Local Reaction Environment Deviations within Gas Diffusion Electrode Pores for CO2 Electrolysis

Esaar N. Butt, Johan T. Padding, Remco Hartkamp*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The local conditions inside a gas diffusion electrode (GDE) pore, especially in the electrical double layer (EDL) region, influence the charge transfer reactions and the selectivity of desired CO2ER products. Most GDE computational models ignore the EDL or are limited in their applicability at high potentials. In this work, we present a continuum model to describe the local environment inside a catalytic pore at varying potentials, electrolyte concentrations and pore diameters. The systems studied in this work are based on an Ag catalyst in contact with KHCO3 solution. Our study shows that steric effects dominate the local environment at high cathodic potentials (≪−25 mV vs pzc at the OHP), leading to a radial drop of CO2 concentration. We also observe a drop in pH value within 1 nm of the reaction plane due to electrostatic repulsion and attraction of OH and H+ ions, respectively. We studied the influence of pore radii (1-10 nm) on electric field and concentrations. Pores with a radius smaller than 5 nm show a higher mean potential, which lowers the mean CO2 concentration. Pores with a favourable local environment can be designed by regulating the ratio between the pore radius and Debye length.

Original languageEnglish
Article number014504
Number of pages8
JournalJournal of the Electrochemical Society
Volume171
Issue number1
DOIs
Publication statusPublished - 2024

Funding

This work is part of the research programme Towards large-scale electroconversion systems (TOeLS) financed by Shell and the Topsectors Chemistry, HTSM and Energy.

Keywords

  • CO electrochemical reduction
  • gas diffusion electrode
  • lectric double layer
  • modelling
  • steric effects

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