High-performance Oxygen Evolution Reaction Catalysts Research Articles

Transition metal-doped V-shaped RuO2 103 nanotwins as highly active electrocatalysts for enhanced oxygen evolution in acidic media

Efficient and stable catalysts for the oxygen evolution reaction (OER) in acidic environments are essential for hydrogen production through electrolysis. The paper reported the transition metal-doped RuO2 103 nanotwins (RuO2 103-NTs), as cost-effective and high-performance catalysts for acidic OER. The MRu-VO defect models were constructed by introducing transition metal (Ag, Mn, Fe, Co, Cu, and Zn) doped surfaces. Thereinto, the AgRu-VO doped structure exhibited remarkable OER activity in acidic conditions, achieving a reduced overpotential of 0.37 eV. Furthermore, we investigated the synergistic effect of the Ag and oxygen vacancies (VO) in conjunction with grain boundaries. Above results revealed that an increase in the content of Ag and VO resulted in a decrease in structural stability, leading to a more disordered structure. By analyzing the adsorption energy, energy band center and charge transfer in bimetallic-doped NTs, we observed that the presence of MRu-AgRu-VO (M = Mn, Co, Fe) significantly promotes the positive shift of d band center and the increase of charge transfer. This effect ultimately led to a decrease in the overpotential of the rate-determining step to 0.27 eV, thereby enhancing the intrinsic activity of RuO2.

Highly efficient oxygen evolution catalysts prepared by bacteria Desulfovibrio caledoniensis and Pseudomonas stutzeri based on Ni-Fe foam

Oxygen evolution reaction (OER) has gained increasing attention among researchers due to its significance in energy conversion. However, the sluggish kinetics of the OER present notable challenges. In this work, we present an energy-efficient, cost-effective, widely applicable, and scaled-up biological preparation method to prepare OER catalytic materials with high activity and stability based on bacteria and inexpensive Ni-Fe foam under mild conditions. Anaerobic sulfate-reducing bacterium Desulfovibrio caledoniensis and aerobic Pseudomonas stutzeri are the typical microorganisms and the OER performance of their products is not clear. Electrochemical measurements show that the catalyst prepared via D. caledoniensis exhibits a low overpotential of only 247 mV to achieve 10 mA cm−2 and a low Tafel slope of 46 mV dec-1, while the catalyst prepared via P. stutzeri has an overpotential and Tafel slope of 259 mV and 71 mV dec-1, respectively. Therefore, these catalysts exhibit excellent catalytic activities. Furthermore, they have a good stability of more than 40 h at 10 mA cm−2 which is far superior to that of the majority of reported NiFe-based OER catalysts. This work shows new insights into the preparation and development of high-performance OER catalysts in mild conditions.

(Digital Presentation) The Effects of Sulfur-Oxygen Ratio at the Heterogeneous Interface on Oxygen Evolution Reaction Performance of Ni3S2@Ni3Fe Catalysts for Alkaline Water Electrolysis

Alkaline water electrolysis is the important pathway for the green hydrogen generation, where oxygen evolution reaction (OER) kinetics is limited due to the sluggish proton-coupled electron transfer in the four-electron reaction. It’s very important for the design of high-performance OER catalysts in order to improve its kinetics performance. Here, porous heterogeneous Ni3S2@Ni3Fe catalysts are prepared on nickel mesh (NM) by the electrodeposition process. Oxygen atoms are introduced into Ni3S2 by the vulcanization processes, and different S-O atom ratios are adjusted by varying vulcanization temperature. The influence of S-O ratio at heterogeneous interface on OER performance of Ni3S2@Ni3Fe is systematacially investigated. The results indicate that high S-O ratio improves the OER performance of Ni3S2-xOx@Ni3Fe, which is attributed to H2O adsorption ability enhancement on Ni3Fe surface due to the formation of unique heterogeneous electronic structure by density function theory (DFT) calculation analysis. The prepared NM/Ni3S2-xOx@Ni3Fe (vulcanization temperature at 300 oC) electrode exhibits the improved OER performance in 30 wt% KOH solutions at high current density up to 1000 mA cm-2. It provides the guidance for the design of high-performance Ni3S2-based heterogeneous catalysts by introducing oxygen atom and increasing the sulfur-oxygen ratio. Figure 1

Strain Engineering of the NiTe/Ni2P Heterostructure to Boost the Oxygen Evolution Reaction.

