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Title: Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K

Here, a critical step toward the rational design of new catalysts that achieve selective and efficient reduction of CO 2 to specific hydrocarbons and oxygenates is to determine the detailed reaction mechanism including kinetics and product selectivity as a function of pH and applied potential for known systems. To accomplish this, we apply ab initio molecular metadynamics simulations (AIMμD) for the water/Cu(100) system with five layers of the explicit solvent under a potential of –0.59 V [reversible hydrogen electrode (RHE)] at pH 7 and compare with experiment. From these free-energy calculations, we determined the kinetics and pathways for major products (ethylene and methane) and minor products (ethanol, glyoxal, glycolaldehyde, ethylene glycol, acetaldehyde, ethane, and methanol). For an applied potential ( U) greater than –0.6 V (RHE) ethylene, the major product, is produced via the Eley–Rideal (ER) mechanism using H 2O + e . The rate-determining step (RDS) is C–C coupling of two CO, with ΔG = 0.69 eV. For an applied potential less than –0.60 V (RHE), the rate of ethylene formation decreases, mainly due to the loss of CO surface sites, which are replaced by H*. The reappearance of C 2H 4 along with CH 4 at Umore » less than –0.85 V arises from *CHO formation produced via an ER process of H* with nonadsorbed CO (a unique result). This *CHO is the common intermediate for the formation of both CH 4 and C 2H 4. These results suggest that, to obtain hydrocarbon products selectively and efficiency at pH 7, we need to increase the CO concentration by changing the solvent or alloying the surface.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States); Univ. of Rochester, Rochester, NY (United States)
Publication Date:
Grant/Contract Number:
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: 8; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
California Inst. of Technology (CalTech), Pasadena, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; reaction mechanism; electrocatalysis; copper; QM metadynamics; free-energy reaction barriers
OSTI Identifier:
1342801
Alternate Identifier(s):
OSTI ID: 1464954

Cheng, Tao, Xiao, Hai, and Goddard, III, William A. Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K. United States: N. p., Web. doi:10.1073/pnas.1612106114.
Cheng, Tao, Xiao, Hai, & Goddard, III, William A. Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K. United States. doi:10.1073/pnas.1612106114.
Cheng, Tao, Xiao, Hai, and Goddard, III, William A. 2017. "Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K". United States. doi:10.1073/pnas.1612106114.
@article{osti_1342801,
title = {Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K},
author = {Cheng, Tao and Xiao, Hai and Goddard, III, William A.},
abstractNote = {Here, a critical step toward the rational design of new catalysts that achieve selective and efficient reduction of CO2 to specific hydrocarbons and oxygenates is to determine the detailed reaction mechanism including kinetics and product selectivity as a function of pH and applied potential for known systems. To accomplish this, we apply ab initio molecular metadynamics simulations (AIMμD) for the water/Cu(100) system with five layers of the explicit solvent under a potential of –0.59 V [reversible hydrogen electrode (RHE)] at pH 7 and compare with experiment. From these free-energy calculations, we determined the kinetics and pathways for major products (ethylene and methane) and minor products (ethanol, glyoxal, glycolaldehyde, ethylene glycol, acetaldehyde, ethane, and methanol). For an applied potential (U) greater than –0.6 V (RHE) ethylene, the major product, is produced via the Eley–Rideal (ER) mechanism using H2O + e–. The rate-determining step (RDS) is C–C coupling of two CO, with ΔG‡ = 0.69 eV. For an applied potential less than –0.60 V (RHE), the rate of ethylene formation decreases, mainly due to the loss of CO surface sites, which are replaced by H*. The reappearance of C2H4 along with CH4 at U less than –0.85 V arises from *CHO formation produced via an ER process of H* with nonadsorbed CO (a unique result). This *CHO is the common intermediate for the formation of both CH4 and C2H4. These results suggest that, to obtain hydrocarbon products selectively and efficiency at pH 7, we need to increase the CO concentration by changing the solvent or alloying the surface.},
doi = {10.1073/pnas.1612106114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 8,
volume = 114,
place = {United States},
year = {2017},
month = {2}
}

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Electrochemical CO2 Reduction on Metal Electrodes
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Electrochemical reduction of carbon dioxide at various series of copper single crystal electrodes
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Ab initiomolecular dynamics for liquid metals
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Ab initio molecular-dynamics simulation of the liquid-metal�amorphous-semiconductor transition in germanium
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