Effect of composition of Pd_{10 − x}Cu_x (x = 2, 3, 4, and 5) alloy nanoparticles on their electrocatalysis for methanol oxidation

It is well accepted that the structure, composition, and properties of solid materials are closely related with one another. In this regard, studying the relationship between the composition/structure and electrocatalytic properties can provide a great deal of insights to the design of new catalyst with enhanced electrochemical properties. In this work, Pd_{10 − x}Cu_x nanoparticle (NP) catalysts with different Pd/Cu ratios (x = 2, 3, 4, and 5) were prepared and compared for their electrocatalytic properties for methanol oxidation reaction (MOR). Sonochemical reactions in ethylene glycol of metal precursors produced these NPs with most of the features other than the composition the same with one another. Based on the characterization data by XRD, TEM and other methods, x = 2 sample has the face-centered cubic (FCC) structure, x = 5 sample the body-centered cubic structure, and x = 3 and 4 samples mixtures of the two structures. The catalytic properties data show a volcano-type behavior with the change of composition, peaking at x = 3. The observed trends of electrocatalysis can be explained in terms of the composition and structure. The Pd₇Cu₃ catalyst shows higher activity than any of related Pd-Cu NP catalysts in the literature.