Effect of stress on dissolution/precipitation of platinum: Implications concerning core–shell catalysts and cathode degradation in proton exchange membrane fuel cells

• Published in: Journal of power sources 2011-11, Vol.196 (22), p.9204-9212
• Main Authors: Parthasarathy, Preethy, Virkar, Anil V.
• Format: Article
• Language: English
• Subjects: Applied sciences; Catalysis; Catalyst; Catalysts; Direct energy conversion and energy accumulation; Dissolution; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Foils (structural shapes); Fuel cells; Nanostructure; Platinum; Proton exchange membrane fuel cells; Shells; Stress; Tensile stress; Wire
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2011.07.027

► We investigate the effect of stress on dissolution/precipitation of platinum. ► We demonstrate that tensile stress suppresses dissolution of platinum. ► Tensile stress in Pt shell enhances core-shell catalyst stability. ► Ag@Pt and Au@Pt should be stable, and Cu@Pt and Ni@Pt should be unstable. Effect of applied stress on dissolution/precipitation of platinum was investigated. Two platinum wires/foils were partially immersed in a PtCl 4 solution in DMSO. A tensile load was applied to one wire/foil and the other one was left load free. The wire/foil subjected to a tensile load developed a positive potential (became cathodic) with respect to the unstressed wire/foil. This observation suggests that under a tensile stress, the chemical potential of Pt decreases. This result suggests design strategies for core–shell catalysts used in proton exchange membrane fuel cells (PEMFCs). Nanosize catalyst particles are under compression due to the Gibbs–Thompson effect. Core–shell catalysts have additional stresses in the shell depending upon lattice parameters of the core and the shell. The present results suggest that stable core–shell catalysts for PEMFC with Pt shell should be designed such that the shell is under a tensile stress (or reduced compression compared to monolithic catalyst particles). The present results also suggest that from the standpoint of stability, the lattice parameter of the core should be larger than that of the shell.