A controlled composition-based method—that is, the microwave-assisted ethylene glycol (MEG) method—was successfully developed to prepare bimetallic PtxRu100−x/C nanoparticles (NPs) with different alloy compositions. This study highlights the impact of the variation in alloy composition of PtxRu100−x/C NPs on their alloying extent (structure) and subsequently their catalytic activity towards the methanol oxidation reaction (MOR). The alloying extent of these PtxRu100−x/C NPs has a strong influence on their Pt d-band vacancy and Pt electroactive surface area (Pt ECSA); this relationship was systematically evaluated by using X-ray absorption (XAS), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), density functional theory (DFT) calculations, and electrochemical analyses. The MOR activity depends on two effects that act in cooperation, namely, the number of active Pt sites and their activity. Here the number of active Pt sites is associated with the Pt ECSA value, whereas the Pt-site activity is associated with the alloying extent and Pt d-band vacancy (electronic) effects. Among the PtxRu100−x/C NPs with various Pt:Ru atomic ratios (x=25, 50, and 75), the Pt75Ru25/C NPs were shown to be superior in MOR activity on account of their favorable alloying extent, Pt d-band vacancy, and Pt ECSA. This short study brings new insight into probing the synergistic effect on the surface reactivity of the PtxRu100−x/C NPs, and possibly other bimetallic Pt-based alloy NPs.
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