Photochemistry of Ethanol on Rutile TiO₂(110): Breaking Two Bonds with One Hole

Understanding the mechanism of ethanol (EtOH) photochemistry is of significance for photocatalytic H2 production. Here, we reported a systematical study of EtOH photochemistry on rutile (R)–TiO2(110), aiming to illustrate how photogenerated holes and electrons are involved in bond breaking. We found that the yields of aldehyde from the ethoxy group and EtOH photooxidation on R–TiO2(110) are proportional to the square root of the photon flux, demonstrating that one hole can induce molecular EtOH decomposition to aldehyde. The initial O–H bond cleavage occurs mainly via a proton-coupled hole transfer process, and the C–H bond cleavage is a hole-mediated process, leaving two electrons on the surface, in agreement with the “current doubling effect”. In addition, the rate of aldehyde formation from the ethoxy group is about 3 orders of magnitude faster than that from EtOH, suggesting that the O–H bond cleavage determines the rate of EtOH photochemistry. The results may considerably broaden our understanding of TiO2 photocatalysis