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Title: Role of weakly bound complexes in temperature-dependence and relative rates of MxOy + H 2O ( M = Mo, W) reactions

Results of a systematic comparison of the Mo xO y + H 2O and W xO y + H 2O reaction rate coefficients are reported and compared to previous experimental and computational studies on these reactions. W xO y clusters undergo more direct oxidation by water to yield W xO y+1 + H 2, while for Mo xO y clusters, production of Mo xO yH 2 (trapped intermediates in the oxidation reaction) is comparatively more prevalent. However, Mo xO y clusters generally have higher rate coefficients than analogous W xO y clusters if Mo xO y+1H 2 formation is included. Results of calculations on the M 2O y + H 2O (M = Mo, W; y = 4, 5) reaction entrance channel are reported. They include charge-dipole complexes formed from long-range interactions, and the requisite conversion to a Lewis acid-base complex that leads to M xO y+1H 2 formation. The results predict that the Lewis acid-base complex is more strongly bound for Mo xO y clusters than for W xO y clusters. The calculated free energies along this portion of the reaction path are also consistent withmore » the modest anti-Arrhenius temperature dependence measured for most Mo xO y + H 2O reactions, and the W xO y + H 2O reaction rate coefficients generally being constant over the temperature range sampled in this study. For clusters that exhibit evidence of both water addition and oxidation reactions, increasing the temperature increases the branching ratio toward oxidation for both species. In conclusion, a more direct reaction path to H 2 production may therefore become accessible at modest temperatures for certain cluster stoichiometries and structures.« less
Authors:
 [1] ; ORCiD logo [1] ;  [1] ;  [1]
  1. Indiana Univ., Bloomington, IN (United States)
Publication Date:
Grant/Contract Number:
FG02-07ER15889
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 7; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Indiana Univ., Bloomington, IN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1469677
Alternate Identifier(s):
OSTI ID: 1238389

Kafader, Jared O., Ray, Manisha, Raghavachari, Krishnan, and Jarrold, Caroline Chick. Role of weakly bound complexes in temperature-dependence and relative rates of MxOy– + H2O (M = Mo, W) reactions. United States: N. p., Web. doi:10.1063/1.4941829.
Kafader, Jared O., Ray, Manisha, Raghavachari, Krishnan, & Jarrold, Caroline Chick. Role of weakly bound complexes in temperature-dependence and relative rates of MxOy– + H2O (M = Mo, W) reactions. United States. doi:10.1063/1.4941829.
Kafader, Jared O., Ray, Manisha, Raghavachari, Krishnan, and Jarrold, Caroline Chick. 2016. "Role of weakly bound complexes in temperature-dependence and relative rates of MxOy– + H2O (M = Mo, W) reactions". United States. doi:10.1063/1.4941829. https://www.osti.gov/servlets/purl/1469677.
@article{osti_1469677,
title = {Role of weakly bound complexes in temperature-dependence and relative rates of MxOy– + H2O (M = Mo, W) reactions},
author = {Kafader, Jared O. and Ray, Manisha and Raghavachari, Krishnan and Jarrold, Caroline Chick},
abstractNote = {Results of a systematic comparison of the MoxOy– + H2O and WxOy– + H2O reaction rate coefficients are reported and compared to previous experimental and computational studies on these reactions. WxOy– clusters undergo more direct oxidation by water to yield WxOy+1– + H2, while for MoxOy– clusters, production of MoxOyH2– (trapped intermediates in the oxidation reaction) is comparatively more prevalent. However, MoxOy– clusters generally have higher rate coefficients than analogous WxOy– clusters if MoxOy+1H2– formation is included. Results of calculations on the M2Oy– + H2O (M = Mo, W; y = 4, 5) reaction entrance channel are reported. They include charge-dipole complexes formed from long-range interactions, and the requisite conversion to a Lewis acid-base complex that leads to MxOy+1H2– formation. The results predict that the Lewis acid-base complex is more strongly bound for MoxOy– clusters than for WxOy– clusters. The calculated free energies along this portion of the reaction path are also consistent with the modest anti-Arrhenius temperature dependence measured for most MoxOy– + H2O reactions, and the WxOy– + H2O reaction rate coefficients generally being constant over the temperature range sampled in this study. For clusters that exhibit evidence of both water addition and oxidation reactions, increasing the temperature increases the branching ratio toward oxidation for both species. In conclusion, a more direct reaction path to H2 production may therefore become accessible at modest temperatures for certain cluster stoichiometries and structures.},
doi = {10.1063/1.4941829},
journal = {Journal of Chemical Physics},
number = 7,
volume = 144,
place = {United States},
year = {2016},
month = {2}
}