Hydrogenation and Structuration of TiO2 Nanorod Photoanodes: Doping Level and the Effect of Illumination in Trap-States Filling

Both electronic properties and light absorption are key features in materials engineering to achieve efficient photoelectrodes for water splitting. Adjusting the potential drop inside the nanostructured semiconductor material through modification of the electronic properties is mandatory to drive efficiently the photogenerated charges. In this work, a hydrogen reduction treatment on titanium dioxide rutile nanorod based photoanodes has been performed in order to adjust the donor density to maximize electron–hole separation. Also, incident photon-to-current efficiency (IPCE) measurements and the effect of a light bias have been elucidated, finding relevant differences in low illumination conditions due to nonfilled trap states. A physical model is proposed to show the role of the donor density on the overall performance of the photoanodes under study. The obtained productivity was enhanced by structuring the conductive glass substrates where TiO2 nanorods were grown, resulting in a 20% increase of the photocurrent density.