Simultaneous modulation of surface composition, oxygen vacancies and assembly in hierarchical Co₃O₄ mesoporous nanostructures for lithium storage and electrocatalytic oxygen evolution

We developed a facile solution reductive method to simultaneously tune the surface composition, oxygen vacancies and three dimensional assembly in Co₃O₄ hierarchical nanostructures. The controllable surface composition, oxygen vacancies together with hierarchical micro/nanoarchitectures resulted in superior electrochemical properties when used as the anode materials for lithium-ion batteries and as an electrocatalyst for the oxygen evolution reaction. The excellent electrochemical performance is attributed to the synergistic effects of novel hierarchical morphology, crystal structure of the active materials, the improvement of intrinsic conductivity and inner surface area induced by the oxygen vacancies. The present strategy not only provides a facile method to assemble novel hierarchical architectures, but also paves a way to control surface structures (chemical composition and crystal defects) in other transition-metal compounds, and thus will hold great promise in the fields of energy storage and conversion.