Surface Pourbaix diagram of AgPd nanoalloys and its application in formate oxidation reaction

Surface Pourbaix diagrams for 38-atom AgPd nanoalloys with different Ag/Pd ratio are constructed based on the density functional theory calculations, with an increasing electrode potential, the adsorbed hydroxides increase on the surface of nanoparticle and convert to oxygen atoms partially sunk into subsurface. AgPd nanoalloys with a core-shell structure have an improved oxidation resistance compared with pure nanoparticle and Ag atoms on nanoalloys surface could suppress Pd dissolution and oxidation. It is newfound that a substitutional introduction of Pd atoms into the core of AgPd nanoalloys could suppress the oxide formations and increase the oxidation resistance, and a substitutional introduction of Ag atoms onto the surface of Pd₃₈ nanoparticle could suppress Pd dissolution. Among all the calculated AgPd nanoalloys, Ag₁₈Pd₂₀ has an excellent durability against electrochemical dissolution and oxidation. Experimentally, the activity of as-synthesized Ag₄₈Pd₅₂ nanoalloy notably increases with increasing the upper limit potential from 0.3 to 0.5 V under cyclic voltammetry test of formate oxidation reaction (FOR). Increased oxidation state of Ag atoms on electrocatalyst surface, which is confirmed by Mulliken charge analysis, has been identified as the key to prompt the FOR activity enhancement.