Local Silver Site Temperature Critically Reflected Partial and Complete Photooxidation of Ethanol Using Ag–TiO2 as Revealed by Extended X‑ray Absorption Fine Structure Debye–Waller Factor

• Published in: Journal of physical chemistry. C 2021-07, Vol.125 (27), p.14689-14701
• Main Authors: Fukuhara, Daiki, Joseph, Moses Tuhafeni, Loumissi, Tarik, Zhang, Chao, Itoi, Takaomi, Zhang, Hongwei, Izumi, Yasuo
• Format: Article
• Language: eng ; jpn
• Subjects: C: Chemical and Catalytic Reactivity at Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.1c04076

The critical factors in choosing the reaction pathway for photocatalysis are often unclear. In this study, for a typical Ag–TiO2 photocatalyst, the control factors of partial and complete oxidation of ethanol were investigated using kinetics, UV–visible and emission spectroscopy, and silver K-edge extended X-ray absorption fine structure. Low concentrations of O2-derived intermediate species that were not detected by curve-fitting analysis could be monitored under the photocatalytic conditions based on the local temperature of Ag sites provided by the Debye–Waller factor and the correlated Debye model. The site temperature monitoring was extended to Ag nanoparticles growing from 0.5 to 3.6 nm under photocatalytic reaction conditions. The Ag site temperature reached 404 K under reductive conditions to dehydrogenate ethanol into acetaldehyde, whereas it was 363–368 K under oxidative conditions owing to O2-derived species forming CO2, CH4, and H2O to suppress localized surface plasmon resonance. Under UV light, partial ethanol oxidation to acetaldehyde and O2 activation for complete oxidation to CO2 and H2O proceeded over TiO2. However, under visible light, the C–C bond cleavage to CO2 and CH4 and complete oxidation to CO2 and H2O combined with the O2-derived species transferred from the TiO2 surface proceeded over Ag0 nanoparticles.