Effect of water content on Oxygen Reduction Reaction (ORR) kinetics on supported Pt catalyst: A rotating disk electrode study

Abstract

The oxidation of water at potentials above 0.7V has been viewed as a potential problem for Ft on the cathode side of a Proton Exchange Membrane Fuel Cell (PEMFC). Pt alloys have shown a minimization or shift to higher potentials the oxide formation due to water oxidation. As a result, an increase in the Oxygen Reduction Reaction (ORR) activity has been observed. Not all of the Pt alloys show the same improvement in ORR activity which raises the question of what role does an alloy play in improving the cathodic overpotential losses. If the minimization of PtOH formation was the primary reason for poor ORR activity, then substantial improvement should be seen for Pt if the water content of the electrolyte was reduced and/or the activity of water and thus its interaction with Pt was also decreased. By looking at how much ORR activity improves for Pt in a more anhydrous environment would help explain the role different alloying metals play with Pt but also suggest new directions for new Pt based alloys, particularly in tailoring the electronic properties of Pt. This is also a chance to get preliminary information on how cathode catalysts will behave in elevated temperature fuel cells where the relative humidity is expected to be lower.