Combined Ce-doping and electrochemical activation strategies for boosting the supercapacitance of NiCoO

Abstract

Heteroatom doping and electrochemical activation have been reported to improve electrochemical performance of electrode materials. However, there is no report about the combination of these two methods to enhance the electrochemical performance of NiCo-oxides. Herein, Ce-doped NiCoO nanocones are grown on porous nickel foam, and electrochemical activation tactic is utilized to further boost the electrochemical performance. Through adjusting the Ce-doping dosage, the optimized NiCoCe-0.25 sample presents the highest capacitance of 1800 F g−1, greatly higher than that of pristine NiCoO (969.4 F g−1). The optimized NiCoCe-0.25 is selected as initial electrode for seeking the best activation condition. The activation process in KOH electrolyte triggers the formation of nanosheets on the surface of nanocones, followed by the growing of thin nanosheets. Therefore, the activation mechanism of Ce-doped NiCoO involves the generation and growing of nanosheets, accompanied by the composition transition from oxides to hydroxides/oxyhydroxides. When lasted for 430 CV cycles, the activation product delivers the maximum capacitance of 3795.8 F g−1 (1897.9 C g−1) at 1 A g−1. The superior performance is attributed to the interconnected framework structure consisted of nanosheets and nanoparticles, as well as the optimized composition. When utilized as positive electrode in a supercapacitor device, Ce-doped NiCoO electrode exhibits a high specific capacitance, cycling stability, and energy density. Therefore, Ce-doping and electrochemical activation tactic can be integrated for enhancing the supercapacitance performance of metal oxides.