Constructing Monolayer Fe Clusters as Model Catalysts for CO₂ Electroreduction

Area of Science:

• Surface Science
• Electrocatalysis
• Materials Science

Background:

• Understanding active sites and structure-activity relationships is crucial for advancing electrocatalytic reactions.
• Iron-based materials are widely studied for CO2 electroreduction (CO2RR), but the exact role of iron remains unclear.
• Developing model catalysts with well-defined structures is essential to overcome these challenges.

Purpose of the Study:

• To construct and investigate monolayer iron clusters (ML-Fe) on Au(111) as model catalysts for CO2RR.
• To elucidate the structure-activity relationships of iron catalysts at the atomic scale.
• To understand how changes in iron cluster size affect catalytic performance and reaction pathways.

Main Methods:

• Fabrication of monolayer Fe clusters on a single-crystal Au(111) substrate using vapor deposition under ultrahigh vacuum (UHV).
• Atomic-scale characterization of Fe cluster size using scanning tunneling microscopy (STM).
• Electrocatalytic performance evaluation for CO2RR and theoretical calculations to analyze reaction mechanisms.

Main Results:

• Successfully constructed tunable monolayer Fe clusters (ML-Fe) with sizes around 2 nm on Au(111).
• ML-Fe catalysts achieved over 60% Faradaic efficiency (FE) for CO production during CO2RR.
• Larger iron nanoparticles promoted hydrogen evolution reaction (HER) due to stronger *CO intermediate binding.

Conclusions:

• Atomic-scale monolayer Fe clusters serve as effective model catalysts for studying CO2RR.
• Catalyst structure, specifically Fe cluster size, critically influences selectivity between CO2RR and HER.
• This work provides a foundation for designing well-defined catalysts to probe structure-activity relationships in electrocatalysis.