An intrinsic mechanism of surface reconstruction of cobalt-based oxide intermediated by oxygen vacancies

Oxygen vacancies enable modulating the dissolution of metal cations and surface reconstruction of transition metal oxides into metal oxyhydroxide for oxygen evolution reaction (OER), while the intrinsic reconstructing mechanism is still undiscovered. Herein, CoMoO4 with an optimal level of oxygen vacancy experiences controllable reconstruction into CoOOH, which holds an ultralow overpotential of 234 mV at a current density of 10 mA cm−2 and low Tafel slope of 58 mV dec−1, and its intrinsic catalytic activity increases around 57%. Raman spectroscopy indicates oxygen vacancies stimulate the formation of amorphous hydrous Co(OH)2 as an intermediate at a lower potential, accompanied by the eruptive evolution into well-crystallized CoOOH with potential rising as small as 0.05 V. Coherent reconstructing behaviours intermediated by oxygen vacancy also validates in CoWO4 and Co2VO4, opening one brilliant and universal avenue to tune OER activity of metal oxyhydroxides precisely in controllable manners.