Thermally induced chemical evolution in polyimide films investigated by X ray photoelectron spectroscopy

Thermally modified polyimide films based on 1,4-Phenylene diamine (p-PDA) and 3,3,4,4 - Benzophenone tetracarboxylic dianhydride (BTDA) were prepared and their chemical structure transformation after thermal treatment at 350 degrees C-500 degrees C was investigated. X-ray diffraction results revealed an increase in the polymer chain order for all treated PI samples as a consequence of the thermal treatment and chain interaction. TGA analysis showed that the heat treatment promoted different thermal degradation profiles. Electron spin resonance evidenced a large population of free radicals as a result of homogeneous bond cleavage when the thermal treatment was performed at 500 degrees C. X-ray photoelectron spectroscopy analysis indicated that the chemical structure transformation not only occurs on the outer surface but also in the sub-surface layer. These results show that controlled fast thermal treatment can produce materials with specific characteristics and may serve as a general strategy for changing both structural and chemical properties of the polymers. POLYM. ENG. SCI., 58:943-951, 2018. (c) 2017 Society of Plastics Engineer

Improvement On Direct Ethanol Fuel Cell Performance By Using Doped-nafion® 117 Membranes With Pt And Pt-ru Nanoparticles

Nafion® 117 membranes doped with Pt (4 × 10 -4 mol L-1 or 8 × 10-4 mol L-1 H2PtCl6 solution), and with Pt-Ru (4 × 10 -4 mol L-1 H2PtCl6 and 2 × 10-4 mol L-1 RuCl3 solutions) nanoparticles have been synthesized using a simple and scalable absorption-reduction method. The chemical integrity of the membranes was confirmed by 13C and 19F solid-state NMR. The pore microstructure of the membranes was preserved after the doping process, according to SAXS measurements. The tests of the direct ethanol fuel cells (DEFC) performance at 90 C exhibited up to 38% and 56% increase at the maximum power densities for Pt doped-Nafion ® membrane from lower and higher concentration of H 2PtCl6 solution, respectively, compared to bare Nafion® membranes. Additionally, a Pt-Ru doped-membrane tested at 110 C exhibited the highest power density. Such superior performances may be attributed to a synergistic effect between the extra amount of active catalytic sites inside the pore structure for the electrochemical oxidation of ethanol, thus preventing ethanol crossover, and the excellent proton migration properties conferred by the pore microstructure of Nafion®. These results demonstrate that the doped-Nafion® membrane has a good capacity to improve the performance of DEFC, and provided further clarification on the synthesis process of polymer electrolyte doped-membranes in fuel cell technology. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.38271206012068Hotza, D., Diniz Da Costa, J., Fuel cells development and hydrogen production from renewable resources in Brazil (2008) International Journal of Hydrogen Energy, 33, pp. 4915-4935Wang, Y., Chen, K.S., Mishler, J., Cho, S.C., Adroher, X.C., A review of polymer electrolyte membrane fuel cells: Technology, applications, and needs on fundamental research (2011) Applied Energy, 88, pp. 981-1007Sharma, S., Pollet, B.G., Support materials for PEMFC and DMFC electrocatalysts - A review (2012) Journal of Power Sources, 208, pp. 96-119Silva, R.A., Hashimoto, T., Thompson, G.E., Rangel, C.M., Characterization of MEA degradation for an open air cathode PEM fuel cell (2012) International Journal of Hydrogen Energy, 37, pp. 7299-7308Wu, J., Yuan, X.Z., Wang, H., Blanco, M., Martin, J.J., Zhang, J., Diagnostic tools in PEM fuel cell research: Part i electrochemical techniques (2008) International Journal of Hydrogen Energy, 33, pp. 1735-1746Cheng, X., Zhang, J., Tang, Y., 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532-537Liu, J., Zhao, T., Liang, Z., Chen, R., Effect of membrane thickness on the performance and efficiency of passive direct methanol fuel cells (2006) Journal of Power Sources, 153, pp. 61-67Andreadis, G., Tsiakaras, P., Ethanol crossover and direct ethanol PEM fuel cell performance modeling and experimental validation (2006) Chemical Engineering Science, 61, pp. 7497-7508Devrim, Y., Erkan, S., Baç, N., Eroglu, I., Improvement of PEMFC performance with Nafion/inorganic nanocomposite membrane electrode assembly prepared by ultrasonic coating technique (2012) International Journal of Hydrogen Energy, 37, pp. 16748-16758Tricoli, V., Proton and methanol transport in poly(perfluorosulfonate) membranes containing Cs+ and H+ cations (1998) Journal of the Electrochemical Society, 145, pp. 3798-3801Antonucci, P.L., Aricò, A.S., Cretì, P., Ramunni, E., Antonucci, V., Investigation of a direct methanol fuel cell based on a composite Nafion®-silica electrolyte for high temperature operation 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Spectroscopic And Electrochemical Study Of [ru(nh3)5oh2]3+, [ru(nh3)5cl]2+, And [os(nh3)5oh2]3+ Immobilized On Thin Film Of Ti(iv) Oxide Dispersed On The Silica Gel Surface

