Fabrication of CoSe/CoP with rich selenium- and phosphorus-vacancies and heterogeneous interfaces for asymmetric supercapacitors.

CoSe/CoP with rich Se- and P-vacancies and heterogeneous interfaces (v-CoSe/CoP) is grown on the surface of nickel foam via a two-step strategy: electrodeposition and NaBH reduction, which can be used as the cathode material in asymmetric supercapacitors. The SEM characterization reveals the honeycomb-like structure of the v-CoSe/CoP, and the results of EPR, XPS and HRTEM reveal the existence of anionic vacancies and heterogeneous interfaces in the v-CoSe/CoP. The as-fabricated v-CoSe/CoP exhibits high specific capacitance (3206 mF cm at 1.0 mA cm) and cyclic stability (91 % capacitance retention after 2000 cycles). An asymmetric supercapacitor is assembled by using the v-CoSe/CoP and activated carbon (AC) as cathode and anode materials, respectively, which displays a high energy density of 40.6 Wh kg at the power density of 211.5 W kg. The outstanding electrochemical performances of the v-CoSe/CoP might be ascribed to the synergistic effects of Se- and P-vacancies and the heterogeneous interfaces in the v-CoSe/CoP.