Preparation of Co₃S₄/rGO Composites and their supercapacitor performances

Graphene, with its two-dimensional structure, offers high mechanical flexibility and excellent conductivity, but its tendency to stack and aggregate in practical applications reduces the effective surface area, resulting in rapid capacity degradation. To overcome this, we in situ grow rod-like Co₃S₄ structures on rGO, forming a highly conductive and mechanically stable composite. The Co₃S₄ nanoparticles serve as active sites for redox reactions, significantly improving the specific capacitance, while the rGO matrix enhances electron transport and mitigates the issues of volume expansion during charge/discharge cycles. The Co₃S₄/rGO composite is synthesized via a two-step hydrothermal process, and the effects of sulfuration temperature and time on electrochemical performance are systematically explored. The results show that the Co₃S₄/rGO-160-8 composite, synthesized at 160 °C for 8 hours, achieves a specific capacitance of 1442.5 F g⁻¹ at 1 A g⁻¹ and exhibits a capacity retention of 93.3% after 5000 cycles at 4 A g⁻¹. Furthermore, the Co₃S₄/rGO-160-8//AC asymmetric supercapacitor delivers an energy density of 47.0 Wh kg⁻¹ at 749.8 W kg⁻¹ power density, with only an 8.9% capacity loss after 5000 cycles, demonstrating excellent cycling stability. This novel composite material offers a promising approach for high-performance supercapacitors, balancing high energy density, excellent rate performance, and long-term stability.