Modulating CoP nanowire arrays via ZnO-coating-boosted Ni doping for high-performance hybrid supercapacitors

Abstract

Slow reaction kinetics and large volume change limit the application of cobalt phosphide (CoP) in supercapacitors. Defect engineering and surface coating are regarded as two effective strategies for them. Herein, nickel (Ni) doped CoP (Ni-CoP) nanowire arrays are vertically grown on the surface of activated carbon cloth, followed by zinc oxide (ZnO) coating via an atomic layer deposition method. Ni doping can optimize electron redistribution of CoP to promote its electron transport and generate more active sites. Coated ZnO can not only inhibit the volume change of Ni-CoP during cyclic charge and discharge processes, but also provide additional pseudocapacitance. Benefiting from the synergistic effect of the Ni doping and ZnO coating, the optimal Ni-CoP@ZnO-6 demonstrates a high specific capacity of 877 C g⁻¹ at 1 A g⁻¹ and capacity retention of 83.3% at 15 A g⁻¹. Compared with Ni-CoP, the Ni-CoP@ZnO-6 shows an increased cyclic stability of 15.29% after 10,000 cycles. The assembled hybrid supercapacitor combining Ni-CoP@ZnO-6 with activated carbon has an energy density of 25.7 Wh kg⁻¹ at 459.3 W kg⁻¹, and 2 serially connected HSCs can power a light-emitting diode and timer. The work offers a novel strategy to promote the electrochemical performance of transition-metal compounds for supercapacitors.