Abstract
Hydrogen production using photocatalytic reactions from biomass is one of the most promising methods for a sustainable energy system. Among the many complex factors affecting the reaction rate is the so-called "synergetic or synergistic effect - the phenomenon in which the combined action of two things is greater than the sum of their effects individually" of the polymorph of the semiconductor. In this work we have investigated Au-TiO2 photo-catalysts for the production of hydrogen from ethanol. We have synthesised Au particles of similar sizes on TiO2 nanoparticles also of similar sizes but of different polymorphs. It was found that Au-TiO2 anatase is about two orders of magnitude more active that Au/TiO2 rutile. Yet, it was also found that when the anatase and rutile particles are present together the reaction rate is higher than that observed over Au-TiO2 anatase alone. One possible reason for this enhancement is the increase in the number of excited electrons (rutile phase) together with a decrease in the rate of electron-hole recombination (anatase phase) at the interface.