Discovering highly efficient and stable non-precious metal catalysts for the oxygen evolution reaction (OER) is crucial for energy conversion in water splitting. However, preparing high-performance OER catalysts and elucidating the structural changes in the process are still challenging. Herein, we synthesize the NiTe/Ni2P heterostructure and demonstrate the strain engineering of NiTe/Ni2P via the lattice incompatibility between the phosphide and the telluride. The strain engineering of the NiTe/Ni2P heterostructure not only significantly boosts the OER activity but also effectively stabilizes the intrinsic structure of the catalyst after the OER process by using the in situ-produced metal salt as a protection layer. After the OER stability test, no oxyhydroxide phase is observed, and in situ Raman spectroscopy reveals that a voltage-dependent phase transition appears during the OER, which is different from most previously reported Ni-based catalysts, for which the generation of irreversible NiOOH occurs after the OER. Density functional theory calculations further reveal that the tensile strain of Ni2P will inhibit the presence of irreversible phase transitions of Ni2P into NiOOH due to the weak adsorption ability of the oxygen species caused by strain engineering. In short, this work opens a new gate for using strain nanotechnology to design high-performance OER catalysts.

Electronic Structure Modulation of Fe-N4-C for Oxygen Evolution Reaction via Transition Metal Dopants and Axial Ligands.

The popular single-atom catalyst (SAC) Fe-N4 is generally believed to be an excellent oxygen reduction reaction (ORR) electrocatalyst, which is less active in the oxygen evolution reaction (OER). Herein, FeM-N6 configuration catalysts (M = Fe, Co, Ni, Cu, Ag, and Au) were constructed for the oxygen evolution reaction by embedding M dopants on Fe-N4 systems based on the density functional theory. The electronic structure analysis reveals that the Fe-M metal interactions play dominant roles in regulating the d orbital distributions of Fe sites, which in turn alter the catalytic OER performance. Subsequent thermodynamic results indicate that the potential-determining step (PDS) for all catalysts is the formation of OOH*, which exhibits a tendency of decreased overpotentials with enhanced metal interactions. Apart from these, the effects of axial ligands on the OER activity of the catalysts in practical conditions were considered. Generally, most of the axial ligands are found to be thermodynamically favorable for the OER process. Interestingly, a competitive relationship of the electrons from the d orbital of Fe sites was found between the axial ligand and the adsorbed intermediate species during the reaction, which raises the energy barrier for OH* to O* conversion and can even alter the PDS in certain cases. The present work sheds new light on the design of future high-performance OER catalysts.

One-step preparation of anti-ferromagnetic single-atom nickel to improve oxygen evolution reaction of photoelectrochemical water splitting

Noble metal single-atom catalysts (SACs) have been extensively investigated due to their unique electronic structure and high-efficiency catalytic performance. However, there are relatively few studies on the preparation of non-noble metal single atoms and their application in oxygen evolution reaction (OER). In this paper, nickel single-atom catalyst was prepared using a facile one pot method. Ni-SAC-2.5% showed uniform SACs distribution and anti-ferromagnetic property as evidenced by the aberration-corrected high resolution electron microscopy and the first-principle calculations, achieving the lowest overpotential of 220 mV (10 mA/cm2) and stable performance in 1 M KOH solution. Meanwhile, it exhibited the largest specific capacitance value of 1.77 mF/cm2 and the lowest charge transfer resistance value of 40.75 Ω due to the accelerated kinetic process. First-principle calculations further confirmed the lowest computed overpotential of 0.54 eV for Ni-SAC-2.5%. However, Ni small clusters and nanoclusters with superparamagnetic performance were observed when the Ni content was further increased to 3.5% and 4.5%, resulting in higher overpotentials of 0.85 eV and 2.01 eV for OER process as indicated by the theoretical simulation. This paper provides a facile method to prepare non-noble metal SACs and useful guidance for designing high performance OER catalysts.

