In situ growth of NiCo sub(2)S sub(4) nanotube arrays on Ni foam for supercapacitors: Maximizing utilization efficiency at high mass loading to achieve ultrahigh areal pseudocapacitance

Self-standing NiCo sub(2)S sub(4) nanotube arrays have been in situ grown on Ni foam by the anion-exchange reaction and directly used as the electrode for supercapacitors. The NiCo sub(2)S sub(4) nanotube in the arrays effectively reduces the inactive material and increases the electroactive surface area because of the ultrathin wall, which is quite competent to achieve high utilization efficiency at high electroactive materials mass loading. The NiCo sub(2)S sub(4) nanotube arrays hybrid electrode exhibits an ultrahigh specific capacitance of 14.39 F cm super(-2) at 5 mA cm super(-2) with excellent rate performance (67.7% retention for current increases 30 times) and cycling stability (92% retention after 5000 cycles) at a high mass loading of 6 mg cm super(-2). High areal capacitance (4.68 F cm super(-2) at 10 mA cm super(-2)), high energy density (31.5 Wh kg super(-1) at 156.6 W kg super(-1)) and high power density (2348.5 W kg super(-1) at 16.6 Wh kg super(-1)) can be achieved by assembling asymmetric supercapacitor with reduced graphene oxide at a total active material mass loading as high as 49.5 mg. This work demonstrates that NiCo sub(2)S sub(4) nanotube arrays structure is a superior electroactive material for high-performance supercapacitors even at a mass loading of potential application-specific scale.