Controlled Pt adlayers were deposited on commercial Ru nanoparticles (NPs) using an industrially scalable one-pot ethylene glycol (EG) reduction based method and were characterized by X-ray diffraction (XRD), electrochemical (EC) CO stripping voltammetry, inductively-coupled plasma 10 optical emission spectrometry (ICP-OES), X-ray photonemission spectroscopy (XPS), and transmission electron microscope (TEM). Compared with the previously used spontaneous deposition , the wet chemistry based EG method is less technical demanding, i.e., no need to handle high-temperature hydrogen reduction, offers a better control of the Pt packing density (PD), enables the formation of stable segregated Pt surface adlayers for optimal tuning and use of Pt, and 15 prevents effectively NPs sintering. Two batches of a total of 11 (8 vs 3) samples with different values of Pt PD ranging from 5% to 93% were prepared with a time interval of more than 18 months between the sytheses of the two batches of samples and an excellent reproducibility of results was observed. All samples were investigated in terms of methanol (MeOH) electrooxidation (EO) by cyclic voltammetry (CV) and chronoamperometry (CA). Although the peak 20 current of CV increased as the Pt content increased, the long-term steady-state MeOH electrooxidation current density of the Pt-decorated Ru NPs measured by CA showed a volcano curve as a function of the Pt PD, with the maximum appearing at the PD of 31%. The optimal peak activity was ~150% higher than that of the industrial benchmark PtRu (1:1) alloy NPs and could deliver the same performance at a half electrode material cost. Fundamentally, such a volcano curve in the 25 reaction current is the result of the two competing processes of the EO of MeOH: the triple dehydrogenation of MeOH that prefers more Pt ensemble sites and the elimination of poisonous CO that is enhanced by more adjacent Ru/Pt sites via the so-called bifunctional mechanism and also by possible electronic effect at the low Pt coverages.
Citation: Physical Chemistry Chemical Physics
Pub Type: Journals
Electrochemistry, catalysis, nano particles