Operando Local pH Measurement within Gas Diffusion Electrodes Performing Electrochemical Carbon Dioxide Reduction
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.
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.Attached Files
Supplemental Material - jp1c06265_si_001.pdf
Files
Name | Size | Download all |
---|---|---|
md5:4bfe31e7841f989b01f50ec76d70c4e9
|
41.6 MB | Preview Download |
Additional details
- Eprint ID
- 110944
- DOI
- 10.1021/acs.jpcc.1c06265
- Resolver ID
- CaltechAUTHORS:20210917-215610705
- Department of Energy (DOE)
- DE-SC0021266
- Resnick Sustainability Institute
- NSF Graduate Research Fellowship
- DGE-1745301
- Created
-
2021-09-17Created from EPrint's datestamp field
- Updated
-
2022-05-10Created from EPrint's last_modified field
- Caltech groups
- Liquid Sunlight Alliance, Resnick Sustainability Institute