Abstract
Process conditions during catalytic reactions induce significant changes in surface chemistry and structure of bi- (mono) metallic nanoparticles leading to their deactivation, and this can ultimately affect the reactions long-term performance. Here PtCu and Pt model nanoparticles are prepared by microwave synthesis and characterized by X-ray diffraction (XRD). Surface chemical and morphological changes of the nanoparticles during high-temperature oxidation and reduction treatments cycle are correlated by near in situ X-ray photoelectron spectroscopy (XPS) and ex situ transmission electron microscopy (TEM) - energy-dispersive X-ray spectroscopy (EDS) studies. At 300 °C the surface atomic composition of the PtCu nanoparticles switches reversibly upon the cycle and at the same time their morphology and composition are maintained. At 400 °C, the surface atomic composition does not fully restore and, while the shape is maintained, the size and composition are not. This occurs by a mechanism of Cu leaching out from the nanoparticles. These data delineate potential operating conditions for stable PtCu nanocatalysts.
Highlights
Nanocatalysts have emerged as a new class of materials, since they exhibit superior properties for a range of catalytic processes as compared to their bulk counterparts [1]
Nanocatalysts participating in heterogeneous catalytic processes usually encounter harsh reaction environments, such as gases and high temperatures which are responsible for their deactivation
PtCu bimetallic NPs with small particle size (≤9 nm) and narrow size distributions have been synthesized for catalytic applications mainly by chemical routes, such as the one-pot hydrothermal method [11], co-reduction of platinum and copper precursors [12], modified polyol process [8] and co-reduction of the precursors using a combination of surfactants and solvents [13]
Summary
Nanocatalysts have emerged as a new class of materials, since they exhibit superior properties for a range of catalytic processes as compared to their bulk counterparts [1]. PtCu bimetallic NPs with small particle size (≤9 nm) and narrow size distributions have been synthesized for catalytic applications mainly by chemical routes, such as the one-pot hydrothermal method [11], co-reduction of platinum and copper precursors [12], modified polyol process [8] and co-reduction of the precursors using a combination of surfactants and solvents [13]. The results were correlated with changes in morphology and composition of the NPs, under similar conditions, studied by TEM-EDS
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