Tuning the photoelectrochemistry of nanoporous anatase electrodes by modification with gold nanoparticles: Development of cathodic photocurrents

In oxygen-saturated 0.05 M NaOH, anatase nanoporous electrodes modified with gold nanoparticles show, under Xe arc-lamp illumination, cathodic photocurrents at E < −0.35 VAg/AgCl in addition to the typical anodic photocurrents due to water photooxidation at higher potentials. These cathodic photocurrents are suppressed either in the absence of dissolved oxygen or in the presence of methanol, a hole acceptor. Their appearance also depends on the nature of the gold nanoparticle capping agent. Such a behavior is understood according to an enhanced electron transfer to solution via the gold nanoparticles and to simultaneous hole and electron diffusion through the anatase nanoporous network.