Interfacial Adsorbate Competition Regulates Intermediate Stabilization and Onset Potential in Acidic CO2
Adrián Pinilla-Sánchez1, Suraj Panja2,3, Bárbara Polesso1
1ICFO - Institut de Ciències Fotòniques, the Barcelona Institute of Science and Technology, Castelldefels Barcelona 08860, Spain.
Journal of the American Chemical Society
|February 26, 2026
Summary
Anion interactions significantly impact electrochemical CO2 reduction (CO2R) selectivity in acidic media. Sulfate adsorption inhibits CO2R, while hydroxyl coadsorption enables intermediate formation, guiding catalyst design for improved performance.
Area of Science:
- Electrochemistry
- Catalysis
- Surface Science
Background:
- Electrochemical CO2 reduction (CO2R) is crucial for carbon utilization but faces selectivity challenges, especially from the hydrogen evolution reaction (HER) in acidic conditions.
- While proton source and cation concentration effects are known, the influence of anions on CO2R selectivity remains largely unexplored.
Purpose of the Study:
- To investigate the role of anionic species in copper-catalyzed CO2R under acidic conditions.
- To elucidate the mechanisms by which anions affect CO2R selectivity and intermediate formation at relevant current densities.
Main Methods:
- In situ surface-enhanced Raman spectroscopy (SERS) was employed during CO2R on copper gas diffusion electrodes.
- Theoretical simulations were combined with experimental data to analyze anion interactions and reaction pathways.
Main Results:
- Sulfate adsorption was found to inhibit CO2R at low pH by delaying the formation of key intermediates.
- Hydroxyl species coadsorption was observed to enable intermediate formation, influencing CO stabilization and coverage.
- Anion competition was identified as a critical factor regulating the selectivity towards multicarbon products.
Conclusions:
- Anion interactions play a pivotal role in governing CO2R selectivity in acidic electrolytes.
- Understanding these interactions provides essential guidance for designing advanced catalyst-electrolyte interfaces to optimize CO2R performance and minimize HER.
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