Ethanol photoreactions over Au–Pd/TiO2

Abstract

A prototype Au-Pd/TiO 2 catalyst was prepared, characterized and tested for the photoreaction of ethanol. XPS Au4f and Pd3d indicated that the as-prepared material is composed of metallic Au, metallic Pd as well oxidized Pd (Pd 2? ). Ar ion sputtering (5 min) of the catalyst surface resulted in almost total reduction of Pd 2? to metallic Pd in addition to considerable reduction of surface Ti cations to Ti 3? and Ti 2? cations; XPS Au4f lines were not affected. Transmission electron microscopic studies indicated that Au particles have a mean particle size of about 3.5 nm while Pd particles are smaller 1-1.5 nm in size. UV excitation of the catalyst in ultrahigh vacuum (UHV) conditions resulted in the formation of acetaldehyde and hydrogen in addition to photodesorption of the reactant ethanol. Hydrogen production, representing ca. 30 % of the desorbing products, was delayed compared to acetaldehyde desorption. This was interpreted as due to kinetic effect whereby initially most electrons transferred to the conduction band are trapped by surface hydroxyls as well inevitable presence of oxygen in the powder accelerating acetaldehyde formation (dehydrogenation). Only once most oxygen-containing species have reacted and molecular hydrogen was formed. To our knowledge, this is the first UHV in situ study of hydrogen production from ethanol photocatalytically over M/TiO 2 system.

Photocatalytic production of hydrogen from biomass-derived feedstocks

“…photocatalysts [283]. Ar sputtering was used to further reduce palladium to its metallic form [284]. Deposition methods using urea were also reported for the preparation of AuPd nanoparticles on TiO2 inverse opals with ethanol photoreforming activity [285].…”

Study of ethanol reactions on H2 reduced Au/TiO2 anatase and rutile: effect of metal loading on reaction selectivity

“…We have studied the application of Au supported TiO 2 catalyst for the photocatalytic activity towards hydrogen production from ethanol. [20][21][22][23][24][25][26] These catalysts have shown promising results and have led to some progress in understanding the role of Au during photo-catalytic reactions. Since then there is a growing interest in the photocatalytic activity of Au supported TiO 2 catalysts.…”

Influence of heat treatment temperature on bonding and oxidation resistance of diamond particles coated with TiO2 film

“…When the temperature exceeded 600°C, large amounts of Ti 4+ and Ti 2+ film and a small amount of Ti 3+ existed in TiO 2 . 13 The change of Ti chemical valence was due to the removement of the free carbon in the film, Ti-O-C bond formed between TiO 2 film and diamond substrate during this process; thus, the Ti 3+ content in the film decreased and Ti 2+ content increased.…”