Effective hydrogenation of TiO2 photocatalysts with CH3OH for enhanced water splitting: A computational and X-ray study

• Published in: Applied surface science 2019-09, Vol.488, p.546-554
• Main Authors: Wang, Tsai-Te, Raghunath, Putikam, Lin, Yu-Chang, Lin, Yan-Gu, Lin, Ming-Chan
• Format: Article
• Language: English
• Subjects: DFT calculation; Hydrogen evolution; Methanol treated titania; XANES spectra
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.05.239

We have investigated computationally and experimentally the efficacy of CH3OH treatment of anatase TiO2 nanoparticles (NPs) and compared the results obtained with H2 as the hydrogenation source. The results indicate that TiO2 NPs heated at 300 °C in 120 Torr of CH3OH vapor is more effective than the samples heated under 800 Torr of H2 at the same temperature. Ultraviolet-visible spectroscopy (UV-VIS), Photoluminescence spectroscopy (PL) and X-ray diffraction spectroscopy (XRD) were employed to study the optical property. The effect of temperature of hydrogenation has been systematically studied for NPs in the 200–450 °C range for both H-sources based on H2 evolution, employing Xe lamp as the light source. The hydrogenated TiO2 NPs using H2 and CH3OH have been analyzed by soft X-ray absorption near-edge structure analyses with and without Xe lamp irradiation in situ. The result indicates that CH3OH hydrogenation can induce a much stronger TiO interaction along direction dz2 and increase the unoccupied DOS of Ti t2g states. This is why the CH3OH treated TiO2 exhibits a greater photo-activity. The crucial role of the hydrogenation using CH3OH was also investigated systematically and confirmed by quantum-chemical calculations with complementary synchrotron-based X-ray techniques. The results are consistent with the predicted barriers for the formation of H atoms on the TiO2 surface, 4–9 kcal/mol, considerably lower than that in the H2 case, 48 kcal/mol. [Display omitted] •The role of hydrogenation using CH3OH was studies by calculation and X-ray technique.•CH3OH hydrogenation can induce a strong TiO interaction along direction dz2.•CH3OH hydrogenation can increase the unoccupied DOS of Ti t2g states.•CH3OH treated TiO2 exhibits a good photo-activity.