g-C₃N₄/TiO₂ composite catalysts for the photo-oxidation of toluene: Chemical and charge handling effects

The interaction between carbon nitride and titania in g-C₃N₄/TiO₂ materials is analyzed from a new perspective. The composite materials are prepared using a well crystallized anatase substrate over which carbon nitride (0.5–4 wt%, promoted or not with Mn) is deposited. The catalysts are characterized using a multitechnique approach. In addition, a kinetic formalism using a rigorous intrinsic expression of light was developed in order to reveal information concerning the chemical and charge carrier effects occurring in the materials. Together with the measurement of the adsorption of the main organic molecules involved in the reaction showed that toluene photo-oxidation follows a hydroxyl-mediated mechanism. Moreover, the work shows that the rate of available hydroxyl radicals at the surface of the solids controls activity in the g-C₃N₄/TiO₂ catalysts. The contact between components also affects the hydroxyl radical interaction with the reactant and intermediate molecules of the photo-oxidation, modulating the selectivity.