AgPd nanoparticles for electrocatalytic CO₂ reduction: bimetallic composition-dependent ligand and ensemble effects

Abstract

Monodisperse AgPd nanoparticles (NPs) were synthesized and studied as an efficient catalyst for electrocatalytic CO₂ reduction by modulating bimetallic compositions. The mechanistic studies, based on density functional theory (DFT) calculations and environmental diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) analysis, revealed that the incorporation of Ag in AgPd NPs can effectively weaken CO adsorption on all possible Pd surface sites (the ligand effects), and more importantly, disrupt the strongest multi-centered CO-binding sites (the ensemble effects). With properly tuned CO adsorption, which is ordinarily too strong over pure Pd, Ag₁₅Pd₈₅ NPs were found to be the best composition for the efficient production of CO. They deliver a unity conversion of CO₂ to CO with a high mass activity of 15.2 mA mg_metal^-1 at -0.8 V vs. the reversible hydrogen electrode (RHE) and high stability with minimal change in the CO faradaic efficiency (FE_CO) after 12 hours of operation.