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 CO 2 RR and are ideal model catalysts for establishing structure‐electrocatalytic property relationships at the atomic level. However, extant Cu clusters employed in the CO 2 RR predominantly yield 2e − products. Herein, two model Cu 4 (MMI) 4 and Cu 8 (MMI) 4 ( t BuS) 4 clusters (MMI=2‐mercapto‐1‐methylimidazole) are prepared to investigate the synergistic effect of Cu + and adjacent S sites on the CO 2 RR. Cu 4 (MMI) 4 can reduce CO 2 to deep‐reduced products with a 91.0 % Faradaic efficiency (including 53.7 % for CH 4 ) while maintaining remarkable stability. Conversely, Cu 8 (MMI) 4 ( t BuS) 4 shows a remarkable preference for C 2+ products, achieving a maximum FE of 58.5 % with a C 2+ 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 CO 2 RR, extensively enhancing the adsorption capacity of *CO intermediate. Moreover, kinetic analysis and theoretical calculations confirm that S sites facilitate H 2 O 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 CO 2 RR pathway at the atomic level.