XRD and XPS Analysis of As-Prepared and Conditioned DMFC Array Membrane Electrode Assemblies

Catalysts prepared by the Adams and Reetz method were ranked against a Johnson Matthey PtRu catalyst in an array fuel cell in the direct methanol fuel cell (DMFC) mode. The Reetz and Johnson Matthey PtRu catalysts were found to be equivalent. The catalysts were analyzed in membrane and electrode assemblies (MEA) before and after fuel cell performance evaluation. The X-ray diffraction (XRD) analysis showed no changes of the crystalline phases before and after fuel cell evaluation. However, the X-ray photoelectron spectroscopy (XPS) showed that in the electrode containing the Reetz catalyst, substantial loss of Ru at the MEA surface occurred during fuel cell operation. Loss of Ru also occurred at the MEA surface containing the Johnson Matthey catalyst while an enrichment of Ru on the electrode surface containing the Adams catalyst was observed. A lattice parameter analysis of all catalysts showed Pt enrichment in the alloy phase, with the largest enrichment in the Adams catalyst.