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

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 gamma-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.

Automated summary

A hydrogen processing strategy is developed to improve the performance of LaNi5 as an electrocatalyst for the oxygen evolution reaction (OER). The surface of LaNi5 is reconstructed into a porous hetero-nanoarchitecture composed of gamma-NiOOH nanocrystals, which optimizes the charge transfer and structural integrity. The hydrogen-processed OER catalyst shows a significantly reduced overpotential and remarkable stability in alkaline media, making it a promising candidate for industrial applications.