Electrodeposition of three-dimensional ZnO@MnO2 core–shell nanocables as high-performance electrode material for supercapacitors

Abstract

Hybrid nano-architecture for supercapacitors has been designed by growing three-dimensional ZnO@MnO2 core–shell nanocables on Ti/RuO2 + TiO2 substrate (titanium plate covered with RuO2+TiO2 coating). Electrochemical depositions were utilized for constructing this core–shell nanostructure, which involved potentiostastic deposition of ZnO nanorod arrays and potentiodynamic deposition of multivalent and partially hydrous manganese oxide. According to cyclic voltammetry and galvanostatic charge–discharge measurements, ZnO@MnO2 core–shell nanocables electrode exhibits higher specific capacitance and better rate capability than those of pure MnO2 electrode. The specific capacitances of ZnO@MnO2 core–shell nanocables reach 537.8 F g−1 at a scan rate of 5 mV s−1 and 613.5 F g−1 at a current density of 1 A g−1. Electrochemical impedance spectroscopies also confirm that ZnO@MnO2 core–shell nanocables electrode has better electrochemical characteristics. Furthermore, ZnO@MnO2 core–shell nanocables losses 10.2% of the initial capacitance after 5000 charge–discharge cycles, which demonstrates its excellent cycling stability. These results indicate that the electrochemical property of manganese oxide has been greatly enhanced due to the supporting of ZnO nanorod arrays, and ZnO@MnO2 core–shell nanocables is promising electrode material for high-performance supercapacitors.