Facile and Efficient Atomic Hydrogenation Enabled Black TiO 2 with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

• Published in: Advanced energy materials 2019-09, Vol.9 (33)
• Main Authors: Wang, Xiaodan, Mayrhofer, Leonhard, Hoefer, Markus, Estrade, Sonia, Lopez‐Conesa, Lluis, Zhou, Hao, Lin, Yuanjing, Peiró, Francesca, Fan, Zhiyong, Shen, Hao, Schaefer, Lothar, Moseler, Michael, Braeuer, Guenter, Waag, Andreas
• Format: Article
• Language: English
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201900725

Black TiO 2 has demonstrated a great potential for a variety of renewable energy technologies. However, its practical application is heavily hindered due to lack of efficient hydrogenation methods and a deeper understanding of hydrogenation mechanisms. Here, a simple and straightforward hot wire annealing (HWA) method is presented to prepare black TiO 2 (H–TiO 2 ) nanorods with enhanced photo‐electrochemical (PEC) activity by means of atomic hydrogen [H]. Compared to conventional molecular hydrogen approaches, the HWA shows remarkable effectiveness without any detrimental side effects on the device structure, and simultaneously the photocurrent density of H–TiO 2 reaches 2.5 mA cm −2 (at 1.23 V vs reversible hydrogen electrode (RHE)). Due to the controllable and reproducible [H] flux, the HWA can be developed as a standard hydrogenation method for black TiO 2 . Meanwhile, the relationships between the wire temperatures, structural, optical, and photo‐electrochemical properties are systematically investigated to verify the improved PEC activity. Furthermore, the density functional theory (DFT) study provides a comprehensive insight not only into the highly efficient mechanism of the HWA approach but also its favorably low‐energy‐barrier hydrogenation pathway. The findings will have a profound impact on the broad energy applications of H–TiO 2 and contribute to the fundamental understanding of its hydrogenation.