The mass commercialization of low temperature fuel cells is significantly inhibited by high materials costs and poor service life which can largely be attributed to platinum (Pt) loading requirements, degradation, and durability issues at the cathode. To understand electrocatalyst degradation/durability issues, platinum and platinum alloy thin films as well as platinum nanoparticles were studied using transmission electron microscopy, chemical analysis, and in-situ electrochemical scanning probe microscopy [1] to elucidate particle coarsening mechanisms that result in a lower electrochemical surface area (ECSA). Results of these studies indicate that the stability of platinum films are directly related the voltage at which the fuel cell is operated. Additionally, the stability of Pt nanoparticles was shown to be directly related to particle size as a function of potential. Studies of platinum alloy thin films suggest that increased stability of the film surface can be achieved, the degree of which is strongly dependent on the alloy metal.The dependence of Pt and Pt alloy stability on potential generally indicates that separate degradation/coarsening mechanisms are operational at different potentials. For higher potentials (~800 and above), dissolution-redeposition of Pt from the surface of nanoparticles has been established. For potentials from ~400 to 800 V, one must also consider surface diffusion transport as a potential coarsening mechanism. Finally, these results will be discussed in general as pertaining to nanoscale materials in electrochemical systems.[1] Q. Xu, T. He, and D. Wipf, Langmuir 2007  , 23, 9098-9103

Stability of platinum and platinum alloys in proton exchange membrane fuel cells

246th National Meeting (2013)

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