[Ru(NH3)5H2O]3+, [Ru(NH3)5Cl]2+ and [Os(NH3)5H2O]3+ were supported on the hydrated titanium alkoxide grafted on silica gel surface. The mononuclear complexes on the matrix surface have been characterized by specific surface area, elemental analysis, UV-Vis spectroscopy and electrochemical techniques (cyclic voltammetry, differential pulse polarography). These supported species exhibit one defined band on the visible region of the electronic spectrum: band [Ru(NH3)5H2O]3+ (668 nm), [Ru(NH3)5 Cl]2+ (676 nm) and [Os(NH3)5H2O]3+ (825 nm), attributed to MIII → TiIV (M = Ru(III) and Os(III)) metal to metal charge transfer process. For the mononuclear anchored species [Ru(NH3)5H2O]3+, [Ru(NH3)5Cl]2+ and [Os(NH3)5H2O]3+, the (E1/2) for the M(III)/M(II) couple at 25°C are, respectively: -0.22, -0.28, and - 1.15 V versus SCE. A formation of an oxo bridge Ti-O-M(NH3)5 (M = Ru, Os) and chloro bridge Ti-Cl-Ru(NH3)5 was postulated for the grafted complexes on the SiO2/TiO2 surface. © 2000 Elsevier Science B.V.1922-2322772282Siperko, L.M., Kuwana, T., (1983) Electrochim. Acta, 130, p. 765Gushikem, Y., Peixoto, C.R.M., Rodrigues-Filho, U.P., Kubota, L.T., Stadler, E., (1996) J. Colloid Interface Sci., 184, p. 236Denofre, S., Gushikem, Y., Castro, S.C., Kawano, Y., (1993) J. Chem. Soc., Faraday Trans., 89, p. 1057Hoffmann, M.T., Neiva, S.M.C., Martins, M.R., Franco, D.W., (1992), p. 257. , H.A. Mottola, J.R. Steinmezt (Eds.), Chemically Modified Surfaces, Elsevier, New YorkNeiva, S.M.C., Santos, J.A.V., Moreira, J.C., Gushikem, Y., Vargas, H., Franco, D.W., (1995) Langmuir, 9, p. 239Lorencetti, L., Gushikem, Y., Kubota, L.T., Neto, G.O., Fernandes, J.R., (1995) Mikrochim. Acta, 117, p. 239Kubota, L.T., Gouvea, F., Andrade, A.N., Milagres, B.G., Neto, G.O., (1996) Electrochim. Acta, 41, p. 1465Rebenstorf, B., Andersson, S.L.T., (1990) J. Chem. Soc., Faraday Trans., 86, p. 2783Kubota, L.T., Milagres, B.G., Gouvea, F., Neto, G.O., (1996) Anal. Lett., 29, p. 893Walcarius, A., (1998) Electroanalysis, 10, p. 1217Kubota, L.T., Gushikem, Y., (1992) Electochim. Acta, 37, p. 2477Carmo, D.R., Gushikem, Y., Franco, D.W., (1999), p. 325. , J.P. Blitz, C.B. Little (Eds.), Fundamental and Applied Aspects of Chemically Modified Surfaces, The Royal Society of Chemistry, CambridgeFord, P.C., (1970) Coord. Chem. Rev., 5, p. 75Taube, H., (1979) Pure Appl. Chem., 51, p. 901Stritar, J.A., Taube, H., (1969) Inorg. Chem., 8, p. 2281Taube, H., (1981) Comm. Inorg. Chem., 1, p. 17Forlano, P., Baraldo, L.M., Olabe, J.A., Della Védora, C.O., (1994) Inorg. Chim. Acta, 223, p. 37Bezerra, C.W.B., Silva, S.C., Gambardella, M.T.P., Santos, R.H.A., Plicas, L.M.A., Tfouni, E., Franco, D.W., (1999) Inorg. Chem., 38, p. 5660Wilkins, R.G., (1991) Kinetics and Mechanism of reactions of Transition Metal Chemistry, second ed., p. 183. , Wenhein, New YorkEllis, I.D., Sykes, G., (1973) J. Chem. Soc., Dalton Trans., p. 573Kubota, L.T., (1993), Ph.D. Dissertation, Unicamp, BrazilShriver, D.F., (1969) Manipulation of Air Sensitive Compounds, , Mc-Graw-Hill, New YorkDixon, N.E., Lawrance, G.A., Lay, P.A., Sargeson, A.M., (1984) Inorg. Chem., 23, p. 2940Meyer, T., Taube, H., (1968) Inorg. Chem., 7, p. 2369Lay, P.A., Mangunson, R.H., Sen, J., Taube, H., (1982) J. Am. Chem. Soc., 104, p. 7658Kalcher, K., Kauffmann, J.M., Wang, J., Svancara, I., Vytras, K., Neuhold, Z., Zang, Z.C., (1995) Electroanalysis, 7, p. 5Kormann, C., Bahnemann, D.W., Hoffmann, M.R., (1991) Environ. Sci. Technol., 25, p. 494Kondo, M.M., (1996), Ph.D. Dissertation, Delaware University, USACheng, S.F., Tsai, S.-J., Lee, Y.F., (1995) Catal. Today, 26, p. 87Adegite, A., Iyun, J.F., Ojo, J.F., (1977) J. Chem. Soc., Dalton Trans., 2, p. 115Allen, A.D., Stevens, J.R., (1972) Can. J. Chem., 51, p. 92Krentizen, H., (1976), Ph.D. Dissertation, Stanford University, USABhur, J.D., (1978), Ph.D. Dissertation, Stanford University, USATaube, H., (1976) Surv. Prog. Chem., 6, p. 31Endicott, J.F., Taube, H., (1989) Inorg. Chem., 4, p. 437Endicott, J.F., Taube, H., (1962) J. Am Chem. Soc., 84, p. 4984Kubota, L.T., Gushikem, Y., Perez, J., Tanaka, A., (1995) Langmuir, 11, p. 1009Kubota, L.T., Gushikem, Y., (1993) J. Electroanal. Chem., 362, p. 219Lim, H.S., Baclay, D.J., Anson, F., (1972) Inorg. Chem., 11, p. 1460Coleman, G.M., Gesler, J.W., Shirley, F.A., Kuemptel, J.R., (1973) Inorg. Chem., 12, p. 1036Shi, C., Anson, F., (1997) Inorg. Chem., 36, p. 263

