Fabrication of CoSe₂/CoP with rich selenium- and phosphorus-vacancies and heterogeneous interfaces for asymmetric...

CoSe₂/CoP with rich Se- and P-vacancies and heterogeneous interfaces (v-CoSe₂/CoP) is grown on the surface of nickel foam via a two-step strategy: electrodeposition and NaBH₄ reduction, which can be used as the cathode material in asymmetric supercapacitors. The SEM characterization reveals the honeycomb-like structure of the v-CoSe₂/CoP, and the results of EPR, XPS and HRTEM reveal the existence of anionic vacancies and heterogeneous interfaces in the v-CoSe₂/CoP. The as-fabricated v-CoSe₂/CoP exhibits high specific capacitance (3206 mF cm^-2 at 1.0 mA cm^-2) and cyclic stability (91 % capacitance retention after 2000 cycles). An asymmetric supercapacitor is assembled by using the v-CoSe₂/CoP and activated carbon (AC) as cathode and anode materials, respectively, which displays a high energy density of 40.6 Wh kg^-1 at the power density of 211.5 W kg^-1. The outstanding electrochemical performances of the v-CoSe₂/CoP might be ascribed to the synergistic effects of Se- and P-vacancies and the heterogeneous interfaces in the v-CoSe₂/CoP.