EQCM Study on Anodic Dissolution of Platinum in Acid Solutions Containing Chloride Ions

摘要

In this study, the influence of chloride ion on the anodic dissolution of platinum has been studied by using Electrochemical Quartz Crystal Microbalance (EQCM) to clarify the deterioration mechanism of platinum catalyst in the PEFC. Platinum was electroplated on a gold electrode of EQCM in 2% H_2PtCl_6 solution and used as the working electrode. A mass gain of the platinum electrode was observed during anodic polarization in 0.5M H_2SO_4 solution ([Cl~-] free solution) due probably to the formation of Pt oxide. On the other hand, a mass loss due to the dissolution of Pt as chloride complex ions was observed in more positive potentials than 0.8SV vs. SHE in 1M HCl solution. As the chloride concentration increased, platinum showed a higher dissolution rate. From the comparison of the mass change and amount of charge, it was found that the chloride complex is mainly PtCl_4~(2-). The EQCM results revealed that the dissolution of Pt is accelerated in higher potentials than 0.85 V in the presence of chloride ions. The results agreed well with those of ICP analysis of solutions after the anodic polarizations.