Constructing trimetallic catalyst via sequential ion-exchange for enhanced ampere-level water oxidation

Electrocatalytic water splitting has emerged as a promising route for sustainable hydrogen production. However, the sluggish oxygen evolution reaction (OER) severely restricts its overall efficiency. Herein, a trimetallic electrocatalyst was rationally designed and synthesized via a sequential ion-exchange strategy. The as-prepared Fe/NiCoO₂, featuring the multi-metallic electronic synergy and unique hierarchical architecture, provides high intrinsic activity, abundant active sites, and efficient mass diffusion. Benefiting from these compositional and structural merits, the electrode delivers ultralow overpotentials of 248 and 353 mV at current densities of 10 and 500 mA cm⁻², respectively, with a small Tafel slope of 39.15 mV dec⁻¹. Furthermore, Fe/NiCoO₂ exhibits exceptional long-term stability over 200 h under high current densities of 500 mA cm⁻², outperforming the benchmark noble-metal-based catalysts. In-situ Raman spectroscopy reveals that the initial Fe/NiCoO₂ undergoes self-reconstruction into Fe/NiCoOOH during the OER process. Density functional theory (DFT) calculations certify that the incorporation of Fe into NiCoO₂ effectively tunes the 3d-orbital electron distribution, which optimizes the adsorption energies of oxygen-containing intermediates and enhances charge transfer kinetics. This study provides a promising strategy for designing noble-metal-free catalysts with tailored nanostructures and multi-active site configurations to facilitate efficient industrial-scale water oxidation.