(487m) Survey of Commercial Carbon Supported Platinum Catalysts: Durability Studies for Automotive Applications

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are an exciting new technology that offers the potential for being a part of the solution to the energy crisis as well as providing an environmentally benign alternative to the combustion engine particularly in automotive applications. Today's state of the art PEMFC's fall short of DOE's standards for mass commercialization. The key shortcomings of this technology are cost and durability.1 Limited cathode durability (carbon supported platinum nanoparticles), during start-stop cycling, is a significant impediment. This project will explore the issues surrounding poor durability for various commercially available catalysts using an accelerated program that mimics start-stop potential cycling.

Currently, there are many studies that independently investigate the impact of catalyst size, distribution, or carbon support structure with respect to durability. Unfortunately, these studies are not comparable, since they use differing accelerated durability test protocols which have been shown to have varying effects on durability. This study seeks to cohesively link the commercial catalyst activity to durability.

A thin film rotating disk electrode (RDE) was used to monitor electrochemical surface area and oxygen reduction reaction activity for the various catalyst types investigated, following the procedure described by Gasteiger et. Al.2 The following accelerated potential protocol was used in this study: ? 5000 cycles, stepping for five second holds (1.2 V ? 0.65 V vs. RHE) at room temperature. The data collected for samples of average particle sizes ranging from, 4.8 nm and 2.3 nm, reported initial results suggesting enhanced stability for the larger particle size. These results' trends are consistent with the Gibbs-Thompson effect, predicting increased stability at particle sizes of 5 nm and above.

This study will be a continued survey of the commercially available carbon supported catalysts, with the findings being some preliminary results. Future work will continue to probe the effects of particle size and carbon support, as well as extending to other possible degradation accelerants, such as temperature, crystallographic orientation, electrolyte and others. The study will also investigate the effects of using different accelerated testing protocols. This work will strive to improve the understanding of design criteria for more active/durable catalysts.

Acknowledgements

Start-up Funding Provided by the Center for Manufacturing Research

References

1. de Bruijn, F. A; Dam, V. A. T; Janssen, G. J. M. Fuel Cells. 2008. No. 1, 3 ? 22.

2. Gasteiger, H. A; Kocha, S. S; Sompalli, B; Wagner, F. T. Applied Catalysis B: Environmental. 2005. 56, 9 ? 35.