Water photolysis with a cross-linked titanium dioxidenanowire anode

Abstract

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 μm. 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 μm) TiO₂ nanowire films, however, indicating that the effect stems from enhanced light retention by nanoparticle scattering.