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Title: The degree of rate control of catalyst-bound intermediates in catalytic reaction mechanisms: Relationship to site coverage

Abstract

The degree of rate control (DRC) quantifies how much the energy of each species in a reaction mechanism (e.g., catalyst-bound intermediates and transition states) affects the net reaction rate. It thus plays an important role in understanding catalyst activity and selectivity and in efforts to find better catalysts. We show here that under steady-state reaction conditions, the DRC for any catalyst-bound intermediate n (Xn) is proportional to its fractional population of catalyst sites (θn), X n = - σ × θ n , where the proportionality constant σ is given by σ = Σ i X i × n i .In this report, Xi is the DRC of the transition state in step i, ni is the number of catalyst sites of the same type required for the elementary step i, and the sum is over all transition states (or elementary steps) i. While only a few transition states typically have non-negligible DRCs, this simple sum (or weighted average of elementary-step site requirements) includes only a few terms (and only one term when there is a single rate-determining step). We also show that the DRCs of reactants and catalyst depend upon the choice of zero-energy reference, but simplify to zero when their standard states are used as the zero-energy references.

Authors:
 [1]; ORCiD logo [1]
  1. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Research Org.:
Univ. of Washington, Seattle, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
OSTI Identifier:
1597976
Alternate Identifier(s):
OSTI ID: 1574047
Grant/Contract Number:  
FG02-96ER14630
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 381; Journal Issue: C; Journal ID: ISSN 0021-9517
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; kinetics; mechanism; adsorbate; catalyst-bound intermediate; rate-controlling species

Citation Formats

Mao, Zhongtian, and Campbell, Charles T. The degree of rate control of catalyst-bound intermediates in catalytic reaction mechanisms: Relationship to site coverage. United States: N. p., 2019. Web. https://doi.org/10.1016/j.jcat.2019.09.044.
Mao, Zhongtian, & Campbell, Charles T. The degree of rate control of catalyst-bound intermediates in catalytic reaction mechanisms: Relationship to site coverage. United States. https://doi.org/10.1016/j.jcat.2019.09.044
Mao, Zhongtian, and Campbell, Charles T. Tue . "The degree of rate control of catalyst-bound intermediates in catalytic reaction mechanisms: Relationship to site coverage". United States. https://doi.org/10.1016/j.jcat.2019.09.044. https://www.osti.gov/servlets/purl/1597976.
@article{osti_1597976,
title = {The degree of rate control of catalyst-bound intermediates in catalytic reaction mechanisms: Relationship to site coverage},
author = {Mao, Zhongtian and Campbell, Charles T.},
abstractNote = {The degree of rate control (DRC) quantifies how much the energy of each species in a reaction mechanism (e.g., catalyst-bound intermediates and transition states) affects the net reaction rate. It thus plays an important role in understanding catalyst activity and selectivity and in efforts to find better catalysts. We show here that under steady-state reaction conditions, the DRC for any catalyst-bound intermediate n (Xn) is proportional to its fractional population of catalyst sites (θn), Xn=-σ×θn, where the proportionality constant σ is given by σ=ΣiXi×ni.In this report, Xi is the DRC of the transition state in step i, ni is the number of catalyst sites of the same type required for the elementary step i, and the sum is over all transition states (or elementary steps) i. While only a few transition states typically have non-negligible DRCs, this simple sum (or weighted average of elementary-step site requirements) includes only a few terms (and only one term when there is a single rate-determining step). We also show that the DRCs of reactants and catalyst depend upon the choice of zero-energy reference, but simplify to zero when their standard states are used as the zero-energy references.},
doi = {10.1016/j.jcat.2019.09.044},
journal = {Journal of Catalysis},
number = C,
volume = 381,
place = {United States},
year = {2019},
month = {11}
}