Tandem Electrocatalytic CO₂ Reduction with Efficient Intermediate Conversion over Pyramid-Textured Cu-Ag Catalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical CO2 reduction (E-CO2R) offers a sustainable route to chemicals and fuels when powered by renewable electricity.
• Tandem catalysis is crucial for achieving the product selectivity needed for commercial E-CO2R applications.

Purpose of the Study:

• To develop and demonstrate a two-step tandem electrocatalytic E-CO2R system with efficient intermediate conversion.
• To investigate the performance of bimetallic catalysts with spatially separated active sites on a textured scaffold.

Main Methods:

• Fabrication of a Si(100) scaffold etched into micron-sized pyramids with {111} facets.
• Deposition of separated, micron-scale areas of Ag (for CO production) and Cu (for further reduction) using high-angle physical vapor deposition.
• Tuning relative surface coverages of Ag and Cu by adjusting the deposition angle.

Main Results:

• Bimetallic pyramid tandem catalysts exhibited higher current densities and significantly lower Faradaic efficiencies for CO compared to control catalysts.
• Efficient conversion of the intermediate CO on Ag to more reduced products on Cu was observed.
• A bimetallic catalyst with near-equal Ag and Cu coverage produced methane with 62% FE at -1.1 V_RHE, achieving a partial current density of 12.7 mA cm⁻².
• Estimated intermediate conversion yield of 80-90% for CO, approaching mass-transport limitations.

Conclusions:

• Spatially separated bimetallic catalysts on textured silicon scaffolds enable efficient tandem E-CO2R.
• This approach significantly enhances methane production selectivity and efficiency.
• The developed tandem system shows promise for sustainable chemical and fuel generation from CO2.