Stability For Overall Water Splitting Research Articles

Enriched edge sites of ultrathin Ni3S2/NiO nanomeshes promote surface reconstruction for robust electrochemical water splitting

Developing highly efficient nonnoble bifunctional electrocatalysts for both the H2 evolution reaction (HER) and O2 evolution reaction (OER) is essential but challenging for overall water splitting (OWS). Ni based catalysts are proved as promising candidates for water splitting, which usually undergo surface reconstruction by transforming into nickel oxyhydroxides as active sites. Although evidence suggests that the reconstruction originates from the exchange of surface lattice oxygen with the OH- in the electrolyte under electric field, modulating the reconstruction of Ni based catalysts remains a great challenge. Herein, we propose an edge sites enrichment strategy to promote the active phase evolution. The one-step synthesized ultrathin Ni3S2/NiO nanomeshes exhibited an ultrathin porous structure which contain abundant edge sites and Ni3S2/NiO in-plane interface sites. Owing to the unique structure, Ni3S2/NiO nanomeshes possessed an affinity feature to proton and OH-, resulting in a faster reconstruction from Ni3S2 to Ni(OH)2 than Ni3S2 bulk which subsequently converted into γ-NiOOH and a lower adsorption barrier for H*. Consequently, the Ni3S2/NiO nanomeshes exhibited outstanding OER activity (300 mV at 200 mA cm−2) and unexpected HER activity (73 mV at 10 mA cm−2) in 1.0 M KOH. Remarkably, the nanomeshes achieved an ultralow voltage of 1.41 V at 10 mA cm−2 with excellent stability for overall water splitting, which prevailed over most of the reported catalysts. Moreover, the nanomeshes performed a H2 yield of 900 µmol/h in a solar-assisted water splitting system with a H2 minimum sales price of $1.77/kg, much lower than that of the commercial catalyst ($7.18/kg). This work sets a new benchmark of monometallic bifunctional catalysts for industrial water splitting and provides new insights into the synthesis of 2D nanomeshes.

Interface Engineering via Ti3C2Tx MXene Enabled Highly Efficient Bifunctional NiCoP Array Catalysts for Alkaline Water Splitting.

Developing a non-noble metal-based bifunctional electrocatalyst with high efficiency and stability for overall water splitting is desirable for renewable energy systems. We developed a novel method to fabricate a heterostructured electrocatalyst, comprising a NiCoP nanoneedle array grown on Ti3C2Tx MXene-coated Ni foam (NCP-MX/NF) using a dip-coating hydrothermal method, followed by phosphorization. Due to the abundance of active sites, enhanced electronic kinetics, and sufficient electrolyte accessibility resulting from the synergistic effects of NCP and MXene, NCP-MX/NF bifunctional alkaline catalysts afford superb electrocatalytic performance, with a low overpotential (72 mV at 10 mA cm-2 for HER and 303 mV at 50 mA cm-2 for OER), a low Tafel slope (49.2 mV dec-1 for HER and 69.5 mV dec-1 for OER), and long-term stability. Moreover, the overall water splitting performance of NCP-MX/NF, which requires potentials as low as 1.54 and 1.76 V at a current density of 10 and 50 mA cm-2, respectively, exceeded the performance of the Pt/C∥IrO2 couple in terms of overall water splitting. Density functional theory (DFT) calculations for the NCP/Ti3C2O2 interface model predicted the catalytic contribution to interfacial formation by analyzing the electronic redistribution at the interface. This contribution was also evaluated by calculating the adsorption energetics of the descriptor molecules (H2O and the H and OER intermediates).

