Photo-catalytic reduction of oxygenated graphene dispersions for supercapacitor applications

Reduced graphene oxide (rGO) obtained from aqueous graphene oxide (GO) tends to agglomerate with time and hinders the commercial scale applications for high-density energy storage. Here, we report a photo-catalytic reduction of GO dispersions in N-Methyl-2-Pyrrolidone (NMP) under deep UV light ( λ ∼ 253 nm) for 60 min. The obtained hydrophobic rGO dispersions are electrochemically stable for more than 160 d and exhibit a high Brunauer–Emmet–Teller (BET) surface area of ∼260 m² g⁻¹. The NMP being a dipolar aprotic solvent serves as an electron donor and its high dipole moment enhances the electrochemical stability of rGO. Furthermore, the fabricated supercapacitor exhibits a high specific capacitance, charge retention, energy and power density of ∼220 F g⁻¹ (current density of 0.5 A g⁻¹), up to 1000 charging/discharging cycles, 7.32 Wh kg⁻¹ and 130 W kg⁻¹, respectively. The high stability of dispersion and electrochemical performance of synthesized rGO is envisaged for potential applications in high density energy storage and conductive inks for flexible electronics. (paper)