Stable Bifunctional Electrocatalysts Research Articles

Fe2P nanoparticles embedded on Ni2P nanosheets as highly efficient and stable bifunctional electrocatalysts for water splitting

• Fe 2 P nanoparticles embedded on Ni 2 P nanosheets has been synthesized. • Fe 2 P/Ni 2 P HS delivers superior catalytic performance for water splitting. • The electron redistribution near heterointerface optimizes the ΔG H* of P sites. • The Fe 2 P/Ni 2 P heterointerface results in abundant active sites. It is urgent to develop highly efficient, stable and low-cost bifunctional electrocatalysts for overall water splitting. Herein, an iron-nickel phosphide (Fe 2 P/Ni 2 P) heterostructure, constructed by Fe 2 P nanoparticles embedded on Ni 2 P nanosheets, is strategically fabricated on nickel foam via a facile process. As a bifunctional electrocatalyst, the Fe 2 P/Ni 2 P heterostructure delivers a very low overpotential of 64 mV (or 185 mV) to reach current density of 10 mA cm −2 for hydrogen (or oxygen) evolution reaction. When simultaneously employed as both the anode and cathode electrodes, it demonstrates an ultralow cell voltage of 1.49 V@10 mA cm −2 for full water splitting with nearly 100% Faradaic efficiency, and superior long-term stability even over 100 h. Density functional theory calculations manifest that a strong heterointerface interaction could cause electron redistribution near the Fe 2 P/Ni 2 P heterointerface and optimize the Δ G H* of P sites, thus enhancing catalytic activity. Additionally, the 3D porous heterostructure is benefit to expose rich active sites and facilitate ion diffusion and gas bubble release, thus promoting the catalytic performance. This work opens up a new strategical approach for rational design of metal phosphide-based heterostructures as highly efficient and stable bifunctional electrocatalysts for water splitting.

Long-range interconnected nanoporous Co/Ni/C composites as bifunctional electrocatalysts for long-life rechargeable zinc-air batteries

Zinc–air batteries are considered to be a promising candidate for use as a sustainable power source, due to their higher energy density and more economical features. However, it is necessary to design efficient and durable electrocatalysts, especially the durability, for bifunctional oxygen reduction (ORR) and oxygen evolution reactions (OER). Therefore, it is imperative to developing reliable zinc-air batteries with long-lasting cycle lifetime. Herein, we report long-range interconnected nanoporous Co/Ni/C composites in µm-length scale as highly active and stable bifunctional electrocatalysts for long-life rechargeable zinc-air batteries. The composite catalysts consist of N and S co-doped hollow carbon and carbon-encapsulated CoNi alloy nanoparticles, which serve as catalytically active sites for the ORR/OER. Meanwhile, the long-range interconnected nanoporous carbon structure in µm-length scale favors fast ion and electron transfer during the reactions, and can prevent the catalyst deterioration against nanoparticles collapse and agglomerate into large ones during the long-term battery operation. As a result, compared to the commercial precious metal-based catalysts, the Co/Ni/C composite catalysts exhibit a significantly improved stability towards the ORR/OER with small activity decay after 100 h/10 h of operation under chronoamperometric polarization. Especially, the resulting zinc-air battery demonstrates remarkable cycling stability exceeding 620 h and 430 h at 5 and 10 mA cm−2, respective.

Interfacing Co3Mo with CoMoOx for synergistically boosting electrocatalytic hydrogen and oxygen evolution reactions

Constructing strong coupling interface of metal and metal oxides is of great significance to design high-efficiency and stable bifunctional electrocatalysts for water splitting. In this work, an integrated electrode comprising of Co3Mo nanoalloys and porous CoO/Co2Mo3O8 hybrid nanosheets (Co3Mo/CoMoOx) was developed via a facile topological transformation by directly annealing of CoMoO4 under H2 atmosphere. This topological transformation endows the resultant Co3Mo/CoMoOx heterostructures with abundant and strong coupling interfaces, which could synergistically strengthen the conductivity of the catalyst and accelerate the charge transfer kinetics. Benefiting from the unique heterostructure and synergy among the different domains, the optimized Co3Mo/CoMoOx exhibits promising HER and OER performance with overpotentials of 26 and 256 mV at 10 mA cm−2, respectively. Furthermore, as-assembled Co3Mo/CoMoOx||Co3Mo/CoMoOx possesses a cell voltage of 1.54 V at 10 mA cm−2 in alkaline solution, which is preferable to many other reported bifunctional catalysts. This work shed a light on the design of efficient integrated bifunctional electrocatalyst by synergistically coupling of CoMo-based alloys with metal oxides.

