Binder-less fabrication, some surface studies, and enhanced electrochemical performance of Co, Cu-embedded MnO2 thin film electrodes for supercapacitor application

Abstract

We report the fabrication of nanocystalline MnO2 thin film-based electrode on a predeposited indium tin oxide (ITO) film on the glass substrate, using a binderless and simple two-electrode electrofabrication approach. Effects of Co and Cu incorporation on microstructural and electrochemical performance of the electrode were optimally and extensively investigated. The experimental results for the optimum fabrication conditions for Co@MnO2 and Cu@MnO2 and pure MnO2 thin film-based electrode samples showed uniqueness in microstructural features, degrees of crystallinity and roughness, and high electrochemical energy storage performance. Co@MnO2 film electrode exhibited remarkable specific capacitance (1068 Fg-1) and areal capacity (25.78 mAh cm−2) as against other electrode films (Cu@MnO2 and pure MnO2) which exhibited specific capacitances 837 and 438 F g−1 and areal capacities 10.6 and 4.9 mAh cm−2, respectively. Exceptional stabilities were also recorded for the composite samples (87.2% and 84.4% for Cu@MnO2 and Co@MnO2 thin film electrodes, respectively) against the pure MnO2 film electrode sample (77.8%), after 2000 cycles. In addition, the short time constants (1.27 s and 1.31 s) were respectively realized for the fabricated Co@MnO2 and Cu@MnO2 electrode films as against the pure MnO2 electrodes (4.35 s). These features observed in the composite electrode samples demonstrated an exhibition of faster ion response and higher rate capability by the samples. Moreover, the incorporation of Co into the MnO2 electrode material relatively improved the supercapacitive activeness by enhancing the charge transition and transport.