Customizable Interfacial Solvation via Hydrogel Mediation for Enhanced C-C Coupling in CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Interfacial water structure is crucial for CO2 electroreduction selectivity.
• Molecular-level control over interfacial solvation for C-C coupling is limited.
• Copper (Cu) catalysts are widely studied for CO2 electroreduction.

Purpose of the Study:

• To develop a strategy for precisely regulating interfacial solvation in CO2 electroreduction.
• To quantitatively correlate interfacial solvation with C-C coupling efficiency.
• To enhance the selectivity towards C2+ products in CO2 electroreduction using Cu catalysts.

Main Methods:

• Fabrication of an ultrathin, ion-cross-linked, water-retentive hydrogel layer on Cu (Cu-IWH).
• Utilizing in situ Raman spectroscopy to investigate interfacial structures and complexes.
• Employing density functional theory (DFT) calculations to elucidate reaction mechanisms.
• Testing catalyst performance in a membrane electrode assembly (MEA) electrolyzer.

Main Results:

• The Cu-IWH catalyst demonstrated controlled modulation of interfacial electrostatics and hydration.
• Formation of Cu·OHad·K+(H2O)n* interfacial complexes was observed, correlating with enhanced C2+ selectivity.
• Optimized catalyst achieved 87.5% C2+ Faradaic efficiency at -1.2 A cm-2 and stable operation over 800 h.
• Scaled-up MEA system showed 81.5% C2+ selectivity at 40 A.

Conclusions:

• Hydrogel-mediated interfacial solvation engineering is a tunable approach for CO2 electrocatalysis.
• The strategy effectively promotes C-C coupling by controlling interfacial water structure and local environment.
• This method offers a promising pathway for efficient and selective CO2 electroreduction to valuable products.