Hydrogen photo-production from ethanol on TiO2: a surface science and catalysis study

Abstract

In this work we present an overview of the photo-reaction of ethanol over the surface of TiO2 (110) single crystal under photo-excitation and compare it to that over Au/TiO2 nano-particle. Over rutile TiO2(110) surface ethanol is present mainly in ethoxide (CH3CH2O(a)) form at 300K as evidenced by the presence of XPS C1s peak at 286.5 eV due to the -CH2-O(a) function; (a) for adsorbed. DFT computation of the same system indicated that the surface coverage is 50% or less in line with previous experimental results [1]. Exposing a pre-dosed surface to UV light in presence of oxygen resulted in the formation of acetaldehyde (CH3CHO(g); (g) for gas phase) with the extent of reaction depending on the square root of the O2 pressure in the 10-10 - 10-6torr range. Over the Au/TiO2 powder system we have focused the attention on the production of hydrogen as the oxidation of ethanol of ethanol to acetaldehyde has been previously studied [2]. The reaction is found to be sensitive to the polymorph nature of TiO2 with anatase showing two orders of magnitudes higher activity than rutile. We have also addressed the TiO2 particle size effect on the reaction and found that the TiO2 particles, in the 150 to 10 nm range, to have the same reactivity.