Interface engineering of hierarchical flower-like N, P, O-doped NixPy self-supported electrodes for highly efficient water-to-hydrogen fuel/oxygen conversion

Rational construction of efficient bifunctional catalysts with robust catalytic activity and durability is significant for overall water splitting (conversion between water and hydrogen fuel/oxygen) using non-precious metal systems. In this work, the hierarchically porous N, P, O-doped transition metal phosphate in the Ni foam (NF) electrode (hollow flower-like NPO/NixPy@NF) was prepared through facile hydrothermal method coupled with phosphorization treatment. The hierarchical hollow flower-like NPO/NixPy@NF electrodes exhibited high bifunctional activity and stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solutions. The optimized electrode showed low overpotentials of 76 and 240 mV for HER and OER to reach a current density of 10 mA cm−2, respectively. Notably, the NPO/NixPy@NF electrode only required a low voltage of 1.99 V to reach the current densities of 100 mA cm−2 with long-term stability for overall water splitting using the NPO/NixPy@NF|| NPO/NixPy@NF cell, surpassing that of the Pt/C-RuO2 (2.24 V@ 100 mA cm−2). The good catalytic and battery performance should be attributed to i) the open hierarchical structure that enhanced the mass transfer; ii) a highly conductive substrate that accelerated the electron transfer; iii) the rich heterojunction and strong synergy between Ni2P and Ni5P4 that improved the catalytic kinetic; iv) the proper-thickness amorphous phosphorus oxide nitride (PON) shell that realized the stability. This work demonstrates a promising methodology for designing bifunctional transition metal phosphides with high performance for efficient water splitting.

Ammonia-assisted Ni particle preferential deposition in Ni-Fe pyrophosphates on iron foam to improve the catalytic performance for overall water splitting

Designing efficient and cost-effective electrocatalysts for overall water splitting remains a major challenge in hydrogen production. Herein, ammonia was introduced to pyrophosphate chelating solution assisted Ni particles preferential plating on porous Fe substrate to form coral-like Ni/NiFe-Pyro electrode. The pyrophosphate with multiple complex sites can couple with nickel and iron ions to form an integrated network structure, which also consists of metallic nickel due to the introduction of ammonia. The large network structure in Ni/NiFe-Pyro significantly enhances the synergistic effect between nickel and iron and then improves the electrocatalytic performance. As a result, the coral-like Ni/NiFe-Pyro@IF exhibits good electrocatalytic activity and stability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The electrolyzer assembled with Ni/NiFe-Pyro@IF as cathode and anode just needs a low water-splitting voltage of 1.54 V to obtain the current density of 10 mA cm−2. Meanwhile, the stability test of Ni/NiFe-Pyro@IF is performed at the current densities ranging from 10 to 400 mA cm−2 for 50 h without any significant decay, indicating robust catalytic stability for overall water splitting. This strategy for synthesizing metal/metal pyrophosphate composites may provide a new avenue for future studies of efficient bifunctional electrocatalysts.

A Au nanoparticle anchored stannatranone-pillared MOF as a duo-active electrocatalyst for overall water splitting

The design and construction of a duo-active electrocatalyst with effective performance and enhanced stability for overall water splitting.

Self-supporting hierarchical Co3O4-nanowires@NiO-nanosheets core-shell nanostructure on carbon foam to form efficient bifunctional electrocatalyst for overall water splitting

Designing cost-effective and robust bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desired in hydrogen production from overall water splitting, but still suffers great challenges due to the sluggish catalytic OER/HER kinetics. In this paper, a surface/defect engineering strategy is developed to synthesize three-dimensional (3D) carbon foam (CF)-supported unique hierarchical Co3O4 nanowires@NiO nanosheets core–shell nanostructured catalyst (NiO@Co3O4/CF) with rich oxygen-vacancies as a novel bifunctional catalyst for alkaline water splitting electrolysis. Benefited from the synergy of the 3D hierarchical core–shell structure and rich oxygen vacancies, the as-obtained NiO@Co3O4/CF shows both excellent OER (η200 = 325 mV, η500 = 374 mV) and HER (η10 = 104 mV) activities with low Tafel slopes (64.26 mV dec−1 for OER and 109.14 mV dec−1 for HER, respectively) and outstanding stability. A simple overall water splitting electrolysis cell assembled by this bifunctional NiO@Co3O4/CF as both OER and HER catalysts requires only a cell voltage of 1.53 V to obtain the current density of 10 mA cm−2 and displays a long-term stability. This work has successfully developed an approach for rational design and novel synthesis of metal oxide hybrids as bifunctional electrocatalysts with high activity and stability for overall water splitting.

