Evaluation of nafion-SiOsub(2) hybrids as electrolytes in PEMFC operating at high temperature
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2008
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INTERNATIONAL SOCIETY OF ELECTROCHEMISTRY, 6th
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Nafion-SiO2 hybrid membranes were prepared by the incorporation of SiO2 into
commercial Nafion 115 and evaluated as electrolytes in H2/O2 proton exchange
membrane fuel cells (PEMFC). Hybrid membranes were produced by in-situ sol-gel
method with different SiO2 contents by using Tetraethyl Ortosilicate (TEOS) as the
silicon precursor. The catalytic parameters, such as the nature of alcohol (methanol,
ethanol, and 2-propanol); concentration of the acid catalyst (HNO3, 0.2-2.0 mol L-1);
reaction temperature (25-90ºC); and the precursor concentration (0.5-2.0 mol L-1) were
studied. Gravimetric analysis revealed that degree of incorporation of SiO2 is in the 4-
10 wt% range. The obtained values are strongly dependent, mainly, on both the alcohol
nature and TEOS concentration. Energy dispersive X-ray analysis (EDX) showed that
the inorganic phase is well distributed across the membrane thickness, indicating that
the synthesis methodology provides homogeneous dispersion of the nanoparticles into
the polymeric matrix. The stability of the hybrids was evaluated after successive
washings in H2SO4 0,5 mol.L-1 and water at 70ºC employed to remove surface residues.
The water uptake data have showed a ~50% increase for the hybrid membranes in
comparison to Nafion 115. Gas diffusion electrodes were prepared with Pt/C catalyst
(E-tek, 20 %wt) with a loading of 0.4 mg cm-2 for both anode and cathode. Polarization
curves of fuel cells operating with water-saturated hydrogen and oxygen gases were
obtained galvanostatically with 5 cm2
electrode area single cells. Measurements were
carried out in the 80 - 130ºC temperature range with total absolute pressure of 3 atm
(RH=100%) and at 130 °C with reduced relative humidity (RH = 75 and 50%). The
polarization curves using hidryds Nafion-SiO2 5% (wt/wt) with electrolyte showed that
the addition of a inorganic phase has not changed significantly the ohmic drop
polarization of fuel cells and up to 120ºC both the pure Nafion and Nafion-SiO2 hybrids
display comparable performances. With further increase in the operating temperature to
130ºC the performance of the Nafion-SiO2 hybrid was maintained and, in contrast, the
unmodified Nafion showed a pronounced decrease of the performance. Such different
temperature dependence represents a performance of ~40% superior of the Nafion-SiO2
hybrid at 130ºC in comparation with unmodified Nafion. This response is probably
attributed to the higher water retention capacity of the SiO2 present in hybrids
membrane, in agreement with the water uptake data.
In summary, hybrids based on Nafion-SiO2 were effectively prepared by the
incorporation of the inorganic phase into commercial Nafion by an optimized sol-gel
route. A significant enhancement of the fuel cell performance was evidenced at 130ºC,
indicating that ionic conductivity was sustained at high temperature, probably, due to
the increase of the water retention capacity of the hybrids conferred by the hygroscopic
property of the SiO2.
Como referenciar
DRESCH, M.A.; ISIDORO, R.A.; FONSECA, F.C.; LINARDI, M.; SANTIAGO, E.I. Evaluation of nafion-SiOsub(2) hybrids as electrolytes in PEMFC operating at high temperature. In: INTERNATIONAL SOCIETY OF ELECTROCHEMISTRY, 6th, Foz do Iguacu, PR. Abstract... p. 326-327. Disponível em: http://repositorio.ipen.br/handle/123456789/19313. Acesso em: 30 Dec 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.