Promoting CO 2 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 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.
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