A simple room–temperature acid capture strategy to controllably tune oxygen vacancy in Co3O4 for oxygen evolution reaction

Oxygen vacancy (Vo) engineering is considered as a general but effective way to improve the oxygen evolution reaction (OER) performance of transition metal oxides (TMOs). However, the deep understanding of Vo is still limited. In this work, a simple room–temperature acid capture strategy is employed to create Vo in TMOs. As discovered in the case of commercial Co3O4 microspheres, the Vo can be tuned by the acid capture time. As the acid capture time is growing, the concentration of Vo increases. Moderate Vo concentration created by controlled acid capture time (less than 32 h) can elevate the electrical conductivity and optimize the electronic structure. With overlong acid capture time (reaching 64 h), excessive Vo will present, leading to enlarged energy band gap, declined electrical conductivity as well as collapsed structure of Co3O4 microspheres, which is detrimental to the exposure of catalytic sites and accessibility of electrolyte. Consequently, the resultant Co3O4 −Vo− 32 (32 represents acid capture time) obtains a balanced Vo concentration while retaining structure integrity, thus displaying a better OER performance than the counterparts.