Ni‐Based High‐Entropy Alloys Synthesized Under Mild Conditions for Efficient Water Splitting Catalysis

The high-entropy alloy NiCoFeMoRu, synthesized through hydrothermal-annealing reduction, undergoes dynamic surface reconstruction during water electrolysis, facilitating efficient water splitting into hydrogen and oxygen. The restructured interfaces display remarkable bifunctional activity for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), with enhanced stability resulting from synergistic atomic configurations.

Abstract

High-entropy alloys (HEAs) have emerged as promising electrocatalysts for water splitting; however, their conventional synthesis often requires high temperatures and extreme conditions, limiting their scalability and practical application. In this study, we report a facile one-step hydrothermal method combined with a low-temperature reduction approach to synthesize Ni-based HEAs (NiCoFeMoRu). During the oxygen evolution reaction (OER), the catalyst undergoes an in-situ reconstruction, forming an amorphous phase interspersed among crystalline metal oxide nanoparticles. This structural transformation significantly enhances catalytic performance, achieving an overpotential of 217 mV at 10 mA cm⁻² and 357 mV at 1000 mA cm⁻² and maintaining stability for over 300 h. Furthermore, a two-electrode electrolyzer employing NiCoFeMoRu bifunctional electrodes demonstrates a cell voltage of 1.68 V at 10 mA cm⁻² and 2.47 V at 1000 mA cm⁻² in 1 M KOH electrolyte, highlighting its efficiency for overall water splitting. The amorphous phase, induced by Ru and Mo evolution, not only improves catalytic activity but also reinforces structural integrity by facilitating self-regulation and mitigating structural degradation. This work presents a viable strategy for designing cost-effective, bifunctional HEA electrocatalysts, offering a pathway toward scalable and sustainable hydrogen production.

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