Synthesis of novel 2D g-C3N4/3D CoSe2 hierarchical microflower-like hybrids for high-performance energy-storage applications

The rapid development of new vehicles and portable electronics has continuously pressured advanced renewable energy-storage technologies to deliver exceptional energy-power outputs and long lifetimes. Hybrid supercapacitors attract attention owing to their outstanding power density, high specific capacitance, and excellent cycling stability. In this study, two-dimensional (2D) g-C3N4 nanosheets and 3D CoSe2 hierarchical microflower heterojunction electrodes were synthesized using a facile hydrothermal preparation method, and their electrochemical performances were evaluated. Surface morphology analysis demonstrated that the g-C3N4 nanosheets were well-dispersed on the CoSe2 hierarchical microflower surface. The interstitial contact between CoSe2 and gC3N4 effectively narrowed the bandgap energy, enhanced the electrical conductivity, and improved the electrochemical properties. Electrochemical analysis indicated rapid reaction kinetics and significant energy-storage capacity for the CoSe2/g-C3N4 heterojunction electrode. Notably, the CoSe2/g-C3N4 heterojunction electrode achieved a specific capacitance of 1024.4 F/g at 1 A/g. The assembled CoSe2/g-C3N4 heterojunction hybrid supercapacitor device exhibited a high energy (62 Wh/kg), high power density (775 W/kg), and remarkable lifespan after 10,000 cycles. The developed electrode is promising for energy-related device applications.