Expanded graphite/reduced graphene oxide hybrid architecture functionalized with RuO2 nanoclusters for high performance energy storage

In this study, a one-step thermal process was employed to functionalize a graphene-based composite consisting of expanded graphite (EG) and reduced graphene oxide (rGO) with ruthenium nanoclusters of 2–3 nm in diameter. The Ru/EG-rGO nanocomposites were optimized by varying the EG content and annealing temperature, revealing their effects on substrate interconnectivity, nanoparticle binding affinity, and the degree of reduction of graphene oxide (GO) and ruthenium chloride. The optimized Ru/EG-rGO nanocomposite, with a 1:1 ratio of EG:GO and annealing temperature of 350 °C, exhibited the highest specific capacitance at 382 F g⁻¹ in 0.5 M H₂SO₄. In a symmetric capacitor configuration, the material demonstrated superior performance compared to other Ru-based supercapacitors, achieving a high energy density of 22.1 Wh kg⁻¹ at a power density of 0.5 kW kg⁻¹, and retained 13.6 Wh kg⁻¹ at a power density of 10 kW kg⁻¹. Furthermore, the material showcased remarkable durability, retaining 97 % of the initial capacitance after 10,000 cycles at 5 kW kg⁻¹. The high performance and stability, combined with the ease of fabrication, makes this novel Ru/EG-rGO nanocomposite promising for supercapacitor applications, and the design strategies demonstrated in this work can be further applied to the development and large-scale fabrication of energy storage materials.