One-Electron Water Oxidation Intermediate on TiO2 P25 Probed by Ultrafast Attenuated Total Reflection

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.