Electrochemical Properties Of [ru(edta)(h2o)]- Immobilized On A Zirconium (iv) Oxide-coated Silica Gel Surface

[Ru(edta)(H2O)]- is strongly adsorbed on a zirconium(IV) oxide-coated silica gel surface. The immobilized complex showed an electrochemical response due to the Ru(II)/Ru(III) redox couple. By substituting the coordinated water molecule in the adsorbed complex, the midpoint potentials shifted in the order (in mV) water, -290; thiocyanate, -200; pyridine, -180; 4-cyanopyridine, -80: and pyrazine, -50 vs SCE.1841236240Steiger, B., Anson, F.C., (1994) Inorg. Chem., 33, p. 5767Abruna, H.D., (1988) Coord. Chem. Rev., 86, p. 135Barisci, J.N., Wallace, G.G., (1991) Anal. Lett., 24, p. 2059Cassidy, J.F., Vos, J.G., (1988) J. Electrochem. Soc., 135, p. 863Zaldivar, G.A.P., Gushikem, Y., (1992) J. Electroanal. Chem., 337, p. 165Kubota, L.T., Gushikem, Y., (1993) J. Electroanal. Chem., 362, p. 219Zaldivar, G.A.P., Gushikem, Y., Benvenutti, E.V., De Castro, S.C., Vasquez, A., (1994) Electrochim. Acta, 39, p. 33Da Cunha, L.J.V., Andreotti, E.I.S., Gushikem, Y., (1995) J. Braz. Chem. Soc., 6, p. 271Peixoto, C.R.M., Kubota, L.T., Gushikem, Y., (1995) Anal. Proc., 32, p. 503Kubota, L.T., Gushikem, Y., Perez, J., Tanaka, A.A., (1995) Langmuir, 11, p. 1009Milagres, B.G., Kubota, L.T., De Oliveira Neto, G., (1996) Electroanalysis, 8, p. 689Shimizu, K., Matsubara, T., Satô, G.P., (1974) Bull. Chem. Soc. Jpn., 47, p. 1651Bajaj, H.C., Van Eldik, R., (1988) Inorg. Chem., 27, p. 4052Matsubara, T., Creutz, C., (1979) Inorg. Chem., 18, p. 1956Matsubara, T., Creutz, C., (1978) J. Am. Chem. Soc., 100, p. 6255Araki, K., Rein, F.N., Camera, S.G., Toma, H.E., (1992) Trans. Met. Chem., 17, p. 535Bajaj, H.C., Van Eldik, R., (1990) Inorg. Chem., 29, p. 2855Oyama, N., Anson, F.C., (1978) J. Electroanal Chem., 88, p. 289Oyama, N., Anson, F.C., (1979) J. Am. Chem. Soc., 101, p. 1634Mukaida, M., Okuno, H., Ishimori, T., (1965) Nippon Kagaku Zasshi, 86, p. 589Perez, J., Tanaka, A.A., Gonzalez, E.R., Ticianelli, E.A., (1994) J. Electrochem. Soc., 141, p. 431Gushikem, Y., Iamamoto, M.S., (1990) J. Colloid Interface Sci., 134, p. 275Veselý, V., Pekárek, V., (1972) Talanta, 19, p. 219Chatterjee, D., Bajaj, H.C., Das, A., (1995) J. Chem. Soc. Dalton Trans., p. 2497Bard, A.J., Faulkner, L.R., (1980) Electrochemical Methods, Fundamentals and Applications, , Wiley, New YorkShigehara, K., Oyama, N., Anson, F.C., (1982) J. Am. Chem. Soc., 103, p. 2552Kubota, L.T., Gushikem, Y., (1993) J. Electroanal. Chem., 362, p. 219Toma, H.E., Creutz, C., (1977) Inorg. Chem., 16, p. 545Shepherd, R.E., Taube, H.E., (1973) Inorg. Chem., 12, p. 139

