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Nilles CK, Borkowski AK, Bartlett ER, Stalcup MA, Lee HJ, Leonard KC, Subramaniam B, Thompson WH, Blakemore JD. Mechanistic Basis of Conductivity in Carbon Dioxide-Expanded Electrolytes: A Joint Experimental-Theoretical Study. J Am Chem Soc 2024; 146:2398-2410. [PMID: 38252883 DOI: 10.1021/jacs.3c08145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Electrolyte conductivity contributes to the efficiency of devices for electrochemical conversion of carbon dioxide (CO2) into useful chemicals, but the effect of the dissolution of CO2 gas on conductivity has received little attention. Here, we report a joint experimental-theoretical study of the properties of acetonitrile-based CO2-expanded electrolytes (CXEs) that contain high concentrations of CO2 (up to 12 M), achieved by CO2 pressurization. Cyclic voltammetry data and paired simulations show that high concentrations of dissolved CO2 do not impede the kinetics of outer-sphere electron transfer but decrease the solution conductivity at higher pressures. In contrast with conventional behaviors, Jones reactor-based measurements of conductivity show a nonmonotonic dependence on CO2 pressure: a plateau region of constant conductivity up to ca. 4 M CO2 and a region showing reduced conductivity at higher [CO2]. Molecular dynamics simulations reveal that while the intrinsic ionic strength decreases as [CO2] increases, there is a concomitant increase in ionic mobility upon CO2 addition that contributes to stable solution conductivities up to 4 M CO2. Taken together, these results shed light on the mechanisms underpinning electrolyte conductivity in the presence of CO2 and reveal that the dissolution of CO2, although nonpolar by nature, can be leveraged to improve mass transport rates, a result of fundamental and practical significance that could impact the design of next-generation systems for CO2 conversion. Additionally, these results show that conditions in which ample CO2 is available at the electrode surface are achievable without sacrificing the conductivity needed to reach high electrocatalytic currents.
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Affiliation(s)
- Christian K Nilles
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Ashley K Borkowski
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Elizabeth R Bartlett
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Matthew A Stalcup
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
- Department of Chemical and Petroleum Engineering, University of Kansas, 1530 W 15th Street, Lawrence, Kansas 66045, United States
| | - Hyun-Jin Lee
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
| | - Kevin C Leonard
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
- Department of Chemical and Petroleum Engineering, University of Kansas, 1530 W 15th Street, Lawrence, Kansas 66045, United States
| | - Bala Subramaniam
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
- Department of Chemical and Petroleum Engineering, University of Kansas, 1530 W 15th Street, Lawrence, Kansas 66045, United States
| | - Ward H Thompson
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James D Blakemore
- Center for Environmentally Beneficial Catalysis, University of Kansas, 1501 Wakarusa Drive, Lawrence, Kansas 66047, United States
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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Sulphur vs NH Group: Effects on the CO 2 Electroreduction Capability of Phenylenediamine-Cp Cobalt Complexes. Molecules 2023; 28:molecules28052364. [PMID: 36903610 PMCID: PMC10005266 DOI: 10.3390/molecules28052364] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/02/2023] [Accepted: 03/03/2023] [Indexed: 03/08/2023] Open
Abstract
The cobalt complex (I) with cyclopentadienyl and 2-aminothiophenolate ligands was investigated as a homogeneous catalyst for electrochemical CO2 reduction. By comparing its behavior with an analogous complex with the phenylenediamine (II), the effect of sulfur atom as a substituent has been evaluated. As a result, a positive shift of the reduction potential and the reversibility of the corresponding redox process have been observed, also suggesting a higher stability of the compound with sulfur. Under anhydrous conditions, complex I showed a higher current enhancement in the presence of CO2 (9.41) in comparison with II (4.12). Moreover, the presence of only one -NH group in I explained the difference in the observed increases on the catalytic activity toward CO2 due to the presence of water, with current enhancements of 22.73 and 24.40 for I and II, respectively. DFT calculations confirmed the effect of sulfur on the lowering of the energy of the frontier orbitals of I, highlighted by electrochemical measurements. Furthermore, the condensed Fukui function f - values agreed very well with the current enhancement observed in the absence of water.
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Hopkins Leseberg JA, Henke WC, Douglas JT, Oliver AG, Sydora OL, Blakemore JD. Spectroscopic Interrogation of the Reduction of Model Chromium Precatalysts for Olefin Oligomerization. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Julie A. Hopkins Leseberg
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Wade C. Henke
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Justin T. Douglas
- Nuclear Magnetic Resonance Laboratory, Molecular Structures Group, University of Kansas, 2034 Becker Drive, Lawrence, Kansas 66047, United States
| | - Allen G. Oliver
- Department of Chemistry and Biochemistry, University of Notre Dame, 149 Stepan Chemistry, Notre Dame, Indiana 46556, United States
| | - Orson L. Sydora
- Research & Technology, Chevron Phillips Chemical, Kingwood, Texas 77339, United States
| | - James D. Blakemore
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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