Published: Oct. 4, 2021

Xihan Chen* and Tanja Cuk

J. Phys. Chem. C 2021, 125, 33, 18204, DOI: 10.1021/acs.jpcc.1c05026

Water oxidation is considered as one of the most important reactions in solar-to-fuel generation. The initial catalytic intermediates formed on an ultrafast timescale play a great role in controlling water oxidation reaction. Here, we use ultrafast in situ infrared attenuated total reflectance spectroscopy to study the initial water oxidation intermediates at a state-of-the-art TiO2 P25/aqueous interface. We observe a Ti–O vibration near 850 cm–1 possibly in the anatase phase, suggested to be a subsurface vibration as a result of hole localization on the P25 surfaces. Such a subsurface Ti–O vibration is found to couple to reactant dynamics (water librations). This experiment suggests that a subsurface vibration could be a distinctive infrared reporter of reaction intermediates for water oxidation on titania surfaces.