The morphology and porosity of electrocatalysts play essential roles on gas evolution reactions, such as OER and HER in water splitting. Therefore, rational design of highly efficient multifunction electrocatalysts with optimized nanostructures is of great importance for sustainable energy conversion processes. Herein, hollow petal-like Co3O4 nanoflakes could be readily available through calcining the corresponding MOFs(Metal-organic frameworks) nanoflower precursor, which could be controllable synthesized by a novel template-free protocol. Through modulating reaction conditions, the morphology and porosity of the catalysts could be controlled, which could directly influence on the catalytic activities of OER and HER. The super-hydrophilic hollow petal-like Co3O4 nanoflakes effectively facilitate mass transfer and ease gas bubbling, which contribute to a promoted bifunctional electrocatalytic activity for both HER and OER, as well as overall water splitting (A stable 10 mA cm(-1) water-splitting current can be reached by just applying 1.67 V, which is comparable to other recently reported catalysts in alkaline media). The hollow Co3O4 microflowers that reported here confirm the significance of structural features effect on electrocatalyst performance, which will open up a new approach to design high-performance electrode materials for gas evolution reactions. (C) 2019 Elsevier Ltd. All rights reserved.