Graphene oxide photochemical transformations induced by UV irradiation during photocatalytic processes

In present work, the stability and photochemical transformations of graphene oxide (GO) under UV irradiation in water dispersion, and during photocatalytic processes, in the system containing TiO2 thin films, were examined. Under UV light, the appearance of defects in GO flakes structure was observed, and the intensification of flakes deterioration was noted in the presence of semiconductor. It was found that the type of UV light source determines the scale of degradation of GO flakes dispersed in water. Using the two types of UV light sources: fluorescent and xenon lamps, which differ in radiation intensity (15 mW/cm(2) and 223 mW/cm(2)) the size of holes in GO flakes was estimated to be approximately 2 nm and 34 nm, respectively. To evaluate of TiO2 influence on GO decomposition GO flakes were deposited onto TiO2 thin films. The degradation process during irradiation of TiO2 thin films coated with GO in water was quantified by measuring GO flakes area. After 120 min of UV irradiation with the Xe lamp, the surface coverage of TiO2 with GO flakes decreased from 51% to 22%. Without access to light, no changes were registered. Analysis of structural changes is supported with SEM, AFM and TEM microscopy and spectroscopic studies consisting UV-Vis, FT-IR, XPS and Raman spectroscopy. Also, the influence of organic pollutant on the GO degradation process is discussed, revealing that the degradation of GO and contaminant are competitive and occur simultaneously.

Automated summary

This study investigated the stability and photochemical transformations of graphene oxide (GO) under UV irradiation and during photocatalytic processes, particularly in the presence of TiO2 thin films. It was found that the type of UV light source significantly affects the degradation of GO flakes, and TiO2 thin films can accelerate the degradation process of GO.