Electrochemically formed PtFeNi alloy nanoparticles on defective NiFe LDHs with charge transfer for efficient water splitting

Efficient and stable bifunctional electrocatalysts for water splitting is essential for producing hydrogen and alleviating huge energy consumption. Meanwhile, charge transfer engineering is an efficient approach to modulate the localized electronic properties of catalysts and tune the electrocatalytic performance. Herein, we tactfully fabricate PtFeNi alloys/NiFe layered double hydroxides (LDHs) heterostructure by an easily electrochemical way with a small amount of Pt. The experimental and theoretical results unravel that the charge transfer on the alloy clusters modulated by the defective substrates (NiFe LDHs), which synergistically optimizes the adsorption energy of the reaction intermediates. The electrocatalyst exhibits an ultra-low overpotential of 81 and 243 mV at the current density of 100 mA cm−2 for hydrogen evolution and oxygen evolution, respectively. Furthermore, the overall water splitting indicates that PtFeNi alloys/NiFe LDHs presents an ultra-low overpotential of 265 and 406 mV to reach the current density of 10 and 300 mA cm−2, respectively. It proves that the PtFeNi alloys/NiFe LDHs catalyst is an excellent dual-function electrocatalyst for water splitting and promising for industrialization. This work provides a new electrochemical approach to construct the alloy heterostructure. The prepared heterostructures act as an ideal platform to investigate the charge re-distribution behavior and to improve the electrocatalytic activity.

Interface Engineering of Anti-Perovskite Ni3FeN/VN Heterostructure for High-Performance Rechargeable Zinc–Air batteries

High-performance rechargeable zinc–air battery is highly relying on the efficient and stable bifunctional electrocatalysts. Herein, an anti-perovskite Ni3FeN/VN heterostructure encapsulated N–doped graphene (Ni3FeN/VN–NG) was synthesized by a two-step transformation of trimetallic NiFeV–layered double hydroxide. The Ni3FeN/VN–NG showed excellent bifunctional catalytic activity (ΔE = 0.69 V) and stability. The excellent bifunctional electrocatalytic performance is benefited from the extraordinary catalytic behavior of Ni3FeN/VN heterostructure. The intrinsic metallic properties and remarkable superconductivity of anti-perovskite Ni3FeN can enhance the electrocatalytic performance. Density functional theory calculations confirm that the electronic coupling between Ni3FeN and VN facilitates the charge transfer between the two components, simultaneously generates abundant catalytic active sites at the heterogeneous interface. When the Ni3FeN/VN–NG was used as the air cathode, in zinc–air battery, the zinc–air battery exhibits a high-power density of 168 mW cm−2 and a long cycle life of over 200 h.

Hierarchical 3D flower like cobalt hydroxide as an efficient bifunctional electrocatalyst for water splitting

• Transition metal oxide/hydroxides grown on nickel foam (NF) by hydrothermal method. • Co(OH) 2 /NF showed higher OER activity with low overpotential of 230 mV@10 mA cm -2 . • MnO 2 /NF delivered better HER activity with an overpotential of 150 mV@10 mA cm -2 . • The Co(OH) 2 ||Co(OH) 2 electrolyzer demonstrated a cell voltage of 1.61 V@10 mA cm -2 . • The electrolyzer offered an excellent long-term stability of 80 hours@100 mA cm -2 . The development of cost-effective and extremely stable bifunctional electrocatalysts is highly challenging due to the sluggish kinetics of oxygen evolution reaction (OER) compared to hydrogen evolution reaction (HER). So finding a suitable electrocatalyst for the respective OER and HER activity is highly essential. The best OER and HER electrocatalyst demands enhanced kinetics with increased surface area, active sites, and lower charge transfer resistances at the interfaces. Hence, improving the efficiency of an electrocatalyst for bifunctional activity would be advantageous for OWS. Here, we have reported nickel hydroxide (Ni(OH) 2 ), manganese dioxide (MnO 2 ), and cobalt hydroxide (Co(OH) 2 ) self-supported transition metal oxide/hydroxides grown nickel foam (NF) substrate by simple hydrothermal method for overall water splitting (OWS) in alkaline medium. The Co(OH) 2 /NF show a low overpotential of 230 mV for OER, whereas MnO 2 /NF exhibits low overpotential of 150 mV for HER to accomplish a current density of 10 mA cm −2 . Though, MnO 2 exhibits low overpotential for HER, the current density is lower compared to Co(OH) 2 due to lower surface area and conductivity. The full electrolyzer constructed from Co(OH) 2 ||Co(OH) 2 show a lowest cell voltage of 1.61 V and with an anion exchange membrane H-cell delivers a cell voltage of 1.68 V at 10 mA cm −2 in 1M KOH. A long-term stability studies (80 hours) on Co(OH) 2 ||Co(OH) 2 demonstrate robustness of the prepared electrodes and confirms the superior bifunctional electrocatalytic activity to replace the expensive noble metals.

