Enhancing Oxygen Evolution Electrocatalysis in Heazlewoodite: Unveiling the Critical Role of Entropy Levels and Surface Reconstruction

Abstract Entropy engineering has proven effective in enhancing catalyst electrochemical properties, particularly for the oxygen evolution reaction (OER). Challenges persist, however, in modulating entropy and understanding the dynamic reconfiguration of high‐entropy sulfides during OER. In this study, an innovative in situ corrosion method is introduced to convert low‐valent nickel on a nickel foam substrate into high‐entropy heazlewoodite (HES/NF), significantly boosting OER performance. By synthesizing a series of low‐, medium‐, and high‐entropy heazlewoodites, the intrinsic factors influence catalyst surface evolution and electrocatalytic activity is systematically explored. Employing a combination of in situ and ex situ characterization techniques, it is observed that HES/NF dynamically transforms into a stable hydroxide oxide (MOOH)‐sulfide composite under OER conditions. This transition, coupled with lattice distortion, optimizes the electrostatic potential distribution, ensuring superior catalytic activity and preventing surface sulfide deactivation through the formation of stable HES‐MOOH species. This synergy enables HES/NF to achieve remarkably low overpotentials: 172.0 mV at 100.0 mA cm ⁻² and 229.0 mV at an extreme current density of 300.0 mA cm ⁻² . When paired with a Pt/C cathode, HES/NF exhibits rapid kinetics, outstanding stability, and exceptional water‐splitting performance. The scalable, cost‐effective approach paves the way for advanced electrocatalyst design, promising breakthroughs in energy storage and conversion technologies.