The Influence of the Strong Metal–Support Interaction in the Photocatalytic Hydrogen Evolution Reaction from Pt-Loaded Titania

Tuning hydrogen evolution cocatalysts to suppress unwanted side and back reactions is critical for obtaining high catalytic efficiency and stability in photocatalysts comprising noble metal particles. The reactivity of such particles on reducible oxidic support materials, such as titania, can be tuned by exploiting the so-called strong metal–support interaction (SMSI). Yet a fundamental understanding of the effect of the SMSI on the catalytic activity remains lacking, in particular in photocatalytic systems. Such insights, however, are crucial for rationally designing catalysts and exploiting the full potential of this phenomenon. Herein, we utilize the photocatalytic gas-phase oxidation of alcohols on Pt-loaded TiO2, in combination with DFT simulations on TiOx/Pt(111), to gain an atomistic understanding of the effects of the SMSI on the hydrogen evolution reaction. We perform heat treatments at different temperatures in vacuum and investigate the resulting photoreactivity of methanol. The measurements show that annealing to 700 K alters the photoactivity depending on cocatalyst loading and the initial degree of titania reduction. Furthermore, scanning tunneling microscopy reveals the effect of temperature on cluster dispersion. Finally, we conduct theoretical simulations on a model system, which suggest that defects in very thin titania films can act as hydrogen evolution centers, outlining a yet unconsidered pathway for hydrogen formation on encapsulated Pt particles.