Constructing Monolayer Fe Clusters as Model Catalysts for CO<sub>2</sub> Electroreduction
Hengpan Yang, Huizhu Cai, Kai Song, Shijie He, Shangzhao Feng, Zhi Chen, Xue Zhang, Qi Hu, Chuanxin He
Abstract
Constructing model catalysts to clarify the active sites and elucidate structure–activity relationships represents a bottleneck issue in electrocatalytic reactions. For instance, Fe-based materials have been widely investigated for various electrocatalytic reactions, e.g., CO 2 electroreduction (CO 2 RR). However, the precise role of Fe in the catalytic mechanism remains debated and is under extensive investigation due to the complex properties of those catalysts. Herein, we successfully construct a series of monolayer Fe clusters (ML-Fe) on a single-crystal Au(111) substrate via vapor deposition under ultrahigh vacuum (UHV) conditions, which serve as model catalysts for CO 2 RR. Notably, the size of Fe clusters can be tuned at the atomic scale (∼2 nm) as observed by scanning tunneling microscopy (STM). Experimental and theoretical calculations demonstrate that ML-Fe achieves >60% Faradaic efficiency (FE) for CO production during CO 2 RR. When the Fe layer further increases to form nanoparticles, Fe sites exhibit stronger electron interaction and binding strength with *CO intermediates, consequently shifting the dominant reaction pathway from CO 2 RR to hydrogen evolution (HER). This work could provide valuable insights into designing model catalysts with well-defined active sites to investigate the structure–activity relationships in diverse electrocatalytic systems.