Synergistically Integrating Nickel Porous Nanosheets with 5d Transition Metal Oxides Enabling Efficient Electrocatalytic Overall Water Splitting

Abstract

An integration hydrogen adsorption benign component such as a metal with an oxygen-containing reactant adsorption benign component such as metal oxide allows for efficient overall water splitting in alkaline solutions and yet remains a considerable challenge. Herein, 5d transition metal oxide WO2 and WO3 (denoted as WO x ) nanoparticles are purposely integrated with a porous Ni nanosheet array grown on nickel foam (NF) to design a strongly coupled Ni/WO x /NF porous nanosheet array electrocatalyst. Through the anion exchange of Ni­(OH)2 nanosheets with tungstate, followed by hydrogenation treatment, abundant Ni/WO x interfaces with strong coupling interaction are generated. Benefiting from the strong synergies between Ni and WO x and the unique nanostructure, Ni/WO x /NF only requires the overpotentials of 42 mV for hydrogen evolution reaction (HER) and 395.7 mV for oxygen evolution reaction (OER) to achieve the current densities of 10 and 100 mA cm–2, respectively. Furthermore, the Ni/WO x /NF can achieve a current density of 10 mA cm–2 at a low cell voltage of 1.54 V in a two-electrode system. This work opens a novel avenue for the design of high-performance but low-cost electrocatalysts for overall water splitting.

Semicrystalline IrOx with Abundant Boundaries for Overall Water Splitting

“…The exploitation of new inorganic catalytic materials for efficient overall water splitting via accelerating the two half-reactions, namely, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is of great significance for the development of the hydrogen economy. − To date, Ir/Ru oxides and metallic Pt are still the benchmark catalysts for OER and HER in terms of activity and stability, respectively. , In an integrated electrolyzer, the practical implementation of monofunctional electrocatalysts is usually limited by the mismatched working conditions . It is also noted that the development of efficient bifunctional catalysts for both OER and HER in the same solution is necessary, based on the fact that device fabrication can be simplified and thus the cost can be reduced. , However, most of the developed bifunctional electrocatalysts currently can be applied in only alkaline electrolytes. − To survive under a strongly acidic and oxidative environment for acidic overall water splitting at faster kinetics, the use of noble metals as the electrocatalysts is indispensable. − In spite of the wide application of noble metals, , individual Ir/Ru oxides or metallic Pt is monofunctionally active with regard to water splitting ut supra. , Designing bifunctional activities of noble metals remains challenging. In addition, the change in the proton concentration on one electrode is inevitable during water splitting processes, and thus, the bifunctional noble metal catalysts are also required to be efficient over a wide pH range.…”

Synergizing Cobalt Ruthenium Alloy with Chromium Oxyhydroxide for Highly Efficient Electrocatalytic Water Splitting

“…Integration of metal/alloy with metal oxide/(oxy)­hydroxide into multiphase catalysts through the interface engineering strategy is regarded as an effective approach to designing efficient and stable bifunctional catalysts. , Generally, metal/alloy in such multiphase catalysts favors the hydrogen adsorption and desorption and promotes the charge transfer rate. − The metal oxides/(oxy)­hydroxides with a strong oxygen-containing intermediate adsorption energy capability facilitate the water dissociation in the Volmer step of HER and contribute to the proceeding of OER catalysis. , Furthermore, the strong electronic interaction between metal/alloy and metal oxide/(oxy)­hydroxide near the interface enables the charge redistribution, which is conducive to optimizing the reaction adsorption energy, thus enhancing the catalytic activity. , Many intriguing alloy/metal oxide electrocatalysts, such as Co 3 Mo/CoMoO x , CuCo/CuCoO x , CoFe/CoFe 2 O 4 , NiCo/NiCo-OH, and NiFeMn/NiFeMn-oxyhydroxide, have been developed and exhibited enhanced HER and OER performances compared to the single-component counterparts. Indeed, in these reported catalysts, the metal oxyhydroxides normally in situ generated from the surface self-reconstruction of the metal oxide/hydroxide precatalyst during the OER process act as the real active species for OER catalysis owing to the high inherent activity of high-valent metal active sites. ,, However, many reported heterogeneous electrocatalysts comprising of bimetallic alloys and metal oxides/hydroxides exhibited unsatisfactory HER and OER performances due to the limited synergistic effect between the different components, insufficient conductivity, and inaccessible active sites in the formed core–shell structure.…”

Rare earth metal (Sm)-doped NiMnO3 nanostructures for highly competent alkaline oxygen evolution reaction

“…Transition metal oxides are promising materials for various applications, such as for use in lithium-ion batteries, supercapacitors, water oxidation, hydrogen production, and urea oxidation. 6 However, they have limited application due to their poor conductivity and insufficient active sites. Attempts have been made to overcome these issues by various approaches, such as the incorporation of metal ions, the introduction of carbon-based materials and quantum dots, etc.…”