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The importance of grand-canonical quantum mechanical methods to describe the effect of electrode potential on the stability of intermediates involved in both electrochemical CO_2 reduction and hydrogen evolution

Zhang, Haochen and Goddard, William A., III and Lu, Qi and Cheng, Mu-Jeng (2018) The importance of grand-canonical quantum mechanical methods to describe the effect of electrode potential on the stability of intermediates involved in both electrochemical CO_2 reduction and hydrogen evolution. Physical Chemistry Chemical Physics, 20 (4). pp. 2549-2557. ISSN 1463-9076. https://resolver.caltech.edu/CaltechAUTHORS:20180110-102226313

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Abstract

The rational design of electrocatalysts to convert CO_2 to fuel requires predicting the effect of the electrode potential (U) on the binding and structures of the intermediates involved in CO_2 electrochemical reduction (CO2ER). In this study, we used grand-canonical quantum mechanics (GC-QM) to keep the potential constant during the reactions (rather than keeping the charge constant as in standard QM) to investigate the effect of Uon adsorption free energies (ΔGs) of 14 CO_2ER intermediates on Cu(111) as well as the intermediates involved in the competitive hydrogen evolution reaction (HER). In contrast to most previous theoretical studies where ΔGs were calculated under constant charge (= 0, neutral), we calculated ΔGs under constant potential (U = 0.0, −0.5, −1.0, and −1.5 V_(SHE)). By comparing the ΔGs calculated under constant U (= 0.0 V_(SHE)) to those calculated under constant charge, we found differences up to 0.22 eV which would change the rates at 298 K by a factor of about 5300. In particular we found that the adsorption of species with a C O functional group (i.e., *COOH, *CO, and *CHO) strengthened by up to 0.16 eV as U became more negative by 1 V, whereas the adsorption of –O– species (i.e., *OH, *OCH3, *COH, and *CHOH) weakened by up to 0.20 eV. For the (111) index surfaces of Cu, Au, Ag, Ir, Ni, Pd, Pt and Rh, we investigated the effect of U on the reaction free energy (ΔG) at pH = 0 for the crucial elementary steps for CO_2ER (*CO + (H+/e−) → *CHO, ΔG = (ΔG_(*CHO) – ΔG_(*CO)) + eU) and HER (* + (H+/e−) → *H, ΔG = ΔG_(*H) + eU. Our results indicated that the influence of U on (ΔG_(*CHO) – ΔG_(*CO)) was metal dependent. In contrast, the energy for converting a proton in solution to H* on the surface, ΔG_(*H), was barely affected by U(for the studied metals). Overall we found substantial differences (MAD > 0.18 eV) between the ΔGs calculated under U = −1.0 V_(SHE) (relevant to experiments) and those calculated under constant charge (= 0, neutral) common to most theoretical investigations. Therefore, we strongly recommend application GC-QM to obtain accurate energetics for CO_2ER.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1039/c7cp08153gDOIArticle
http://pubs.rsc.org/en/Content/ArticleLanding/2018/CP/C7CP08153GPublisherArticle
http://www.rsc.org/suppdata/c7/cp/c7cp08153g/c7cp08153g1.pdfPublisherSupplementary Information
ORCID:
AuthorORCID
Zhang, Haochen0000-0002-2774-5868
Goddard, William A., III0000-0003-0097-5716
Lu, Qi0000-0002-0380-2629
Cheng, Mu-Jeng0000-0002-8121-0485
Alternate Title:The importance of grand-canonical quantum mechanical methods to describe the effect of electrode potential on the stability of intermediates involved in both electrochemical CO2 reduction and hydrogen evolution
Additional Information:© 2018 the Owner Societies. Received 5th December 2017, Accepted 1st January 2018, First published on 3rd January 2018. H. C. Z. and Q. L. acknowledge financial support from the National Natural Science Foundation of China (grant number 21606142). M. J. C. acknowledges financial support from the Ministry of Science and Technology of the Republic of China under grant no. MOST 105-2113-M-006-017-MY2. W. A. G. acknowledges financial support from the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC0004993. We wish to thank the supercomputer centre at the Tsinghua National Laboratory for Information Science and Technology for providing computational resources. There are no conflicts to declare.
Group:JCAP
Funders:
Funding AgencyGrant Number
National Natural Science Foundation of China21606142
Ministry of Science and Technology (Taipei)MOST 105-2113-M-006-017-MY2
Department of Energy (DOE)DE-SC0004993
Issue or Number:4
Record Number:CaltechAUTHORS:20180110-102226313
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180110-102226313
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84229
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Jan 2018 18:50
Last Modified:09 Mar 2020 13:19

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