Abstract

The limited energy density and poor electrical conductivity of conventional supercapacitor electrodes restrict their application in advanced energy storage systems. In this work, BiCoO3/g-C3N4 nanocomposites with different compositions were synthesized via solid-state mixing of hydrothermally prepared BiCoO3 and thermally treated g-C(3)N(4)obtained through thermal treatment, to combine the redox activity of BiCoO3 with the sable, nitrogen-rich framework of g-C3N4. Structural analysis confirms the formation of well-integrated hybrid materials with improved interfacial interaction. Electrochemical studies show that g-C3N4 exhibits electric double-layer capacitance, while BiCoO3 delivers a high specific capacitance of 710 F g(- 1). The composite electrodes show better electrochemical performance, with BiCoO3/g-C3N4-90 giving a specific capacitance of 161.5 F g(- 1) at 1 A g(- 1), a moderate energy density of 3.46 Wh kg(- 1), and a power density of about 6600 W kg(- 1). The electrode also shows stable cycling behaviour, retaining around 94-95% of its capacitance after 2000 cycles. The improved performance is ascribed to the combined surface capacitive and Faradaic contributions, which enhance charge transfer and ion transport.