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Title: The Trans Effect in Electrocatalytic CO 2 Reduction: Mechanistic Studies of Asymmetric Ruthenium Pyridyl-Carbene Catalysts

Abstract

A comprehensive mechanistic study of electrocatalytic CO 2 reduction by ruthenium 2,2':6',2"-terpyridine (tpy) pyridyl-carbene catalysts reveals the importance of stereochemical control to locate the strongly donating N-heterocyclic carbene ligand trans to the site of CO 2 activation. Computational studies were undertaken to predict the most stable isomer for a range of reasonable intermediates in CO 2 reduction, suggesting that the ligand trans to the reaction site plays a key role in dictating the energetic profile of the catalytic reaction. A new isomer of [Ru(tpy)(Mebim-py)(NCCH 3)] 2+ (Mebim-py is 1-methylbenzimidazol-2-ylidene-3-(2'-pyridine)) and both isomers of the catalytic intermediate [Ru(tpy)(Mebim-py)(CO)] 2+ were synthesized and characterized. Experimental studies demonstrate that both isomeric precatalysts facilitate electroreduction of CO 2 to CO in 95/5 MeCN/H 2O with high activity and high selectivity. Cyclic voltammetry, infrared spectroelectrochemistry, and NMR spectroscopy studies provide a detailed mechanistic picture demonstrating an essential isomerization step in which the N-trans catalyst converts in situ to the C-trans variant. Insight into molecular electrocatalyst design principles emerge from this study. First, the use of an asymmetric ligand that places a strongly electron-donating ligand trans to the site of CO 2 binding and activation is critical to high activity. Second, stereochemical control to maintain themore » desired isomer structure during catalysis is critical to performance. Lastly, pairing the strongly donating pyridyl-carbene ligand with the redox-active tpy ligand proves to be useful in boosting activity without sacrificing overpotential. These design principles are considered in the context of surface-immobilized electrocatalysis.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [2]; ORCiD logo [1]
  1. Univ. of North Carolina, Chapel Hill, NC (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Alliance for Molecular PhotoElectrode Design for Solar Fuels (AMPED); Brookhaven National Lab. (BNL), Upton, NY (United States); Univ. of North Carolina, Chapel Hill, NC (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
OSTI Identifier:
1566597
Grant/Contract Number:  
SC0012704; SC0001011; ECCS-1542015; CHE-1726291
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 141; Journal Issue: 16; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; catalysis (homogeneous); catalysis (heterogeneous); electrocatalysis; solar (fuels); photosynthesis (natural and artificial); defects; charge transport; materials and chemistry by design; mesostructured materials; synthesis (novel materials); synthesis (self-assembly); redox reactions; ligands; catalysts; isomerization; molecular structure

Citation Formats

Gonell, Sergio, Massey, Marsha D., Moseley, Ian P., Schauer, Cynthia K., Muckerman, James T., and Miller, Alexander J. M. The Trans Effect in Electrocatalytic CO2 Reduction: Mechanistic Studies of Asymmetric Ruthenium Pyridyl-Carbene Catalysts. United States: N. p., 2019. Web. doi:10.1021/jacs.9b01735.
Gonell, Sergio, Massey, Marsha D., Moseley, Ian P., Schauer, Cynthia K., Muckerman, James T., & Miller, Alexander J. M. The Trans Effect in Electrocatalytic CO2 Reduction: Mechanistic Studies of Asymmetric Ruthenium Pyridyl-Carbene Catalysts. United States. doi:10.1021/jacs.9b01735.
Gonell, Sergio, Massey, Marsha D., Moseley, Ian P., Schauer, Cynthia K., Muckerman, James T., and Miller, Alexander J. M. Thu . "The Trans Effect in Electrocatalytic CO2 Reduction: Mechanistic Studies of Asymmetric Ruthenium Pyridyl-Carbene Catalysts". United States. doi:10.1021/jacs.9b01735. https://www.osti.gov/servlets/purl/1566597.
@article{osti_1566597,
title = {The Trans Effect in Electrocatalytic CO2 Reduction: Mechanistic Studies of Asymmetric Ruthenium Pyridyl-Carbene Catalysts},
author = {Gonell, Sergio and Massey, Marsha D. and Moseley, Ian P. and Schauer, Cynthia K. and Muckerman, James T. and Miller, Alexander J. M.},
abstractNote = {A comprehensive mechanistic study of electrocatalytic CO2 reduction by ruthenium 2,2':6',2"-terpyridine (tpy) pyridyl-carbene catalysts reveals the importance of stereochemical control to locate the strongly donating N-heterocyclic carbene ligand trans to the site of CO2 activation. Computational studies were undertaken to predict the most stable isomer for a range of reasonable intermediates in CO2 reduction, suggesting that the ligand trans to the reaction site plays a key role in dictating the energetic profile of the catalytic reaction. A new isomer of [Ru(tpy)(Mebim-py)(NCCH3)]2+ (Mebim-py is 1-methylbenzimidazol-2-ylidene-3-(2'-pyridine)) and both isomers of the catalytic intermediate [Ru(tpy)(Mebim-py)(CO)]2+ were synthesized and characterized. Experimental studies demonstrate that both isomeric precatalysts facilitate electroreduction of CO2 to CO in 95/5 MeCN/H2O with high activity and high selectivity. Cyclic voltammetry, infrared spectroelectrochemistry, and NMR spectroscopy studies provide a detailed mechanistic picture demonstrating an essential isomerization step in which the N-trans catalyst converts in situ to the C-trans variant. Insight into molecular electrocatalyst design principles emerge from this study. First, the use of an asymmetric ligand that places a strongly electron-donating ligand trans to the site of CO2 binding and activation is critical to high activity. Second, stereochemical control to maintain the desired isomer structure during catalysis is critical to performance. Lastly, pairing the strongly donating pyridyl-carbene ligand with the redox-active tpy ligand proves to be useful in boosting activity without sacrificing overpotential. These design principles are considered in the context of surface-immobilized electrocatalysis.},
doi = {10.1021/jacs.9b01735},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 16,
volume = 141,
place = {United States},
year = {2019},
month = {4}
}

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Works referencing / citing this record:

A new polypyridyl‐based Ru (II) complex as a highly efficient electrocatalyst for CO 2 reduction
journal, January 2020

  • Daryanavard, Marzieh; Masoumpour, Marziyeh Sadat
  • Applied Organometallic Chemistry, Vol. 34, Issue 3
  • DOI: 10.1002/aoc.5389

Effect of PDI ligand binding pattern on the electrocatalytic activity of two Ru(II) complexes for CO 2 reduction
journal, February 2020

  • Shi, Ning‐ning; Xie, Wang‐jing; Gao, Wei‐song
  • Applied Organometallic Chemistry, Vol. 34, Issue 4
  • DOI: 10.1002/aoc.5551