Conventional chemical oxidation routes for the production of graphene oxide (GO), such as the Hummers’ method, suffer from environmental and safety issues due to their use of hazardous and explosive chemicals. These issues are addressed by electrochemical oxidation methods, but such approaches typically have a low yield due to inhomogeneous oxidation. Herein we report a two-step electrochemical intercalation and oxidation approach to produce GO on the large laboratory scale (tens of grams) comprising (1) forming a stage 1 graphite intercalation compound (GIC) in concentrated sulfuric acid and (2) oxidizing and exfoliating the stage 1 GIC in an aqueous solution of 0.1 M ammonium sulfate. This two-step approach leads to GO with a high yield (>70 wt %), good quality (>90%, monolayer), and reasonable oxygen content (17.7 at. %). Moreover, the as-produced GO can be subsequently deeply reduced (3.2 at. % oxygen; C/O ratio 30.2) to yield highly conductive (54 600 S m^–1) reduced GO. Electrochemical capacitors based on the reduced GO showed an ultrahigh rate capability of up to 10 V s^–1 due to this high conductivity.

Three-dimensional (3D) graphene oxide/polypyrrole (GO/PPy) composite electrodes have been fabricated via one-step electrochemical co-deposition in an aqueous solution containing pyrrole monomers, GO and LiClO₄. The concentration of GO in the solution plays an important role in controlling the morphologies of the as-deposited GO/PPy composites, and a relatively low concentration of 0.1 mg mL⁻¹ is favorable for the formation of a 3D interconnected structure. The unique 3D interconnected structure ensures fast diffusion of electrolyte ions through the electrode. As a result, the GO/PPy composite electrode with a mass loading of 0.26 mg cm⁻² exhibits the highest specific capacitance of 481.1 F g⁻¹, while the electrode with a larger mass loading of 1.02 mg cm⁻² delivers the best area capacitance of 387.6 mF cm⁻², at a current density of 0.2 mA cm⁻². Moreover, the GO/PPy composite electrodes exhibit good rate capability with capacitance retentions over 80% when the current density load increases from 0.2 to 10 mA cm⁻². Both the aqueous and solid-state supercapacitors based on GO/PPy composite electrodes show excellent capacitive properties with good cycling stability, indicating their suitability for applications in energy storage and management.