In-situ growth of hierarchical CuO@Cu3P heterostructures with transferable active centers on copper foam substrates as bifunctional electrocatalysts for overall water splitting in alkaline media

To fulfill the growing demand for green H 2 fuels, low-cost, efficient, and stable bifunctional electrocatalysts must be developed. Herein, a hierarchical CuO@Cu 3 P/CF nanowire core-shell heterostructure with transferable active centers was developed for a bifunctional electrocatalyst with high activity. In this system, the transfer of electrochemically active centers between Cu 3 P and CuO is used to facilitate the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. Particularly, Cu 3 P acts as the active center for HER, while the active center shifts to CuO for OER reaction, and Cu 3 P acts as a co-catalyst to improve the conductivity of the system. Benefit from superhydrophilicity's high electrochemical surface area and synergistic effect of CuO core and Cu 3 P shell, and CuO@Cu 3 P/CF shown significant catalytic activity for hydrogen or oxygen evolution, requiring low overpotentials of 144 and 267 mV to achieve a current density of 10 mA cm −2 . In addition, the assembled CuO@Cu 3 P/CF-based electrolyzer exhibit excellent overall water splitting performance with a low operating voltage of 1.75 V at 10 mA cm −2 and a negligible decrease in catalytic activity. This gives encouraging evidence for the utility of our catalysts in application areas. • CuO@Cu 3 P/CF was successfully synthesized via growth-oxidation-phosphidation procedure. • Nanostructured substrate integrated growth ensured good mechanical bonding between CuO@Cu 3 P and CF. • The rough surface and stacked nanosheets make it easy for liquids to penetrate between the nanosheets. • The OER active site is derived from Cu III produced from Cu II after the cathodic oxidation reaction.

Facile Generation of a Stable Bi-Functional Mixed Phase Fe3O4/Fe-N4 Electrocatalyst for Rechargeable Zinc-Air Battery

The successful commercialization of rechargeable zinc-air batteries requires an inexpensive and stable bifunctional oxygen electrocatalyst which can efficiently facilitate both the oxygen reduction reaction (ORR) as well as oxygen evolution reaction (OER). In this paper, we are reporting a simple and effective route to introduce nitrogen functionalities coordinated with Fe to generate ORR active Fe-N4 species. Fe-N-C catalytic sites are known to play an active role towards ORR; however, the higher oxidation state of Fe has been speculated to be good for OER. This method generates a mixture of numerous ORR active and OER active phases. The superior ORR activity of the catalyst, prepared by annealing at 800 °C consists of the mixed phases of Fe-N4, Fe3O4, and Fe3C. The oxygen bifunctional activity measured in terms of ΔE value (1.06 V) makes it suitable for the cathode of an aqueous zinc-air battery. The catalyst remains stable for approximately 63 h of continuous charging-discharging cycles with a high specific capacity of 689 mAh g−1 with a constant charge-discharge voltage gap.

Incorporation of Cu/Ni in Ordered Mesoporous Co-Based Spinels to Facilitate Oxygen Evolution and Reduction Reactions in Alkaline Media and Aprotic Li-O2 Batteries.

Ordered mesoporous CuNiCo oxides were prepared via nanocasting with varied Cu/Ni ratio to establish its impact on the electrochemical performance of the catalysts. Physicochemical properties were determined along with the electrocatalytic activities toward oxygen evolution/reduction reactions (OER/ORR). Combining Cu, Ni, and Co allowed creating active and stable bifunctional electrocatalysts. CuNiCo oxide (Cu/Ni≈1 : 4) exhibited the highest current density of 411 mA cm−2 at 1.7 V vs. reversible hydrogen electrode (RHE) and required the lowest overpotential of 312 mV to reach 10 mA cm−2 in 1 m KOH after 200 cyclic voltammograms. OER measurements were also conducted in the purified 1 m KOH, where CuNiCo oxide (Cu/Ni≈1 : 4) also outperformed NiCo oxide and showed excellent chemical and catalytic stability. For ORR, Cu/Ni incorporation provided higher current density, better kinetics, and facilitated the 4e− pathway of the oxygen reduction reaction. The tests in Li−O2 cells highlighted that CuNiCo oxide can effectively promote ORR and OER at a lower overpotential.

