Fabrication of NiO–ZnO-modified g-C3N4 hierarchical composites for high-performance supercapacitors

Abstract In this work, NiO and ZnO co-modified g-C3N4 (NiO–ZnO@g-C3N4) hierarchical nanocomposite was synthesized using a simple hydrothermal method and used as a high-performance supercapacitor electrode. NiO–ZnO@g-C3N4 consisted of NiO nanoparticles, ZnO nanoparticles, and g-C3N4 nanosheets, in which the g-C3N4 nanosheets served as the matrix for the attachment of NiO and ZnO nanoparticles. Electrochemical tests showed that NiO–ZnO@g-C3N4 displayed an improved electrochemical performance compared with pure NiO. The specific capacitance of NiO–ZnO@g-C3N4 was 726.7 F g−1 at a current density of 0.5 A g−1, which was about 2.1 times higher than that of pure NiO (346.2 F g−1). The capacitance remained at 78% after 1000 cycles at 5 A g−1, demonstrating the good cycle performance of NiO–ZnO@g-C3N4. Moreover, the energy density of NiO–ZnO@g-C3N4 reached 7.91 Wh kg−1 at a power density of 160 W kg−1. The enhanced performance of the NiO–ZnO@g-C3N4 hierarchical nanocomposite was attributed to its unique structure and composition.