Reviving Oxygen Evolution Electrocatalysis of Bulk La–Ni Intermetallics via Gaseous Hydrogen Engineering

Abstract A hydrogen processing strategy is developed to enable bulk LaNi₅ to attain high activity and long‐term stability toward the electrocatalytic oxygen evolution reaction (OER). By a combination of in situ Raman and quasi in situ X‐ray absorption (XAS) spectra, secondary‐electron‐excited scanning transmission electron microscopy (STEM) patterns as well as the Rietveld method and density functional theory (DFT) calculations, it is discovered that hydrogen‐induced lattice distortion, grain refinement, and particle cracks dictate the effective reconstruction of the LaNi₅ surface into a porous hetero‐nanoarchitecture composed of uniformly confined active γ‐NiOOH nanocrystals by La(OH)₃ layer in the alkaline OER process. This significantly optimizes the charge transfer, structural integrity, active‐site exposure, and adsorption energy toward the reaction intermediates. Benefiting from these merits, the overpotential (322 mV) at 100 mA cm⁻² for the hydrogen‐processed OER catalyst deposited on nickel foam is reduced by 104 mV as compared to the original phase. Notably, it exhibits remarkable stability for 10 days at an industrial‐grade current density of more than 560 mA cm⁻² in alkaline media.