Copper Doping Boosts Electrocatalytic CO 2 Reduction of Atomically Precise Gold Nanoclusters.

Unraveling the atomistic synergistic effects of nanoalloys on the electrocatalytic CO 2 reduction reaction (eCO 2 RR), especially in the presence of copper, is of paramount importance. However, this endeavor encounters significant challenges due to the lack of the crystallographically determined atomic-level structure of appropriate monometallic and bimetallic analogues. Herein, we report a one-pot synthesis and structure characterization of a AuCu nanoalloy cluster catalyst, [Au 15 Cu 4 (DPPM) 6 Cl 4 (C≡CR) 1 ] 2+ (denoted as Au 15 Cu 4 ). Single-crystal X-ray diffraction analysis reveals that Au 15 Cu 4 comprises two interpenetrating incomplete, centered icosahedra (Au 9 Cu 2 and Au 8 Cu 3 ) and is protected by six DPPM, four halide, and one alkynyl ligand. The Au 15 Cu 4 cluster and its closest monometal structural analogue, [Au 18 (DPPM) 6 Br 4 ] 2+ (denoted as Au 18 ), as model systems, enable the elucidation of the atomistic synergistic effects of Au and Cu on eCO 2 RR. The results reveal that Au 15 Cu 4 is an excellent eCO 2 RR catalyst in a gas diffusion electrode-based membrane electrode assembly (MEA) cell, exhibiting a high CO Faradaic efficiency (FE CO ) of >90%, and this efficiency is substantially higher than that of the undoped Au 18 (FE CO : 60% at -3.75 V). Au 15 Cu 4 exhibits an industrial-level CO partial current density of up to -413 mA/cm 2 at -3.75 V with the gas CO 2 -fed MEA, which is 2-fold higher than that of Au 18 . The density functional theory (DFT) calculations demonstrate that the synergistic effects are induced by Cu doping, where the exposed pair of AuCu dual sites was suggested for launching the eCO 2 RR process. Besides, DFT simulations reveal that these special dual sites synergistically coordinate a moderate shift in the d-state, thus enhancing its overall catalytic performance.