In Situ Synthesis of NiFeLDH/A-CBp from Pyrolytic Carbon as High-Performance Oxygen Evolution Reaction Catalyst for Water Splitting and Zinc Hydrometallurgy.

Nickel-iron-layered double hydroxide (NiFeLDH) is one of the promising catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes, but its conductivity limits its large-scale application. The focus of current work is to explore low-cost, conductive substrates for large-scale production and combine them with NiFeLDH to improve its conductivity. In this work, purified and activated pyrolytic carbon black (CBp) is combined with NiFeLDH to form an NiFeLDH/A-CBp catalyst for OER. CBp not only improves the conductivity of the catalyst but also greatly reduces the size of NiFeLDH nanosheets to increase the activated surface area. In addition, ascorbic acid (AA) is introduced to enhance the coupling between NiFeLDH and A-CBp, which can be evidenced by the increase of Fe-O-Ni peak intensity in FTIR measurement. Thus, a lower overvoltage of 227 mV and larger active surface area of 43.26 mF·cm-2 are achieved in 1 M KOH solution for NiFeLDH/A-CBp. In addition, NiFeLDH/A-CBp shows good catalytic performance and stability as the anode catalyst for water splitting and Zn electrowinning in alkaline electrolytes. In Zn electrowinning with NiFeLDH/A-CBp, the low cell voltage of 2.08 V at 1000 A·m-2 results in lower energy consumption of 1.78 kW h/KgZn, which is nearly half of the 3.40 kW h/KgZn of industrial electrowinning. This work demonstrates the new application of high-value-added CBp in hydrogen production from electrolytic water and zinc hydrometallurgy to realize the recycling of waste carbon resources and reduce the consumption of fossil resources.

Trace Lattice S Inserted RuO2 Flexible Nanosheets for Efficient and Long-Term Acidic Oxygen Evolution Catalysis.

Pursuing highly active and long-term stable ruthenium (Ru) based oxygen evolution reaction (OER) catalyst for water electrolysis under acidic conditions is of great significance yet a tremendous challenge to date. To solve the problem of serious Ru corrosion in an acid medium, the trace lattice sulfur (S) inserted RuO2 catalyst is prepared. The optimized catalyst (Ru/S NSs-400) has shown a record stability of 600 h for the solely containing Ru (iridium-free) nanomaterials. In the practical proton exchange membrane device, the Ru/S NSs-400 can even sustain more than 300 h without obvious decay at the high current density of 250mA cm-2 . The detailed investigations reveal that S doping not only changes the electronic structure of Ru via forming RuS coordination for high adsorption of reaction intermediates but also stabilizes Ru from over-oxidation. This strategy is also effective for improving the stability of commercial Ru/C and homemade Ru-based nanoparticles. This work offers a highly effective strategy to design high-performance OER catalysts for water splitting and beyond.

(Digital Presentation) The Effects of Sulfur-Oxygen Ratio at the Heterogeneous Interface on Oxygen Evolution Reaction Performance of Ni3S2@Ni3Fe Catalysts for Alkaline Water Electrolysis

Alkaline water electrolysis is the important pathway for the green hydrogen generation, where oxygen evolution reaction (OER) kinetics is limited due to the sluggish proton-coupled electron transfer in the four-electron reaction. It’s very important for the design of high-performance OER catalysts in order to improve its kinetics performance. Here, porous heterogeneous Ni3S2@Ni3Fe catalysts are prepared on nickel mesh (NM) by the electrodeposition process. Oxygen atoms are introduced into Ni3S2 by the vulcanization processes, and different S-O atom ratios are adjusted by varying vulcanization temperature. The influence of S-O ratio at heterogeneous interface on OER performance of Ni3S2@Ni3Fe is systematacially investigated. The results indicate that high S-O ratio improves the OER performance of Ni3S2-xOx@Ni3Fe, which is attributed to H2O adsorption ability enhancement on Ni3Fe surface due to the formation of unique heterogeneous electronic structure by density functional theory (DFT) calculation analysis. The prepared NM/Ni3S2-xOx@Ni3Fe (vulcanization temperature at 300 oC) electrode exhibits the improved OER performance in 30 wt% KOH solutions at high current density up to 1000 mA cm-2. It provides the guidance for the design of high-performance Ni3S2-based heterogeneous catalysts by introducing oxygen atom and increasing the sulfur-oxygen ratio.

