductivity. In this paper, Fe 7 S 8 /FeS 2 heterostructured nanosheets with interface structures and defect sites are prepared via a facile hydrothermal method. Fe 7 S 8 /FeS 2 /C electrocatalysts are constructed through the addition of carbon powder to weaken the electron transfer barrier. As expected, Fe 7 S 8 /FeS 2 /C requires the overpotential of 262 mV and 198 mV to reach 10 mA/cm2 toward oxygen evolution reaction and hydrogen evolution reaction, respectively. Moreover, Fe 7 S 8 /FeS 2 /C attains a voltage of 1.67 V at 10 mA/cm2 and maintains long-term stability for 24 h toward overall water splitting in a two-electrode system. The excellent activity can be related to interface structures and surface defect sites, which boost the charge transfer rate owing to the rich active sites. Fe 7 S 8 /FeS 2 /C exhibits the good performance toward overall water splitting due to the heterojunction structures and defect sites. [Display omitted] • Fe 7 S 8 /FeS 2 heterostructured nanosheets are hydrothermally prepared. • Fe 7 S 8 /FeS 2 nanosheets expose interface structures and defect sites. • Fe 7 S 8 /FeS 2 /C exhibits the good performance toward overall water splitting. • The good activity is associated with interface structures and defect sites. [ABSTRACT FROM AUTHOR]

[Display omitted] As a consequence of the depletion of fossil fuels and an increasing population, the global energy crisis has driven researchers to explore innovative energy storage and conversion (ESC) devices, such as fuel cells, electrolyzers and chemical looping systems. In order to enhance the energy conversion efficiency of these electrochemical devices, high performance and stable electrocatalysts are essential to accelerate the sluggish electrochemical kinetics, e.g. oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and redox reaction. In recent years, as cost-effective and high-efficient catalysts, perovskite oxides have attracted much attention. In addition, the potential of perovskite electrocatalysts may be further boosted due to their flexible composition and tunable electronic structures. This review provides the readers with a comprehensive understanding and updated information of improvements towards the electrocatalytic performances of perovskite oxides. It will focus on research papers regarding low to intermediate temperature electrochemical devices, e.g., water splitting, fuel cells, chemical looping technology and three-way catalysis (TWC) published over the last five years. Various design strategies for optimizing the conductivity and catalytic activity of perovskite are discussed in detail. In the end, this review discusses challenges for the future researches in regard to perovskite based electrocatalysts. [ABSTRACT FROM AUTHOR]