Mo-doping-assisted electrochemical transformation to generate CoFe LDH as the highly efficient electrocatalyst for overall water splitting

Facile preparation of efficient, low-cost, and stable bifunctional electrocatalysts for overall water splitting remains a big challenge. Herein, we successfully synthesized Mo-doped CoFe layered double hydroxides (Mo-doped CoFe LDH/NF) nanosheets by electrochemical transformation of Mo-doped CoFe prussian blue nanocubes on nickel foam (Mo-doped CoFe PBA/NF) for highly efficient overall water splitting. The catalyst exhibits outstanding oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance after electrochemical transformation, which is due to the abundant edge defects of Mo-doped CoFe LDH/NF can expose more active sites. Meanwhile, Mo6+ has a strong electron absorption ability, which could adjust the electronic structure and stabilize the high valence active sites. It only requires a low overpotential for OER (331 mV) and HER (227 mV) to reach 100 mA cm−2 in alkaline media, respectively. Notably, when it was employed as a bifunctional electrode, Mo-doped CoFe LDH/NF displays a low potential of 1.55 V to reach 100 mA cm−2 coupled with long-term water splitting stability in an alkaline electrolyte. This work not only developed a novel method for the synthesis of efficient double-layer hydroxide catalysts, but also paved the way for the rational design of bifunctional electrocatalysts with practical application value.

Bimetal phosphide as high efficiency and stable bifunctional electrocatalysts for hydrogen and oxygen evolution reaction in alkaline solution.

The development of low-cost, high-efficiency, and stable bifunctional electrocatalysts for large-scale water electrolysis is very important for the sustainable development of energy. In this paper, the nickel cobalt phosphide (CoNiP) microstructure was prepared by the “in situ growth-ion exchange-phosphating” method. Due to the flake structure and the synergistic effect of the bimetal, the synthesized CoNiP microstructure exhibited high electrocatalytic activity and stability for hydrogen and oxygen evolution in alkaline electrolyte. The optimized CoNiP showed low overpotential of 116 mV at 10 mA cm−2 for hydrogen evolution reaction and 400 mV at 50 mA cm−2 for oxygen evolution reaction in KOH solution. In addition, it exhibited long-term stability at a high constant current density of 100 mA cm−2 for 48 hours at room temperature and for 65 hours at 80 °C without significant degradation. Theoretical results showed that the introduction of Co and P atoms could reduce the reaction barrier and improve the electron transfer ability. This work provides a simple and economical way for the synthesis of electrocatalytic bimetal phosphide catalysts.

2d B Imetallic Metal-Organic Frameworks as Efficient and Stable Bifunctional Electrocatalysts for W Ater Splitting

2d B Imetallic Metal-Organic Frameworks as Efficient and Stable Bifunctional Electrocatalysts for W Ater Splitting

Bimetallic Ni–Mo nitride@N-doped C as highly active and stable bifunctional electrocatalysts for full water splitting

NiMoN-2 nanosheets were used as bifunctional catalysts and exhibited high total water decomposition activity. Only a cell voltage of 1.58 V was required to attain a current density of 10 mA cm−2.

3D Urchin-like Hierarchical Black TiO2 Hollow Nanospheres: A Highly Active and Stable Electrocatalyst for Water Oxidation in Alkaline and Neutral Media

Highly proficient, earth-abundant, long-term stable bifunctional electrocatalysts are very much desired for overall water splitting reactions. The present paper describes one such stable bifunctional electrocatalyst, 3D hollow nanostructured hierarchical hydrogenated TiO2 (H-TiO2) prepared by low-temperature treatment. The H-TiO2 electrocatalyst can catalyze oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with a low overpotential of 270 and 128 mV at 10 mA cm–2 in alkaline media. Moreover, it exhibits an unusual catalytic activity in neutral electrolyte as well. The corresponding lower Tafel values indicate faster reaction kinetics on the H-TiO2 surfaces. When H-TiO2 is implemented as both the anode and cathode in a two-electrode system for overall water splitting in alkaline and neutral media, it only needs 1.57 and 2.11 V to reach a current density of 10 mA cm–2 and displays good durability for 12 h. The results suggest that Ti3+ and abundant oxygen vacancies in H-TiO2 favor HER and OER, which might originate from the enhanced electrical conductivity and rapid charge transfer rate due to the controlled interplay of the favoring factors. Thus, the present research work demonstrates a promising strategy for developing a highly efficient, stable, and carbon-free substitute for noble metal-based electrocatalysts for the overall water splitting in alkaline and neutral media.

