Self-templated transformation of Co-ZIF-L into hierarchical porous CoS2/Co-Ni LDHs with improved electrochemical activities

Abstract

CoS2/Co-Ni layered double hydroxides (LDHs) with a rational tailored pore structure are developed by partial sulfurization of Co-ZIF-L and subsequent Ni2+ etching for the transformation of zeolitic imidazolate frameworks (ZIFs) to layered double hydroxides. The as-synthesized CoS2/Co-Ni LDHs maintain the leaf-like structure and have rich hierarchical pores. More importantly, CoS2 nanoparticles are uniformly embedded among Co-Ni LDH layers, facilitating mass diffusion and favorably exposing more active sites. Benefiting from these desirable compositional and structural features, a remarkable specific capacitance (capacity) of 1784 F/g (223 mAh/g) at 1 A/g is delivered by CoS2/Co-Ni LDHs. Furthermore, the as-assembled CoS2/Co-Ni LDH//activated carbon as the asymmetric supercapacitor device also exhibits a high energy density of 125 Wh/kg at a power density of 800 W/kg and a superb capacitance retention of 98 % after 5000 cycles, outperforming many Co-Ni LDH based electrode materials reported in the literature.