Formic acid electro-oxidation at PtAu alloyed nanoparticles synthesized by pulsed laser ablation in liquids

A series of mono dispersed Pt sub(x)Au sub(100-x) alloy nanoparticles (NPs), with x varying from 0 to 100, were prepared by pulsed laser ablation in liquids, using a series of targets that were made by mixing pure Pt and pure Au powders. The structures of Pt sub(x)Au sub(100-x) alloy NPs were assessed by transmission electron microscopy and X-ray diffraction. A face-centered solid solution is obtained over the whole composition range, and the particle size increases from 2.5 to 5.3 nm as x is increased from 0 to 100. The electrocatalytic performances of the Pt sub(x)Au sub(100-x) alloy NPs towards the formic acid oxidation were investigated by cyclic voltammetry and chronoamperometry. On as-prepared Pt sub(x)Au sub(100-x) alloy NPs, oxidation of formic acid occurs through dehydrogenation, while dehydration is the privileged mechanism on as-prepared mixtures of Pt and Au NPs. However, after a series of CV in 0.5 M H sub(2)SO sub(4), both types of catalysts are able to oxidize formic acid according to the dehydrogenation pathway. After 600 s of electrolysis, the mass activities of Pt sub(x)Au sub(100-x) alloy NPs is a factor of two larger than that of mixtures of pure Pt and pure Au NPs with the same surface composition, although both types of catalysts display similar activity with respect to the total electrochemically active surface area.