Operando Mossbauer Spectroscopic Tracking the Metastable State of Atomically Dispersed Tin in Copper Oxide for Selective CO2 Electroreduction

Authors：Chen, Ruru; Zhao, Jian; Li, Yifan; Cui, Yi; Lu, Ying-Rui; Hung, Sung-Fu; Wang, Shifu; Wang, Weijue; Huo, Guodong; Zhao, Yang; Liu, Wei; Wang, Junhu; Xiao, Hai^*; Li, Xuning^*; Huang, Yanqiang; Liu, Bin^*

Source：Journal of the American Chemical Society, 2023, 145(37): 20683-20691.

DOI：10.1021/jacs.3c06738

• REDUCTION
• IDENTIFICATION
• CATALYSIS

Metastable state is the most active catalyst state that dictates the overall catalytic performance and rules of catalytic behaviors; however, identification and stabilization of the metastable state of catalyst are still highly challenging due to the continuous evolution of catalytic sites during the reaction process. In this work, operando Sn-119 M & ouml;ssbauer measurements and theoretical simulations were performed to track and identify the metastable state of single-atom Sn in copper oxide (Sn-1-CuO) for highly selective CO2 electroreduction to CO. A maximum CO Faradaic efficiency of around 98% at -0.8 V (vs. RHE) over Sn-1-CuO was achieved at an optimized Sn loading of 5.25 wt. %. Operando M & ouml;ssbauer spectroscopy clearly identified the dynamic evolution of atomically dispersed Sn4+ sites in the CuO matrix that enabled the in situ transformation of Sn4+-O-4-Cu2+ to a metastable state Sn4+-O-3-Cu+ under CO2RR conditions. In combination with quasi in situ X-ray photoelectron spectroscopy, operando Raman and attenuated total reflectance surface enhanced infrared absorption spectroscopies, the promoted desorption of *CO over the Sn4+-O-3 stabilized adjacent Cu+ site was evidenced. In addition, density functional theory calculations further verified that the in situ construction of Sn4+-O-3-Cu+ as the true catalytic site altered the reaction path via modifying the adsorption configuration of the *COOH intermediate, which effectively reduced the reaction free energy required for the hydrogenation of CO2 and the desorption of the *CO, thereby greatly facilitating the CO2-to-CO conversion. This work provides a fundamental insight into the role of single Sn atoms on in situ tuning the electronic structure of Cu-based catalysts, which may pave the way for the development of efficient catalysts for high-selectivity CO2 electroreduction.

• Institution
  清华大学; 中国科学院