Photoreduction of Graphene Oxides: Methods, Properties, and Applications

In view of mass-production and solution-processing capabilities, graphene oxides (GOs), generally prepared by chemical oxidation of graphite and subsequent exfoliation in aqueous solution, are widely used as an effective route to graphene-like materials. However, the oxygen-containing groups (OCGs) on the graphene sheets make GO insulating, which significantly restricts its applications, especially for electronics. Therefore, reduction methods that are used to remove OCGs become critical. In recent years, in addition to thermal and chemical reduction, photoreduction has emerged as an appealing alternative because photoreduction does not rely on either high temperature or toxic chemicals. In this progress report, the recent development of the photoreduction of GOs and their unique properties are highlighted, as well as their related applications. Photoreduction strategies including photothermal reduction, catalytic/catalyst-free photochemical reduction, and solid state/in-solution laser reduction are summarized. Moreover, photoreduction of GO permits exquisite control over film conductivities, residual oxygen contents, porosity, and surface wettability, which lead to various functionalities towards a wide range of applications, such as field-effect-transistors ( FETs), flexible electrodes, sensors, supercapacitors, Li-ion batteries, photovoltaic devices, and photocatalysis. It is anticipated that, with the rapid progress of photoreduction methodology, GOs would be more competitive in the graphene-oriented applications.