Cu-Ag tandem electrodes with controlled Ag overlayer thickness for tunable CO₂ reduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical CO2 reduction (eCO2R) is crucial for sustainable chemical production.
• Tandem catalysts combining CO-selective metals (e.g., Ag) with C-C coupling metals (e.g., Cu) offer tunable product selectivity.
• Controlling interfacial properties is key to optimizing catalyst performance.

Purpose of the Study:

• To investigate the effect of silver overlayer thickness on Cu-Ag tandem electrodes for eCO2R.
• To understand how nanometer-scale thickness variations influence product distribution and reaction pathways.
• To establish silver overlayer thickness as a tunable parameter for catalyst design.

Main Methods:

• Fabrication of Cu-Ag tandem electrodes with precisely controlled silver overlayer thicknesses (0.9-150 nm) using physical vapor deposition.
• Electrocatalytic performance evaluation under flow-cell conditions.
• In situ Raman spectroscopy to identify reaction intermediates.

Main Results:

• Product selectivity showed a non-monotonic dependence on silver thickness.
• Methane (CH4) formation was significantly enhanced, peaking at ~10 nm silver thickness.
• C2+ selectivity initially decreased with increasing silver thickness up to 10 nm, then increased.
• In situ Raman spectroscopy indicated a thickness-dependent competition between *CHx-CO and *CHx-H pathways.

Conclusions:

• Silver overlayer thickness is a critical parameter for controlling eCO2R selectivity in Cu-Ag tandem catalysts.
• Optimizing the interfacial structure through controlled silver deposition enables tailored product formation, such as enhanced methane production.
• This work provides insights into catalyst design for efficient electrochemical CO2 conversion.