Overview on microfluidic reactors in photocatalysis: Applications of graphene derivatives

Microreactor technology represents one of the many methods for process intensification. Microreactors (MRs) truly inherit their tremendous properties from the dimensions of the reaction environment and their advantages cannot be overemphasized. They have remarkable heat and mass transfer rates, short molecular diffusion distance, good laminar flow, and better spatial illumination homogeneity as compared to conventional reactors due to their high surface-to-volume ratio. This review presents state-of-the-art information on the applications of this technology to photocatalytic processes involving the use of graphene (GR) derivatives, either alone or in combination with inorganic semiconductor to form nanocomposites. The latter are hybrid photocatalysts leveraging on the remarkable properties of GR, which include high electron mobility, excellent specific surface area, good mechanical and thermal properties. Because of the resulting high photonic efficiency, enhanced interfacial surface area and reduced electron-hole recombination, such catalysts are increasingly studied and tested in photocatalysis. The utilization of GR derivatives to drive advanced oxidation processes within MRs has, thus, the potential to afford a better efficiency and economic feasibility for such devices. However, studies on the application of MRs to photocatalytic processes involving the use of GR-derived semiconductors are very limited at this stage. It is hoped that this overview will serve as eye-opener for researchers, and create the needed awareness that more work is still needed to be done, in order to be able to actualize and explore the potentials of MRs. Full understanding of this technology would help in going into more details in the modelling of challenging photocatalytic reactions and in gathering enough data that can help increase photocatalytic efficiency and trigger eventual commercialization of the presented technologies.