Influence of Surface-Related Phenomena on Mechanism, Selectivity, and Conversion of TiO2-Induced Photocatalytic Reactions

Heterogeneous photocatalysis is the result of an inextricable connection of several factors differently contributing to the overall process. Photon absorption is the "sine qua non" condition for the reaction to occur. In fact, photons can be considered as immaterial reactants, and all of the phenomena related to the interaction of light-matter play a prominent role. However, other factors contribute in a concerted way to address the reaction, so that the relative contribution of each of them is often difficult to evaluate. In this framework, the present paper highlights some aspects of the interaction of TiO2 surface-adsorbate species that could be underestimated and their influence on the conversion, selectivity, and mechanisms of photocatalytic reactions. To this aim, some paradigmatic examples on the adsorption of water and organics on TiO2 are reported.