Hydrogen production by photoreforming of biofuels using Au, Pd and Au–Pd/TiO2 photocatalysts

We have prepared a variety of Au, Pd and Au–Pd catalysts loaded onto P25 titania to determine how effective these materials are for the anaerobic, ambient temperature reforming of alcohols with water to produce hydrogen, and to examine the effect of the preparation method on their performance. Catalysts produced by both incipient wetness (IW) methods and by colloidal methods are successful materials for producing hydrogen, with the IW catalysts proving to be the best for the same metal loading. It is shown that, although gold catalysts generally have lower hydrogen yield than for Pd, alloying Au with Pd gives more active materials than either alone at the same weight loading, due to a synergistic effect. The catalysts are active for reforming a range of alcohols, generally producing CO2, H2 and an alkane. However, it is essential for good activity to have an H at the α-position to the oxygenate function, and so, carboxylic acids and ketones do not work. These catalysts generally show a maximum in activity at low loadings of metal (∼0.5 wt%) due to a requirement for maximising the active interface between the metal nanoparticles and the photo-active titania.