Impact of Solvent on Photocatalytic Mechanisms: Reactions of Photodesorption Products with Ice Overlayers on the TiO2(110) Surface

Journal Article · Thu Apr 07 04:00:00 EDT 2011 · Journal of Physical Chemistry C, 115(13):5886-5893

DOI:https://doi.org/10.1021/jp111839j· OSTI ID:1011797

Shen, Mingmin; Henderson, Michael A

The effects of water and methanol ice overlayers on the photodecomposition of acetone on rutile TiO2(110) were evaluated in ultrahigh vacuum (UHV) using photon stimulated desorption (PSD) and temperature programmed desorption (TPD). In the absence of ice overlayers, acetone photodecomposed on TiO2(110) at 95 K by ejection of a methyl radical into the gas phase and formation of acetate on the surface. With ice overlayers, the methyl radicals are trapped at the interface between TiO2(110) and the ice. When water ice was present, these trapped methyl radicals reacted either with each other to form ethane or with other molecules in the ice (e.g., water or displaced acetone) to form methane (CH4), ethane (CH3CH3) and other products (e.g., methanol), with all of these products trapped in the ice. The new products were free to revisit the surface or depart during desorption of the ice. When methanol ice was present, methane formation came about only from reaction of trapped methyl radicals with the methanol ice. Methane and ethane slowly leaked through methanol ice overlayers into vacuum at 95 K, but not through water ice overlayers. Different degrees of site competition between water and acetone, and between methanol and acetone led to different hydrogen abstraction pathways in the two ices. These results provide new insights into product formation routes and solution-phase radical formation mechanisms that are important in heterogeneous photocatalysis.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1011797
• Report Number(s): PNNL-SA-76587; KC0302010
• Journal Information: Journal of Physical Chemistry C, 115(13):5886-5893, Journal Name: Journal of Physical Chemistry C, 115(13):5886-5893 Journal Issue: 13 Vol. 115; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
08 HYDROGEN
10 SYNTHETIC FUELS
ACETATES
ACETONE
AIR PURIFICATION
DESORPTION
ETHANE
GAS-PHASE
GASEOUS ACETONE
HETEROGENEOUS PHOTOCATALYSIS
HYDROGEN
HYDROGEN-ATOM ABSTRACTION
METHANE
METHANOL
METHANOL GLASSES
METHYL RADICALS
PHOTOCATALYSIS
PHOTONS
RADICALS
RUTILE
SOLVENTS
THIN-FILMS
TITANIUM- DIOXIDE
WATER
WATER- VAPOR