Surface characteristics and photoelectrocatalytic capabilities of nanoporous titanium dioxide/tin indium oxide composite thin film electrodes

This study applied a prolonged DC magnetron sputtering technique to prepare two nanoporous columnar and well-crystallized titanium dioxide/tin indium oxide (TiO2/ITO) composite thin film electrodes for photoelectrocatalytic reactions. The visible light enabled TiO2/ITO electrode was obtained by carbon doping while sputtering thin-film TiO2 onto the proposed ITO substrate. Both photoelectrocatalytic hydrogen generation and dimethyl sulfoxides (DMSO) degradation experiments were conducted for evaluating the photoelectrocatalytic capabilities of the prepared samples. The contribution of ITO co-doping on photocatalytic activities of hetero-structured photocatalysts was investigated in the study. The experimental results show both samples primarily in anatase TiO2 crystallization phase. Due to a higher sputtering power is applied for carbon-doped TiO2/ITO (CTI) film preparation, the tin ions of ITO permeate into TiO2 film to form a crystalline Ti1−xSnxO2 interfacial layer, which results in CTI film with a higher photocatalytic oxidation rate of than the simple TiO2/ITO (STI). The dimethyl sulfoxides (DMSO) degradation rate by CTI is about 2.83-fold higher than by STI. Conversely, the STI, prepared at a lower sputtering power, produced much higher photocurrent density (∼230 μA cm−2) and hydrogen yield rate (∼15.67 μmol cm−2 h−1) than the CTI owing to forming a higher Schottky barrier at the TiO2/ITO interface of STI film. These findings suggest that the interfacial characteristics of the TiO2/ITO film importantly affect their photocatalytic activities. This study also demonstrates that the prolonged DC magnetron sputtering technique can be applied to prepare thin-film photocatalysts with selective application purposes if suitable sputtering conditions can be carefully selected.