Abstract: Stabilizing anode for oxygen evolution (OER) in chlorine-containing electrolytes is a significant challenge. Adding corrosion inhibitors in electrolytes can alleviate this problem, but the type and dosage of corrosion inhibitors need a lot of exploration, and side reactions may occur to reduce current efficiency. Herein, we prepared a FeCoNiMnMo High entropy alloy (HEA) electrode for OER in simulated seawater without corrosion inhibitors. It exhibits great electrocatalytic activity (overpotential (η) = 237 mV at 10 mA cm^-2) and excellent stability (200 h at 100 mA cm^-2). Experiments and Density Functional Theory (DFT) calculation show that the protective layer containing K₂MoO₄ is the crucial factor for chlorine resistance of FeCoNiMnMo electrode. The tightly adsorbed state of Cl^- and K₂MoO₄ ensures that other oxides are not corroded. And the externally added K₂MoO₄ cannot protect the electrode. In addition, the high-entropy effect of HEA reduces the dissolution of the alloy. This work provides an efficient way to prepare a noble-free HEA catalyst that can stabilize oxygen evolution in corrosive electrolytes.

Key words: High entropy alloy, Oxygen evolution reaction, Corrosion inhibitor, Chlorine resistance, K₂MoO₄