Enhancing bifunctional electrodes of oxygen vacancy abundant ZnCo2O4 nanosheets for supercapacitor and oxygen evolution

Earth-abundant spinel ZnCo2O4 is considered as promising electrode materials in the fields of energy storage (e.g. supercapacitor) and conversion (e.g. electrocatalytic water oxidation), but it is still limited by the insufficient material utilization efficiency and poor conductivity. Herein, the two-dimensional ZnCo2O4 nanosheets with abundant oxygen vacancies (OV-ZnCo2O4 nanosheets) have been constructed by facile hydrothermal approach and NaBH4 reduction treatment. The experimental and theoretical calculation results reveal that the as-prepared materials possess enhanced electrical conductivity, modulated electronic structure, increased active sites, and optimal adsorption energies for intermediates. As a supercapacitor electrode, the OV-ZnCo2O4 nanosheets deliver inspiring specific capacitance of 2110.6F g−1 at 1 A g−1. Furthermore, the asymmetric supercapacitor (ASC) assembled by OV-ZnCo2O4 nanosheets//active carbon (AC) exhibits a high energy density of 34.6 Wh kg−1 at a power density of 160 W kg−1. As an electrocatalyst for oxygen evolution reaction (OER), the OV-ZnCo2O4 nanosheets only need remarkably low overpotential of 324 mV to achieve a current density of 10 mA cm−2 in 0.1 M KOH. This work provides an effective strategy for construction of multifunctional electrochemical energy materials.