STRUCTURE AND REACTIVITY OF PLATINUM-COPPER ALLOY PARTICLES SUPPORTEDON ZSM-5

Electronic and structural properties of highly dispersed Pt-Cu alloys supported on zeolite HZSM-5 with narrow particle size distribution (1- 2 nm) were studied by transmission electron microscopy, X-ray photoele ctron spectroscopy, and Fourier transform infrared spectroscopy of che misorbed carbon monoxide. FTIR of adsorbed CO proved to be the most se nsitive tool for the detection of alloy formation. Dilution of the pla tinum surface with copper can be recognized by the absence of dipole-d ipole interaction between the chemisorbed CO molecules (geometric effe ct). A strong red shift of the vibration frequency of linearly bonded CO in conjunction with an increase of the relative intensity of bridge -bonded CO is discussed in terms of an electronic effect. All spectros copic methods demonstrate the ready reoxidation and redispersion of th e copper component of the particles and the reversible formation of th e alloy again by repeated reduction.