Investigation on Reactivity and Selectivity of Electrocatalytic CO2 Reduction in Photochemically Synthesized Ag19 and Alloyed Ag19Cu2 and Ag12Cu7 Nanoclusters

Atomically precise nanoclusters are desirable for understanding the structure–property relationships in the electrocatalytic CO₂ reduction reaction (eCO₂RR), but suitable related models are lacking, especially those of low- or zerovalent noble metal nanoclusters and their alloyed analogues. We first developed a photochemical method toward silver nanocluster Ag₁₉(4-^tBuPhC≡C)₁₄(Dpppe)₃(SbF₆)₃ (Ag₁₉-2e) and then related copper-doped alloyed nanocluster Ag₁₂Cu₇(4-^tBuPhC≡C)₁₄(Dpppe)₃Cl₃(SbF₆)₂ (Ag₁₂Cu₇-0e). Herein, we present a larger alloyed nanocluster, Ag₁₉Cu₂(4-^tBuPhC≡C)₁₆(Dpppe)₄(SbF₆)₃ (Ag₁₉Cu₂-2e) and investigate the relationship between the structures and the eCO₂RR performance of those related nanoclusters. The UV–vis and mass spectra revealed that Ag₁₉Cu₂-2e forms via light-induced Ag₁₉-2e generation followed by Cu(II) attachment. eCO₂RR tests showed that Ag₁₉-2e is the least efficient, while its dicopper alloyed Ag₁₉Cu₂-2e favors formate, highlighting the important role of copper doping in regulating Ag cluster catalysis. This conclusion is further confirmed by the good catalytic performance of Ag₁₂Cu₇-0e, which demonstrated the best C₁ product selectivity for both CO and formate. Experimental and theoretical calculations indicate that its excellent catalytic performance is attributed to the removal of Cl ligands, exposing active Ag sites for launching the eCO₂RR process. This work not only demonstrates that copper-doped silver nanoclusters significantly enhance catalytic activity but also reveals that varying copper doping levels enable modulation of product selectivity in eCO₂RR.

This study establishes three structurally related nanocluster catalytic models and reveals that Cu-doping level significantly influences the eCO₂RR product selectivity of Ag nanoclusters.