Microwave synthesis of NiMn2O4/Ni-foam: Efficient bifunctional electrocatalysts for overall water splitting

The development of efficient and earth-abundant electrocatalysts for water splitting is necessary and crucial. In this study, NiMn2O4 nanosheets and nanosphericals were grown on Ni foam by microwave synthesis at 150 °C and 175 °C and the corresponding synthesized materials were referred to as NIM-150 and NIM-175, respectively. These materials were subsequently used as bifunctional electrocatalysts for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting. The NIM-175 electrocatalyst showed a lower overpotential of 250 mV for the OER and 248 mV for the HER at 10 mA cm−2, and a smaller Tafel slope of 218 mV dec−1 for the OER and 198 mV dec−1 for the HER, compared to NIM-150. The NIM-150 and NIM-175 electrocatalysts exhibited excellent stability for overall water splitting.

Mo-doped Ni3S4 nanosheets grown on carbonized wood as highly efficient and durable electrocatalysts for water splitting

Rational design and fabrication of nonprecious metal-based electrocatalysts with high activity and excellent stability for overall water splitting (OWS) is still a grand challenge. Here we report a novel electrocatalyst constructed by incorporating molybdenum into the Ni3S4 lattices grown on carbonized wood (denoted as Mo-Ni3S4/CW). Experimental results and density functional theory (DFT)-based calculations demonstrate that lattice expansion of Ni3S4 caused by Mo doping optimizes adsorption energy of hydrogen/oxygen species and regulates local charge density of active sites, which promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Also, a nickel (oxy)hydroxide (Ni-OOH) layer generated via surface reconstruction of Ni3S4 nanosheets improves the intrinsic activity for OER. Moreover, the 3D low-tortuosity porous CW substrate increases the exposure of active specific surface, accelerates the rates of electron transfer, electrolyte diffusion, and gas products escaping. Accordingly, an optimized electrocatalyst (Mo-Ni3S4/CW-0.4) exhibits ultralow overpotentials of 17 and 240 mV for HER and OER at 10 mA cm−2, respectively. Besides, an electrolyzer composed of Mo-Ni3S4/CW-0.4 electrodes as both the anode and cathode shows a low cell voltage of 1.46 V at 10 mA cm−2 while maintaining superior durability over 50 h for OWS. Further, it requires only 0.19 V to achieve 10 mA cm−2 for hydrazine oxidation-assisted water electrolysis, indicating highly attractive potential for economical hydrogen production coupling with pollutants treatment.

Synergistic Coupling of CoFe-LDH Nanosheets with Cu3P Nanoarrays for Efficient Water Splitting

A crucial requirement for overall water splitting (OWS) is the creation of highly active bifunctional electrocatalysts. In this study, a CoFe-LDH (LDH = layered double hydroxide) nanosheet is integrated on a Cu3P nanowire to form heterogeneous structure Cu3P@CoFe-LDH/CF. Studies prove that the formation of a p–n heterojunction between Cu3P and CoFe-LDH promotes the charge-transfer reaction. Due to the synergistic contribution of the heterogeneous structure, Cu3P@CoFe-LDH/CF displays promising electrocatalytic activity. The overpotentials of 293 mV at 100 mA cm–2 for oxygen evolution reaction and 181 mV at 100 mA cm–2 for hydrogen evolution reaction are achieved in 1 M KOH. In addition, the alkaline electrolyzer of Cu3P@CoFe-LDH/CF||Cu3P@CoFe-LDH/CF shows a low cell voltage of 1.45 V at 10 mA cm–2 as well as great stability for OWS. This work provides a facile method to enhance the electrocatalytic activity by constructing heterogeneous structures with p–n heterojunctions, which holds significant promise for application in renewable energy technology.

