Tuning the local coordination environment of silver(I) coordination networks with counterions for enhanced electrocatalytic CO₂ reduction

Very recently, the local coordination environment of active sites has been found to strongly influence their performance in electrocatalytic CO₂ reduction by tuning the intrinsic kinetics of CO₂ activation and intermediate stabilization. It is imperative to elucidate the mechanism for such an influence towards the rational design of efficient catalysts; however, the complex interactions between the multiple factors involved in the system make it challenging to establish a clear structure-performance relationship. In this work, we chose ion-intercalated silver(I)-based coordination networks (AgCNs) with a well-defined structure as a model platform, which enables us to understand the regulation mechanism of counterions as the counterions are the only tuning factor involved in such a system. We prepared two isostructural AgCNs with different intercalation ions or counterions of BF₄⁻ and ClO₄⁻ (named as AgCNs-BF₄ and AgCNs-ClO₄) and found that the former has a more competitive CO₂ electroreduction performance than the latter. AgCNs-BF₄ achieves the highest Faradaic efficiency for CO₂ to CO of 87.1% at −1.0 V (vs. RHE) with a higher partial current density, while AgCNs-ClO₄ exhibits only 77.2% at the same applied potential. Spectroscopic characterizations and theoretical calculation reveal that the presence of \({\rm{B}}{{\rm{F}}_4}^ - \) is more favorable for stabilizing the COOH* intermediate by weakening hydrogen bonds, which accounts for the superior activity of AgCNs-BF₄.