Influence of Nafion ® film on oxygen reduction reaction and hydrogen peroxide formation on Pt electrode for proton exchange membrane fuel cell

Abstract

The influence of Nafion ® film on ORR kinetics and H 2O 2 formation on a Pt electrode was investigated using RRDE in 0.1 M HClO 4. It was found that the Nafion ®-coated Pt system showed lower apparent ORR activity and more H 2O 2 production than the bare Pt electrode system. From the temperature sensitivity, it was revealed that the apparent activation energies of ORR in the Nafion ®-coated Pt system were lower than the bare Pt electrode system, and the H 2O 2 formation was suppressed with the increase of the temperature. In order to analyze the results furthermore, other systems (0.1/1.0 M, HClO 4/CF 3SO 3H) with the bare Pt electrodes were also examined as references. It was exhibited that the ORR kinetic current, the H 2O 2 formation, and the apparent activation energies of 1.0 M CF 3SO 3H system were close to those of the Nafion ®-coated Pt system. We concluded that the orientation of anion species of Nafion ® and CF 3SO 3H to the Pt surface via water molecules, as well as a fluorocarbon polymer network of Nafion ®, might block O 2 adsorption, resulting in the smaller effective surface area of the Pt electrode for ORR, the smaller ORR kinetic current, and the more H 2O 2 production.