C+ ion implanted single crystal diamond with amorphous surface for efficient oxygen evolution catalysis

Oxygen evolution reaction (OER) is critical in water splitting for green hydrogen gas production due to its sluggish kinetics; however, commercial OER catalysts commonly suffer from high cost, low catalytic activity and poor stability. Herein, we developed a C+ ion implantation method to modify single crystal diamond, and the resultant surface amorphous layer not only raised the active site number but also increased the content of the C=O group, thus significantly improving the OER activity. The C+ ion implanted high-temperature and high-pressure (C+-HTHP) and chemical vapor deposition (C+-CVD) diamonds both exhibit low OER overpotential with η10 of 317 mV and 325 mV respectively, superior to those of HTHP diamond (360 mV), CVD diamond (395 mV) and RuO2 (364 mV). The potentiostatic testing shows that the C+ implanted diamonds almost didn't undergo the rise of OER overpotential upon catalysis for more than 12 h at a current density of 10 mA cm−2, suggesting a high catalytic stability, owing to the strong bonding between single crystal diamond and amorphous carbon layer. For the first time, we utilized carbon ion implantation to prepare diamond-based high-performance OER catalyst, which broadens the understanding of carbon-based materials in OER catalysis.

Transfer learning aided high-throughput computational design of oxygen evolution reaction catalysts in acid conditions

Sluggish oxygen evolution reaction (OER) in acid conditions is one of the bottlenecks that prevent the wide adoption of proton exchange membrane water electrolyzer for green hydrogen production. Despite recent advancements in developing high-performance catalysts for acid OER, the current electrocatalysts still rely on iridium- and ruthenium-based materials, urging continuous efforts to discover better performance catalysts as well as reduce the usage of noble metals. Pyrochlore structured oxide is a family of potential high-performance acid OER catalysts with a flexible compositional space to tune the electrochemical capabilities. However, exploring the large composition space of pyrochlore compounds demands an imperative approach to enable efficient screening. Here we present a high-throughput screening pipeline that integrates density functional theory calculations and a transfer learning approach to predict the critical properties of pyrochlore compounds. The high-throughput screening recommends three sets of candidates for potential acid OER applications, totaling 61 candidates from 6912 pyrochlore compounds. In addition to 3d-transition metals, p-block metals are identified as promising dopants to improve the catalytic activity of pyrochlore oxides. This work demonstrates not only an efficient approach for finding suitable pyrochlores towards acid OER but also suggests the great compositional flexibility of pyrochlore compounds to be considered as a new materials platform for a variety of applications.

Bi-Phase NiCo2S4-NiS2/CFP Nanocomposites as a Highly Active Catalyst for Oxygen Evolution Reaction

Pursuing oxygen evolution reaction (OER) catalysts with high activity and stability is attracting many researchers. Here, we first designed and synthesized a biphasic three-dimensional structured catalyst of nickel–cobalt sulfide NiCo2S4-NiS2/CFP, which is a nickel–cobalt sulfide composite decorated on carbon fiber paper (CFP) by a one-step hydrothermal method. It exhibited an overpotential of about 165 mV at a current density of 10 mA cm−2 and a small Tafel slope of 81.54 mV dec−1. Furthermore, the long-term stability of the NiCo2S4-NiS2/CFP nanocomposite was 90.0% of the initial current density even after 12 h. The excellent catalytic performance of the NiCo2S4-NiS2/CFP nanocomposite can be attributed to several aspects. Firstly, the petal-like morphology of the NiCo2S4-NiS2 nanocomposite exposes more active sites. Secondly, the stability of the composite catalyst is significantly enhanced by its firm anchoring on the CFP. Thirdly, the catalytic performance was significantly improved by the addition of mixed valence of Ni or Co on the {111} plane of spinel NiCo2S4. Finally, the three-dimensional CFP substrate provides an efficient pathway and a stable integrated structure for the transmission of electrons and ions. Our one-step hydrothermal synthesis method provides a simple and economical way to obtain high-performance and robust OER catalysts.

