Interfacial charge transfer mediated by bridging and terminal hydroxyls on the (001) and (101) facets of TiO2 in the photocatalytic degradation of toluene

Abstract

Understanding the key factors that influence the interfacial transfer of charge carriers is crucial for improving the photocatalytic degradation of volatile organic compounds (VOCs). Herein, TiO₂ samples with dominantly exposed (001) and (101) facets were synthesized. The density and types of hydroxyls on these facets were modified through alkali treatment. The surface photovoltage spectrum was measured in various atmospheres to analyze the interfacial charge transfer processes. The alkali treatment created additional terminal hydroxyls (OH_t) on the (001) facets and bridging hydroxyls (OH_b) on the (101) facets. OH_t enhanced the migration of holes toward the (001) facets, and OH_b facilitated the migration of electrons toward the (101) facets, thereby promoting charge separation. The accumulation of holes on the (001) facets was limited in the absence of OH_t. H₂O significantly enhanced charge separation in the presence of O₂ and toluene, thereby improving both the adsorption and degradation of toluene. This work provides new insights into the interfacial processes involved in photocatalytic degradation of VOCs.