Thin film TiO2 photoanodes for water photolysis prepared by dc magnetron sputtering

The TiO2 thin film photoanodes for hydrogen generation by water photolysis have been prepared by dc reactive magnetron sputtering. Optical monitoring of the plasma emission with the feedback signal I/I0 controlling the reactive gas admission and reflecting the target oxidation state has been used. X-ray diffraction GID and AFM studies have revealed the systematic evolution of the microstructure with I/I0, from that of well-crystallized mixture of anatase and rutile at the lowest I/I0 (oxidized target) to that of amorphous state with finely dispersed rutile grains at the highest I/I0 (metallic target). It has been demonstrated that the microstructure of TiO2 affects to a large extent the optical and photoelectrochemical properties of the photoanodes. Optical band gap Eopt and the photocurrent response have been found to increase systematically with a decreasing feedback signal I/I0. The best efficiency, i.e. the highest IPCE (incident photon-to-current conversion efficiency) has been obtained for the TiO2 photoanodes sputtered at I/I0 = 0.09 from the oxidized target.