Stepwise Photocatalytic Dissociation of Methanol and Water on TiO2(110)

We have investigated the photocatalysis of partially deuterated methanol (CD3OH) and H2O on TiO2(110) at 400 nm using a newly developed photocatalysis apparatus in combination with theoretical calculations. Photocatalyzed products, CD2O on Ti5c sites, and H and D atoms on bridge-bonded oxygen (BBO) sites from CD3OH have been clearly detected, while no evidence of H2O photocatalysis was found. The experimental results show that dissociation of CD3OH on TiO2(110) occurs in a stepwise manner in which the O–H dissociation proceeds first and is then followed by C–D dissociation. Theoretical calculations indicate that the high reverse barrier to C–D recombination and the facile desorption of CD2O make photocatalytic methanol dissociation on TiO2(110) proceed efficiently. Theoretical results also reveal that the reverse reactions, i.e, O–H recombination after H2O photocatalytic dissociation on TiO2(110), may occur easily, thus inhibiting efficient photocatalytic water splitting.