Interstitial C‐Atom Insertion‐Assisted High‐Entropy Engineering Boosts Ultrastable Ampere‐Level Oxygen Evolution

ABSTRACT Active and stable noble metal‐free oxygen evolution reaction (OER) electrocatalysts are required for high‐performance water splitting using renewable energy. Here, we report that interstitial C atoms doping into high‐entropy transition metal oxide nanosheets (IC‐HETMO NSs) can extend the OER durability in alkalinity by approximately two orders of magnitude over that of HETMO NSs, along with excellent activity. IC‐HETMO NSs deliver a low overpotential of 260 mV in 1.0 M KOH at 500 mA cm −2 while maintaining 8000 h (over 11 months), demonstrating notable stability and activity under the tested conditions. Operando spectroscopy measurements, together with first‐principles analyses, support that IC‐HETMO NSs preferably follow a low‐energy pathway involving direct * O─ * O radical coupling from adsorbed water, resulting in electrocatalytic stability. The calculations also confirm that C‐doping can optimize metal–O covalency, thus allowing enhanced resistance to over‐oxidation and demetallation. In practical anion‐exchange membrane water electrolysis, IC‐HETMO NSs‐based electrolyzer exhibits a low voltage of 1.68 V and good stability at 1.0 A cm −2 for 2950 h at 60°C.