Synergistic coupling of IrNi/Ni(OH)2 nanosheets with polypyrrole and iron oxyhydroxide layers for efficient electrochemical overall water splitting

The design of electrocatalysts with excellent activity and stability for overall water splitting is highly desirable, and remains a challenge. Constructing heterojunctions onto the same substrate is beneficial for the integration of a water-splitting reaction. Herein, self-supported IrNi/Ni(OH)2@PPy and IrNi/Ni(OH)2@FeOOH are fabricated by coupling polypyrrole (PPy) and iron oxyhydroxide (FeOOH) on IrNi/Ni(OH)2 nanosheets array, respectively. Benefiting from the nanosheet structure, composition, and heterogeneous interface, the as-constructed IrNi/Ni(OH)2@PPy and IrNi/Ni(OH)2@FeOOH catalysts can efficiently drive the hydrogen evolution reaction and oxygen evolution reaction, respectively. Moreover, the electrolyzer consisting of IrNi/Ni(OH)2@PPy and IrNi/Ni(OH)2@FeOOH for water splitting requires only a low cell voltage of 1.49 V to deliver 10 mA cm−2. This study provides a useful strategy for constructing efficient electrocatalysts by synergistic composition modulation and interface engineering.

Controlled tuning the morphology of CoNiP catalysts with ultra-high activity for water splitting at large current densities in alkaline medium

Developing efficient, robust and low-cost bifunctional electrocatalyst with high activity and strong stability for overall water splitting has received extensive attention. Herein, a 3D porous nanoflower spherical catalyst Co6Ni4P/NF was synthesized by one-step pulse electrodeposition, and regulating morphology of nanostructure through tuning the ratio of Co2+ and Ni2+ in the planting bath. This morphology combined the superiorities of the 3D spherical and the 2D film structures, which not only retain a large specific surface area, but also ensure the high-density of active sites. The as-prepared Co6Ni4P/NF only needs overpotentials of 336 mV and 373 mV to reach the large current density 1000 mA cm−2 for HER and OER and shows long-term stability under alkaline condition. Meanwhile, to drive overall water splitting requires only the cell voltages of 1.56 V, 1.61 V and 2.19 V to reach 50, 100 and 1000 mA cm−2. In this work, the influence of catalyst morphology is discussed specifically, and we find the nanoflower spherical Co6Ni4P/NF presents the best performance compared with nanospheres and nanosheets in overall water splitting process, which is appealing to practical application at large current condition.

Ni3S2/Co9S8 embedded poor crystallinity NiCo layered double hydroxides hierarchical nanostructures for efficient overall water splitting

Nickel–cobalt bimetallic layered double hydroxides (NiCo LDHs) are potential electrocatalysts with high performance and stability for overall water-splitting. However, its weak conductivity limits its practical applications. Herein, a simple hydrothermal in-situ conversion strategy is employed for constructing the novel heterogeneous electrocatalyst of Ni3S2/Co9S8 embedded poor crystallinity (Pc) NiCo LDH nanosheet arrays grown on the Ni foam (Pc-NiCo LDH/ Ni3S2/Co9S8), which can improve the conductivity via regulating the crystallinity. The crystallinity of NiCo LDH is well regulated by adjusting the amount of sulfur source, and the construction of Ni3S2/Co9S8 heterostructure exposes more active sites, improves the electrical conductivity, enhances the electronic interaction between NiCo LDH and Ni3S2/Co9S8, and significantly promotes the kinetics of water splitting. The optimized Pc-NiCo LDH/Ni3S2/Co9S8 hierarchical structure as both the anode and cathode exhibit the overall water splitting performance with the cell voltage of only 1.744 V to achieve the current density of 50 mA cm−2 in the alkaline media and shows the competitive H2 and O2 production rate of 6.4 and 3.1 μL s−1, respectively, suggesting its potential practical applications. This work provides a novel idea for the design of multiphase composite electrocatalysts applied in water splitting.

