Ag-Sn Bimetallic Catalyst with a Core-Shell Structure for CO₂ Reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Converting carbon dioxide (CO2) into valuable chemicals is crucial for mitigating emissions.
• Electrochemical CO2 reduction requires catalysts to overcome activation energy barriers.
• First-row transition metals show potential but suffer from oxidation due to high oxygen affinity.

Purpose of the Study:

• To design and synthesize Ag-Sn core-shell electrocatalysts for efficient CO2 conversion.
• To investigate the role of a partially oxidized shell in catalytic performance.
• To understand the mechanism of CO2 activation and formate production.

Main Methods:

• Synthesis of Ag-Sn bimetallic electrocatalysts with core-shell nanostructures.
• Electrochemical characterization to evaluate catalytic activity and selectivity.
• Density-functional theory (DFT) calculations to elucidate reaction mechanisms and active sites.

Main Results:

• An optimal catalyst with a ~1.7 nm SnOx shell achieved ~80% formate Faradaic efficiency and ~16 mA cm-2 partial current density at -0.8 V vs RHE.
• DFT calculations revealed oxygen vacancies on SnO(101) are crucial for CO2 activation.
• A linear correlation was found between CO2- adsorption energy at oxygen vacancies and catalytic performance.

Conclusions:

• Ag-Sn core-shell nanostructures with partially oxidized shells are effective for CO2 electroreduction to formate.
• Oxygen vacancies in the SnOx shell play a critical role in stabilizing intermediates and enhancing catalytic activity.
• The study provides insights into catalyst design for selective CO2 conversion and identifies key descriptors for performance optimization.