Operando spectroscopies capturing surface reconstruction and interfacial electronic regulation by FeOOH@Fe2O3@Ni(OH)2 heterostructures for robust oxygen evolution reaction

Developing high-performance and low-cost electrocatalysts for oxygen evolution reaction (OER) and understanding the phase evolution in the catalytic process are vital to improving the overall efficiency of electrochemical water splitting. Herein, a hybrid heterogeneous FeOOH@Fe2O3@Ni(OH)2 electrocatalyst with robust OER intrinsic activity and a low overpotential of 269 mV to obtain a current density of 100 mA cm−2 and a Tafel slope value of 60.15 mV dec−1 is effectively prepared. The dynamic surface evolution has been detected by in-situ Raman spectroscopy, which exposes that FeOOH@Fe2O3@Ni(OH)2 is reconstituted as Ni(Fe)OOH demonstrated as catalytically active species under high potential. X-ray photoelectron spectroscopy analysis indicates that partial electrons of Ni in the heterogeneous interface transfer to Fe. Furthermore, partial Fe doping of NiOOH under high potential accompanied by the oxidized Ni3+ with optimized d-orbit electronic configuration for nearly unity eg occupancy results in proper chemisorption bonding strength for oxygen reaction intermediates and is conducive to enhancing OER reaction kinetics. This work provides ideas that multicomponent heterostructure can adjust the electronic structure of iron and nickel to enhance the intrinsic activity of OER, which could help with the design and synthesis of high-performance OER catalysts used in energy storage and conversion.

Embedding Group VIII Elements into a 2D Rigid pc-C3N2 Monolayer to Achieve Single-Atom Catalysts with Excellent OER Activity: A DFT Theoretical Study

Under DFT calculations, a systematic investigation is carried out to explore the structures and oxygen evolution reaction (OER) catalytic activities of a series of 2D single-atom catalyst (SAC) systems, which are constructed by doping the transition metal (TM) atoms in group VIII into the cavities of rigid phthalocyanine carbide (pc-C3N2). We can find that when Co, Rh, Ir and Ru atoms are doped in the small or large cavities of a pc-C3N2 monolayer, they can be used as high-activity centers of OER. All these four new TM@C3N2 nanostructures can exhibit very low overpotential values in the range of 0.33~0.48 V, even smaller than the state-of-the-art IrO2 (0.56 V), which indicates considerably high OER catalytic activity. In particular, the Rh@C3N2 system can show the best OER performance, given that doped Rh atoms can uniformly serve as high-OER-active centers, regardless of the size of cavity. In addition, a detailed mechanism analysis was carried out. It is found that in these doped pc-C3N2 systems, the number of outer electrons, the periodic number of doped TM atoms and the size of the embedded cavity can be considered the key factors affecting the OER catalytic activity, and excellent OER catalytic performance can be achieved through their effective cooperation. These fascinating findings can be advantageous for realizing low-cost and high-performance SAC catalysts for OER in the near future.

Ultra-low palladium engineered nickel sulfide heterostructure supported on 3D nickel foam as a highly efficient and stable electrocatalyst for water oxidation

• 0.1PdNiS/NF requires only 275 mV overpotential to achieve a current density of 10 mAcm -2 , which is less than NiS/NF (385 mV) and commercial RuO 2 /NF (370 mV). • The Tafel slope of 0.1PdNiS/NF (65 mVdec -1 ) is lower than NiS/NF (132 mVdec -1 ) and commercial RuO 2 /NF. • 0.1PdNiS/NF demonstrated exceptional durability for approximately 14 hours at 10 mAcm -2 . • TOF of 0.1PdNiS was calculated to be 1.31 s -1 at an overpotential of 320 mV, which is greater than the NiS/NF (0.5 s -1 ). Electrochemical water splitting (EWS) has been a crucial process in the production of green fuels (oxygen and hydrogen) for a sustainable energy economy. One of the key processes in the EWS is water oxidation or the oxygen evolution reaction (OER). It is highly desirable to create cost-effective, efficient, and robust electrocatalysts for OER. Here, we present ultra-low Pd doped NiS-NiS 2 heterostructure on NF (0.1PdNiS/NF) grown in-situ by acid etching followed by a simple hydrothermal sulfurization method for excellent OER electrocatalytic activity in alkaline media. Interestingly, low overpotential of 275 mV is required for the 0.1PdNiS/NF to achieve a current density of 10 mAcm -2 , which is less than both NiS/NF (385 mV) and commercial RuO 2 /NF (370 mV). Because of the strong electronic interaction between Pd and NiS, 0.1PdNiS/NF has a small Tafel slope of 65 mV/dec and has shown excellent durability for approximately 14h. Therefore, the findings described above provide significant insights in the design of high-performance OER catalysts with ultra-low precious metal loading.

