Rutile TiO₂ as an Anode Material for Water-Splitting Dye-Sensitized Photoelectrochemical Cells

Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) use a wide bandgap metal oxide semiconductor functionalized with a light-absorbing dye and water-oxidation catalyst to harvest light and drive water oxidation, respectively. We demonstrate here that the rutile polymorph of TiO 2 (r-TiO 2 ) is a promising anode material for WS-DSPECs. Recombination between the injected electron and oxidized sensitizer with r-TiO 2 is an order of magnitude slower than with anatase TiO 2 (a-TiO 2 ), with injection yields approaching 100%. Studies with a reductive quencher demonstrate that r-TiO 2 is significantly more efficient than a-TiO 2, while exhibiting greater dye stability. Furthermore, comparison of direct band gap excitation photocurrent generation for bare and sensitized r-TiO 2 suggests that the sensitizer functions as a light harvester and redox mediator.