Customized O─O Radical Coupling Route on High‐Density Fe─N─C Catalysts for Stable Industrial‐Scale Water Oxidation

ABSTRACT Low‐cost, efficient, and durable oxygen evolution reaction (OER) catalysts are essential for advancing large‐scale hydrogen production via anion‐exchange membrane water electrolysis. However, current state‐of‐the‐art catalysts are hindered by insufficient operational stability at high current densities and a lack of precise control over reaction pathways under dynamic operating conditions. In this work, theoretical calculations reveal a continuous regulatory effect of Fe site density on the adsorption energies of key OER intermediates on Fe─N─C single‐atom catalysts. Experimental results further demonstrate that by progressively increasing the Fe site density, the surface * OH coverage can be finely tuned, enabling a controllable switch of the OER mechanism from an adsorption evolution mechanism to an oxide pathway mechanism (OPM). A high‐density Fe─N─C catalyst (HDFe‐N‐C, Fe loading 14.7 wt.%) following OPM exhibits remarkable electrochemical stability, operating continuously for 2000 h at 500 mA cm −2 with a low overpotential of 288 mV. When integrated into an anion‐exchange membrane electrolyzer, the device achieves 5 A cm −2 at only 2.15 V and maintains stable performance for 500 h.