Proton-Tuned Surface Chemistry Promotes Multicarbon Formation in Acidic CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Catalysis
• Green Chemistry

Background:

• Acidic electrolytes offer a promising route for carbon dioxide electroreduction to multicarbon (C2+) products, potentially mitigating carbon loss seen in other media.
• Achieving high C2+ selectivity at efficient current densities is hindered by competing one-carbon (C1) product formation.

Purpose of the Study:

• To investigate the effect of proton availability on C2+ production during acidic CO2 electroreduction.
• To enhance C2+ selectivity and efficiency by manipulating electrolyte pH.

Main Methods:

• Electrochemical CO2 reduction experiments were conducted in acidic media with varying proton concentrations (pH 2 to pH 1).
• In situ Raman spectroscopy was employed to analyze surface species and reaction mechanisms.
• Computational simulations were used to understand the role of proton concentration on surface intermediates.

Main Results:

• Increasing proton concentration from pH 2 to pH 1 significantly enhanced C2+ faradaic efficiency from 23.9 ± 2.7% to 48.1 ± 0.6%.
• The C2+/C1 product ratio improved from 0.4 to 1.6 with increased proton availability.
• In situ Raman and simulation data indicated that higher proton concentration promotes *CO coverage and favors a low-frequency *CO binding configuration on copper, facilitating C-C coupling.

Conclusions:

• Proton availability is a critical factor in promoting C2+ selectivity in acidic CO2 electroreduction.
• Optimizing proton concentration can lead to energy-efficient and selective production of valuable multicarbon chemicals.
• The findings provide a new strategy for improving CO2 electroreduction performance by controlling electrolyte acidity.