Hydrogen Photo-production from ethanol on TiO_2: a surface science and catalysis study

摘要

In this work we present an overview of the photo-reaction of ethanol over the surface of TiO_2 (110) single crystal under photo-excitation and compare it to that over Au/TiO_2 nano-particle. Over rutile TiO_2(110) surface ethanol is present mainly in ethoxide (CH_3CH_2O(a)) form at 300K as evidenced by the presence of XPS Cls peak at 286.5 eV due to the -CH_2-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 (CH_3CHO(g); (g) for gas phase) with the extent of reaction depending on the square root of the O_2 pressure in the 10~(-10) - 10~(-6) torr range. Over the Au/TiO_2 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 TiO_2 with anatase showing two orders of magnitudes higher activity than rutile. We have also addressed the TiO_2 particle size effect on the reaction and found that the TiO_2 particles, in the 150 to 10 nm range, to have the same reactivity.