Tuning the Co pre-oxidation process of Co3O4 via geometrically reconstructed F−Co−O active sites for boosting acidic water oxidation

Cobalt-based oxides are potential alternatives to noble metal catalysts for acidic oxygen evolution reaction (OER), however, their activity and stability are limited by the surface reorganization of cobalt oxide into Co(IV)=O active phase of pure Co3O4 with the retarded OER kinetics. Herein, we report a geometrically reconstructed active site F−Co−O of Co3O4-xFx phase by forming F electron-dominated sharing effect, which prominently regulates the Co pre-OER feature of pure Co3O4 catalyst, and displays an unconventional electrochemical behavior for remarkably boosted acidic water oxidation. The Co3O4-xFx catalyst exhibits a relatively low overpotential of 349 mV at 10 mA cm−2 and operation durability of 120 h at 100 mA cm−2 for acidic OER, making it one of the best-performing non-noble metal catalysts. The in-depth mechanistic analysis via quasi in-situ/operando techniques and density functional theory proves the ability of F to adjust Co pre-oxidation reaction on Co3O4-xFx and reproduces the remarkable activity of OER over Co3O4-xFx, as well as detailing the switchable rate-determining step and catalytic mechanisms for exceptionally enhanced performance. This work opens the feasible avenues for designing acidic OER catalysts of non-precious metal oxides toward commercial water electrolysis.