Enhanced Photoelectrochemical Water Splitting Performance of Ni/Si-doped TiO2 Photoanode Fabricated through Electrochemical Reduction in Aqueous Solutions

Ni/Si-doped TiO2 nanostructures were prepared by anodizing Ti-1Ni-5Si alloy. The electrochemical reduction in the aqueous solutions was a simple and effective method to self-dope Ti3+ into Ni/Si-doped TiO2 nanostructures. It was found that electrochemical reduction in neutral aqueous solution (pH 7) was more effective than that in either acidic aqueous solution (pH 3) and basic aqueous solution (pH 13). The stable reduced Ni/Si-doped TiO2 photoanode obtained in the neutral aqueous solution exhibited an excellent photoelectrochemical water splitting performance due to the increased Ti3+ and oxygen vacancies species, which not only extended the visible-light absorption range but also promoted the charge transfer and separation process. A remarkable photocurrent density of 2.41 mA cm−2 at 0 V vs Ag/AgCl was achieved, corresponding to a photoconversion efficiency of 1.12%, which was 5.9 times that of the undoped TiO2 photoanode (0.19%).