UV-Assisted Fabrication of Green Quality rGO with Wavelength-Dependant Properties

Reduction of graphene oxide (GO) has emerged as one of the most feasible and cost-efficient routes to graphene-based materials. While many approaches reliant on the use of chemicals and/or irradiation are known to restore the π-bonds and partially revive the properties of graphene, they suffer from issues such as scalability, waste generation, and adaptability to wide variety of product needs. Herein, a simple, yet versatile solid-state method for tuning the properties of GO by balancing the competing mechanisms of graphitization and defect generation is reported. Such demand cannot be met by the current irradiation-based reduction routes. Healing of π-πbonds and graphitization are found to be promoted by UVC radiation, whereas defect production and amorphisation are distinctly prominent with UVA treatment. The healed rGO films are suitable for production of supercapacitors in commercial-size configurations with competitive volumetric energy densities (rGO electrode capacitance of 194.3 F/cm³ translated to electrode energy density of 27 W h/L), whereas the defective graphene (UVA treated) was found to increase the permeance of GO nanofiltration membranes to fivefold without suppressing its rejection characteristics. It is shown that critical selection of wavelengths of the UV light is key to tune the final properties of rGO for targeted applications.