Electrochemical reduction induced self-doping of oxygen vacancies into Ti–Si–O nanotubes as efficient photoanode for boosted photoelectrochemical water splitting

Abstract

Self-doping of oxygen vacancies (VO) states into TiO2-based nanotubes was an efficient way for improving photoelectrochemical (PEC) water splitting properties. Here we induced oxygen vacancies into Si-doped TiO2 (Ti–Si–O) nanotubes on Ti–Si alloy via a facile electrochemical surface reduction, and applied it for PEC water splitting. Systematic studies revealed that the self-doped oxygen vacancies not only promoted optical absorption of the doped nanotubes but also enhanced separation-transport processes of the photo-generated charge carriers, and thus resulted in improved PEC water splitting properties. The VO/Ti–Si–O co-doping system exhibited a higher photocurrent density of 1.63 mA/cm2 at 0 V vs. Ag/AgCl. Corresponding solar-to-hydrogen efficiency could reach 0.81%, which was about 5.4 times that of undoped TiO2. It's believed that elements doping and oxygen vacancies self-doping synergistic strategy employed in this work, may provide theoretical and practical significance for designing and fabricating efficient TiO2-based nanostructures photoanodes in PEC water splitting for boosted solar-to-hydrogen conversion.