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Facile and efficient atomic hydrogenation enabled black TiO₂ with enhanced photo‐electrochemical activity via a favorably low‐energy‐barrier pathway

: Wang, X.; Mayrhofer, L.; Höfer, M.; Estrade, S.; Lopez-Conesa, L.; Zhou, H.; Lin, Y.; Peiró, F.; Fan, Z.; Shen, H.; Schäfer, L.; Moseler, M.; Bräuer, G.; Waag, A.


Advanced energy materials 9 (2019), Nr.33, Art. 1900725, 14 S.
ISSN: 1614-6840
ISSN: 1614-6832
Fraunhofer IST ()
atomic hydrogenation; black titania; density functional theory; electron energy loss spectroscopy; photo-electrochemical property; transmission electron microscopy

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.