Xps Analysis Of Electronic Density Of Iron Tetraazamacrocycle Through Fe 2p Binding Energies On The 3-imidazolilpropyl-modified Surface Of Oxidized N-si(100)

This paper describes the preparation of metallo-organic thin films of [FeTIM(CH3CN)2]2+ complex, where TIM stands for 2,3,9,10-tetramethyl-1,4,8,11-traazacyclotetradeca-1,3,8,10-tetraene on oxidized silicon wafer, SiO2/Si, previously treated with 3-imidazolilpropyltrimethoxysilane, 3-IPTS. X-ray photoemission lines of Fe 2p were used to probe the iron chemical environment in the physically and chemically adsorbed macrocycle complexes. As FeTIM can bind CO, NO or N-heterocyele, a built-on Si wafer sensor device could be envisaged for these molecules. Copyright © 2004 John Wiley & Sons, Ltd.36812141217Mirkhalaf, F., Whittaker, D., Schiffrin, D.J., (1998) J. Electroanal. Chem., 452, p. 203Cao, C., Fadeev, A.Y., McCarthy, T.J., (2001) Langmuir, 17, p. 757Magalhães, J.L., Moreira, L.M., Rodrigues-Filho, U.P., Giz, M.J., Pereira-Da-Silva, M.A., Landers, R., Vinhas, R.C.G., Nascente, P.A.P., (2002) Surf. Interface Anal., 33, p. 293Baldwin, D.A., Pfeifer, R.M., Reichgot, D.W., Rose, N.J., (1993) J. Am. Chem. Soc., 95, p. 5152Hamilton, D.E., Lewis, T.J., Kildahl, N.K., (1979) Inorg. Chem., 12, p. 3364Moreira, J.C., Gushikem, Y.J., (1990) Colloid Interface. Sci, 107, p. 70Moulder, J.F., Stickle, W.F., Sobol, P.E., Bomben, K.D., (1992) Handbook of X-ray Photoelectron Spectroscopy, , Perkin-Elmer: Eden Prairie, MNLeclercq, G., Pireaux, J.-J., (1995) J. Electron Spectrosc. Relat. Phenom., 71, p. 141Horr, T.J., Arora, P.S., (1997) Coll. Surf. A: Physicochem. Eng. Asp., 126, p. 113Méndez, A., Bosch, E., Rosés, M., Neue, V.D., (2003) J. Chromatogr. A, 986, p. 33Kovacs, D., Shepherd, R.E., (1979) J. Inorg. Biochem., 10, p. 67Joly, W.L., (1984) Modern Inorganic Chemistry, p. 171. , McGraw-Hill: SingaporePankratov, A.N., Uchaeva, I.M., Doronin, S.Yu., Chernova, R.K., (2001) J. Struct. Chem., 42, p. 739Maksic, Z.B., Vianello, R., (2002) J. Phys. Chem., 106, p. 419Kabir, S., Sapse, A.-M., (1991) J. Comput. Chem., 12, p. 114