(485c) Platinum Monolayers On Ruthenium for the Oxygen Reduction Reaction (ORR)

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.