Electrochemical study of Pt-Pd, Pt-Ru, Pt-Rh and Pt-Sn/C in acid media for hydrogen adsorption-desorption reaction

摘要

Four platinum-based binary catalysts (Pt-Ru, Pt-Rh, Pt-Sn, Pt-Pd/C) used for hydrogen adsorption-desorption reaction were investigated by cyclic voltammetry in 0.5 M H_2SO_4 at room temperature. For all the metallic alloys the difference between the total anodic and cathodic charges (1 and 50 cycles) is related to the amount of second metal dissolution. Changes in surface composition during continuous potential cycling are also due to the preferential dissolution of a second metal component. Comparison of the changes in electrosorption properties with the amount of metal dissolved leads to the conclusion that the surface involved in chemisorption reactions consisted of no more than a few atomic layers. The good electrocatalytic behavior for the Pt-Ru/C system is only attributed to the synergic effect of the second metal, which can cause a strong hydrogen adsorption (Q_H~c). The particle sizes were also determinate by conventional physical dispersion method. This method enabled us to observe the shape and size of the particles by transmission electron microscopy (TEM).