In-situ plasma hydrogenated TiO₂ thin films for enhanced photoelectrochemical properties

In this paper, we report the effect of in-situ plasma hydrogenation of TiO2 (iH:TiO2) thin films by the incorporation of known amount of hydrogen in the Ar plasma during rf-sputter deposition of TiO2 films. As compared to pristine TiO2 films (∼0.43 mA/cm2 at 0.23 V vs Ag/AgCl), hydrogenated TiO2 showed enhanced photoelectrochemical activity in terms of improved photocurrent density of ∼1.08 mA/cm2 (at 0.23 V vs Ag/AgCl). These results are explained in terms of reduction in band gap energy, shift in valence band maximum away from the Fermi level, improved donor density and more negative flat band potential in iH:TiO2 sample. The presence of Ti2+ states in iH:TiO2 films in addition to Ti3+ states in pristine TiO2 act as additional electronic states in the TiO2 band gap and increases the optical absorption in the visible region. This method of in-situ hydrogenation can be used as a general method for improving the properties of metal oxide thin films for photoelectrochemical and photocatalytic applications