Interaction of H2O, CH3OH, (CH3)2O, CH3CN, and Pyridine with the Superacid Perfluorosulfonic Membrane Nafion: An IR and Raman Study

Buzzoni, R.; Bordiga, Silvia; Ricchiardi, Gabriele; Spoto, Giuseppe; Zecchina, Adriano

doi:10.1021/j100031a023

Cited by 245 publications

(463 citation statements)

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“…the change in the structure of the water polyassociates with increasing concentration of Al and a variation in the conditions for the competing sorption of water and the gaseous components present in air. In reality, when a high degree of hydration of the surface exists, water not only interacts with primary adsorption sites but also becomes part of the molecular aggregates which contain the Brönsted acid sites and several molecules of water bound to such a site (Zecchina et al 1995;Buzzoni et al 1995). However, only a relatively small number of surface hydroxy groups exhibit a high acidity as demonstrated by calorimetric titration data (Drago et al 1997).…”

Section: Resultsmentioning

confidence: 99%

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The Influence of Aluminium Concentration on the Hydration of ZSM-5-Type Zeolites in Aqueous Suspensions

Туров

Brei

Khomenko

et al. 2000

Adsorption Science & Technology

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ABSTRACT:The 1 H NMR spectral technique has been applied to the study of samples of ZSM-5-type zeolites. These samples were synthesized using the template procedure and possessed various aluminium concentrations in their crystal lattice. The characteristics of the adsorbed water layers and the values of the free surface energy of the adsorbents were determined. It was established that, for aqueous suspensions of zeolites, the highest concentration of water in the pores was characteristic of the sample containing the lowest amount of aluminium. It was suggested that the amount of water in the pores is determined not so much by the concentration of primary adsorption sites as by the conditions under which the development of water clusters occurs as well as by the competing sorption of water and ambient air.

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Section: Resultsmentioning

confidence: 99%

“…Earlier, we conducted such researches on samples of silicalite Chodorowski et al 1988). As a result, it was shown that water hardly penetrated into the pores of the adsorbent, even though some water molecule clusters were formed on defects in the crystal lattice.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Aluminium Concentration on the Hydration of ZSM-5-Type Zeolites in Aqueous Suspensions

Туров

Brei

Khomenko

et al. 2000

Adsorption Science & Technology

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“…12 The complexities in the Λ-C 1/2 curves suggested the presence of a variety of species, such as "triple ions" and other higher ion aggregates. On the other hand, trifluoromethanesulfonic acid in benzonitrile gave a monotonical Λ-C 27 We have determined, by means of conductometry, the dimer formation constants of not only acids in DMF 4 , but also salts, CF 3 COOLi in propylene carbonate 18 and sodium diphenyl phosphate (Na + (PhO) 2 PO 2 -) in acetone. 26 …”

Section: Methodsmentioning

confidence: 99%

Appearance of Maxima on Conductometric Titration Curves of Sulfonic Acids and the Evidence of Strong Homoconjugation Reactions in Benzonitrile

Hojo

Chen

1999

ANAL. SCI.

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The conductometric titrations of acids with bases usually give decreasing or increasing straight lines from the beginning to the equivalence point in protic solvents. However, in aprotic solvents, such as acetone 1 and acetonitrile 2 , maxima at the half equivalence point on titration curves have been observed for carboxylic acids with amine bases. The cause of the maxima at the half equivalence point has been attributed to homoconjugation reactions 2 between an acid (HA) and the conjugate base anion (A -) on the neutralization: B+2HA BH + ... H 2 A -. In a poorly solvating solvent, nitrobenzene, the maxima could be observed even at the one-third, and not at the half equivalence point, suggesting the formation of an A -(HA) 2 -type homoconjugate species. 3 We have reported maxima on conductometric titration curves of phosphoric, phosphonic, and related organophosphorus acids with triethylamine in DMF. 4 The stability of the homoconjugated species was found to depend much upon the number of OH groups involved homoconjugation reactions, e.g., not (PhO) 2 PO(OH) but PhOPO(OH) 2 gave a maximum in DMF, regardless of the acidities of the acids.Gunduz et al. 5 stressed an important role of the base strength of a conjugate anion upon the appearance of maxima in conductometric titrations of substitutedacetic and benzoic acids. In acetonitrile, the equilibrium constants of the homoconjugation reactions of acetate and benzoate ions with two acid moleclues (A -+2HA A -(HA) 2 , K homo ) have been determined to be 5.7×10 7 and ca. 1×10 7 , respectively. 6 Some phenols, especially 3,5-dinitrophenol etc.1,7 can form the homoconjugate species in aprotic solvents. The homoconjugation reaction or the appearance of a maximum on conductometric curve of sulfuric acid (SO 2 (OH) 2 ) has been observed in acetonitrile 2,8 and acetone. 9 However, maxima on conductometric curves for sulfonic acids (RSO 2 (OH)) have not been reported so far, even though fairly large homoconjugation constants of sulfonic acids were obtained in acetonitrile. 10 An sulfonic acid has only a single OH group, while sulfuric acid has two OH groups in the molecule. Therefore, the stability of the homoconjugated species from an sulfonic acid must have been too small to give a maximum on the titration curve; this point encouraged us to perform the present study.Sulfonic acids are rather strong acids (e.g., pK a =0.7 for benzenesulfonic acid) 11 in aqueous solution, however, the acidities of the acids are extremely weakened in aporic solvents. 10,12 The dissociation and homoconjugation constants of methanesulfonic and related acids have been determined in propylene carbonate, and compared with those in acetonitrile. 13 We have reported 14 on the formation constants of "triple ions" of trialkylammonium sulfonates and nitrate through hydrogen bonding forces as well as Coulombic forces in benzonitrile. Judging from the 1:1 association and "triple ion" formation constants of R 3 NH + A -in benzonitrile, the basicity of the conjugate anions were found to increase as follo...

