Electrochemical behavior of Pd–Pt–Au alloys

Pd–Pt–Au alloys were prepared as limited volume electrodes by metal codeposition at constant potential from chloride solutions. Alloy surface state was examined by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The alloys were characterized electrochemically in acidic solution (0.5 M H2SO4) by cyclic voltammetry (CV). Potential regions of hydrogen electrosorption and surface oxidation are clearly distinguishable. The influence of electrode potential and alloy composition on the amount of absorbed hydrogen was investigated. Hydrogen absorption capacity of Pd–Pt–Au alloys increases with decreasing potential and the α–β phase transition is shifted positively with increasing Au content and negatively with increasing Pt content in the bulk. At relatively high potentials the amount of absorbed hydrogen exhibits a maximum for ca. 15–25 at.% Au in the bulk, while for low potentials a monotonic decrease in hydrogen absorption capacity with increasing bulk concentration of both alloying metals (Pt, Au) is observed.