Augmenting overall water splitting with transition-metal-doped NiCr-LDH as a bifunctional electrocatalyst

초록

Concerning efficient water splitting, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) play pivotal roles in enabling large-scale clean hydrogen production and sustainable energy solutions. However, the OER is limited by kinetic challenges due to the complexity of multistep proton-coupled electron transfer processes. Non-noble metal-based catalysts particularly layered double hydroxides (LDHs) have shown high catalytic efficiency owing to their large surface area, tunable chemical composition, and diverse nanostructures. NiCr-LDH, a layered double hydroxide composed of Ni2+ and Cr3+ ions, exhibits a unique structure that enhances its electrochemical properties for water splitting. In this study, we synthesized M−NiCr−LDH (M: Ru, Mn, Co, Fe) using a two-step hydrothermal process with varying transition metal concentrations and evaluated their electrochemical performance in an alkaline electrolyte. Incorporating the dry cathode anion exchange membrane water electrolyzer (AEMWE) system considerably improved hydrogen production, achieving a current density of 462.5mA cm−2 at 2.0 V, with scalability demonstrated through electrode expansion. Theoretical studies revealed that Fe, Ru-NiCr-LDH outperformed undoped NiCr-LDH by optimizing the electronic structure and reducing activation energies for critical steps. Specifically, Ru doping facilitated H* adsorption with the most favorable Gibbs free energy, while Fe doping enhanced the *O → *OOH step. Hence, this approach, which leverages the incorporation of transition metal ions, is a highly effective strategy for strengthening electrocatalytic water oxidation and reduction processes in alkaline media by increasing active site availability, thus offering considerable potential for broader applications in other catalytic systems using various hydroxide-based materials. © 2025

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