A Combined Rotating Disk Electrode/X-Ray Diffraction Study of Co Dissolution from Pt1−xCox Alloys

The oxygen reduction activity of a series of Pt 1−x Co x catalysts (with high Co content) sputter-deposited onto 3M's nano-structured thin film support was measured with Rotating Disk electrode techniques. The oxygen reduction reaction (ORR) activity was found to be much higher than that measured on pure Pt (3–4 times higher absolute activity at 1000 mV for the same Pt loading). The ORR activity was only weakly dependent on the Co content (as-sputtered). With repeated potential cycling it was, however, somewhat unstable, likely primarily as a result of poisoning of the catalyst surface with electrolyte impurities during the long term test protocol. Ex-situ x-ray diffraction measurements of the disks during testing showed loss of bulk Co from the lattice, resulting in loss of a large fraction of the initial Co content.