Laser Preset of MnO _x Layer on High‐Entropy Alloy Surface for Ampere‐Level Ultra‐Stable OER Performance

ABSTRACT Electrocatalytic water splitting offers an efficient pathway for producing renewable hydrogen, which is considered a key strategy toward global carbon neutrality. Yet, under harsh industrial operating conditions, the catalyst inevitably undergoes dynamic structural reconstruction, oxidative dissolution of active sites, and mechanical detachment during high‐potential anodic oxygen evolution reaction (OER), severely limiting their activity and stability. Here, we present an MnO _x (composed of Mn ₃ O ₄ and Mn ₂ O ₃ ) layer on the FeCoNiCrMn high‐entropy alloy (HEA) surface (denoted as HEA‐ML) via laser powder bed fusion (LPBF) process and reveal that the MnO _x layer suppresses multimetal dissolution in HEA and mitigates excessive surface reconstruction under OER conditions. Furthermore, the MnO _x layer featuring a porous and rough surface enhances water adsorption and bubble diffusion, thereby accelerating interfacial mass transfer and OER kinetics. These outstanding features endow the catalyst to exhibit both excellent activity (227 ± 2 mV at 10 mA cm ⁻² ) and industrial‐grade ultra‐stable OER performance (operating stably for 1500 h at 1.0 A cm ⁻² ). Our research findings provide new insights into the structure‐activity‐stability relationship of HEA electrocatalysts and demonstrate a novel approach for designing industrially viable OER catalysts with high activity and ultra‐stability.