10.1021/cs200063q.s001
Dangguo Gong
Dangguo
Gong
Vishnu Priya Subramaniam
Vishnu Priya
Subramaniam
James G. Highfield
James G.
Highfield
Yuxin Tang
Yuxin
Tang
Yuekun Lai
Yuekun
Lai
Zhong Chen
Zhong
Chen
In Situ Mechanistic Investigation at the Liquid/Solid Interface by Attenuated Total Reflectance FTIR: Ethanol Photo-Oxidation over Pristine and Platinized TiO<sub>2</sub> (P25)
American Chemical Society
2011
Situ Mechanistic Investigation
Platinized TiO 2
spectroscopic marker
platinized forms
metal nanodeposits
reaction mechanism
photocatalytic oxidation
energy crisis
photocatalytic reactions
acetate
intermediate
chemical oxidant
Reflectance FTIR
Attenuated
surface
ethanol mineralization
H 2 generation
TiO 2
reaction pathway
2011-08-05 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/In_Situ_Mechanistic_Investigation_at_the_Liquid_Solid_Interface_by_Attenuated_Total_Reflectance_FTIR_Ethanol_Photo_Oxidation_over_Pristine_and_Platinized_TiO_sub_2_sub_P25_/2625220
There is growing interest in applying photocatalysis to help solve both the energy crisis and effectively combat environmental contamination. However, it is difficult to investigate photocatalytic reactions at the liquid/solid interface to unravel the reaction mechanism by conventional (ex situ) surface analytical techniques. In this study, Attenuated Total Reflectance-FTIR spectroscopy, adapted for optical pumping, was used to observe in situ the surface of TiO<sub>2</sub> (Degussa P25, in both pristine and platinized forms) during photocatalytic oxidation of ethanol aqueous solution. It shows the feasibility to investigate not only the reaction pathway and the rate-determining step, but also the change in state of the catalyst under working conditions. During ethanol photo-oxidation over pristine TiO<sub>2</sub>, band gap excitation caused the progressive accumulation of trapped electrons, as recognized by their characteristic quasi-continuum absorption, implying that photoreduction does not proceed at a significant rate under these conditions. Consistent with this view, only weak infrared features due to adsorbed intermediates were observed. Over platinized TiO<sub>2</sub>, the noble metal nanodeposits promote photodehydrogenation and photoactivation of dioxygen. In addition to observing strong bands diagnostic of various intermediates, the presence or absence of a band around 2050 cm<sup>–1</sup>, typical of Pt-CO<sub>ad</sub>, served as a valuable spectroscopic marker of the instantaneous availability of the chemical oxidant. As such, mechanistic parallels were found between photoreforming (with H<sub>2</sub> generation) and photo-oxidation (to acetate), with acetaldehyde being a common intermediate in both processes. The rate-determining step in ethanol mineralization was found to be photodecomposition of adsorbed acetate.