Water photolysis with a cross-linked titanium dioxide nanowire anode†

We report efficient water photolysis using a cross-linked TiO2 nanowire anode containing mixed anatase and rutile phases. Under simulated AM 1.5 G illumination, the peak solar energy conversion efficiency is measured to be 1.05%, a new record for TiO2 photoanodes. A photocurrent density as high as 2.6 mA cm 2 is observed when the film thickness is 22 mm. These observations indicate that the high surface area architecture afforded by the cross-linked TiO2 nanowires enables both long optical path lengths and high photon-to-electron conversion efficiency. We also report photocurrent in the visible range due to sub-band gap absorptions, which is enhanced by up to a factor of 10 when the TiO2 nanowires are coated with gold or silver nanoparticles. This enhancement is observed only in thinner (up to 1 mm) TiO2 nanowire films, however, indicating that the effect stems from enhanced light retention by nanoparticle scattering.