Facile and Efficient Atomic Hydrogenation Enabled Black TiO2 with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

• Published in: Advanced energy materials 2019-09, Vol.9 (33), p.n/a
• 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
• Subjects: atomic hydrogenation; black titania; Density functional theory; Electrochemical analysis; electron energy loss spectroscopy; Energy technology; Hydrogen storage; Hydrogenation; Nanorods; Optical properties; Photoelectric effect; Photoelectric emission; photo‐electrochemical property; Side effects; Titanium dioxide; transmission electron microscopy; Wire
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201900725

Black TiO2 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 TiO2 (H–TiO2) 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–TiO2 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 TiO2. 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–TiO2 and contribute to the fundamental understanding of its hydrogenation. A simple and straightforward hot wire annealing (HWA) method enables black TiO2 (H–TiO2) nanorods with enhanced photo‐electrochemical (PEC) activity by means of atomic hydrogen [H]. Compared with conventional molecular hydrogenation, the atomic hydrogenation favorably chooses a low‐energy‐barrier pathway resulting in mild and efficient hydrogenation conditions which largely promote the black TiO2 in practical energy applications.