Interface engineering of iron-doped multiphase nickel hydroxide as an effective electrocatalyst for oxygen evolution reaction

The exploration of catalysts for oxygen evolution reaction (OER) using the advantages of interface engineering is an attractive strategy for achieving highly efficient electrochemical water splitting. In this study, Fe-doped multiphase nickel hydroxide (Fe-α,β-Ni(OH)2) was successfully prepared with a unique interface by modulating the Fe2+ and Fe3+ ratios in a feasible one-step hydrothermal process. This multiphase catalyst powder significantly contributed to the OER performance, with a low overpotential of 259 mV at 10 mA cm−2 (grown on carbon cloth substrates, 260 mV at 100 mA cm−2) and excellent catalytic stability during the 70-h OER process under extreme conditions. Based on the experimental and theoretical results, the unique interface between the Fe-α-Ni(OH)2 and Fe-β-Ni(OH)2 phases optimized the adsorption free energies of oxygen-containing intermediates and accelerated the formation of Ni3+ active species during the OER, leading to a large electrochemically active surface area (ECSA), which considerably enhanced the OER performance. This study provides novel insight into interface engineering and the design of high-performance OER catalysts based on earth-abundant transition-metal elements.

Anomalous Ru dissolution enabling efficient integrated CO2 electroreduction in strong acid

Recently, emerging acidic conditions CO2 electrolyzer overcomes the limitations of lower carbon utilization efficiency due to carbonate/bicarbonate formation in neutral/alkaline media, which offers a promising route to the realization of carbon cycle and environment optimization. Nevertheless, an integral CO2 conversion electrolyzer must consider the sluggish reaction kinetics of the oxygen evolution reaction (OER), especially in acid media. Herein, we demonstrate a significant improvement in anodic OER performance by tailoring the surface structure of RuO2 catalyst with potassium. The obtained K-RuO2 electrocatalyst can reach 10 mA/cm2 only with an overpotential of 170 mV and exhibits prolonged stability, showing overwhelming catalytic performance compared to RuO2. Advanced synchrotron radiation-based multi-techniques (SRMS) and theory calculations demonstrate the remarkable performance originating from the anomalous dissolution, which caused by consciously initiated K generating enhanced ratio of active RuCUS sites for K-RuO2. When K-RuO2 pairs with cathodic CO2RR catalyst of bismuth, it achieves the result of lower cell voltage and nearly 4-fold longer durability in strong acid compared to RuO2 catalyst. This work provides a deep insight into the true active structure of anode RuO2 catalyst, paves a new way to design high-performance noble metal-based catalysts for acidic OER, and finally contributes to the advancement of CO2 electrolysis.

Fabrication of NiFe-MOF/cobalt carbonate hydroxide hydrate heterostructure for a high-performance electrocatalyst of oxygen evolution reaction

