Improving the catalytic activity of Au/Pd core–shell nanoparticles with a tailored Pd structure for formic acid oxidation reaction

Abstract

Unique morphology-tunable Au/Pd core–shell nanoparticles were synthesized by galvanic replacement of preformed Cu on hollow Au cores using different PdCl₂ concentrations. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical analysis. The results showed that the structure of the nanocrystalline Pd on the hollow Au core surface was strongly dependent on the PdCl₂ concentration. It was found that Pd²⁺ ions transport and react in the porous Cu layer, helping to create a continuous but porous structure which enlarges the Pd surface area and increases the electrochemical activity. In addition, the Au/Pd core–shell nanoparticles displayed superior electrochemical performance and stability in formic acid oxidation than commercial Pd black, especially for the ones synthesized using 2.5 mM PdCl₂. The enhanced electrocatalytic performance may be attributed to the optimum electronic coupling effect caused by the interaction between the specific Pd structure and the hollow Au core.