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恵子, 木村; 弘行, 西村; いづみ, 木村; 伊平, 岩田; 純也, 水谷

doi:10.4327/jsnfs.37.343

Cited by 6 publications

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“…XANES analysis of the 1:1 composition shows the actual ratio to be 62:38 ͑Pt:Mo͒. The most probable reason for this discrepancy is based on a limit of solubility of Mo in the Pt, which according to prior reports 39,40 is approximately ϳ27 atom %. This limit of solubility is controversial, with somewhat higher values reported elsewhere.…”

Section: Resultsmentioning

confidence: 96%

Electrocatalysis of CO Tolerance by Carbon-Supported PtMo Electrocatalysts in PEMFCs

Mukerjee

Urian

Lee

et al. 2004

J. Electrochem. Soc.

121

104

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This paper is a full version of an earlier short communication, where significantly higher ͑up to threefold͒ CO tolerance was reported for PtMo/C ͑atomic ratio, Pt:Mo, 3:1͒ relative to the current state-of-the-art PtRu/C ͑1:1͒ in a proton exchange membrane fuel cell ͑PEMFC͒ under standard operating conditions ͑85°C, 100% humidification, with H 2 ϩ 100 pm CO//O 2 ). We report significantly different behavior for PtMo/C in contrast to PtRu/C, wherein there is negligible variation in CO tolerance ͑100 ppm CO in H 2 ) with variations in alloying compositions ͑Pt:Mo, 1:1 to 5:1͒. Further, in contrast to Pt/C and PtRu/C, significantly lower variations in overpotential losses is observed for PtMo/C as a function of temperature ͑55-115°C͒ and CO concentrations ͑5-100 ppm, balance H 2 ). In addition, excellent long-term stability is reported for PtMo/C ͑1:1͒ under steady-state conditions ͑constant potential conditions at 0.6 V͒ for a total duration of 1500 h, with anode gas composition varied between pure H 2 and those with 100 ppm CO, with or without the presence of other reformate gases ͑primarily CO 2 and N 2 ). These are discussed in the context of detailed physicochemical characterization of the nanoparticles using a combination of X-ray diffraction, transmission electron microscopy, and in situ synchrotron X-ray absorption spectroscopy.CO tolerance in reformer-based low-and medium-temperature proton exchange membrane fuel cells ͑PEMFCs͒ is crucial for the viability of this technology for transportation and portable power applications. The choice of an appropriate anode electrocatalyst with low susceptibility to CO poisoning and a high kinetic rate for hydrogen oxidation is therefore paramount. Despite its superior activity for anodic, hydrogen oxidation, and interfacial stability under acidic pH conditions and the operating temperatures of an actual PEMFC, electrocatalysis by Pt/C suffers from the problem of high polarization losses due to CO poisoning. This is especially true for temperatures below 115°C.The large affinity for CO chemisorption at potentials lower than ϳ0.65 V on Pt/C necessitates the search for other nanophase Ptbased electrocatalysts capable of initiating CO oxidation, preferably close to the hydrogen oxidation potential. This need manifested in the ''bifunctional'' 1,2 approach, where a second, more oxidizable element, present either as an admetal or as an alloying element, initiates the CO oxidation at lower potentials. The result is enough bare surface on Pt crystallites to efficiently oxidize hydrogen at lower overpotentials.Prior literature, involving several decades of research, is replete with investigations of alloys such as PtSn, 3,4 PtRh, 5 PtRu, 6-8 and Pt with adsorbing adatoms such as Ge, Sb, and Sn, 2,9 etc. In recent years nanophase PtRu electrocatalysts have received renewed attention as promising candidates for CO oxidation in PEMFCs. 10-12 A recent report by Oetjen et al., 13 using steady-state polarization data, indicates a fourfold performance enhancement with highly dispersed ...

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