Fabricating reduced graphene oxide films with high volumetric capacitive performances via thermal and acid treatment

Considering the growing requirement for high-performance energy storage devices, active electrode materials with high volumetric performance are urgently needed, but only few reports devote to the preparation of reduced graphene oxide (rGO) with high gravimetric specific capacitance (C_g) and volumetric specific capacitance (C_v). Here, the thermally treated dense rGO films are further treated with concentrated sulfuric acid to achieve the high C_g, C_v and cycling stability. The optimal film possesses high density of about 2.04 g cm⁻³ and exhibits the maximal C_g and C_v of about 242.3 F g⁻¹ and 494.3 F cm⁻³ in 1.0 mol L⁻¹ H₂SO₄ electrolyte based on the two-electrode testing system. Furthermore, the optimal film shows excellent cycling stability in 1.0 mol L⁻¹ H₂SO₄ (90.2% capacitance retention after 10000 cycles) and excellent rate capability. It is believed that this strategy can be developed as an effective process to prepare rGO-based materials with high capacitive performance for compact energy storage device.