Ordered intermetallic Pt–Cu nanoparticles for the catalytic CO oxidation reaction

Abstract

Platinum-based intermetallic nanoparticles (NPs), using the abundantly available element copper, with an average particle size of 4–5 nm on a γ-Al₂O₃ support were prepared successfully to reduce the consumption of Pt for the removal of CO through the catalytic oxidation reaction from flue gases. Intermetallic Pt–Cu NPs (Pt₃Cu, PtCu, and PtCu₃) with a Pt loading weight of 5 wt% were prepared on the γ-Al₂O₃ support by a simple wet impregnation method followed by calcination at various temperatures (500–800 °C) in a H₂ environment and they were characterized by powder X-ray diffraction analysis (pXRD), high resolution transmission electron microscopy (HR-TEM), selective area electron diffraction (SAED) method, etc. Despite the higher synthesis temperature of these intermetallic NPs, they were not agglomerated and formed a highly ordered intermetallic structure. The surface of the intermetallic Pt–Cu NPs with cubic-type structure (Pt₃Cu and PtCu₃) is enclosed of {200} facets, regardless of the significant difference in their compositions. Whereas the surface of rhombohedral-type intermetallic PtCu NPs is enclosed of {104} facets. Although the Pt-loading weight of these intermetallic NPs was the same, Pt₃Cu NPs showed a stable and enhanced catalytic activity compared to the other intermetallic PtCu and PtCu₃ NPs. Pt₃Cu NPs showed an onset and maximum conversion temperature of 50 and 125 °C, respectively. The intermetallic phase between Pt and Cu of Pt₃Cu NPs did not decompose; however, the intermetallic phase did decompose for PtCu and PtCu₃ NPs after catalytic CO oxidation. Unlike PtCu and PtCu₃ NPs, the Pt₃Cu NPs were not agglomerated and they were finely dispersed even after catalytic CO oxidation.