Electrochemical oxidation to construct a nickel sulfide/oxide heterostructure with improvement of capacitance†
Supercapacitors have been widely recognized as a promising device for the storage of renewable energy. Herein, a facile electrochemical oxidation strategy is described to construct a nickel sulfide/oxide heterostructure which enhances the specific areal capacitance of Ni3S2 electrodeposited on nickel foam. The resulting heterostructure electrode exhibits high areal capacitance, 65 times that of the as-prepared Ni3S2 electrode (2035 mF cm−2vs. 31 mF cm−2 at a current density of 8 mA cm−2), while still maintaining great stability, showing no performance degradation after 5000 charge–discharge cycles. Its exceptional capacitance, advanced rate capability, and superior cycling stability are attributed to the transformed composition and unique nanostructure achieved during electrochemical oxidation, which can provide a large electrochemically active surface area, fast electron/electrolyte ion transport, and robust structural stability. Such a low-cost and facile strategy can be potentially applicable to prepare many other materials for supercapacitor applications.