Dangers of post oil peak scenario, political uncertainty, greenhouse emissions and consistently increasing oil prices have impacted several growing economies. Thereby there is need to move to alternative cleaner and abundant sources of energy. One of the alternatives is a hydrogen economy. Hydrogen fuelled proton exchange membrane (PEMFC) fuel cells have consistently demonstrated great promise as future source of energy due to their high conversion efficiency, lower temperature of operation and lack of greenhouse emissions. Till now Pt has been found to be the best electrocatalyst for the oxygen reduction reaction (ORR) due to higher electrocatalytic activity and stability. One of the major impediments in the commercialization of polymer electrolyte membrane fuel cell is the low activity and higher loading of Pt electrocatalyst used for oxygen reduction. The quest for more active, less expensive and highly stable ORR catalyst thrives the fuel cell research from Pt dispersed contemporary catalyst to Pt alloys. In recent years lot of emphasis has been put on Pt alloy catalysts because of even higher activity and lower cost as compared to Pt catalysts only.

In this work we demonstrate Pt-alloy catalysts supported on carbon as ORR catalysts in PEMFC. These catalysts are prepared to liquid based impregnation and thermal annealing route. We have done half cell measurements on these catalysts in a RDE and full characterization in single cell PEMFC. To obtain the active phase of our catalyst we do in-situ as well as ex-situ pretreatment. The in-situ method is the electrochemical de-alloying while the ex-situ is the chemical de-alloying. Our Pt25Cu75 have consistently shown enhanced activity [1,3,4], Pt20Cu20Co60 [2] has also shown promising results. We have further done durability analysis on these catalysts in real PEMFC's by potential cycling under different humidity and varied potential window conditions. Further to corroborate above we have also done stability analysis on a half cell set up in a high-throughput 16 channel combinatorial set up. EPMA imaging analysis of the cross-section of as prepared MEA's, de-alloyed MEA's and tested MEA's shows the migration of Pt and Cu over the crossection of the MEA.

To analyze the ORR kinetics before and after cycling : catalytic parameters like activation energy, transfer coefficient, reaction order and exchange current density are deduced by a simple Butler Volmer based thermodynamic model (5).

1. Ratndeep Srivastava, Prasanna Mani, Nathan Hahn and Peter Strasser, “Efficient Oxygen Reduction Fuel Cell Electrocatalysis on Voltammetrically De-alloyed Pt-Cu-Co Nanoparticles”, 47, 8988-8991 Angewandte Chemie Int. Ed (2007)

2. Prasanna Mani, Ratndeep Srivastava and Peter Strasser, “De-alloyed PtCu core shell nanoparticle for use in PEM fuel cell cathodes,” In press 10.1021/jp0776412, Journal of Physical Chemistry C.

3. Prasanna Mani, Ratndeep Srivastava, Chengfei Yu, and Peter Strasser “In situ inlayer dealloying of Pt-M intermetallics for high performance PEMFC electrode layers: MEA activity and durability studies” Polymer Electrolyte Membrane Fuel Cells 7, Electrochemical Society Transactions (2007).

4. Shirlaine Koh, Chengfei Yu, Prasanna Mani, Ratndeep Srivastava, Peter Strasser, “Activity of ordered and disordered Pt-Co alloy phases for the electro reduction of oxygen in catalysts with multiple coexisting phases” , 72 (1), Oct 2007,50-56

5. K.C Neyerlin, Wenbin Gu, Jacob Jorne and Hubert A Gasteiger, “Determination of Catalytic Unique Parameters for the Oxygen Reduction Reaction in a PEMFC”, Journal of Electrochemical Society, 153 (10), A 1995-A1963 (2006).