One-step phosphating synthesis of CoP nanosheet arrays combined with Ni2P as a high-performance electrode for supercapacitors

Abstract

A transition metal phosphide is an excellent candidate for supercapacitors due to its superior electrical conductivity and high theoretical capacity. In addition, compared with traditional 3D nano-materials, 2D nanosheets possess a greater specific surface area and shorter electron transport distance. In this study, a reasonable approach is proposed for the synthesis of ZIF-67 nanosheets on nickel foam with subsequent phosphorization by chemical vapor deposition (CVD) to obtain flake-like CoP combined with Ni₂P (NCP/NF), in which nickel foam serves as the current collector as well as the resource of Ni to form Ni₂P. Benefiting from the nanosheet array of CoP, the NCP/NF can improve the capacity of Ni₂P from 0.57 C cm⁻² to 1.43 C cm⁻² at 1 mA cm⁻². Furthermore, the NPC/NF/reduced graphene oxide (RGO) asymmetric supercapacitor (ASC) shows an energy density of 26.9 μW h cm⁻² at a power density of 0.896 mW cm⁻², and excellent cycling performance with a capacity retention of 93.75% after 5000 cycles at 10 mA cm⁻².