CO Tolerance of Pt alloy electrocatalysts for polymer electrolyte fuel cells and the detoxification mechanism

Citation
H. Igarashi et al., CO Tolerance of Pt alloy electrocatalysts for polymer electrolyte fuel cells and the detoxification mechanism, PHYS CHEM P, 3(3), 2001, pp. 306-314
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
ISSN journal
1463-9076 → ACNP
Volume
3
Issue
3
Year of publication
2001
Pages
306 - 314
Database
ISI
SICI code
1463-9076(2001)3:3<306:CTOPAE>2.0.ZU;2-T
Abstract
The electrocatalytic activity for H-2 oxidation in the presence of 100 ppm CO has been investigated on a series of binary Pt alloy electrocatalysts wi th non-precious metals of various compositions. Regardless of the compositi on, Pt-Fe, Pt-Ni, Pt-Co and Pt-Mo alloys have been found to exhibit excelle nt CO tolerance in H-2 oxidation, similar to that of the Pt-Ru alloy. At th ese CO-tolerant electrodes, the equilibrium coverage of CO was suppressed t o values less than ca. 0.6. Based on X-ray photoelectron spectroscopy (XPS) data, it was found that the surfaces of all non-precious metal alloys are composed of a thin Pt layer with an electronic structure different from tha t of pure Pt, indicating an increased 5d vacancy of Pt in the layers of the CO-tolerant alloys. The CO coverage, particularly with multi-bonding, was lowered due to decreased electron donation from the Pt band to the 2 pi* or bital of CO. A weakening of bond strength between the Pt skin layer and CO was also indicated by in situ FTIR, suggesting that the H-2 oxidation sites are not blocked by CO due to its enhanced mobility. Thus, the mechanism of CO tolerance described above at the Pt skin on alloy surfaces is proposed as a "detoxification mechanism''.