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Title: Mechanistic insights into electrochemical reduction of CO 2 over Ag using density functional theory and transport models

Electrochemical reduction of CO 2 using renewable sources of electrical energy holds promise for converting CO 2 to fuels and chemicals. Since this process is complex and involves a large number of species and physical phenomena, a comprehensive understanding of the factors controlling product distribution is required. While the most plausible reaction pathway is usually identified from quantum-chemical calculation of the lowest free-energy pathway, this approach can be misleading when coverages of adsorbed species determined for alternative mechanism differ significantly, since elementary reaction rates depend on the product of the rate coefficient and the coverage of species involved in the reaction. Moreover, cathode polarization can influence the kinetics of CO 2 reduction. Here in this work, we present a multiscale framework for ab initio simulation of the electrochemical reduction of CO 2 over an Ag(110) surface. A continuum model for species transport is combined with a microkinetic model for the cathode reaction dynamics. Free energies of activation for all elementary reactions are determined from density functional theory calculations. Using this approach, three alternative mechanisms for CO 2 reduction were examined. The rate-limiting step in each mechanism is **COOH formation at higher negative potentials. However, only via the multiscale simulation wasmore » it possible to identify the mechanism that leads to a dependence of the rate of CO formation on the partial pressure of CO 2 that is consistent with experiments. Additionally, simulations based on this mechanism also describe the dependence of the H 2 and CO current densities on cathode voltage that are in strikingly good agreement with experimental observation.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [4] ; ORCiD logo [5]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint Center for Artificial Photosynthesis; Univ. of Illinois, Chicago, IL (United States). Department of Chemical Engineering
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint Center for Artificial Photosynthesis; Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemistry
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint Center for Artificial Photosynthesis
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint Center for Artificial Photosynthesis; Univ. of California, Berkeley, CA (United States). Department of Chemistry
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint Center for Artificial Photosynthesis; Univ. of California, Berkeley, CA (United States). Department of Chemical and Biomolecular Engineering
Publication Date:
Grant/Contract Number:
AC02-05CH11231; SC0004993
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 42; Related Information: © 2017, National Academy of Sciences. All rights reserved.; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; CO2 reduction; electrocatalysis; mechanism; density functional theory; transport model
OSTI Identifier:
1396063
Alternate Identifier(s):
OSTI ID: 1426740