Promoting CO Electroreduction to Hydrocarbon Products via Sulfur-Enhanced Proton Feeding in Atomically Precise Thiolate-Protected Cu Clusters.

Thiolate-protected Cu clusters with well-defined structures and stable low-coordinated Cu species exhibit remarkable potential for the CORR and are ideal model catalysts for establishing structure-electrocatalytic property relationships at the atomic level. However, extant Cu clusters employed in the CORR predominantly yield 2e products. Herein, two model Cu(MMI) and Cu(MMI)(BuS) clusters (MMI=2-mercapto-1-methylimidazole) are prepared to investigate the synergistic effect of Cu and adjacent S sites on the CORR. Cu(MMI) can reduce CO to deep-reduced products with a 91.0 % Faradaic efficiency (including 53.7 % for CH) while maintaining remarkable stability. Conversely, Cu(MMI)(BuS) shows a remarkable preference for C products, achieving a maximum FE of 58.5 % with a C current density of 152.1 mA⋅cm. In situ XAS and ex situ XPS spectra reveal the preservation of Cu species in Cu clusters during CORR, extensively enhancing the adsorption capacity of *CO intermediate. Moreover, kinetic analysis and theoretical calculations confirm that S sites facilitate HO dissociation into *H species, which directly participate in the protonation process on adjacent Cu sites for the protonation of *CO to *CHO. This study highlights the important role of Cu-S dual sites in Cu clusters and provides mechanistic insights into the CORR pathway at the atomic level.