NaBH4 reduction of TiSiO nanotubes photoanode for high-efficiency photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting based on doping-modified one-dimensional (1D) TiO2 is a promising approach to sustainable hydrogen evolution. Here we successfully fabricated high-efficiency reduced TiSiO nanotubes photoanode through anodizing two-phase TiSi alloy and one step NaBH4 reduction, and investigated its PEC water splitting properties. It was found that Si-doped TiO2 nanotubes mainly grew at the α-Ti region of Ti5Si alloy substrate, and they easily dissolved at the Ti5Si3 phase region of the alloy. Both Si element and Ti3+/oxygen vacancy (VO) were successfully doped into the oxide nanotubes, resulting in enhanced optical absorption and facilitated separation of photogenerated electron-hole pairs. The reduced TiSiO nanotubes photoanode with co-doped Si element and Ti3+/VO could have a high photocurrent density of 1.39 mA/cm2 at 0 V vs. Ag/AgCl. The solar to hydrogen efficiency could reach 0.88% and it was 4.89 times that of undoped TiO2. It demonstrated that co-doping of Si and Ti3+/VO shows great potential in improving the PEC water splitting properties of undoped TiO2.