Preparation of ZnO/two-layer self-doped black TiO2 nanotube arrays and their enhanced photochemical properties

Highly efficient TiO2 photoanodes can be achieved by enhancing electrical conductivity and improving charge separation and transfer. In this paper, Ti foils were used to fabricate TiO2 nanotubes by anodic oxidation and ZnO/two-layer self-doped black TiO2 nanotubes were prepared by electrochemical reduction and a hydrothermal method. The formed black TiO2 nanotubes have a better photoconversion efficiency and the maximum photoconversion efficiency increased by 59% compared with the pure nanotubes. The deposition of ZnO further improves the maximum photoconversion efficiency to 456% based on black TiO2. The photocurrent responses also increase by about 5 times in our results. This work is instructive for the development of highly robust and efficient photoanode materials in fields including photoelectrochemistry and photocatalysis.