Toward a Comprehensive Understanding of Photocatalysis: What Systematic Studies and Alcohol Surface Chemistry on TiO₂(110) Have to Offer for Future Developments

Heterogeneous photocatalyticsystems are usually described basedon electrochemistry, which the vast majority of interpretations andstrategies for optimizing photocatalysts rely on. Charge carrier dynamicsare usually in the spotlight, whereas the surface chemistry of thephotocatalyst is neglected. This is unjustified, because studies onalcohol photoreforming on metal-decorated rutile single crystals revealedthat the electrochemical reaction model is not generally applicable.Hence, many photocatalytic reactions may proceed in a different mannerand the thermal chemistry needs to be accounted for. The new mechanismis particularly relevant for reactions in gaseous environments inthe absence of solvated ionic species. Here, we compare both mechanismsand highlight their differences and consequences for photocatalysis.Based on alcohol photochemistry, we demonstrate the importance ofthermal reactions in photocatalytic mechanisms and the relevance ofsystematic studies in different environments for a holistic understandingof photocatalysis.