Reduced graphene oxide: Control of water miscibility, conductivity, and defects by photocatalysis

A TiO₂-based photocatalytic reaction is demonstrated to synthesize water miscible reduced graphene oxide (RGO) sheets with conductivity comparable to that of bulk graphite. Unlike the conventional chemical/thermal reduction pathways which effectively deoxygenated the oxidized graphite, the photocatalytic method removes oxygen functional groups selectively to afford excellent conductivity restoration yet maintaining its water miscibility. The controlled redox capabilities of the photocatalyst serve as an effective modulation tool to tune the conductivity restoration and suppression of hydrophobicity. Moreover, the evolution of defect minimization/generation in a two-step pattern is monitored throughout the photocatalytic process and its association with the conductivity of RGO is established. The insights of defect engineering at the initial stage of graphene oxide (GO) to RGO transformation provides useful information in developing optimum chemical methods to produce large domain and small defect density graphene.