Insight into the Behavior of Interstitial Electrons in CuZn Alloy-Functionalized Covalent Organic Framework Catalysts for Enhanced CO2 Electroreduction.

The development of application-oriented, highly active, and selective CO2 reduction reaction (CO2RR) electrocatalysts for high value-added products is expected to achieve carbon neutrality and solve the problem of energy shortage. Cu-based catalysts, as the most promising catalysts for high value-added product generation, were often limited by slow CO generation and weak CO adsorption in practical applications. Guided by theoretical screening, herein, an atomic-scale CuZn alloy cluster configuration was manipulated on covalent organic frameworks (COFs), and its CO2RR performance was further improved by the regulation of the electron-donor functional groups. Through systematic characterization and theoretical simulations, we for the first time demonstrate and quantify the interstitial electrons in CuZn alloy clusters under the regulation of electron-giving groups. Further in situ surface-enhanced Raman spectroscopy (SERS) and simulation results reveal that the behavior of interstitial electrons with low work function and high mobility occupy the high-energy orbital of the metal and easily transfer to *CO, therefore, the *CO is hydrogenated to *COH before coupling, and then the coupling energy barrier and path are optimized. Due to these attributes, the as-developed CuZn alloy-functionalized COF catalyst (CuZn-COF-OH) exhibits significantly improved activity and selectivity, with >200 mA cm-2 industrial-grade current density and ethylene Faraday efficiency of up to ∼79% at -1.0 V versus RHE. This study provides innovative avenues and insights for the design and development of application-oriented atomic-scale catalysts.