Interfacial Water Structure Governs CO2 Electroreduction Selectivity on Copper via Surface Ligand Functionalization

Area of Science:

• Electrochemistry
• Surface Science
• Catalysis

Background:

• Electrochemical CO2 reduction is crucial for sustainable chemistry.
• Controlling product selectivity in copper (Cu)-catalyzed CO2 reduction is challenging due to competing reaction pathways.
• The balance between CO coupling and protonation kinetics dictates product distribution.

Purpose of the Study:

• To demonstrate that interfacial water engineering via surface ligand functionalization can control Cu-catalyzed CO2 reduction selectivity.
• To investigate the role of surface hydrophobicity and water structure in tuning reaction pathways.
• To achieve selective production of ethylene or methane.

Main Methods:

• Surface ligand functionalization of copper electrodes with alkanethiols (Cu-UDT, Cu-MUA, Cu-MUO) to modify surface hydrophobicity.
• In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) to analyze interfacial water structure and adsorbed CO (*CO).
• Time-resolved SEIRAS to study *CO decay kinetics.

Main Results:

• Surface ligands altered interfacial water structures without changing the Cu active site's electronic properties.
• Cu-MUA created a strongly hydrogen-bonded water network, promoting *CO C-C coupling and high ethylene selectivity.
• Cu-MUO generated a free water environment, enhancing *CO protonation to *CHO and methane selectivity.

Conclusions:

• Interfacial water structure is a key factor in controlling Cu-catalyzed CO2 reduction selectivity.
• Surface ligand functionalization offers a viable strategy to tune reaction pathways and product distribution.
• This approach provides precise control over ethylene versus methane production.