Simultaneous Top‐Down and Bottom‐Up Synthesis of Metal‐Free g‐C ₃ N ₄ /Graphene Hybrid via Mechanochemical Exfoliation and Thermal Treatment for High‐Performance Supercapacitors

A dual synthetic strategy is introduced here for the preparation of a hybrid g‐C 3 N 4 /graphene nanocomposite using a cost‐effective ball milling method followed by thermal treatment for supercapacitor applications. Graphite is exfoliated to graphene via a top‐down route, where melamine serves as both the milling agent and the precursor for the bottom‐up synthesis of g‐C 3 N 4 . This approach integrates both materials efficiently, yielding synergistic properties. The hybrid material delivers an ultrahigh specific capacitance of 1415.7 F g −1 at 3 A g −1 , with negligible internal resistance, confirming its excellent energy storage performance. Cyclic voltammetry and Dunn's method analysis reveal significant pseudocapacitive contributions to energy storage. A coin cell supercapacitor with the g‐C 3 N 4 /graphene electrodes exhibits an areal capacitance of 222.3 mF cm −2 (168.3 F g −1 ) at 0.1 mA cm −2 with an energy density of 13.54 μWh cm −2 (23.3 Wh kg −1 ) and a power density of 5.13 mW cm −2 (3885.3 W kg −1 ). The device, after 10,000 galvanostatic charge‐discharge cycles, shows an increase in its activity to 109.9% as a result of the improved diffusion of electrolyte ions over time. A series‐connected arrangement of three symmetric supercapacitors is utilized to power a mini fan and illuminate five green LEDs, highlighting the real‐world applicability.