Metal-organic frameworks (MOFs) have been widely investigated as electrocatalysts for the oxygen evolution reaction (OER). However, their catalytic performance needs to be further improved. Herein, a multi-pronged approach combining multi-metallic MOFs, 2D ultrathin structures and MOF hybridization was attempted. Specifically, the nanocomposite of lamellar NiFe-BTC and nanowire-like cobalt carbonate hydroxide hydrate (CCHH) was prepared on nickel foam (NF) by a two-step method. The as-prepared NiFe-BTC/CCHH/NF nanocomposite displayed excellent OER performance with an overpotential of 270 mV at a current density of 50 mA cm −2 and good stability in 1.0 M KOH. To construct an overall water splitting electrolytic cell, the phosphorization product of CCHH/NF (P-CCHH/NF) with high catalytic activity for hydrogen evolution reaction (HER) was used as the cathode. The water splitting electrolytic cell with NiFe-BTC/CCHH/NF as anode and P-CCHH/NF as cathode was highly efficient and stable, which only needed a voltage of 1.55 V to reach a current density of 10 mA cm −2 . This multi-pronged approach is expected to inspire other researchers to design high-performance OER catalysts. • The NiFe-BTC and CCHH heterostructure was first fabricated on NF based on a multi-pronged design concept. • The NiFe-BTC/CCHH/NF displayed superior OER performance with an overpotential of 270 mV at 50 mA cm −2 and good stability. • The CCHH/NF after phosphorization (P-CCHH/NF) showed high HER activity with a η 10 of 60 mV. • The overall water splitting electrolytic cell with P-CCHH/NF//NiFe-BTC/CCHH/NF only needed a voltage of 1.55 V at 10 mA cm −2 .

Ultra-fast surface reconstruction enabled by the built-in electric field in heterostructured CoS2/CuS for water electrolysis

Transition-metal chalcogenides (TMCs) show great potential as highly efficient and cost-effective electrocatalysts for oxygen evolution reaction (OER). Yet the electrochemical conversion into oxides/hydroxides remains poorly understood. In this work, we develop a built-in, electric-field-induced surface reconstruction strategy for ultra-fast self-activation of transition metal sites in self-supporting CoS 2 /CuS heterostructures. The activated CoS 2 /CuS grown on carbon cloth with oxygenated surface species displays an outstanding OER electrocatalytic activity with ultra-low overpotentials of only 136 mV at the current density of 10 mA cm −2 and 266 mV at 100 mA cm −2 in 1.0 M KOH. Comparative studies via synchrotron radiation X-ray absorption spectroscopy and theoretical calculations are employed to elucidate that the built-in electric field within heterointerfaces significantly promotes the reconstruction efficiency by decreasing the formation energy of (oxy)hydroxide species. We believe this work provides new perspectives to conceive catalysts with ultra-low overpotentials and complements the fundamental comprehension of TMCs’ self-reconstruction mechanism. • The nature of metallic site reconstruction upon OER is revealed via combined XAS and DFT • A simplified reconstruction process enabled by the built-in electric field of CoS 2 /CuS • The self-standing electrode shows practical potential for overall water electrolysis A comprehensive perception of the structural transformation and reconstruction of metallic surface sites upon the OER process is essential for the rational design of high-performance OER catalysts. To simplify the energy-consuming activation process and achieve rapid reconstruction, Man et al. report a built-in electric field strategy for modulating surface dynamics of heterostructured CoS 2 /CuS.

The design and synthesis of Fe doped flower-like NiS/NiS2 catalyst with enhanced oxygen evolution reaction

• A cheap Fe doped flower-like NiS/NiS 2 catalyst for OER is designed and synthesized. • Fe doping regulates the phase composition, heterogeneous interface and OER activity. • Fe-NiS/NiS 2 catalyst demonstrates excellent OER performance, exceeding RuO 2 and NiS 2 . Exploring low-cost and high-activity transition metal-based electrocatalysts for oxygen evolution reaction (OER) is critical toward mass hydrogen generation by water splitting. Herein, a cheap Fe element doped flower-like nickel sulfides catalyst (Fe-NiS/NiS 2 ) is designed and synthesized through facile electrostatic adsorption and sulfuration methods. It is investigated that the Fe doping effectively induces the lattice contraction of nickel sulfides and regulates the phase composition and heterogeneous interfaces, thus enabling high intrinsic OER activity. The Fe-NiS/NiS 2 catalyst shows a high electrochemically active surface area of 150 cm 2 , a small overpotential of 361 mV at 100 mA cm −2 and a low Tafel slope of 61.5 mV dec -1 . Furthermore, the Fe-NiS/NiS 2 exhibits a very excellent structure and performance stability without current attenuation for 24 h at 1.50 V versus reversible hydrogen electrode. This work provides an important insight for the exploitation of low-cost and high-performance OER catalysts with cheap Fe element doping metal sulfides.