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Title: Electron-stimulated reactions in nanoscale water films adsorbed on α-Al 2O 3 (0001)

Abstract

The radiation-induced decomposition and desorption of nanoscale amorphous solid water (D2O) films adsorbed on -Al2O3(0001) surface was studied at low temperature in ultrahigh vacuum using temperature programmed desorption (TPD) and electron stimulated desorption (ESD) with a mono-energetic, low energy electron source. ESD yields of molecular products ( D2, O2 and D¬2O) and the total sputtering yield increased with increasing D2O coverage up to ~15 water monolayers (i.e. ~15 1015 cm-2) to a coverage-independent level for thicker water films. Experiments with isotopically-layered water films (D2O and H2O) demonstrated that the highest water decomposition yields occurred at the interfaces of the nanoscale water films with the alumina substrate and vacuum. However, the increased reactivity of the water/alumina interface is relatively small compared to the enhancements in the non-thermal reactions previously observed at the water/Pt(111) and water/TiO2(110) interfaces. We propose that the relatively low activity of Al2O3(0001) for the radiation-induced production of molecular hydrogen is associated with lower reactivity of this surface with hydrogen atoms, which are likely precursors for the molecular hydrogen.100 eV electrons are stopped in the H 2O portion of the isotopically-layered nanoscale film on α-Al 2O 3(0001) but D 2is produced at the D 2O/alumina interface by mobile electronicmore » excitations and/or hydronium ions.« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1439011
Report Number(s):
PNNL-SA-132648
Journal ID: ISSN 1463-9076; PPCPFQ; KC0307010
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 20; Journal Issue: 17
Country of Publication:
United States
Language:
English

Citation Formats

Petrik, Nikolay G., and Kimmel, Gregory A. Electron-stimulated reactions in nanoscale water films adsorbed on α-Al2O3 (0001). United States: N. p., 2018. Web. doi:10.1039/C8CP01284A.
Petrik, Nikolay G., & Kimmel, Gregory A. Electron-stimulated reactions in nanoscale water films adsorbed on α-Al2O3 (0001). United States. doi:10.1039/C8CP01284A.
Petrik, Nikolay G., and Kimmel, Gregory A. Mon . "Electron-stimulated reactions in nanoscale water films adsorbed on α-Al2O3 (0001)". United States. doi:10.1039/C8CP01284A.
@article{osti_1439011,
title = {Electron-stimulated reactions in nanoscale water films adsorbed on α-Al2O3 (0001)},
author = {Petrik, Nikolay G. and Kimmel, Gregory A.},
abstractNote = {The radiation-induced decomposition and desorption of nanoscale amorphous solid water (D2O) films adsorbed on -Al2O3(0001) surface was studied at low temperature in ultrahigh vacuum using temperature programmed desorption (TPD) and electron stimulated desorption (ESD) with a mono-energetic, low energy electron source. ESD yields of molecular products ( D2, O2 and D¬2O) and the total sputtering yield increased with increasing D2O coverage up to ~15 water monolayers (i.e. ~15 1015 cm-2) to a coverage-independent level for thicker water films. Experiments with isotopically-layered water films (D2O and H2O) demonstrated that the highest water decomposition yields occurred at the interfaces of the nanoscale water films with the alumina substrate and vacuum. However, the increased reactivity of the water/alumina interface is relatively small compared to the enhancements in the non-thermal reactions previously observed at the water/Pt(111) and water/TiO2(110) interfaces. We propose that the relatively low activity of Al2O3(0001) for the radiation-induced production of molecular hydrogen is associated with lower reactivity of this surface with hydrogen atoms, which are likely precursors for the molecular hydrogen.100 eV electrons are stopped in the H2O portion of the isotopically-layered nanoscale film on α-Al2O3(0001) but D2is produced at the D2O/alumina interface by mobile electronic excitations and/or hydronium ions.},
doi = {10.1039/C8CP01284A},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
number = 17,
volume = 20,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2018},
month = {Mon Jan 01 00:00:00 EST 2018}
}