Surface-reconstructed nanoporous (CoNiFe)OOH modulated by Zn(OH) ₄ ²⁻ anions: A synergistic strategy for enhanced oxygen evolution reaction electrocatalysis

The sluggish kinetics of the oxygen evolution reaction (OER) severely limits the efficiency of electrochemical water splitting for sustainable hydrogen production. Developing cost-effective and efficient OER electrocatalysts based on earth-abundant elements is thus highly desirable. Herein, we report a nanoporous (CoNiFe)OOH electrocatalyst decorated with Zn(OH)₄²⁻ anions, synthesized via electrochemical surface reconstruction of ZnO-decorated CoNiFe medium-entropy alloys (MEAs). The reconstructed (CoNiFe)OOH adsorbed with Zn(OH)₄²⁻ anions serves as the real active phase, featuring abundant catalytic sites and enhanced OH⁻ accessibility. Adsorbed Zn(OH)₄²⁻ anions promote OH⁻ transfer and facilitate electron redistribution at the active sites, particularly enhancing Co site activity, as revealed by density functional theory (DFT) calculations. As a result, the optimized CoNiFeZn@NF-EO electrode exhibits outstanding OER performance, achieving a low overpotential of 264 mV at 10 mA·cm⁻², a Tafel slope of 46.6 mV·dec⁻¹, and remarkable long-term stability in alkaline electrolyte. This work provides new insights into the synergistic effect between surface reconstruction and Zn-based species, offering a promising strategy for designing high-performance OER electrocatalysts.