g-C3N4 Modified MnWO4 Nanorods as High-Performance Electrode Materials for Asymmetric Supercapacitors

Abstract

Hybrid nanostructures are transformative in energy storage, offering unparalleled internal and surface properties. However, diffusion-controlled supercapacitors often face challenges like low energy density and poor cycling stability due to sluggish intercalation/deintercalation processes. Here, MnWO₄ nanorods integrated with graphitic carbon nitride (g-C₃N₄) overcome these limitations by enabling a transition from diffusion- to surface-controlled charge storage. The resulting hybrid material achieves an outstanding specific capacitance of 1265 F g^-1 at 1 A g^-1, retaining 91% of its initial capacitance after 5000 cycles at 5 A g^-1. This exceptional performance surpasses that of pure MnWO₄ and MnWO₄ synthesised with surfactants like cetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and sodium lauryl sulfate (SLS). Moreover, the g- C₃N₄-modified asymmetric supercapacitor device (GMW//AC ASC) exhibits a remarkable specific capacitance of 77.24 F g^-1, an energy density of 34.7 W h kg^-1 at a power density of 899.9 W kg^-1, and an impressive 90% retention after 5000 cycles. These findings establish g- C₃N₄-modified MnWO₄ nanorods as a benchmark for designing advanced electrode materials, unlocking new potential for renewable energy storage technologies.