Direct Methanol Fuel Cells: Cathode Evaluation and
                                                Optimization

Thomas, S. C.

doi:10.1149/199827.0327pv

Cited by 15 publications

(16 citation statements)

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“…The orientation of the Pt crystals and Pt particle size are known to determine which reaction is favored. There have been studies that focused on developing Pt catalysts with higher selectivity for ORR [7]. Pt-alloys have also been investigated for use as DMFC cathodes.…”

Section: Introductionmentioning

confidence: 99%

Methanol Tolerance of CN x Oxygen Reduction Catalysts

Biddinger

Ozkan

2007

Top Catal

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Nitrogen-containing carbon nanofiber (CN x ) catalysts grown by acetonitrile pyrolysis over 2 wt% Fe, Co, and Ni impregnated supports of alumina, silica and magnesia were tested for methanol tolerance during the oxygen reduction reaction (ORR) by rotating ring disk electrode (RRDE) method. Catalysts tested in acidic electrolytes containing 1-3 M methanol showed no methanol poisoning during ORR and were inactive for methanol oxidation.

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Section: Introductionmentioning

confidence: 99%

Methanol Tolerance of CN x Oxygen Reduction Catalysts

Biddinger

Ozkan

2007

Top Catal

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“…(ii) Methanol permeation through the membrane from the anode to the cathode side [13,188,190] (so-called methanol cross-over) leads to additional voltage losses on the cathode compared with a H 2 /air PEMFC cathode), caused by the simultaneous occurrence of methanol oxidation and oxygen reduction with typically used platinum catalysts [190]. Furthermore, methanol permeation significantly reduces the DMFC's fuel utilization, u fuel , (also referred to as Faraday efficiency) [188,190], which is the reason why current DMFC technology uses thick membranes despite their higher ohmic resistance penalty. Even with ∼175 µm thick Nafion 117 membranes compared with only ∼25 µm thick membranes used for H 2 /air PEMFCs, methanol cross-over currents, i ×(CH 3 OH) , under OCV conditions are on the order of 50-150 mA cm −2 (see Fig.…”

Section: Fuel Cells For Direct Oxidation Of Liquid Fuelsmentioning

confidence: 99%

“…Even with ∼175 µm thick Nafion 117 membranes compared with only ∼25 µm thick membranes used for H 2 /air PEMFCs, methanol cross-over currents, i ×(CH 3 OH) , under OCV conditions are on the order of 50-150 mA cm −2 (see Fig. 26 [190]). While i ×(CH 3 OH) generally decreases with current density due to concentration gradients in the anode electrode which lower the methanol concentration at the anode/membrane interface, the overall cell fuel conversion efficiency, η fuel , is strongly compromised, particularly at low current densities [188]:…”

Section: Fuel Cells For Direct Oxidation Of Liquid Fuelsmentioning

confidence: 99%

“…The absolute methanol cross-over induced cathode voltage loss in an operating DMFC, however, was quantified only fairly recently, amounting to ∼20 mV at higher current densities and ∼40 mV at low current densities where methanol cross-over rates are largest [190]. Although these voltage losses might seem small, highly active methanoltolerant cathode catalysts not only promise to recover this voltage loss, but might also improve fuel utilization and, thus, fuel efficiency.…”

Section: F Methanol-tolerant Cathodesmentioning

confidence: 99%

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Fuel Cells

Gasteiger

Garche

2008

Handbook of Heterogeneous Catalysis

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IntroductionFuel cells directly convert chemical energy into electrical energy, without the intermediate formation of heat and mechanical energy as in conventional energy conversion devices based on the Carnot cycle. The direct electrochemical energy conversions of H 2 at the anode and O 2 at the cathode occur spatially separated on two electrodes connected by electrolyte and, in principle, allow for higher energy conversion efficiencies as shown in Fig. 1. The largest efficiency differences between Carnotbased and fuel cell-based energy conversion are found in the low power range of <1 MW and especially <100 kW. These efficiency advantages minimize fuel consumption; furthermore, other environmental concerns are alleviated by fuel cells:• zero or ultra-low emission of pollutants and particulates • reduced noise emissions (some moving parts are part of the balance of plant).Despite these conceptual advantages of fuel cells and their long development history since Grove's discovery in 1893 [1], no real fuel cell markets exist as of today. The reason for this is their still high costs, caused mainly by the required materials and their relatively short lifetime in relation to competitive technologies. Their future market introduction is expected at first for portable applications, followed by stationary applications and finally for transportation applications. This expectation is based on the strong commitment of the car industry, the development of better and cheaper materials and the use of modeling methods to improve fuel cell and fuel cell system efficiencies.Among the different fuel cell types, the low-temperature proton exchange membrane fuel cell (PEMFC), the direct methanol fuel cell (DMFC), the high-temperature molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC) play the most important roles; historically, the phosphoric acid fuel cell (PAFC) and alkaline fuel cell (AFC) had significant importance. Caused by the low operating temperature of PEMFCs and DMFCs, electrocatalysis-related issues are more critical than in the case of high-temperature fuel cells. Therefore, although this chapter will give a general description of all fuel cell types, it will provide a more in-depth discussion of the anodic oxidation (i.e. for H 2 , CH 3 OH, etc.) * Corresponding author. and cathodic reduction (i.e. O 2 ) reactions occurring in PEMFCs and DMFCs; where appropriate, findings will be compared with the phosphoric acid fuel cell literature. Working Principles of Fuel CellsFuel cells are electrochemical power sources (ECPS), similar to primary and secondary batteries (also referred to as accumulators). Their working principle is shown schematically in Fig. 2. These electrochemical cells consist of two electrodes separated by an ionically conducting electrolyte. Conversion of chemical energy into electrical energy occurs at the interface between the electronically conducting electrodes and the ionically conducting electrolyte. In principal, the electrodes can operate in two modes, either transforming elec...

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“…However, the use of methanol significantly reduces the activity of Pt catalysts, which is the original MOR catalyst. Intermediate CO poisons the Pt catalyst and causes a rapid drop in performance [1][2][3]. Incorporation of Ru dramatically enhances resistance to CO poisoning [4][5][6] in two ways: a mainly bi-functional mechanism [7,8] and a minor electronic effect [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Effect of heat treatment on PtRu/C catalyst for methanol electro-oxidation

et al. 2009

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The effect of heat treatment on a commercial PtRu/C catalyst was investigated with a focus on the relationship between electrochemical and surface properties. The heat treated PtRu/C catalysts were prepared by reducing the commercial PtRu/C catalyst at 300, 500, and 600°C under hydrogen flow. The maximum mass activity for the methanol electro-oxidation reaction (MOR) was observed in the catalyst heat treated at 500°C, while specific activity for the MOR increased with increasing heat treatment temperature. Cyclic voltammetry (CV) results revealed that the heat treatment caused Pt rich surface formation. The increase in surface Pt was confirmed by X-ray photoelectron spectroscopy; the surface (Pt:Ru) ratio of the fresh catalyst (81:19) changed to (87:13) in the 600°C heat treated catalyst. Quantitative analysis of the Ru oxidation state showed that the ratio of metallic Ru increased with an increase in heat treatment temperature. On the other hand, RuO x H y completely reduced at 500°C and the ratio of RuO 2 slightly decreased with increasing heat treatment temperature.

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Direct Methanol Fuel Cells: Cathode Evaluation and Optimization

Cited by 15 publications

References 0 publications

Methanol Tolerance of CN x Oxygen Reduction Catalysts

Methanol Tolerance of CN x Oxygen Reduction Catalysts

Fuel Cells

Effect of heat treatment on PtRu/C catalyst for methanol electro-oxidation

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