High-surface energy enables efficient and stable photocatalytic toluene degradation via the suppression of intermediate byproducts

Abstract

Photocatalyst deactivation is a fatal obstacle for environmental applications. Most photocatalysts face this universal problem during toluene degradation, even P25 with commercial application values. In order to elucidate the mechanism of P25 deactivation and to develop deactivation-resistant photocatalysts, a comparative study was conducted with a typical photocatalyst (ZnGa₂O₄) possessing high activity for the removal of toluene. It was demonstrated that the surface electronic structure of photocatalysts was a major factor affecting the inactivation rather than their inherent redox capacity as revealed by in situ DRIFTS and density functional theory (DFT). Due to the low surface energy of P25, the main interaction between P25 and reactants was dominated by physical adsorption, which induced the formation of a relatively weak bond and thus rendered it difficult for the toluene molecules to be activated and further oxidized. This led to increased intermediate byproduct accumulation and clogging of the active sites because these byproducts were difficult to be converted in time, ultimately resulting in the final deactivation of the photocatalyst. In contrast, the higher surface energy of ZnGa₂O₄ favored the chemical adsorption of reactants on the catalyst surface, which facilitated the activation of toluene. The unique interaction between the ZnGa₂O₄ with high surface energy and toluene could promote the conversion of pollutants and suppress the generation of byproducts to maintain a high stability of photocatalysts. This work could provide a new perspective for understanding the pivotal role of surface chemistry in the deactivation and development of efficient and stable photocatalysts for the decomposition of VOCs.