Enhancing C₂₊ Product Faradaic Efficiency in CO₂ Reduction Using Fluorine-Stabilized Superhydrophobic Copper (δ+)

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Oxide-derived (OD) Cu catalysts are effective for C2+ production but suffer from metallic state reversion, reducing selectivity.
• Stabilizing the positive oxidation state of copper is crucial for maintaining catalyst performance.

Purpose of the Study:

• To develop a novel strategy for incorporating fluorine (F) into Cu2O nanospheres to enhance catalyst stability and selectivity.
• To investigate the role of fluorine in stabilizing the Cu (δ+) oxidation state and improving C2+ product formation.

Main Methods:

• Hydrofluoric acid (HF) treatment for F incorporation into Cu2O nanospheres.
• Characterization using 19F magic-angle spinning (MAS) solid-state nuclear magnetic resonance (ssNMR) spectroscopy, water contact angle (WCA) measurements, in situ Raman, and in situ ATR-FTIR spectroscopy.
• Density functional theory (DFT) calculations and Bader charge analysis for mechanistic insights.

Main Results:

• Fluorine incorporation stabilized the Cu (δ+) oxidation state, achieving 91.9 ± 2.03% Faradaic efficiency for C2+ products (67% ethylene) at 250 mA cm-2.
• F substitution at oxygen vacancies and formation of a surface HF layer were confirmed by ssNMR.
• Enhanced hydrophobicity (WCA = 161°) suppressed hydrogen evolution reaction (HER).
• In situ studies confirmed prolonged Cu2O stability and elucidated the ethylene production pathway.

Conclusions:

• Fluorine incorporation into Cu2O nanospheres is a viable strategy to stabilize the active oxidation state and enhance selectivity for C2+ products in electrochemical CO2 reduction.
• The enhanced hydrophobicity and electronic effects of fluorine contribute to improved catalyst performance and stability.
• This work provides a new avenue for designing advanced electrocatalysts for efficient CO2 conversion.