The Golden Atomic Ratio in Binary Nanoalloys for Enhanced CO2 Electroreduction: Dual-Metal Synergy of AgPd

An intriguing phenomenon has been observed in various binary nanoalloys for the electrochemical CO₂ reduction reaction (CO₂RR), where an atomic ratio close to 1:3 mostly yields the optimal activity, but its origin remains poorly understood. Here, we synthesized a series of size-uniform Ag_xPd_1–x nanoclusters (NCs) with precisely controlled atomic ratios as a model system to verify its universality and intrinsic derivation since Ag offers a high intrinsic CO selectivity but requires a large overpotential (η) due to weak intermediate binding, while Pd forms CO at a small η but suffers from CO poisoning due to an overly strong CO adsorption. Indeed, Ag_0.25Pd_0.75 NCs with an atomic ratio of 1:3 possessed optimal CO₂RR activity, delivering a nearly 100% CO Faraday efficiency and a maximum energy efficiency of 71.8%. Computational calculations demonstrated that the Ag/Pd atomic ratio of 1:3 induced an optimal electronic structure characterized by a d-band center positioned favorably relative to the Fermi level. This configuration synergistically lowered the energy barrier for *COOH formation and promoted *CO desorption kinetics, as corroborated by in situ spectroscopic analysis, where Ag_0.25Pd_0.75 NCs exhibited attenuated *CO adsorption signals compared with other stoichiometries, indicating enhanced CO desorption capability. This study provides in-depth mechanistic insights into the “golden ratio” in nanoalloys for the CO₂RR and reveals a universal paradigm of designing advanced nanoalloys.