The photoelectrochemical characteristics of oxalate in 0.20 M NaS2O4 at an indium tin oxide (ITO) electrode were investigated. Significant photocurrents were observed upon illumination in both the UV and visible regions with the highest photocurrent at 290 nm. The photocurrent onset was at similar to-0.30 V (vs Ag/AgCl), and it increased linearly with an increase in illumination intensity, indicating that the charge carrier generation process is the limiting factor of the photocurrent generation at the ITO electrode. Deposition of a bovine serum albumin (BSA) monolayer on the ITO electrode surface suppressed the photocurrent, whereas the introduction of a second layer of Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) restored most of the photoelectrochemical response with a photocurrent action spectrum identical to that observed at the ITO electrode, suggesting that the Ru(bpy)(3)(2+) layer promotes charge transfer between oxalate and the ITO electrode, but Ru(bpy)(3)(2+) itself has little if any photoelectrochemical response in the system.