Tailoring graphitic carbon nitride for ultracapacitor electrode application through nanocompositing with SnO₂ and WO₃

Supercapacitors are a promising and necessary pillar that can aid the full-fledged adoption of intermittent renewable energy resources and emerging portable technologies. The performance of supercapacitors largely depends on the physicochemical properties of the electrode materials, which are centred on design and composition. The g-C₃N_4, as a 2D graphitic material, has long been recognised as a suitable electrode material for supercapacitors due to readily available sources. However, limited electro-active surfaces and low conductivities have posed significant challenges. Modifying physicochemical properties through compositing has emerged as a suitable approach to enhance their applicability in energy storage by generating hybrid electrode types. In this context, the current work investigated SnO₂ nanoparticles and WO₃ nanorods as enhancers of g-C₃N₄ nanosheets in binary (WO₃-g-C₃N₄ and SnO₂-g-C₃N₄) and ternary (SnO₂-WO₃-g-C₃N₄) nanocomposites for applications in supercapacitor electrodes. Properties were synergistically tailored; for instance, charge transfer resistance of SnO₂-WO₃-g-C₃N₄, g-C₃N₄, SnO₂-g-C₃N₄, and WO₃-g-C₃N₄ were 1.55, 1.26, 0.8 and 0.48 Ω, respectively. Consequently, incorporation of SnO₂ and WO₃ amplified energy storage by 119% and 172% in binary nanocomposites, while the ternary nanocomposites showed an improvement of 192%. The SnO₂-g-C₃N₄, WO₃-g-C₃N₄ and SnO₂-WO₃-g-C₃N₄ materials attained cycle stability of 70, 96, and 50%, respectively, after 2000 cycles. Other key synergism attributes from the work include morphological transformations that enhanced structural rigidity, intimate connectivity through chemical linkages, improved electro-active surfaces, and additional pseudo-capacitive contributions in the nanocomposites. The studied nanocomposites highlight that g-C₃N₄ can be favourably tuned in this manner and pave the way for significant potential in sustainable electrodes for abundant, clean, and renewable electrochemical energy.