Leveraging a Kinetic Isotope Effect to Investigate Oxygen Reduction Reaction Kinetics on Platinum
George, Thomas Y.
2019
- The oxygen reduction reaction, notable as the cathode reaction in proton exchange membrane fuel cells, is at the forefront of the development of energy conversion and storage technology for environmental sustainability. The reaction is characterized by sluggish kinetics, even on the platinum catalysts predominant in fuel cells, which makes it a limiting factor in energy technology development. ... read moreThis experimental work investigates whether or not a proton transfer is a component in the rate determining step of the oxygen reduction reaction. While the mechanism of the oxygen reduction reaction is the subject of consistent research spanning decades, leveraging a kinetic isotope effect in conditions relevant to the operation of proton exchange membrane fuel cells (acidic environment) provides specific clarity on the rate determining step. A kinetic isotope effect is defined as the ratio of the rate constant of the reaction when protons are available to the rate constant of the reaction when deuterium ions are available. Using a three-electrode setup with platinum catalyst films dried on a rotating disk working electrode, this work demonstrates a kinetic isotope effect of approximately unity, both by extrapolating from the mass transport limited regime of the reaction with the Koutecky-Levich hydrodynamic equation and by extrapolating from the kinetic limited regime of the reaction with a Butler-Volmer kinetic model. Thus, the oxygen reduction reaction does not include a proton transfer in its rate determining step on platinum catalysts under acidic conditions.read less
- ID:
- 5425kp614
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- TARC Citation Guide EndNote
