Controllable Lattice Expansion of Monodisperse Face-Centered Cubic Pd–Ag Nanoparticles for C1 and C2 Alcohol Oxidation: The Role of Core–Sheath Lattice Mismatch

Direct alcohol fuel cells are considered as promising and sustainable power sources to address global climate change as well as energy and environmental problems. However, designing efficient catalysts for the oxidation of alcohol molecules remains challenging. This study reports the synthesis of monodisperse PdAg nanoparticles (NPs) with face-centered cubic structures with controllable alloying degrees and particle diameters for improving oxidation of ethanol and methanol. Interestingly, the lattice enlargement of the silver-rich core leads to the lattice expansion of the palladium-rich sheath. The lattice expansion of the interface of the NPs leads to the upshifting of the d-band center of Pd toward the Fermi level followed by the stronger binding of a small molecule. The PdAg NPs exhibit “volcano-type” behavior, where the maximum electrocatalytic activity is governed by the balance of the adsorption energies of OH* (reactive intermediates) and CO* (blocking species). The Pd5Ag1 NPs exhibit electrocatalytic activities of 2402 and 1541 mA mgPd –1 for ethanol oxidation reaction and methanol oxidation reaction in alkaline solution, respectively, about four and three times those of the commercial Pd/C catalysts. The enhanced mass activities of the catalysts can be further analyzed by density functional theory calculations, indicating that the lattice expansion after including silver would lead to the upshifting of the d-band center followed by the strengthened OH* binding. This work discloses a promising way to build novel nanocatalysts with controllable alloying degrees as efficient fuel cell catalysts.