Metal-organic framework derived r-Ni3S2 nanoparticles with enriched sulfur vacancies for supercapacitor application

Metal sulfides derived from metal-organic framework (MOF) have high porosity and easily changed morphology, so they are widely used in supercapacitors. However, they still have a few shortcomings such as poor cycle performance and low specific capacitance. The experiment shows that the generation of sulfur vacancy can optimize its electrochemical performance. Therefore, this work focuses on preparing porous nickel sulfide derived from Ni-based MOF and introducing sulfur vacancies at room temperature. Pleated nanoparticles of r-Ni3S2 that are composed of petal-like flakes were prepared with rich sulfur vacancies. This morphology has a larger specific surface area and sulfur vacancies also exposes more active sites, increases free charge carriers and reduces Gibbs free energy of surface reaction, which will enhance electrochemical performance. It is demonstrated that the specific capacitance increased significantly after the sodium borohydride reduction treatment, and the capacitance retention rate increased by 32 % after 5000 cycles. In addition, the asymmetric supercapacitor of r-Ni3S2//AC was assembled, which yielded a specific energy density of 33.7 Wh kg−1 at the power density of 1167.8 W kg−1. This research shows great potential in adjusting the crystal structure of compounds to optimize the advanced electrode materials of storage devices.