Visualizing Catalytic Dynamics of Single-Cu-Atom-Modified SnS<sub>2</sub> in CO<sub>2</sub> Electroreduction via Rapid Freeze-Quench Mössbauer Spectroscopy
Ruru Chen, Jian Zhao, Xiong Zhang, Qiao Zhao, Yifan Li, Yi Cui, Miao Zhong, Junhu Wang, Xuning Li, Yanqiang Huang, Bin Liu
Abstract
Effective design and engineering of catalysts for an optimal performance depend extensively on a profound understanding of the intricate catalytic dynamics under reaction conditions. In this work, we showcase rapid freeze-quench (RFQ) Mössbauer spectroscopy as a powerful technique for quantitatively monitoring the catalytic dynamics of single-Cu-atom-modified SnS 2 (Cu 1 /SnS 2 ) in the electrochemical CO 2 reduction reaction (CO 2 RR). Utilizing the newly established RFQ 119 Sn Mössbauer methodology, we clearly identified the dynamic transformation of Cu 1 /SnS 2 to Cu 1 /SnS and Cu 1 /Sn during the CO 2 RR, resulting in an outstanding Faradaic efficiency for formate production (∼90.9%) with a partial current density of 158 mA cm –2 . Results from operando Raman spectroscopy, operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), quasi in situ electron microscopy, and quasi in situ X-ray photoelectron spectroscopy (XPS) measurements indicate that the anchored single Cu atom in Cu 1 /SnS 2 can accelerate the reduction of SnS with in situ formation of Cu 1 /Sn under CO 2 RR conditions, which effectively promote the generation of *CO 2 – /*OCHO intermediates. Theoretical calculations further support that in situ formed Cu 1 /Sn works as active sites catalyzing the CO 2 RR, which reduces the energy barrier for the CO 2 activation and formation of the *OCHO intermediate, thereby facilitating the conversion of CO 2 to formate. The results of this work provide a thorough understanding of the dynamic evolution of Sn-based catalytic sites in the CO 2 RR and shed light for engineering single atoms with an optimized catalytic performance. We anticipate that RFQ Mössbauer spectroscopy will emerge as an advanced spectroscopic technique for enabling a genuine visualization of catalytic dynamics across various reaction systems.