Regulating Ag-Cu synergy effect via Cu doping numbers to boost CO2 electroreduction on Ag14 nanoclusters.

Abstract

Using atomically precise Ag14(SPhF5)12(P(Ph-m-OMe)3)4 nanoclusters as a well-defined platform, we systematically tune the number of Cu dopants to unravel Ag-Cu synergistic effects in electrocatalytic CO2 reduction. A catalyst containing, on average, two Cu atoms per cluster (Ag11.192Cu2.808) delivers a CH4 faradaic efficiency of 17.1% at -1.6 V vs. RHE-dramatically higher than both the over-doped analogue Ag10.463Cu3.537 (11.16%) and the undoped Ag14 parent (∼0%). Density-functional-theory calculations reveal that introducing one to two Cu atoms optimally raises the Cu valence state, strengthening *CO adsorption and thereby accelerating the *CO → *CHO step that governs CH4 formation. These results demonstrate that 'less is more': beyond a critical Cu loading, the cooperative electronic advantages are diminished and activity declines.