Reduction Induced Surface Amorphization Enhances Oxygen Evolution Reaction Activity in Co3O4

Oxygen evolution reaction (OER) is one of the paramount steps in sustainable energy conversion and storage technologies.^1-3 Spinel oxide Co₃O₄ has long been recognized as a promising alternative non-precious OER electrocatalyst for its good activity and low cost. Numerous nanostructured Co₃O₄ materials have been developed in order to acquire better OER performance.^4-6 Herein, we have adopted thermal H₂ annealing and air exposure to modify the surfaces of crystalline Co₃O₄. Our results demonstrate the remarkably enhanced OER activity of the surface modified Co₃O₄ electrocatalyst despite its increased crystal size and reduced surface area. The improved OER performance is believed to be relevant to the very surficial amorphous layer consisting of mixed hydrated cobalt oxyhydroxide/carbonate species on the reduced Co₃O₄.

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