Ultrafast synthesis of Cu/Cu2O/Cu2S@coal-based carbon heterostructure with multiple redox pairs for enhancing specific capacitance in asymmetric supercapacitors

Cu-based compounds are indispensable materials for pseudocapacitors owing to their excellent electrical conductivity and diverse valence states. Their practical performance remains constrained by nanoparticle agglomeration and limited active sites. Herein, a low-temperature pre-oxidation strategy was employed to introduce coal-based carbon surface with abundant C O and = C–H groups, providing uniform anchoring sites for Cu-based compounds. Through flash Joule heating process, these precursors were transformed into a Cu/Cu 2 O/Cu 2 S heterostructure intimately (4.6 s) integrated with the carbon substrate. The lattice defects at the heterostructure promote the adsorption and diffusion of ions, while the coexistence of Cu 0 /Cu + redox pairs enhances reversibility of Faradaic reactions. As a result, the optimized Cu@OMC electrode have good specific capacitance (2041 Fg −1 at 1 A g −1 ) in 6 M KOH. It is assembled into an asymmetric supercapacitor, which has a high energy density of 60.01 Wh kg −1 , a power density of 800.00 W kg −1 , and a specific capacity retention rate of 97.29 % after 10,000 cycles. This study provides a simple and efficient strategy for the preparation of carbon-supported metal compound electrode materials.