Effect of Rare-Earth Element Doping on NiFe-Layered Double Hydroxides for Water Oxidation at Ultrahigh Current Densities

Electrochemical energy conversion processes such as water reduction to produce hydrogen and carbon dioxide reduction into valuable carbon products have attracted great attention as alternative green energy technologies to fossil fuels. Nevertheless, the conversion efficiency and long-term stability of these technologies remain very far from the requirements for industrial applications because of the sluggish kinetics of the oxygen evolution reaction (OER). In this study, La-doped NiFe-layered double hydroxides (LDHs) were synthesized on Ni foam via a facile hydrothermal method and applied as active and stable OER electrochemical catalysts. The La-doped NiFe-LDH having the optimal La doping level exhibits excellent OER catalytic activity with a low overpotential of 309 mV at a high current density of 500 mA cm–2, a low Tafel slope of 42 mV dec–1, and long-term stability in the OER process over 140 h at 100 mA cm–2. Remarkably, the full cell of NiFeLa LDH-2||NiMoOx achieves high current densities of 500 mA cm–2 at the voltage of 1.728 V with superior stability for overall water splitting during 600 h in 1 M KOH. The enhanced OER performance is ascribed not only to the high crystallinity of the nanosheet structure but also to the synergistic electronic interactions between Ni, Fe, and La, which result in a stronger metal–oxygen bond based on d-band theory, more exposed active sites with high-valence states, and increased oxygen vacancies.

The S-Fe(Ni) sub-surface active sites for efficient and stable overall water splitting

Balancing catalytic efficiency and stability is always a critical and challenge issue for energy related research. Here we propose a reaction reconstruction strategy to create active sites in the sub-layer of sulfur-modified transition metal-based catalysts, which can both achieve a high efficiency and exhibit an excellent stability for overall water splitting. The sub-layer active sites of S-Fe and S-Ni are evidenced by the bulk-sensitive X-ray absorption spectroscopy (XAS), while they cannot be observed by the surface-sensitive X-ray photoelectron spectroscopy. Theoretical calculations reveal that the sub-layer active sites can promote the water dissociation and accelerate the formation of high-energy peroxyl groups in anodes to achieve a high efficiency, while the surface layer can protect the sub-layer sites for excellent stability. The high stability is also confirmed by in-situ XAS. As a result, the obtained bi-functional catalyst as both cathode and anode can achieve a current density of 10 mA cm−2 for overall water splitting at a low cell voltage of 1.53 V (1.81 V for 100 mA cm−2), with an excellent stability over 200 h, which outperforms the benchmark Pt/C-RuO2/NF electrodes.

Plasma-spray-enabled microcosmic explosion to construct Ni mesh-based electrodes for water splitting.

Currently, the fabrication of low cost and high efficiency electrocatalysts is a hotspot in the study of water splitting. Herein, plasma spray (PS) was used to induce a microcosmic explosion (me) on Ni mesh to modify the nanoscale Ni for the preparation of me-PS-NM electrodes with excellent hydrogen evolution. We also demonstrated that oxygen evolution could be significantly enhanced after the me-PS-NM electrodes were doped with Fe3+. Both electrodes formed a system exhibiting superior activity and stability for overall water splitting without noble metals.

Cobalt carbonate hydroxides anchored on nanoscale pyrenely-graphdiyne nanowalls toward bifunctional electrocatalysts with high performance and stability for overall water splitting

From the data of theory and experiment, CCH@Pyr-GDY-NWs based on Co-based carbonate hydroxides (CCHs) and pyrenely-graphdiyne nanowalls (Pyr-GDY-NWs) exhibits an outstanding catalytic activity towards overall water splitting (OWS).

