Unveiling the collective effects of moisture and oxygen on the photocatalytic degradation of m-Xylene using a titanium dioxide supported platinum catalyst

The development of practical photocatalytic system is of great significance in pursuit of efficient removal of hazardous volatile organic compounds (VOC) in indoor environments. The photocatalytic degradation (PCD) of VOC, as assessed commonly in terms of conversion efficiency (e.g., into intermediate/by-product species), is affected by the combined effects of multiple variables in the reaction environment such as relative humidity (RH) level and oxygen (O2) content. In this research, the interactive relationship between such variables (e.g., RH from 0 to 100% and the O2 level from 0 to 21%) has been studied using m-xylene (X) as model compound in a dynamic flow reactor system made of the titanium dioxide-supported platinum (Pt/TiO2). Accordingly, the involvement of water (H2O) and O2 is found to synergistically increase the PCD efficiency for the mineralization of xylene through the generation of a large number of reactive oxygen species (ROS: e.g., superoxide anion and hydroxyl radicals from the adsorbed O2 and H2O molecules, respectively) under ultraviolet (UV) irradiation. The detailed information acquired in this research is expected to offer valuable insights into the degradation pathways of aromatic VOC and the interactive roles between PCD process variables, especially water and oxygen.