Surface engineering of Co₃O₄ nanoribbons forming abundant oxygen-vacancy for advanced supercapacitor

The development of high-efficiency metal oxide electrode materials with high reaction kinetics and excellent conductivity are a cutting-edge strategy to obtain high-performance energy storage devices. Forming oxygen vacancy on the surface of the metal oxide tune electronic structure is a feasible approach to boost the electroactive of metal oxides for supercapacitor. Herein, an effective solution reduction method is reported for tuning the electronic structure of Co₃O₄ nanoribbons reacting with NaBH₄ to enhance the faradaic redox reaction for high electrochemical performance. The vacancy-rich defects can endow more electroactive sites and reduce the electrical resistance for the enhanced supercapacitor performance. Therefore, compared to pristine Co₃O₄ (347.4 F g⁻¹), the reduced Co₃O₄ (R-Co₃O₄) shows a high specific capacitance (C_s, 464.9 F g⁻¹) and a reduced charge transfer resistance. The asymmetric supercapacitor (ASC, R-Co₃O₄// active carbon) exhibits an energy density of 18.6 Wh kg⁻¹ at the power density of 400 W kg⁻¹ and excellent cycling stability. Such a feasible approach realizes the electronic tuning by creating oxygen vacancy that provides sufficient active sites and activates the fast faradaic redox reaction with enhanced energy storage ability of redox-active electrode materials.