Heterointerface-composites of g-C₃N₄/Bi₂O₃ multidimensional nanohybrids for diffusion-dominant asymmetric supercapacitors: A modulation toward architected redox-capacitive synergy

Strategizing interfacial synergies between redox-active and conductive nanostructures presents an emerging strategy to transcend intrinsic limitations of conventional supercapacitor electrodes. Herein, we report hierarchically integrated graphitic carbon nitride/bismuth oxide (g-C₃N₄/Bi₂O₃) heterostructured nanocomposites as high-performance supercapacitor electrodes. A dual-step strategy was employed to obtain 2D g-C₃N₄ nanosheets and 1D Bi₂O₃ nanorods. Three stoichiometries were evaluated, with the g-B-2 composition (g-C₃N₄:Bi₂O₃ = 1:3) yielding optimal electrochemical behavior. Structural analysis revealed uniformly dispersed α- Bi₂O₃ nanorods embedded within 2D g-C₃N₄ matrix, forming highly interconnected interface that facilitates rapid ion diffusion and electronic transport. The g-B-2 electrode delivered superior charge storage behavior with specific capacitance of 1208 F g ⁻¹ (2486 mF cm⁻²)) at 8 mA, high energy density of 20.556 Wh/kg, and excellent cycling durability. Kinetic analysis revealed dominant diffusion-controlled faradaic contribution, elevated OH⁻ ion diffusion coefficients, and significant electrochemically active surface area (286.5 cm²), highlighting synergistic interplay of capacitive and pseudocapacitive processes. Furthermore, when assembled into an asymmetric supercapacitor device (g-B-2//AC), the hybrid system operated efficiently at 1.5 V, delivering exceptional power and energy performance metrics, and remarkable stability (>88 % retention over 10,000 cycles). This study elucidates the critical role of nanoscale interface engineering in augmenting electrochemical performance and positions g-C₃N₄/Bi₂O₃ hybrids as a promising paradigm for next-generation high-rate energy storage systems.