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“…Membrane conductivities for pristine and ε-caprolactam-exchanged NRE211 membranes were determined at different relative humidity (RH) (i.e., 10,20,30,40,50,60,70,80,90, and 95%) by applying DC currents at a cell temperature of 80…”

Section: Methodsmentioning

confidence: 99%

“…The cell is equilibrated with a 300 sccm flow of H 2 at various temperatures (30,50,80,90 • C) and 90% RH for 1 h using a Scribner 890E PEMFC test station. The humidity was changed from low (20%) RH to high (95%) RH.…”

Section: Methodsmentioning

confidence: 99%

The Contamination Mechanism and Behavior of Amide Bond Containing Organic Contaminant on PEMFC

Cho

Das

Dinh

et al. 2015

J. Electrochem. Soc.

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This paper presents a study of the effects of an organic contaminant containing an amide bond (-CONH-), ε-caprolactam, on polymer electrolyte membrane fuel cells (PEMFCs). The ε-caprolactam has been detected in leachates from polyphthalamide materials that are being considered for use as balance-of-plant structural materials for PEMFCs. Contamination effects from ε-caprolactam in Nafion membranes are shown to be controlled by temperature. A possible explanation of the temperature effect is the endothermic ring-opening reaction of the amide bond (-NHCO-) of the cyclic ε-caprolactam. UV-vis and ATR-IR spectroscopy studies confirmed the presence of open ring structure of ε-caprolactam in membranes. The ECSA and kinetic current for the ORR of the Pt/C catalyst were also investigated and were observed to decrease upon contamination by the ε-caprolactam. By comparison of the CVs of ammonia and acetic acid, we confirmed the adsorption of carboxylic acid (-COOH) or carboxylate anion (-COO-) onto the surface of the Pt. Finally, a comparison of in situ voltage losses at 80 • C and 50 • C also revealed temperature effects, especially in the membrane, as a result of the dramatic increase in the HFR. Although research efforts have been made to reduce system costs and improve efficiency of polymer electrolyte membrane fuel cells (PEMFCs), cost and durability issues continue to delay their commercialization.1 In addition, because contamination of the stack can affect performance and durability, studies designed to elucidate these effects and mechanisms have been receiving more attention. 1-41In general, three fundamental contamination mechanisms are known: conductivity loss by ion exchange in the membrane/ionomer, Pt contamination by adsorption, and water/mass transport issues induced by changes in the gas diffusion layer (GDL) properties. Alkali, alkaline-earth, or transitional-metal cations such as Li + , Na + , K + , Cs + , Ni 2+ , Cu 2+ , Ca 2+ , and Fe 3+ are well known contaminants that undergo ion exchange [2][3][4][6][7][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] with the proton exchange membrane (PEM) in a PEMFC. Changes in the oxygen reduction reaction (ORR) kinetics at a Pt electrode covered with a Nafion ionomer [20][21][22][23][24] have also been reported. In addition to the decrease in PEM conductivity due to the reaction with cationic contaminants, a structural change also occurs in the ionomer. This structural change appears to be related to the degradation of Pt/C catalyst activity. Catalyst contamination by an adsorption mechanism from feed-gas contaminants such as SO 2 , [8][9] CO, 10 and H 2 S 11 are well known. In addition, we have reported that aniline adsorbs onto the Pt/C electrode because it contains an aromatic ring and a nitrogen atom in the form of an amine group. 31,35 In a recent cost analysis, 36,37 the need for cost reduction of balanceof-plant (BOP) materials increased relative to the need for cost reduction of the stack in PEMFCs. Using off-the-shelf materials ...

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Interaction of H2O, CH3OH, (CH3)2O, CH3CN, and Pyridine with the Superacid Perfluorosulfonic Membrane Nafion: An IR and Raman Study

Cited by 245 publications

References 24 publications

The Influence of Aluminium Concentration on the Hydration of ZSM-5-Type Zeolites in Aqueous Suspensions

The Influence of Aluminium Concentration on the Hydration of ZSM-5-Type Zeolites in Aqueous Suspensions

Appearance of Maxima on Conductometric Titration Curves of Sulfonic Acids and the Evidence of Strong Homoconjugation Reactions in Benzonitrile

The Contamination Mechanism and Behavior of Amide Bond Containing Organic Contaminant on PEMFC

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