Proton-Conducting Properties and Microstructure of Hydrated Tin Dioxide and Hydrated Zirconia

Hara, Shinji; Takano, Shuro; Miyayama, Masaru

doi:10.1021/jp0370369

Cited by 40 publications

(29 citation statements)

References 34 publications

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“…We have previously reported on the preparation of composite membranes incorporating in a SPEEK matrix SnO 2 (nH 2 O [31], which is a proton conducting material due to its partially protonated oxide-hydroxide surface [32][33][34]. The durability and electrochemical characteristics of such membranes were largely improved with respect to pure SPEEK, and their performance in a DMFC single cell operating at 100°C was superior to that of Nafion [31].…”

Section: Introductionmentioning

confidence: 95%

Effect of a Proton Conducting Filler on the Physico‐Chemical Properties of SPEEK‐Based Membranes

Mecheri

D’Epifanio

Pisani³

et al. 2009

Fuel Cells

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Composite membranes based on sulphonated polyetherether ketone (SPEEK) having a 60% degree of sulphonation (DS = 0.6) and containing 23 and 50 wt.‐% hydrated tin oxide (SnO2·nH2O) were prepared and characterised. The lower water uptake (WU) and the higher conductivity values recorded for the composite membranes with respect to pure SPEEK reference suggested the involvement of SnO2·nH2O in the proton conduction mechanism. Pulsed‐field‐gradient spin‐echo (PFGSE) NMR was employed to obtain a direct measurement of water self‐diffusion coefficient in the membranes. Differences were observed between the unfilled SPEEK and the composites, including departures from the normal correlation between water diffusivity and proton conductivity in the case of composites. To better understand the SnO2·nH2O effect on the proton transport properties of the SPEEK‐based membrane, we employed an analytical model that predicts the membrane conductivity as a function of its hydration level and porous structure. The comparison of the model results with the experimental proton conductivity values demonstrated that the tin oxide phase provides additional paths between the water clusters for proton transport, resulting in reduced tortuosity and enhanced proton conductivity. Moreover, the composite showed reduced methanol crossover with respect to the unfilled membrane.

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Section: Introductionmentioning

confidence: 95%

Effect of a Proton Conducting Filler on the Physico‐Chemical Properties of SPEEK‐Based Membranes

Mecheri

D’Epifanio

Pisani³

et al. 2009

Fuel Cells

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“…Moreover, depending on the degree of hydration, many oxides become good proton conductors. Hydrated tin dioxide, for example, exhibits high conductivity at a relatively low humidity, being one of the most effective compound in retaining water [12]. Recently, the addition of SnO 2 nanopowders to polymer electrolyte membranes was found to be extremely beneficial under operating cell condition of 120 °C and low RH [13–15].…”

Section: Introductionmentioning

confidence: 99%

Composite Nafion/Sulfated Zirconia Membranes: Effect of the Filler Surface Properties on Proton Transport Characteristics

et al. 2009

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Due to their strong acidity and water affinity, sulfated zirconia nanoparticles were evaluated as inorganic additives in the formation of composite Nafion-based membranes. Two types of sulfated zirconia were obtained according to the preparation experimental conditions. Sulfated zirconia-doped Nafion membranes were prepared by a casting procedure. The properties of the composite membranes were compared with those of an unfilled Nafion membrane obtained by the same preparation method. The water uptake, measured at room temperature in a wide relative humidity range, was higher for the composite membranes, this confirming the hydrophilic nature of the selected additives. The membrane doped by zirconia particles having the highest sulphate group concentration showed the highest water diffusion coefficient in the whole range of temperature and relative humidity investigated due to the presence of SO42− providing extra acid sites for water diffusion. The proton diffusivity calculated from impedance spectroscopy measurements was compared with water self diffusion coefficients measured by NMR Spectroscopy. The difference between proton and water diffusivity became significant only at high humidification levels, highlighting the role of water in the intermolecular proton transfer mechanism. Finally, great improvements were found when using the composite membrane as electrolyte in a fuel cell working at very low relative humidity.

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“…Figure 4 shows the TG curves of SnO 2 ·nH 2 O and S-SnO 2 powders. As far as SnO 2 ·nH 2 O is concerned, the main weight loss (about 12 % of the total loss), observed in the 50-150 °C range, can be attributed to the loss of physisorbed water, while the loss of structural and bound water occurred gradually between 250 and 450 °C [43][44][45]. The TG profile of S-SnO 2 shows two different weight losses; the first one, occurring in the 50-150 °C range, corresponds to water desorption, whereas the weight loss occurring in the 600-760 °C range (about 4% of the total loss) can be attributed to the splitting off of sulfate groups bound to the surface of SnO 2 crystallites [46].…”

Section: Conductivitymentioning

confidence: 99%

Development of Nafion/Tin Oxide Composite MEA for DMFC Applications

et al. 2010

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Wiley-VCH AbstractNafion composite membranes containing either hydrated tin oxide (SnO 2 ·nH 2 O) or sulfated tin oxide (SSnO 2 ) at 5 wt.% and 10 wt.% were prepared and characterized. The structural and electrochemical features of the samples were investigated using X-ray diffraction, electrochemical impedance spectroscopy, methanol crossover, and direct methanol fuel cell (DMFC) tests. Highest conductivity values were obtained by using S-SnO 2 as filler (0.094 Scm -1 at T=110°C and RH=100%). The presence of the inorganic compound resulted in lower methanol crossover and improved DMFC performance with respect to a reference unfilled membrane. To improve the interface of the membrane electrode assembly (MEA), a layer of the composite electrolyte (i.e., the Nafion membrane containing 5 wt% S-SnO 2 ) was brushed on the electrodes, obtaining a DMFC operating at 110°C with a power density (PD) of 100 mWcm -2 which corresponds to a PD improvement of 52% with respect to the unfilled Nafion membrane.

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Proton-Conducting Properties and Microstructure of Hydrated Tin Dioxide and Hydrated Zirconia

Cited by 40 publications

References 34 publications

Effect of a Proton Conducting Filler on the Physico‐Chemical Properties of SPEEK‐Based Membranes

Effect of a Proton Conducting Filler on the Physico‐Chemical Properties of SPEEK‐Based Membranes

Composite Nafion/Sulfated Zirconia Membranes: Effect of the Filler Surface Properties on Proton Transport Characteristics

Development of Nafion/Tin Oxide Composite MEA for DMFC Applications

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