Oxygen reduction at Pt and Pt 70Ni 30 in H 2SO 4/CH 3OH solution

Abstract

The electrochemical oxygen reduction reaction (ORR) was studied at Pt and Pt alloyed with 30 atom% Ni in 1 M H 2SO 4 and in 1 M H 2SO 4/0.5 M CH 3OH by means of rotating disc electrode. In pure sulphuric acid, the overpotential of ORR at 1 mA cm −2 is about 80 mV lower at Pt 70Ni 30 than at pure Pt. It was found that in methanol containing electrolyte solution the onset potential for oxygen reduction at PtNi is shifted to more positive potentials and the alloy catalyst has an 11 times higher limiting current density for oxygen reduction than Pt. Thus, PtNi as cathode catalyst should have a higher methanol tolerance for fuel cell applications. On the other hand, no significant differences in the methanol oxidation on both electrodes was found using cycling voltammetry, especially regarding the onset potential for methanol oxidation. During all the measurements no significant electrochemical activity loss was observed at Pt 0.7Ni 0.3. Ex-situ XPS investigations before and after the electrochemical experiments have revealed Pt enrichment in the first surface layers of the PtNi.