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 g-C₃N₄ 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.