The Effect of the Hydrogenation Temperature on TiO2 Nanostructures for Photoelectrochemical Water Oxidation



We report the photoelectrochemical (PEC) performance of titanium dioxide (TiO2) based photoanodes for water oxidation as a function of the hydrogenation temperature. The hydrogen-treatment strategy has recently been demonstrated as a simple and effective strategy to improve the performance of TiO2 photoanodes for the PEC water oxidation. However, the performance of those hydrogenated TiO2 photoanodes decreased gradually when the hydrogenation temperature was above 350 °C. This was attributed to the degradation of the fluorine-doped tin oxide (FTO) substrate. To eliminate the influence of the substrate and to evaluate the effect of the hydrogenation temperature on the performance of TiO2 photoanodes, in this study we synthesized rutile, anatase, and mixed-rutil/anatase phase TiO2 nanowire arrays on titanium (Ti) foils. These TiO2 nanowires were hydrogenated in a temperature range between 350 and 550 °C, in which the resistance of Ti foil remained unchanged. We found that the rutile- and anatase-hydrogenated TiO2 photoanodes achieved the optimal performance for PEC water oxidation at a hydrogenation temperature of 350 and 550 °C, respectively. The optimal hydrogenation temperature is believed to be related to the carrier density of TiO2. These results could provide important insights for the improvement of the performance of TiO2 materials as photoelectrodes for PEC water oxidation as well as for other solar-energy conversion devices.