Promoting CO₂ Electroreduction to Hydrocarbon Products via Sulfur‐Enhanced Proton Feeding in Atomically Precise Thiolate‐Protected Cu Clusters

Abstract

Thiolate‐protected Cu clusters with well‐defined structures and stable low‐coordinated Cu+ species exhibit remarkable potential for the CO2RR and are ideal model catalysts for establishing structure–electrocatalytic property relationships at the atomic level. However, extant Cu clusters employed in the CO2RR predominantly yield 2e− products. Herein, two model Cu4(MMI)4 and Cu8(MMI)4(tBuS)4 clusters (MMI = 2‐mercapto‐1‐methylimidazole) are prepared to investigate the synergistic effect of Cu+ and adjacent S sites on the CO2RR. Cu4(MMI)4 can reduce CO2 to deep‐reduced products with a 91.0% Faradaic efficiency (including 53.7% for CH4) while maintaining remarkable stability. Conversely, Cu8(MMI)4(tBuS)4 shows a remarkable preference for C2+ products, achieving a maximum FE of 58.5% with a C2+ current density of 152.1 mA∙cm−2. In situ XAS and ex situ XPS spectra reveal the preservation of Cu+ species in Cu clusters during CO2RR, extensively enhancing the adsorption capacity of *CO intermediates. Moreover, kinetic analysis and theoretical calculations confirm that S sites facilitate H2O 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 CO2RR pathway at the atomic level.