The synergistic effect of carbon nanotubes and graphitic carbon nitride on the enhanced supercapacitor performance of cobalt diselenide-based composites

Recently, transition metal selenides have been investigated extensively as promising electrode materials for high-performance supercapacitors. Herein, multi-component CoSe2/CNTs@g-C3N4 composites are prepared using a two-step hydrothermal method by incorporating one-dimensional CNTs and two-dimensional g-C3N4 nanosheets to form a network-like structure. The CoSe2/CNTs@g-C3N4 composite with a mass ratio of 1 : 3 (CNTs to g-C3N4) shows an ultra-high specific capacity of 445.4 mA h g−1 (3563.0 F g−1) at 1 A g−1, which is more than 2 times that of pure CoSe2. The assembled asymmetric supercapacitor based on CoSe2/CNTs@g-C3N4 delivers a high energy density of 77.1 W h kg−1 at 850 W kg−1. The striking capacitive performance is ascribed to the multi-dimensional synergistic contribution of two kinds of carbon materials to the electric conductivity and spatial structure of the composites, involving the improved charge transfer due to connecting g-C3N4 and the active CoSe2 by the high conductive CNT bridges, and the short ion diffusion pathways on the porous carbon framework constructed by g-C3N4 nanosheets with the assistance of CNTs.