Cobalt oxyhydroxide with highly porous structures as active and stable phase for efficient water oxidation

Providing the direct experimental evidence for confirming active and stable phase in cobalt-based electrocatalysts for oxygen evolution reaction (OER) in alkaline medium is crucial to design and fabricate high-performance electrocatalysts. Herein, we report the in situ fabrication of pure cobalt oxyhydroxide (CoOOH) phase with highly porous structures during OER testing process, which exhibits outstanding performance for OER with a low overpotential of 245 mV at 10 mA cm⁻² and retain stable catalytic activity for 250 h with no appreciable decay. Experimental characterizations revealed that the superior catalytic activity of as-formed CoOOH phase mainly arises from the highly porous structures, which endows the electrocatalyst with high specific surface area (∼200 m² g⁻¹), numerous accessible channels and abundant active sites. Evidence has been produced showing that the in situ formed pure CoOOH is the active and stable phase in cobalt-based electrocatalysts for OER in alkaline medium. In addition, the synthetic strategy applied here could provide a novel way to fabricate nanoporous structures under mild conditions using electrochemical oxidation method.