Flower-Like Nanostructured ZnCo ₂ O ₄ /RuO ₂ Electrode Materials for High Performance Asymmetric Supercapacitors

Abstract

RuO 2 is well known to be an active and expensive metal oxide. In the paper, ZnCo 2 O 4 /RuO 2 nanocomposites were synthesized by simple hydrothermal, impregnation and calcination methods. Due to the multifunctional bridge structure, RuO 2 could not only effectively inhibit the volume change of ZnCo 2 O 4 in long-term work but also provide more redox active sites. The forbidden bandwidth was reduced and the conductivity was improved after doping RuO 2 . Compared with ZnCo 2 O 4 , the density of state of ZnCo 2 O 4 /RuO 2 tended to a higher energy level. ZnCo 2 O 4 /3 wt% RuO 2 electrode exhibited an excellent specific capacitance (1346.56 F g −1 ) and cyclic stability in 6 M KOH aqueous solution. For the first time, the electrochemical performance of ZnCo 2 O 4 /RuO 2 //IrO 2 -ZnO ASC has been evaluated in two-electrode configurations. The supercapacitor exhibited an excellent energy density of 40.89 W h kg −1 at the power density of 740 W kg −1 and a high capacitance retention of 87.5% even after 7000 cycles at a scanning rate of 100 mV s −1 . The ZnCo 2 O 4 /RuO 2 was a promising electrode material for supercapacitors.