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Operando Local pH Measurement within Gas Diffusion Electrodes Performing Electrochemical Carbon Dioxide Reduction

Welch, Alex J. and Fenwick, Aidan Q. and Böhme, Annette and Chen, Hsiang-Yun and Sullivan, Ian and Li, Xueqian and DuChene, Joseph S. and Xiang, Chengxiang and Atwater, Harry A. (2021) Operando Local pH Measurement within Gas Diffusion Electrodes Performing Electrochemical Carbon Dioxide Reduction. Journal of Physical Chemistry C, 125 (38). pp. 20896-20904. ISSN 1932-7447. doi:10.1021/acs.jpcc.1c06265. https://resolver.caltech.edu/CaltechAUTHORS:20210917-215610705

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Abstract

The local pH near the surface of a CO₂ reduction electrocatalyst strongly impacts catalytic selectivity and activity. Here, confocal fluorescence microscopy was used to map the electrolyte pH near a copper gas diffusion electrode during CO₂ reduction with micron spatial resolution in three dimensions. We observed that the local pH increased from pH 6.8 to greater than pH 10 as the current density was increased from 0 to 28 mA/cm² in a 100 mM KHCO₃ electrolyte. Variations in the pH across the surface indicate areas of locally increased activity. Within deep trenches of the active layer, the local pH increases as trench width decreases. Computational models confirm these experimental results and also showed that the catalyst found within narrow trenches is more active than that found at the surface of the electrode. This study suggests that the overpotential required to perform selective CO₂ reduction can be reduced by increasing the density of narrow trench regions in the microporous layer.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acs.jpcc.1c06265DOIArticle
ORCID:
AuthorORCID
Welch, Alex J.0000-0003-2132-9617
Fenwick, Aidan Q.0000-0003-4442-0878
Böhme, Annette0000-0003-1109-3428
Chen, Hsiang-Yun0000-0002-6461-1519
Sullivan, Ian0000-0003-0632-4607
Li, Xueqian0000-0002-1197-3743
DuChene, Joseph S.0000-0002-7145-323X
Xiang, Chengxiang0000-0002-1698-6754
Atwater, Harry A.0000-0001-9435-0201
Additional Information:© 2021 American Chemical Society. Received: July 14, 2021; Published: September 17, 2021. This work was performed within the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266. A.J.W. acknowledges support from the Resnick Sustainability Institute at Caltech for fellowship support and from the National Science Foundation (NSF) Graduate Research Fellowship Program under Base Award No. 174530. The authors thank Justin Bui and Alex King at UC Berkeley for their assistance in developing the COMSOL simulations. Any opinions, findings, and conclusions expressed in this material are those of the authors and do not necessarily reflect those of DOE or NSF. The authors declare no competing financial interest.
Group:Liquid Sunlight Alliance, Resnick Sustainability Institute
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0021266
Resnick Sustainability InstituteUNSPECIFIED
NSF Graduate Research FellowshipDGE-1745301
Subject Keywords:Redox reactions, Layers, Electrical properties, Electrodes, Electrolytes
Issue or Number:38
DOI:10.1021/acs.jpcc.1c06265
Record Number:CaltechAUTHORS:20210917-215610705
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210917-215610705
Official Citation:Operando Local pH Measurement within Gas Diffusion Electrodes Performing Electrochemical Carbon Dioxide Reduction. Alex J. Welch, Aidan Q. Fenwick, Annette Böhme, Hsiang-Yun Chen, Ian Sullivan, Xueqian Li, Joseph S. DuChene, Chengxiang Xiang, and Harry A. Atwater. The Journal of Physical Chemistry C 2021 125 (38), 20896-20904; DOI: 10.1021/acs.jpcc.1c06265
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110944
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:17 Sep 2021 22:25
Last Modified:12 Oct 2021 16:26

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