Fluorine Engineered Self-Supported Ultrathin 2D Nickel Hydroxide Nanosheets as Highly Robust and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Urea Oxidation Reactions.

Developing highly efficient noble-metal-free electrocatalysts with a scalable and environmentally friendly synthesis approach remains a challenge in the field of electrocatalytic water splitting. To overcome this problem, self-supported fluorine-modified 2D ultrathin nickel hydroxide (F-Ni(OH)2 ) nanosheets (NSs) for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) are prepared with a scalable and ascendant one-step synthesis route. The enhanced redox activity, electrical conductivity and a great number of exposed active sites of the heterogeneous catalysts improve charge migration for the electrocatalytic reactions. The density of states of the d orbitals of the Ni atoms significantly increases near the Fermi level, thereby indicating that the Ni atoms near the F-dopants promote electrical conduction in the Ni(OH)2 monolayer. The F-Ni(OH)2 electrocatalyst exhibits notable OER and UOR activity with onset potentials of 1.43 and 1.16V versus RHE, respectively required to reach 10mA cm-2 , which are comparable to those of commercial noble-metal-based electrocatalysts. With RuCo-OH nanospheres, the settled F-Ni(OH)2 ||RuCo-OH cell requires merely 1.55 and 1.37V to reach 10mA cm-2 with superb durability for 24 h in overall water and urea electrolysis, respectively. Overall, high-quality, and efficient noble-metal-free electrocatalysts for overall water and urea electrolysis can be prepared with a simple, scalable, and reproducible preparation method.

Defect-rich CoMoS nanosheets on PANI nanowires as excellent hybrid electrocatalyst for water splitting

Developing economic, efficient, and stable bifunctional electrocatalysts for producing oxygen and hydrogen simultaneously remains challenging. Here, we design and fabricate vertically aligned cobalt molybdenum sulfide (CoMoS) nanosheets on a conductive polyaniline (PANI) nanowire on nickel foam (NF) by a one-step solvothermal synthesis. The hybrid CoMoS-PANI array demonstrates low overpotentials of 250 and 98 mV, to achieve a current density of 10 mA cm–2 in an alkaline solution, for the oxygen and hydrogen evolution reactions, respectively. As an electrolyzer for overall water splitting, CoMoS-PANI/NF, as both the anode and the cathode, exhibits a current density of 10 mA cm–2 at a low cell voltage, 1.58 V. Furthermore, good stability for 50 h at a current density of 20 mA cm–2 during overall splitting suggests that CoMoS-PANI can be promoted as a highly efficient and stable bifunctional catalyst. The upgraded electrocatalytic activity of CoMoS-PANI can be ascribed to its defect-rich structure, the exhibition of the PANI nanowire to effective electron transfer, and the ample of active catalytic sites provided by the synergistic effect of the hybrid structures. This work is a promising step towards the design and exploration of hybrid materials as excellent electrocatalysts for renewable energy generation.

In situ produced Co9S8 nanoclusters/Co/Mn-S, N multi-doped 3D porous carbon derived from eriochrome black T as an effective bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Construction of high-efficiency, low cost and stable non-noble metal catalyst on air cathode is of great importance for design and assembly of rechargeable Zn-air battery. Eriochrome black T (EBT) has phenolic hydroxyl and -N=Ν- groups, which provides multiple coordination sites for metal ions. Herein, Co9S8 nanoclusters implanted in Co/Mn-S,N multi-doped porous carbon (Co9S8@Co/Mn-S,N-PC) are fabricated with the mixture (i.e. EBT, metal precursors and dicyandiamide) by a coordination regulated pyrolysis strategy. Specifically, EBT effectively chelates with the Co and Mn ions, resulting in multiple incorporation and fine modulation of the carbon electronic structures. Meanwhile, its sulfonic acid groups are reduced at such high temperature, accompanied by simultaneously embedding S element in the carbon, ultimately in situ forming Co9S8 nanoclusters. The Co9S8@Co/Mn-S,N-PC performs as an effective bifunctional oxygen catalyst, displaying a positive half-wave potential of 0.85 V and a large limiting current density of 5.89 mA cm−2 for oxygen reduction reaction (ORR) in alkaline media, coupled with a small overpotential of 320 mV at 10 mA cm−2 towards oxygen evolution reaction (OER), outperforming commercial Pt/C and RuO2 catalysts, respectively. Furthermore, the assembled rechargeable Zn-air battery with Co9S8@Co/Mn-S,N-PC exhibits the much better charge/discharge performance and long-term durability (210 h, 630 cycles). This research opens an instructive avenue to develop high-efficient and stable bifunctional oxygen electrocatalysts in energy transformation and storage devices.

