Preparation and Characterization of Perfluorosulfonate‐Free Phosphosilicate Glass‐Based Composite Proton‐Exchange Membrane

Abstract

Based on hydrothermally treated phosphosilicate (SiO2–P2O5) glass and sulfonated poly(ether ether ketone) (SPEEK) polymer, perfluorosulfonate‐free SiO2–P2O5/SPEEK composite membranes are prepared. The morphology, thermal and mechanical properties, pore structure, proton conductivity, water uptake, as well as the fuel cell performances of the SiO2–P2O5/SPEEK composite membranes are investigated. The SiO2–P2O5/SPEEK composite membranes with proton conductive SiO2–P2O5 glass powders of more than 50 wt.% were determined to be flexible due to the incorporation of the SPEEK polymer component, and it showed proton conductivities of above 10–2 S cm–1. A single H2/O2 fuel cell was assembled based on the SiO2–P2O5/SPEEK composite membrane, and was found to release a peak power density of 355.6 mW cm–2 at 68 °C.

Phosphorus stably bonded to a silica gel matrix through niobium bridges

“…The sol-gel synthesis of mixed oxide materials containing SiO 2 and P 2 O 5 has recently attracted great attention as a consequence of their functional properties. In fact, these materials nd applications as proton exchange membranes in fuel cells, [1][2][3][4][5] bioactive materials [6][7][8][9] and exhibit very interesting surface acidic properties, making them very attractive as solid acid catalysts. 10 Diverse protonic conduction abilities as well as Brønsted acid site distributions were found in these materials as a consequence of the variation in the Si/P molar ratio 11 and the preparation procedure 10 altering the distribution of P-species in the siloxane network.…”

Composite proton exchange membranes based on phosphosilicate sol and sulfonated poly(ether ether ketone) for fuel cell applications

“…Clearly, the output power of the fuel cell using the composite membrane 7SPEEK/3(PeSi) is not only significantly higher than that of the cell using pure SPEEK, but also slightly higher than that of cell equipped with Nafion 212 membrane, which is probably because the composite membrane has higher proton conductivity under the measurement conditions. Moreover, the peak power density of the cell using 7SPEEK/3(PeSi) membrane is much higher than the value of 20.8 mW cm À2 released by a fuel cell based on phosphosilicate glass and the value of 355.6 mW cm À2 released by a fuel cell based on the composite membrane of SPEEK and phosphosilicate powders [20,35]. The main reason is probably that the composite membrane 7SPEEK/ 3(PeSi) obtained in this study shows a better flexibility; and therefore, it could endure adequate hot-pressing to acquire better interfacial contacts between the electrolyte membrane and the GDE without causing cracks in the membrane when assembled, which is of great importance for obtain high output power.…”

“…Our previous study showed that phosphosilicate glass possessed an excellent conductivity of above 10 À1 S cm À1 and we also reported a composite membrane based on phosphosilicate glass powders and SPEEK [19,20]. Although the composite membrane displayed relatively good proton conductivity and fuel cell performance; however, the mechanical properties of the composite membrane was affected seriously by the direct incorporation of phosphosilicate powers, insufficient to meet the needs of practical applications.…”

“…Each of the TGA curves features two main degradation steps: the first step in the temperature range of 190e350 C is attributed to the loss of the sulfonic acid groups and the second one above 360 C corresponds to the thermal decomposition of the main chain of SPEEK. The weight loss in the temperature range of 190e350 C is associated with both the elimination of sulfonic acid groups and the loss of water molecules interacting with SO 3 H or SiOH groups through hydrogen bonds [20,26]; and the weight loss above 360 C may be attributed to the Table 1 Atom percentage of each element of the chosen points in Fig. 4 thermal degradation of the polymer main chain.…”

“…In addition, from Fig. 7, it can be clearly seen that the SPEEK has degraded completely at the temperature above 760 C under air conditions; while for the composite membranes, there are some residues above 760 C and the amount of the residues is higher than the amount of phosphosilicate added into the composite membranes, indicating that there are certain amount of the polymer remaining in the residues and that the incorporation of phosphosilicate is able to enhance the thermal stability of the composite membranes, allowing it to be operated in a higher temperature range [20].…”