Carbon supported Ru–Se as methanol tolerant catalysts for DMFC cathodes. Part II: preparation and characterization of MEAs

Abstract

Cathode catalyst layers were prepared and characterized as part of membrane electrode assemblies (MEA) and catalyst coated membranes (CCM) on the basis of carbon supported methanol tolerant RuSe x catalysts. Preparation parameters varied were: catalyst loading (0.5-2 mg RuSe x cm -2 ), PTFE content (0, 6, 18 wt.%), carbon support (Vulcan XC 72 or BP2000), and fraction of RuSe x in the carbon supported catalysts (20, 44, 47 wt.%). The MEAs and cathode catalyst layers were electrochemically characterized under Direct Methanol Fuel Cell (DMFC) operating conditions by recording polarization curves, galvanostatic measurements, and impedance spectra. The morphology of the catalyst layers was investigated by means of confocal laser scan microscopy (CLSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) measurements. MEAs with Ru(44.0 wt.%)Se(2.8 wt.%)/VulcanXC72 cathode catalyst achieved the highest performance of all RuSe x catalysts investigated, i.e.~40 mW cm -2 at 80°C under ambient pressure and k MeOH = k air = 4. This is 40% of the value obtained with commercial platinum cathode catalyst under the same operating conditions. The RuSe x catalysts investigated are stable over a period of more than 1,000 h. This was confirmed by TEM and XRD measurements, where no increase in mean RuSe x particle size (~5 nm) after fuel cell operation was found. Enhancement of specific catalyst activity, mass transport, and active surface offer potential for a further improvement of RuSe x catalyst layers.

Combinatorial Search for Quaternary Methanol Tolerant Oxygen Electro‐Reduction Catalyst

“…At a lower potential of 0.2 V, in Figure 2(b), many spots are shining due to the higher over-potential, and it is shown that the brightest spots are from the PtRuMoSe and PtRuFeSe regions. The bright spots which exhibited low on-set potential kept their higher brightness at 0.2 V. This result can be rationalised by the well-known methanol tolerant effect of Se [13][14][15][17][18][19]. The positive effect of Se is also supported by the poor performance of the Se-free PtRuMoFe region, which has only a few moderately bright spots.…”

“…Most of the methanol tolerant ORR catalysts reported previously are binary systems such as PtCo [2,12], PtFe [7,16], RuSe [11,13,14], PtSe [10], Pd-M (M = transition metals) alloys [4,9] and IrCo [8]. Only few reports dealt with ternary compositions such as MoRuSe [6] and RuSeW [15].…”

Carbon supported Ru–Se as methanol tolerant catalysts for DMFC cathodes. Part I: preparation and characterization of catalysts

“…Se modified Ru-catalysts were further tested in DMFC cathodes at the Research Center Jülich. The results of this investigation are described separately in part II of this contribution [18]. The Se-modification of a commercial Ru/C catalyst represents an easy and convenient approach to obtain Rubased catalysts with enhanced ORR-activities.…”

“…Therefore, the objective of this work is to optimize the catalyst preparation towards reproducible and simplified preparation routes and higher catalytic activities in the ORR as well as to provide adequate amounts of high-performance catalysts for the preparation of catalyst coated membranes (CCM) and their characterization in membrane electrode assemblies (MEA). These results will be discussed in Part II of this contribution [18]. RuSe x /C-catalysts with a Ru-loading of 20 wt.% were obtained by preparing Ru(20 wt.%)/C-intermediates and their subsequent selenization with H 2 SeO 3 .…”

Se-modified Ru nanoparticles as ORR catalysts – Part 1: Synthesis and analysis by RRDE and in PEFCs

“…By first examining the performance of the Se/Ru catalyst for the ORR in the absence of methanol in part 1, we can better separate the effect of the catalyst's ORR activity from the effect of its methanol tolerance on the fuel cell performance in part 2. Although there have been a few reports that have examined the performance of other chalcogenides at the hydrogen-air cathode [30,31] and at the DMFC cathode [32][33][34][35][36], none have specifically demonstrated the conditions under which such catalysts perform better than pure Ru or, in the case of DMFCs, pure Pt catalysts. The former comparison to Ru is important for fundamental understanding, and the latter comparison to Pt is necessary to define the conditions of technological relevance for Ru-based catalysts.…”