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

Abstract

Electrochemical reduction of CO₂ using renewable sources of electrical energy holds promise for converting CO₂ 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 CO₂ reduction. Here in this work, we present a multiscale framework for ab initio simulation of the electrochemical reduction of CO₂ 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 CO₂ reduction were examined. The rate-limiting step in each mechanism is **COOH formation at higher negative potentials. However, only via the multiscale simulation was it possible to identify themore » mechanism that leads to a dependence of the rate of CO formation on the partial pressure of CO₂ that is consistent with experiments. Additionally, simulations based on this mechanism also describe the dependence of the H₂ and CO current densities on cathode voltage that are in strikingly good agreement with experimental observation.« less

Authors:

Singh, Meenesh R.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-3638-8866"
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Goodpaster, Jason D. ^[2]; Weber, Adam Z. ^[3]; Head-Gordon, Martin  ^[4];

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• Search DOE PAGES for ORCID "0000-0002-4309-6669"
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Bell, Alexis T.  ^[5]

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• Search DOE PAGES for ORCID "0000-0002-5738-4645"
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+ Show Author Affiliations

1. Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607,
2. Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455,
3. Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,
4. Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Department of Chemistry, University of California, Berkeley, CA 94720,
5. Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720

Publication Date:

2017-10-02

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1396063

Alternate Identifier(s):

OSTI ID: 1426740

Grant/Contract Number:  

SC0004993; AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 114 Journal Issue: 42; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; CO2 reduction; electrocatalysis; mechanism; density functional theory; transport model