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.

Functional graphene optical sensors are now viable due to the recent developments in hand‐held Raman spectroscopy and the chemical vapor deposition (CVD) of graphene films. Herein, the strain in graphene/poly (methyl methacrylate) sensor coatings is followed using Raman band shifts. The performance of an “ideal” mechanically‐exfoliated single crystal graphene flake is compared to a scalable CVD graphene film. The dry‐transferred mechanically exfoliated sample has no residual stresses, whereas the CVD sample is in compression following the solvent evaporation during its transfer. The behavior of the sensors under cyclic deformation shows an initial breakdown of the graphene‐polymer interface with the interface then stabilizing after several cycles. The Raman 2D band shift rates per unit strain of the exfoliated graphene are ≈35% higher than CVD graphene making the former more strain sensitive. However, for practical wide‐area applications, CVD graphene coatings are still viable candidates as a Raman system can be used to read the strain in any 5 μm diameter spot in the coating to an absolute accuracy of ≈0.01% strain and resolution of ≈27 microstrains (μs), which compares favorably to commercial photoelastic systems.