Highly Selective Electroreduction of CO₂ to Formate Over Intermetallic Ag₃Sn Catalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Silver-tin (Ag-Sn) composites are explored for CO2 reduction reaction (CO2RR) to produce formate.
• Ag-Sn heterostructures and core-shell architectures can enhance formate selectivity, but active sites remain unclear.

Purpose of the Study:

• Identify the precise Ag-Sn active sites responsible for enhanced formate selectivity in CO2RR.
• Investigate the role of the ordered intermetallic Ag3Sn phase in selective CO2-to-formate conversion.

Main Methods:

• Combined theoretical calculations (Density Functional Theory) and experimental synthesis and characterization.
• Electrochemical testing of synthesized Ag3Sn catalysts, including Faradaic efficiency measurements.
• Control experiments with excess Ag or SnO2 and comparison with Ag/SnO2 physical mixtures.

Main Results:

• Ag3Sn, an ordered intermetallic phase, is identified as a pivotal electrocatalyst for selective CO2-to-formate conversion.
• Ag3Sn demonstrated a high Faradaic efficiency of 92.3% for HCOOH production at -1.0 V vs. RHE.
• The intermetallic structure of Ag3Sn is essential for selectivity, outperforming physical mixtures and showing a hydrogen spillover-assisted pathway.

Conclusions:

• Ag3Sn is an effective phase for selective CO2-to-formate conversion.
• Mechanistic insights into cooperative electronic and structural effects in Ag3Sn guide the rational design of CO2RR catalysts.
• This work highlights the importance of intermetallic phases for targeted CO2 reduction products.