The Effect of Impurity Cations on the Oxygen Reduction Kinetics at Platinum Electrodes Covered with Perfluorinated Ionomer

Okada, Tatsuhiro; Ayato, Yuusuke; Satou, Hiroki; Yuasa, Makoto; Sekine, Isao

doi:10.1021/jp010822y

Cited by 94 publications

(81 citation statements)

References 15 publications

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“…It is noteworthy that the Pt contamination can be neglected for Na + contamination. A previous study 5 also reported that cation contamination on the electrode did not affect the Pt catalyst but speculated that there was an effect in the ionomer. In situ CV measurements during the 80 h of NaOH infusion (see the vertical data at 21 h, 45 h, and 78 h in Figure 10a) support the hypothesis of no change in available Pt concentration (i.e., negligible ECSA changes <5%), as shown in Figure 10b (See reference 34 for experimental details).…”

Section: Comparison To Experimental Datamentioning

confidence: 94%

mentioning

confidence: 99%

“…Many previous studies for contamination [3][4][5][6][7][8][9][10][11][12][13] in PEMFCs have shown the sensitivity of performance to low levels of contamination. For example, cation leachates from gaskets or seals, from NH 3 in the fuel, or from catalyst metals [3][4][5][6][7][8][9] are well known contaminants of the membrane through an ion-exchange mechanism. Catalyst contamination by CO through an adsorption mechanism from feed gas contaminants is so well-known that those studies are too numerous to list here.…”

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confidence: 99%

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An Isothermal Model for Predicting Performance Loss in PEMFCs from Balance of Plant Leachates

Cho

Zee

2014

J. Electrochem. Soc.

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A model is presented for the contamination of a proton exchange membrane fuel cell (PEMFC), including adsorption onto the Pt catalyst, absorption into the membrane, and ion exchange with ionomeric components. Model predictions for three sources of voltage loss account for the two-dimensional, time-dependent contamination along the channel and into the membrane. The model is developed by considering the well-known concepts of Langmuir adsorption, partition coefficients, plug flow reactors (PFRs), and dimensionless analysis. The phenomena are shown to be controlled by three important dimensionless groups: a Damköhler number for the contamination reaction rate, a capacity ratio, and a coverage ratio for each contamination mechanism. These groups show how to scale ex situ equilibrium data for in situ predictions. The model predictions are shown to be reasonable when compared to in situ experiment data once ex situ data are used to provide reaction and equilibrium parameters. The predictions enable estimation of tolerance limits for leachates according to each mechanism. For typical parameters, the predicted voltage loss in the electrode ionomer by an ion-exchange mechanism shows slower reaction rates but greater performance losses than other mechanisms. Analysis of the potential for commercialization of proton exchange membrane fuel cells (PEMFCs) shows that the cost of balance of plant (BOP) materials can be as much as 30% of the system cost.1 One opportunity to decrease these costs is to use off-the-shelf materials rather than custom-made materials, if leachates from less expensive materials would not affect performance and life-time.2 This loss in performance is related to the contamination of the membrane 3 as well as the electrodes. Many previous studies for contamination [3][4][5][6][7][8][9][10][11][12][13] in PEMFCs have shown the sensitivity of performance to low levels of contamination. For example, cation leachates from gaskets or seals, from NH 3 in the fuel, or from catalyst metals 3-9 are well known contaminants of the membrane through an ion-exchange mechanism. Catalyst contamination by CO through an adsorption mechanism from feed gas contaminants is so well-known that those studies are too numerous to list here. Examples are also known for SO 2 , 10,11 for H 2 S, 12 and even for details of the reverse water-gas shift reaction of CO 2 . 13The fundamental mechanism of contamination from organic contaminants such as aniline, ε-caprolactam, and diaminotoluene (DAT), [14][15][16][17][18] which have been identified as possible system contaminants, have been studied only briefly and recently, and it has been shown that their impact on PEMFC performance depends on their functional groups. For example, the ion-exchange reaction of the amine group in aniline with the Nafion membrane/ionomer causes a decrease in the number of available proton sites, thereby hindering the transport of protons and increasing ohmic losses. Aniline is also adsorbed on the carbonsupported platinum catalyst through interactions betw...

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Section: Comparison To Experimental Datamentioning

confidence: 94%

mentioning

confidence: 99%

mentioning

confidence: 99%

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An Isothermal Model for Predicting Performance Loss in PEMFCs from Balance of Plant Leachates

Cho

Zee

2014

J. Electrochem. Soc.

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“…We ignore secondary effects such as changes in transport rates of reactants through the catalyst layer, 40,41 increase in peroxide production [40][41][42] or changes in Tafel slopes [43][44][45] as has been reported previously. Also, ion exchange with the membrane can lead to highly non-linear effects at high currents or significant cation exchange.…”

Section: Model Descriptionmentioning

confidence: 99%

Effect of System Contaminants on the Performance of a Proton Exchange Membrane Fuel Cell

