Enhancing the CO₂-to-CO Conversion from 2D Silver Nanoprisms <i>via</i> Superstructure Assembly

Abstract

The electrochemical reduction of CO₂ in a highly selective and efficient manner is a crucial step toward its reuse for the production of chemicals and fuels. Nanostructured Ag catalysts have been found to be effective candidates for the conversion of CO₂-to-CO. However, the ambiguous determination of the intrinsic CO₂ activity and the maximization of the density of exposed active sites have greatly limited the use of Ag toward the realization of practical electrocatalytic devices. Here, we report a superstructure design strategy prepared by the self-assembly of two-dimensional Ag nanoprisms for maximizing the exposure of active edge ribs. The vertically stacked Ag nanoprisms allow the exposure of >95% of the edge sites, resulting in an enhanced selectivity and activity toward the production of CO from CO₂ with an overpotential of 152 mV. The Ag superstructures also demonstrate a selectivity of over 90% for 100 h together with a current retention of ≈94% at -600 mV versus the reversible hydrogen electrode and a partial energy efficiency for CO production of 70.5%. Our electrochemical measurements on individual Ag nanoprisms with various edge-to-basal plane ratios and the Ag superstructures led to the identification of the edge ribs as the active sites thanks to the ≈400 mV decrease in the onset potential compared to that of the Ag (111) basal planes and a turnover frequency of 9.2 × 10^-3 ± 1.9 × 10^-3 s^-1 at 0 V overpotential.