Graphene quantum dots-induced morphological changes in CuCo2S4 nanocomposites for supercapacitor electrodes with enhanced performance

•Graphene quantum dots induce morphology changes of CuCo2S4 by turning the smooth CuCo2S4 surface to particle-constituting hierarchical nanostructure.•The morphology change assists the electrochemical cycling processes as well as the ion diffusion and charge transfer kinetics for improved supercapacitor performances.•GQD/CuCo2S4 electrodes demonstrate a specific capacitance of 1725 F g−1 and retain 90% capacitance after 10,000 cycles.