Magnetic electrode configuration with polypyrrole-wrapped Ni/NiFe2O4 core–shell nanospheres to boost electrocatalytic water splitting

The exploration of transition metal-based electrodes with high efficiency, low-budget and excellent stability for overall water splitting has attracted increasing attention. To optimize the metal oxides as efficient bifunctional electrocatalysts, it is necessary to design not only their atomic and electronic structures but also the macroscopical electrode configuration. Herein, we report the preparation of conductive polypyrrole (PPy)-wrapped Ni/NiFe2O4 (Ni/NiFe2O4@PPy) nanospheres as a promising bifunctional electrocatalyst for the OER and HER. In the material design strategy, the PPy coating improves the conductivity and modulates the ion transmission rate between the electrolyte and Ni/NiFe2O4. The interaction between PPy and Ni/NiFe2O4 regulates the electronic structure and enhances the reaction efficiency of active sites. Furthermore, Ni/NiFe2O4@PPy nanospheres are employed to construct a binder-free magnetic electrode, which can well avoid the blockage of active sites and accelerate the gas release through the loosely assembled catalysts. The Ni/NiFe2O4@PPy with paramagnetic characteristics can be easily recovered for recycling by demagnetizing the electrodes. The specially designed magnetic electrodes show superior electrocatalytic activity with low overpotentials of 127 mV@10 mA cm−2 and 236 mV@100 mA cm−2 for HER and 265 mV@10 mA cm−2 and 370 mV@100 mA cm−2 for OER. The overall water electrolytic cell with Ni/NiFe2O4@PPy electrodes can achieve 10 mA cm−2 at 1.64 V with an excellent long-term stability. This work provides a novel material design and magnetic electrode construction strategy to improve the water splitting performance.

Self-adaptively electrochemical reconstruction of NiFe-layered double hydroxide on Ni foam for high-performance water splitting

As one of the most efficient, low-cost, and readily available electrocatalysts for oxygen evolution reaction (OER) in alkaline environments, the nickel-iron electrocatalyst is of great significance to commercial water splitting. In this study, NiFe-layered double hydroxide loaded on nickel foam (NiFe-LDH/NF) was synthesized via a simple one-step hydrothermal method, whose OER catalytic performance could be successfully optimized by further electrochemical reconstruction. The results show that NF is an effective precursor to loading crystallized Ni(OH)2 nanoparticles during hydrothermal synthesis, leading to the generation of high-performance NiOOH during OER reconstruction. Under the optimal Ni:Fe feeding ratio, Ni2Fe1-LDH/NF requires an ultra-low OER overpotential of 239 mV at 50 mA cm−2 and 260 mV at 100 mA cm−2, whose Tafel slope is only 64.1 mV dec−1. Impressively, Ni2Fe1-LDH/NF also achieves an ultra-low voltage of 1.44 V at 10 mA cm−2 with excellent long-term stability for overall water splitting. Unlike the previous viewpoint that only Ni species dominate surface reconstruction of NiFe-LDH, in this article the decisive influence related to Fe species on the reconstruction layers’ activity and stability is confirmed by electrochemistry, Raman, and XPS analysis during reconstruction process. During OER reconstruction, the surface Ni:Fe ratios can be "self-adaptively" regulated to an appropriate region, thus the stable reconstruction layers rich in NiOOH can be formed as the protective shells for NiFe-LDH. Furthermore, such "self-adaptive" reconstruction, assisted with appropriate initial Ni:Fe feeding ratios, can also stimulate more Ni3+ active sites for OER, benefitting the outstanding catalytic performance of NiFe-LDH/NF for overall water splitting and prospective large-scale application.

In Situ Grown Mn(II) MOF upon Nickel Foam Acts as a Robust Self-Supporting Bifunctional Electrode for Overall Water Splitting: A Bimetallic Synergistic Collaboration Strategy.

