Constructing heterojunction was an efficient way to promote photoelectrochemical (PEC) water splitting performance of TiO2-based nano-photoanode. In this work, we demonstrated the feasible preparation of oxygen vacancies-induced In2O3 (In2O3-x) nanorods/black Si-doped TiO2 (Ti-Si-O) nanotubes heterojunction photoanode for enhanced PEC water splitting. Black Ti-Si-O nanotubes were fabricated through Zn reduction of the as annealed Ti-Si-O nanotubes, followed by In2O3-x, nanorods coupling by a facile electro-depositing and Ar heat treatment. Solar to hydrogen conversion efficiency of the heterojunction photoanode reached as high as 1.96%, which was almost 10 times that of undoped TiO2. The improved PEC properties were mainly attributed to co-doping effects of Si and Ti3+/oxygen vacancy as well as In2O3-x decoration, which resulted in enhanced optical absorption and facilitated separation-transport process of photogenerated charge carriers. Charge transfer process in the composite system and hydrogen production mechanism were proposed. This work will facilitate designing TiO2-based nano-photoanodes for promoting water splitting by integrating with elements doping, oxygen vacancies self-doping and semiconductors coupling. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.