Lowering Activation Overpotential for Oxygen Reduction Reaction (ORR) in a PEM Fuel Cell: New Insights and Directions

摘要

The principle causes of the poor kinetics of the four-electron oxygen reduction reaction can be attributed mainly to the low exchange current density of the oxygen reduction reaction. The high cathodic overpotential loss of ~ 220 mV, at potentials close to the open circuit with the current state of the art low Pt loading electrocatalysts is attributed to a mixed potential that is set up at the oxygen electrode. The mixed potential is due to a combination of slow O2-reduction kinetics and competing anodic process such as Pt-oxide formation and/or impurity oxidation.