Phase-Reconstruction of S-Doped (NiCo)₆W₆C for Efficient and Stable Oxygen Evolution Reaction Electrocatalysis

Developing highly active and stable nonprecious electrocatalysts toward sluggish alkaline oxygen evolution reaction (OER) is essential for large-scale green hydrogen production via electrochemical water splitting. Here we report phase and surface co-reconstruction of S-doped (NiCo)₆W₆C nanoparticles into (NiCo)C_x with amorphous electroactive NiCoOOH layer for highly efficient alkaline OER by W dissolution and NiCo surface oxidation. The W dissolution results in the formation of Brønsted base WO₄^2- ions, which electrostatically accumulate around electrode to promote water dissociation into abundant OH* intermediates, in situ constructing a locally strong alkaline microenvironment to facilitate OH* adsorption on NiCoOOH sites and trigger lattice-oxygen oxidation path. As a result, the heterostructure electrode exhibits superior OER electrocatalysis with low Tafel slope of ∼35 mV dec^-1 in 1 M KOH. It delivers high ampere-level current density of ∼1 A cm^-2 at a low overpotential of 275 mV, and maintains extraordinary stability for over 1000 h.