Enhanced Dissolution Rate of Pt from a Pt–Zn Compound Measured by Channel Flow Double Electrode

Abstract

As a part of a development of a hydrometallurgical recovery method for platinum, the anodic behavior of a Pt–Zn compound (75 atom % of Zn) in hydrochloric acid was examined. The dissolution rates of Pt and Zn from the compound were measured separately at controlled potentials by channel flow double electrode method. Zn dissolved preferentially from the compound at all tested potentials between 0.1 and 1.2 V vs standard hydrogen electrode, and its rate decayed with time due to the generation of a Pt-enriched phase on the compound surface. The dissolution of Pt from the compound was observed at potentials above 0.7 V, which is about the same as the onset potential for dissolution of pure Pt electrode. The dissolution of Pt from the compound accelerated with time, and its rate was much higher than that from pure Pt. Observation of the dissolved surface revealed that a Pt-enriched surface layer with many cracks and a low crystallinity had generated. The increase in the surface area and the low crystallinity caused by the preferential dissolution of Zn were believed to bring about the high rate dissolution of Pt from the compound.