Pt-Au catalysts Keryou, P.A. Sermon

Solids and Surfaces Research Group, Department of Chemistry, Brunei University, Uxbridge, Middlesex UBS 3PH, UK 

Citrate-derived monometallic Pt and bimetallic Pt tAujo. colloidal particles have been prepared and adsorbed onto graphitic supports their adsorptive and catalytic properties are considered as is the wider applicability of this preparative route to heterogeneous catalysts. It appears that P Au,(x,.j dispersed bimetallic particles have properties which are very close to those of bulk materials and therefore that colloidal preparative routes to mono- and bi-metallic catalysts are very promising. However, the cleanliness of surfaces needs to be considered as does the extent of surface emiclunent caused by the method of preparation. 

Two basic approaches have been used in the preparation of metallic colloidal dispersions disintegration of the macroscopic metallic elements or synthesis of particles from metal salts using appropriate reducing agents, ultrasonics, pulse and laser radiolysis [ ]  

The general characteristics of metal colloidal dispersions are weU understood even though the mechanisms by which such metallic particles are formed in the colloidal state aic not This is easily understood if one recognises the complexity of the processes [1] involved in nucleation, growth and coagulation. In order to understand fully and control the preparation, these three steps of course have to be studied individually. Water purity, trace impurities, concentration, cleanliness of the reaction vessel and other factors all have a significant effect on the size and morphology of the particles [1,2] and therefore need to be controlled. 

Over the years separate stable colloids of Pt and Au have been prepared [3,4] with trisodium citrate  

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