As part of a program of research into the generation of hydrogen by the photo-electrolysis of water we have in the first instance addressed the effect of titania crystallite size on photocatalytic water-splitting performance of nanocrystalline sol-gel titania thin films. Nanocrystalline titania sols were made from titanium isopropoxide and nitric acid by standard methods. The crystallite size of the sols was precisely controlled by hydrothermal treatment in autoclaves for 72 hours at 90, 155, 170, 200 and 240 degrees Celsius. Thin films were fabricated on Ti metal substrates by dip-coating and subsequent heating. A range of film thickness was achieved by: using sols of differing viscosity; varying the dip-coat extraction speed; and applying multiple coats. Film thickness and porosity were measured and used to estimate total titania content. Crystallite size was measured and plotted versus treatment temperature.

Water splitting performance in response to artificial insolation by xenon lamp was evaluated using the test apparatus at CSIRO Lindfield, Australia. I/V characteristics and IPCE were measured. Performance in response to natural sunlight was also measured. Plots of performance versus crystallite size, film thickness are presented. The best performing systems, in both absolute terms and per-molar Ti in the film, are emphasised. Limitations to performance are discussed and suggestions for improvements are given. Initial results on heterostructured thin films incorporating the nanoparticulate thin films will also be presented.