Heterogeneous Photocatalysis: Alcohols on Bare and Metal-loaded TiO2(110) and Fe2O3(012)

Abstract

We investigated the (photo)chemistry of alcohols on TiO2(110) and Fe2O3(012) in ultra-high vacuum. Our studies focused on the role of the metal co-catalyst in the photocatalytic reaction by comparing the reactivity of bare and metal-loaded surfaces. We show that photocatalytic reactions are not merely a couple of redox reactions, but an interplay of thermal and photon-driven surface reactions. Our results demonstrated that the co-catalyst plays a crucial role in the outcome of the reaction. On TiO2(110), alcohols are oxidized to the aldehyde/ketone and hydrogen surface species upon illumination. The hydrogen surface species were thermally converted to H2 by the co-catalyst, allowing for a steady-state photocatalytic conversion of alcohols and the continuous production of molecular hydrogen. Using mass spectrometry, we determined turnover frequencies and rate constants. The identification of surface mechanisms on Fe2O3 is less advanced, but there seem to be strong parallels in the photochemistry. Our studies shed light on the fundamental processes involved in photocatalytic reactions on metal-loaded surfaces and contribute to the development of sustainable energy technologies