Self-supported core/shell Co3O4@Ni3S2 nanowires for high-performance supercapacitors

Abstract In this work, three dimensional self-supported Co 3 O 4 @Ni 3 S 2 nanowire arrays on nickel foam substrates are prepared by a multi-step method. The as-synthesized product harvests the advantages of the high electrical conductivity of the Co 3 O 4 nanowire arrays, large surface area provided by the Ni 3 S 2 nanosheets, and the efficient ion diffusion pathway offered by the self-supported structure. The sample is subsequently used as the electrode material for supercapacitors, at a current density of 2 mA cm −2 a charge storage capability of 2.41C cm −2 (5.5 F cm −2 ) was achieved. When the sample is charged and discharged at 50 mA cm −2 for 10000 cycles, a stable capacity of 0.86C cm −2 (1.5 F cm −2 ) can still be maintained at the end of the test. Such a performance is better than those values reported in the literature obtained with similar systems even at a lower current density. We also assemble an asymmetric supercapacitor by pairing the Co 3 O 4 @Ni 3 S 2 nanoarrays with activated carbon, and it shows good cyclability over 10000 cycles. The device yields energy densities of 65 and 32.3 Wh kg −1 at power densities of 361 and 9090 W kg −1 , respectively. Furthermore, it is able to light up 12 red light-emitting diodes, showing promising potential for practical applications.