Effect of Silicotungstic Acid (STA) on the Performance of a Polymer Electrolyte Fuel Cell (PEMFC) Based on Nafion® Cast in Dimethylformamide

Abstract

A casting process for composite Nafion®/STA membranes was achieved. The membrane casting was based on the evaporation of 5% Nafion® solution in N,N′‐dimethylformamide (DMF) with and without silicotungstic acid (STA) as an additive. Optimized parameters for the casting process were determined. The water uptake and the ionic conductivity of the cast membranes were measured. The variation of the volume of Nafion® and the STA concentrations on the water uptake and conductivity of the cast membranes were investigated under various conditions. The sulphuric acid uptake was also determined. The effect of the membrane soaking conditions, on water uptake and conductivity, were determined. The contribution of the (‐SO3H) groups, the STA species, and/or the sulphuric acid to the membrane properties was discussed. The performance of hydrogen/oxygen (H2/O2) PEM Fuel Cells based on the membranes cast with STA was compared to those based on membranes cast without STA. It was shown that the water uptake of the cast membrane increased from 18% to 50% when the STA concentration used in the casting bath increased from 0 to 5 × 10–3�M. For the membrane fabricated without STA, the water uptake and the conductivity do not change with membrane thickness, whereas for the membranes cast with STA, the water uptake and the conductivity increase with membrane thickness. A performance improvement of 0.3 A cm–2 at 0.6 V was obtained with the H2/O2 PEM fuel cell based on membranes cast with STA, compared to the performance of the cell based on membranes cast without STA. On the other hand, this performance improvement, for the cells based on the membranes cast in DMF (0.3 A cm–2 at 0.6 V), is higher than that for the cells based on membranes cast in aqueous electrolyte (0.15 A cm–2 at 0.6 V).It was anticipated that soaking the membranes in sulphuric acid might improve their performance for H2/O2 PEMFC applications.

Molecular dynamics simulation of Keggin HPA doped Nafion® 117 as a polymer electrolyte membrane

“…They reported that the maximum power density for a SiW 4À -based membrane was even lower than that for a bare Naon®-silica membrane. Tian and Savadogo 19,20 fabricated a Naon®/SiW 4À composite membrane with different concentrations of SiW 4À . The water uptake of the SiW 4À doped membrane was signicantly higher than that of Naon® 117 and increased with the SiW 4À concentration.…”

The Ionic Conductivity of a Nafion® 1100 Series of Proton‐exchange Membranes Re‐cast from Butan‐1‐ol and Propan‐2‐ol

“…Cast membranes have also been used in the production of self-humidifying membranes, where hygroscopic oxides, such as SiO 2 [12] TiO 2 [13], silicotungstic acid (STA) [14] and SiO 2 + TiO 2 + nanocrystallites of Pt [15], have been incorporated into the polymer matrix. The platinum provides a catalytic site for the combination of H 2 and O 2 while the water produced is retained by the hygroscopic oxides, providing a low electrical resistance and reduced crossover.…”

Organic/Inorganic Nanocomposite Membranes Development for Low Temperature Fuel Cell Applications

“…The latter membrane compared favorably with recast Nafion ® , which had an areaspecific resistance of 0.19 Ω cm -2 under the same conditions. Savadogo and co-workers (Savadogo, 2004;Tazi & Savadogo, 2000Tian & Savadogo, 2005) prepared composite www.intechopen.com membranes constituted of recast Nafion ® and mixed with appropriate concentration of HPA, namely, silicotungstic acid (STA), phosphotungstic acid (PTA) and phosphomolybdic acid (PMA). It was shown that the water uptake of the various membranes increases in this order: Nafion ® 117 (27%) < Nafion ® /STA (60%) < Nafion ® /PTA (70%) < Nafion ® /PMA (95%).…”