The design of highly efficient, cost-effective non-noble metal-based electrocatalysts with superior stability for overall water splitting (OWS) reactions is of great importance as well as of immense challenge for the upcoming sustainable and green energy conversion technologies. Herein, a convenient and simple in situ solvothermal method has been adopted to fabricate a self-supported, binder-free 3D electrode (Mn-MOF/NF) by the direct growth of a newly synthesized carboxylate-based pristine Mn(II)-metal-organic framework (Mn-MOF) upon the conducting substrate nickel foam (NF). The binder-free Mn-MOF/NF electrode exhibits excellent performances toward OWS with ultralow overpotentials of 280 mV@20 mA cm-2 for the oxygen evolution reaction (OER) and 125 mV@10 mA cm-2 for the hydrogen evolution reaction (HER) with remarkable durability. Mn-MOF/NF can also attain a current density of 10 mA cm-2 with a low cell voltage of 1.68 V in a 0.1 M KOH solution in a two-electrode system for OWS. The direct growth of nonconducting electroactive Mn-MOF materials upon conducting substrate NF provides an excellent mass transport of the electrolyte with a relatively low contact resistance due to the strong catalyst-substrate contact and enhances the efficient electron transport for OWS. The redox chemical etching of the self-sacrificial substrate NF during solvothermal synthesis introduces redox-active Ni2+ in Mn-MOF/NF. Thus, the excellent OWS electrocatalytic activity can mainly be attributed to the bimetallic synergistic collaboration of the two redox active metal centers (Mn2+ and Ni2+) along with the excellent support surface of NF, which provides a high specific surface area and maximum utilization of the electroactive metal ion sites by preventing the self-aggregation of the active sites. The Mn-MOF/NF electrode also exhibits superb stability and durability for a prolonged time throughout the multiple cycles of full water splitting reactions. Therefore, this work elucidates a convenient and smart approach for constructing MOF-based bifunctional electrocatalysts for OWS.

Interface Engineering of NixSy@MnOxHy Nanorods to Efficiently Enhance Overall-Water-Splitting Activity and Stability

HighlightsThree-dimensional (3D) core‐shell heterostructured NixSy@MnOxHy nanorods grown on nickel foam (NixSy@MnOxHy/NF) were successfully fabricated via a simple hydrothermal reaction and a subsequent electrodeposition process.The fabricated NixSy@MnOxHy/NF shows outstanding bifunctional activity and stability for hydrogen evolution reaction and oxygen evolution reaction, as well as overall‐water‐splitting performance.The main origins are the interface engineering of NixSy@MnOxHy, the shell‐protection characteristic of MnOxHy, and the 3D open nanorod structure, which remarkably endow the electrocatalyst with high activity and stability.Exploring highly active and stable transition metal-based bifunctional electrocatalysts has recently attracted extensive research interests for achieving high inherent activity, abundant exposed active sites, rapid mass transfer, and strong structure stability for overall water splitting. Herein, an interface engineering coupled with shell-protection strategy was applied to construct three-dimensional (3D) core‐shell NixSy@MnOxHy heterostructure nanorods grown on nickel foam (NixSy@MnOxHy/NF) as a bifunctional electrocatalyst. NixSy@MnOxHy/NF was synthesized via a facile hydrothermal reaction followed by an electrodeposition process. The X-ray absorption fine structure spectra reveal that abundant Mn‐S bonds connect the heterostructure interfaces of NixSy@MnOxHy, leading to a strong electronic interaction, which improves the intrinsic activities of hydrogen evolution reaction and oxygen evolution reaction (OER). Besides, as an efficient protective shell, the MnOxHy dramatically inhibits the electrochemical corrosion of the electrocatalyst at high current densities, which remarkably enhances the stability at high potentials. Furthermore, the 3D nanorod structure not only exposes enriched active sites, but also accelerates the electrolyte diffusion and bubble desorption. Therefore, NixSy@MnOxHy/NF exhibits exceptional bifunctional activity and stability for overall water splitting, with low overpotentials of 326 and 356 mV for OER at 100 and 500 mA cm–2, respectively, along with high stability of 150 h at 100 mA cm–2. Furthermore, for overall water splitting, it presents a low cell voltage of 1.529 V at 10 mA cm–2, accompanied by excellent stability at 100 mA cm–2 for 100 h. This work sheds a light on exploring highly active and stable bifunctional electrocatalysts by the interface engineering coupled with shell-protection strategy.