Hydrogen Adsorption on Binary Platinum Metal Alloys

Area losses of carbon-supported platinum were determined [87] by electrochemical measurements and by X-ray diffraction. These losses cannot be due to adsorption of impurities since they were detected in roughly the same measure by both techniques. Recrystallization of the supported platinum was suggested [87] as the cause of the reduction of the surface area with time. 

Hydrogen Adsorption on Binary Platinum Metal Alloys 

Examples which illustrate the essential features of binary platinum metal alloys are discussed for three types of alloys in this section  

Platinum-gold alloys represent an example of group b. The electrochemical properties of these alloys have been studied [93—98] extensively. They can exist [99] as homogeneous alloys or as a mixture of a platinum-rich phase and a gold-rich phase a2. The cold-drawn wires used in these investigations [94—98] were of the latter type. It was demonstrated [96—98] that the electrocatalytic properties of the platinum-rich phase are similar to those of platinum. Hydrogen adsorption [96] and methanol oxidation [97] occur only on this phase. The 

The surface composition may be characterized by three parameters a, b, and c. Parameters a and b were determined [94] by approximating the I — U curve of the alloy during the cathodic sweep by a linear com- 

---