One-pot synthesis of tungsten oxynitride/nitrogen-doped graphene with particle-sheet hybrid nanostructure as a highly effective binder-free supercapacitor electrode

High-performance nanoscale composites have achieved predominance as promising materials for supercapacitor applications. Graphene nanosheets decorated with transition metal oxynitride nanoparticles can be highly beneficial in improving supercapacitor properties. However, they are hardly retrieved, and their electrochemical characterizations and inherent charge-storage mechanisms have not been deeply investigated. Herein, tungsten oxynitride decorated nitrogen-doped graphene (WON-NG) is synthesized by a facile one-pot strategy in a particle-sheet hybrid nanostructure. The nanocomposite is grown directly on a nickel foam (NF) as the current collector through the synthesis process. X-ray photoelectron spectroscopy and TEM images have confirmed the particle-sheet hybrid nanostructure of the prepared nanocomposite with tungsten oxynitride nanoparticles and nitrogen-doped graphene nanosheet. The oxygen and nitrogen-based redox groups, which synergistically coexist in the hybrid network, inherently cooperate in the electrochemical activities of the nanocomposite. The electrochemical measurements show that the WON-NG|NF electrode can deliver a superior specific capacitance of 1079.4 F g⁻¹ (4.6 F cm⁻²) at 1 A g⁻¹ in 1 M KOH aqueous electrolyte. In-depth investigations suggest that the diffusive-controlled process governs the charge storage mechanism at all scan rates in the composite for the advantageous porous morphology. The assembled all-solid-state asymmetric supercapacitor device exhibits a high energy density of 81.6 Wh kg⁻¹ and a power density of 5005.4 W kg⁻¹. Also, the designed devise shows an excellent cycle life with 87.7% capacitance retention of 10,000 cycles.