272066 Platinum Monolayers On Ruthenium for the Oxygen Reduction Reaction (ORR)

Wednesday, October 31, 2012: 1:10 PM
317 (Convention Center )
Ariel Jackson, Arnold J. Forman and Thomas F. Jaramillo, Chemical Engineering, Stanford University, Stanford, CA

Platinum is known to be among the best catalysts for oxygen reduction (ORR), though in recent years researchers have discovered that it binds oxygen too strongly for optimum activity. Improvements have come by modifying the Pt-O adsorption strength via alloying platinum with other transition metals such as Pt3Y and Pt3Ni.

To be of practical use the catalysts are prepared as nanoparticles, maximizing surface area and achieving many reaction sites. However,  the percentage of under-coordinated surface sites becomes significant, reducing the catalytic activity due to a stronger Pt-O bond. Additionally, the catalyst will tend to lose surface area (reaction sites) over time due to sintering or Ostwald ripening.

It has been shown that single monolayers of platinum supported on various substrates can exhibit properties drastically different from platinum in its bulk form. This opens up the opportunity for better ORR activity, greater tolerance to surface variations and resistance to active site loss. The purpose of this study is to investigate the effect of several monolayers of platinum on a ruthenium support for ORR. Whereas other studies have only looked at single monolayers of platinum, we are examining the effects of several monolayers, and in nanoparticulate form. We are bounded by a single monolayer of platinum that binds oxygen too weakly and bulk platinum that binds it too strongly.

We have synthesized several structures with different platinum : ruthenium ratios and different morphologies. They have been characterized using spectroscopic, microscopic, and electrochemical techniques to verify composition and structure and tested for their catalytic activity. We will discuss the relationship between the catalysts' structure/composition and its activity.

 


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