Mehrabadi

Dinh

Bender

et al. 2016

J. Electrochem. Soc.

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The performance loss and recovery of the fuel cell due to Balance of Plant (BOP) contaminants was identified via a combination of experimental data and a mathematical model. The experiments were designed to study the influence of organic contaminants (e.g. those from BOP materials) on the resistance of the catalyst, ionomer and membrane, and a mathematical model was developed that allowed us to separate these competing resistances from the data collected on an operating fuel cell. For this reason, based on the functional groups, four organic contaminants found in BOP materials, diethylene glycol monoethyl ether (DGMEE), diethylene glycol monoethyl ether acetate (DGMEA), benzyl alcohol (BzOH) and 2,6-diaminotoluene (2,6-DAT) were infused separately to the cathode side of the fuel cell. The cell voltage and high frequency impedance resistance was measured as a function of time. The contaminant feed was then discontinued and voltage recovery was measured. It was determined that compounds with ion exchange properties like 2,6-DAT can cause voltage loss with non-reversible recovery, so this compound was studied in more detail. The degree of voltage loss increased with an increase in concentration, and/or infusion time, and increased with a decrease in catalyst loadings. The major technical challenges for polymer electrolyte membrane fuel cells (PEMFCs) in general are performance, reliability, durability and cost. There is an opportunity to reduce overall system cost by choosing lower cost balance of plant (BOP) materials for PEMFC systems. However, choosing any new system BOP material (e.g., assembly aids, structural plastics, and hoses) without compromising function, fuel cell performance, or life requires understanding the effects of the contaminants that leach from these materials. The contaminants in a fuel cell system originate from the fuel, air, and the different component materials used in construction.Previous studies 1-28 have reported on the effect of contamination on PEMFCs by impurities found in the fuel, fuel-cell components, or the external environment such as carbon monoxide (CO), 8,9 26 It has been demonstrated that even trace amounts of impurities can severely poison the anode, membrane, and cathode, particularly at low-temperature operation.4 These contaminants impact PEMFC performance by hindering kinetics (e.g. CO and H 2 S) or reducing membrane conductivity (e.g. NH 3 and metal cations). 8,18,19 Several models are available that capture kinetic [24][25][26] and ohmic overpotentials [18][19][20]27,28 during the contamination and recovery studies.Although there has been a lot of research on contamination caused by fuel and air side impurities, the effect of contamination originating from system components have only recently been briefly studied. 29-35These results showed that despite the contamination caused by fuel and air side impurities that can effect only the catalyst (e.g., CO) or the membrane (e.g. metal cations), organic contaminants (e.g., those from BOP materials) can have severe effect...

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“…However, most of the additives are also dissolved and diffused into the membrane of the PEFCs, which results in a decreased proton conductivity of the membrane 25) . .…”

Section: )～24)mentioning

confidence: 99%

Improvement in Catalytic Performance of Carbon Nanotube-supported Metal Nanoparticles by Coverage with Silica Layers

Tanaka

Kishida

2011

J. Jpn. Petrol. Inst.

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Carbon nanotube (CNT)-based composites have attracted a great deal of interest because of their potential application in catalysts. These composites are frequently prepared by the addition of metals or metal oxides to the outer surface of CNT. However, the surface modification of CNT is generally a challenging task, because their surface is chemically inert. In addition, metal or metal oxide particles on CNT are easily aggregated when these are used as catalysts. Recently, we developed CNT-supported metal nanoparticle catalysts covered with silica layers a few nanometers thick. The catalysts show high catalytic activity in spite of coverage of metal nanoparticles with silica layers. In addition, the silica layers which are wrapped around metal particles prevent the sintering of metal particles as well as the detachment of metal particles under severe reaction conditions. In addition, the CNT-supported metal particles covered with silica can be applied to catalysts for the oxygen reduction reaction at cathode in polymer electrolyte fuel cells (PEFCs). Pt catalysts supported on carbon black which are conventional catalysts in the state of the art PEFCs, are seriously deactivated under PEFC cathode conditions such as high potential, low pH and oxygen atmosphere due to the aggregation of Pt metal and the dissolution and re-deposition of Pt metal. We demonstrated that the silica-coated Pt/CNT is electrochemically active in spite of coverage of Pt metal with silica insulator. In addition, the coverage of Pt metal particles with silica layers inhibits the growth of Pt metal particles in size under cathode conditions in PEFCs. The silica-coated Pt/CNT thus shows high durability for the oxygen reduction reaction. The coverage with silica layers also prevents the dissolution of metals other than Pt under cathode conditions. Therefore, our silica-coating method is promising for the development of highly durable non-Pt metal catalysts for use in PEFC cathodes.

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The Effect of Impurity Cations on the Oxygen Reduction Kinetics at Platinum Electrodes Covered with Perfluorinated Ionomer

Cited by 94 publications

References 15 publications

An Isothermal Model for Predicting Performance Loss in PEMFCs from Balance of Plant Leachates

An Isothermal Model for Predicting Performance Loss in PEMFCs from Balance of Plant Leachates

Effect of System Contaminants on the Performance of a Proton Exchange Membrane Fuel Cell

Improvement in Catalytic Performance of Carbon Nanotube-supported Metal Nanoparticles by Coverage with Silica Layers

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