Activating the oxide pathway mechanism via selective intralayer Cl coordination with Ni/Fe sites of hydroxides for robust water oxidation

Abstract

The sluggish kinetics, poor conductivity, and metal dissolution of NiFe hydroxides hinder their application in the alkaline oxygen evolution reaction (OER), highlighting the necessity for structural regulation and mechanistic understanding to meet industrial requirements. Herein, we propose a NiFe(OH)_xCl_y electrocatalyst featuring a fundamentally reconstructed coordination structure and electronic configuration with the highly responsive oxide pathway mechanism (OPM). Lattice-positioned Cl (21.6 wt%) preferentially binds Ni over Fe and compresses metal–oxygen layers, intrinsically optimizing the electronic configuration and structural stability. Moreover, Cl directs hydroxyl substitution at the Ni/Fe–Cl tetrahedral sites, enabling dehydrogenated oxygen to form closer interactions with neighboring hydroxyls via hydrogen bonding, thereby promoting direct O–O coupling and better OER kinetics. NiFe(OH)_xCl_y exhibits an overpotential of 217 mV at 100 mA cm⁻² and 3000-h durability at 1 A cm⁻². The integrated NiFe(OH)_xCl_y‖Pt/C anion exchange membrane water electrolyzer achieves 1 A cm⁻² at only 1.69 V with 1000 h stable operation. This work highlights an intrinsic strategy for structural tuning and mechanistic optimization for industrial OER electrocatalysts.