Electric field-driven one-step formation of vertical p–n junction TiO 2 nanotubes exhibiting strong photocatalytic hydrogen production

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2021-02, Vol.9 (4), p.2239-2247
• Main Authors: Kim, Moonsu, Lee, Jaewon, Je, Minyeong, Heo, Bumgi, Yoo, Hyeonseok, Choi, Heechae, Choi, Jinsub, Lee, Kiyoung
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/D0TA10062E

In this study, vertically aligned p–n junction TiO 2 nanotubes can be formed by anodization of the Ti substrate following the addition of a high electric field in a Pd precursor-containing electrolyte. The bottom region of the TiO 2 nanotubes with a high concentration of Pd because of the high electric field which was induced to be p-type. In contrast, the region with a low Pd concentration (top of the TiO 2 nanotubes) was determined to be n-type, similar to the pristine TiO 2 . The concentration profile of the dopant in TiO 2 nanotubes was investigated via TOF-SIMS and XPS. Defect formation energies in TiO 2 nanotubes were estimated using density-functional theory calculation to understand the p–n junction formation. The p–n junction TiO 2 nanotubes showed a high photocatalytic hydrogen production rate of 25.2 μL cm −2 h −1 under solar light irradiation as a result of the enhancement of visible light photoactivity.