(285a) Development of Multi-Metallic Pt Alloy Electrocatalysts for the Oxygen Reduction Reaction in PEM Fuel Cells
Platinum exhibits superior oxygen reduction reaction (ORR) activity compared with other elements, making it an attractive cathode material for hydrogen fuel cell applications. The main problems with pure platinum electro-catalysts are large activation losses, limited stability, and high material cost. These deficiencies have greatly inhibited the development of efficient, reliable, and inexpensive proton exchange membrane fuel cells (PEM FCs). Previous experimental and computational studies have shown that it is possible to improve the performance of platinum cathodes by selectively tuning the chemical reactivity of catalytic sites through geometric and electronic effects induced by alloying in order to destabilize surface OH.1,2 This has led to the development of a number of Pt-based alloy electrocatalysts for this reaction.3
Our group has previously developed a first principles model that can predict the ORR activity for various Pt alloys.4 I will discuss how we used this model in an attempt to develop multi-metallic alloy electrocatalysts with superior performance compared to pure platinum. I will particularly focus on the design, synthesis, and testing of so-called second generation Pt alloys which contain an alloy core, Pt shell exposed to the reactants, and a protective Au buffer between the alloy core and the Pt shell. Extensive in situ and ex situ characterization verify the atomic and electronic structure of these core-shell Pt electrocatalysts. The oxygen reduction activity is determined through electrochemical testing of supported catalysts on a rotating disc electrode (RDE) in a three-electrode cell. All electrochemical measurements were performed at room temperature in a 0.1M HClO4 electrolyte.
1A. Holewinski, H. Xin, E. Nikolla, S. Linic, Current Opinions in Chemical Engineering, 2, 312, 2013
2A. Holewinski, S. Linic, J. Electrochem. Soc., 159, H864, 2012.
3I. Stephens, A. Borndarenko, U. Grønbjerg, J. Rossmeisl, and I. Chorkendorff, Ener. & Environ. Science 5 (2012) 6477.
4H. Xin, A. Holewinski, S. Linic, ACS Catalysis, 2, 12, 2012.