Solvent Effect on Electrochemical CO₂ Reduction Reaction on Nanostructured Copper Electrodes

Area of Science:

• Electrochemistry
• Catalysis
• Sustainable Chemistry

Background:

• Electrochemical reduction of carbon dioxide (CO2RR) offers a sustainable route to fuels and chemicals.
• Producing hydrocarbons via CO2RR faces challenges like high overpotential and competing hydrogen evolution reaction (HER).
• Electrolyte composition is a key factor in directing CO2RR selectivity over HER.

Purpose of the Study:

• To investigate the solvent effect, specifically water concentration in acetonitrile, on CO2RR using nanostructured copper electrodes.
• To understand the role of water and electrode surface structure in CO2RR selectivity and activity.
• To elucidate the reaction mechanism and intermediate species involved in CO2RR in acetonitrile-based electrolytes.

Main Methods:

• Electrochemical reduction of CO2 using nanostructured copper (CuNC) and polycrystalline copper (Cu) electrodes.
• Online gas chromatography for product analysis (Faradaic efficiency).
• In situ Fourier Transform Infrared (FTIR) spectroscopy to study interfacial species and reaction mechanisms.

Main Results:

• CO2RR is structure-dependent, with CuNC electrodes producing ethylene (10% FE) at >500 mM water concentration.
• CO is the primary product (>85% FE) in acetonitrile, with adsorbed CO being undetected, suggesting inhibited adsorption.
• Water addition to acetonitrile had minimal impact on CO2RR activity and selectivity, indicating it's not crucial for the rate-determining step.

Conclusions:

• Nanostructured copper electrodes show potential for selective CO2RR in acetonitrile-water mixtures.
• Electrode structure and electrolyte composition significantly influence CO2RR pathways.
• Further research is needed to enhance hydrocarbon production and understand the fundamental mechanisms in non-aqueous electrolytes.