Reduced ZnCo2O4@NiMoO4·H2O heterostructure electrodes with modulating oxygen vacancies for enhanced aqueous asymmetric supercapacitors

Abstract

In this work, to obtain electrode materials with exponentially enhanced performance, we first put forward a synergistic strategy to construct a core-shell reduced ZnCo2O4@NiMoO4·H2O heterostructure. This constructed nanostructure makes the utmost of reduced ZnCo2O4 nanowires and NiMoO4·H2O nanosheets, and the prepared electrodes exhibit highly stepped-up electrochemical performance. The reduced ZnCo2O4 electrode with moderate oxygen vacancies yields a capacitance of 1.55 F cm−2, which is significantly increased by 84.5% than that of the pristine electrode. More notably, the obtained core-shell reduced ZnCo2O4@NiMoO4·H2O electrode yields a capacitance of 3.53 F cm−2, which is marvelously increased by 127.7% than that of the reduced ZnCo2O4 electrode, the electrode also shows an excellent 95.4% capacitance retention after 5000 cycles and good electrical conductivity. In addition, the assembled aqueous asymmetric supercapacitor device using the reduced ZnCo2O4@NiMoO4·H2O electrode as positive electrode delivers a high energy density of 2.55 mWh cm−3 at a power density of 0.033 W cm−3, and also shows an outstanding 80.0% capacitance retention after 5000 cycles. Finally, a commercial red LED is successfully powered for more than 15 min to testify the practicality of the devices.