C₃ production from CO₂ reduction by concerted *CO trimerization on a single-atom alloy catalyst

Abstract

The direct electroreduction of carbon dioxide (CO₂) and carbon monoxide (CO) to C₃ products is challenging. The main reason is the competitive C₂ production resulting from a traditional sequential C–C coupling mechanism. As a result, most catalysts could not facilitate C₃ products since the carbon chain growth from C₂ to C₃ competes with C₂ desorption. In this work, we carried out Density Functional Theory (DFT) calculations with implicit solvation effects on densely arrayed Cu nanopyramids (Cu-DANs). We demonstrate that the co-adsorption energy of three *CO intermediates (ΔG(3*CO); from the CO₂ or CO reactant) is a descriptor for C₃ activity. An activity volcano plot was constructed based on this discovery, which can be used to predict the optimal range for ΔG(3*CO) adsorption strength. We demonstrate that by applying the single-atom alloy catalyst strategy, i.e. embedding Ag single metal onto Cu-DANs, we could successfully tune the ΔG(3*CO) strength toward the optimal range. In addition, the adsorbed *CO could form a long carbon chain on such a structure via a one-step concerted trimerization mechanism to form the key C₃ reaction intermediate, avoiding the competitive C₂ desorption pathway. Furthermore, Ag-doped Cu-DANs could effectively retain oxygen atoms in the hydroxyl group, which enabled a pathway towards direct electrosynthesis of a new C₃ product (C₃H₈O₂; 1,2-PDO) beyond the only available n-propanol. Our newly discovered concerted trimerization mechanism in combination with single-atom alloy catalysts paves the way for materials design toward more long-chain oxygenate generation.