Tailoring Holey Graphene Architecture with Sulfur-Doped Oxygen-Deficient MoO₃ for Synergistic Capacitance Enhancement

An eco-friendly, cost-effective strategy is demonstrated for developing efficient supercapacitor (SC) electrode by integrating graphene with oxygen-deficient sulfur-doped MoO₃ (S-MoO_3-x). Graphene is produced via mechanochemical exfoliation of graphite using sucrose as the milling agent, and is then composited with S-MoO_3-x through hydrothermal treatment. Material characterization studies reveal that, during heat treatment, decomposition of sucrose-derived carbon spheres introduced holes in the graphene sheets, leading to the formation of a S-MoO_3-x/holey graphene nanocomposite (S-MoO_3-x/HG). Sulfur doping induces oxygen vacancies, enhancing conductivity and electrochemical performance by modifying the electronic structure of Mo active sites, as evident from material characterization studies. Electrochemical measurements in a three-electrode system are performed to evaluate the capacitance and durability of the S-MoO_3-x/HG electrode. An asymmetric SC pouch cell device is fabricated using S-MoO_3-x/HG as the anode and pure MoS₂ as the cathode, operating at 1.4 V. The device exhibits a maximum energy density of 36.5 Wh Kg^-1 and a power density of 700 W Kg^-1, highlighting its outstanding performance. Notably, the device retains 100% of its capacitance after 15 000 cycles, highlighting its remarkable cycle life and long-term usability. Additionally, two such asymmetric devices are connected in series to power 15 red and yellow light-emitting diodes, further demonstrating their practical application in energy storage systems.