Robust wrinkled MoS2/N-C bifunctional electrocatalysts interfaced with single Fe atoms for wearable zinc-air batteries

The ability to create highly efficient and stable bifunctional electrocatalysts, capable of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the same electrolyte, represents an important endeavor toward high-performance zinc-air batteries (ZABs). Herein, we report a facile strategy for crafting wrinkled MoS2/N-doped carbon core/shell nanospheres interfaced with single Fe atoms (denoted MoS2@Fe-N-C) as superior ORR/OER bifunctional electrocatalysts for robust wearable ZABs with a high capacity and outstanding cycling stability. Specifically, the highly crumpled MoS2 nanosphere core is wrapped with a layer of single-Fe-atom-impregnated, N-doped carbon shell (i.e., Fe-N-C shell with well-dispersed FeN4 sites). Intriguingly, MoS2@Fe-N-C nanospheres manifest an ORR half-wave potential of 0.84 V and an OER overpotential of 360 mV at 10 mA⋅cm-2 More importantly, density functional theory calculations reveal the lowered energy barriers for both ORR and OER, accounting for marked enhanced catalytic performance of MoS2@Fe-N-C nanospheres. Remarkably, wearable ZABs assembled by capitalizing on MoS2@Fe-N-C nanospheres as an air electrode with an ultralow area loading (i.e., 0.25 mg⋅cm-2) display excellent stability against deformation, high special capacity (i.e., 442 mAh⋅g-1Zn), excellent power density (i.e., 78 mW⋅cm-2) and attractive cycling stability (e.g., 50 cycles at current density of 5 mA⋅cm-2). This study provides a platform to rationally design single-atom-interfaced core/shell bifunctional electrocatalysts for efficient metal-air batteries.

Chrysanthemum-like FeS/Ni3S2 heterostructure nanoarray as a robust bifunctional electrocatalyst for overall water splitting

The development of a scalable strategy to prepare highly efficient and stable bifunctional electrocatalysts is the key to industrial electrocatalytic water splitting cycles to produce clean hydrogen. Here, a simple and quick one-step hydrothermal method was used to successfully fabricate a three-dimensional core chrysanthemum-like FeS/Ni3S2 heterogeneous nanoarray (FeS/Ni3S2@NF) on a porous nickel foam skeleton. Compared with the monomer Ni3S2@NF, the chrysanthemum-like FeS/ Ni3S2@NF heterostructure nanomaterials have improved catalytic performance in alkaline media, showing low overpotentials of 192 mV (η10) and 130 mV (η-10) for OER and HER, respectively. This study attests that integrated interface engineering and precise morphology control are effective strategies for activating the Ni3+/Ni2+ coupling, promoting charge transfer and improving the intrinsic activity of the material to accelerate the OER reaction kinetics and promote the overall water splitting performance. The scheme can be reasonably applied to the design and development of transition metal sulfide-based electrocatalysts to put into industrial practice of electrochemical water oxidation.

Tungsten promoted nickel phosphide nanosheets supported on carbon cloth: An efficient and stable bifunctional electrocatalyst for overall water splitting

It is of great significance to develop a highly active, durable and inexpensive bifunctional electrocatalyst for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we report a tungsten-doped nickel phosphide nanosheets based on carbon cloth (W–Ni2P NS/CC) as an efficient bifunctional catalyst through simple hydrothermal and phosphorization for overall water splitting in 1 M KOH. The W–Ni2P NS/CC exhibits excellent electrochemical performance with low overpotentials for HER (η10 = 71 mV, η50 = 160 mV) and OER (η20 = 307 mV, η50 = 382 mV) in 1 M KOH, as well as superior long-term stability. Moreover, W–Ni2P NS/CC as a bifunctional catalyst reveals remarkable activity with a low voltage of 1.55 V to reach a current density of 20 mA cm−2. This work provides a viable bifunctional catalyst for the overall water splitting.