Inorganic additives zirconium phosphates

Zirconium phosphate, which is easily prepared by the addition of a solution of zirconyl nitrate or chloride to a phosphate solution is extremely insoluble and will not dissolve in solutions of high or low pH. It is an inorganic polymer of composition Zr(H2P04)2-H20 and a relative... 

Also the addition of inorganic materials to enhance water retention and/or proton conductivity has had some success, for example, by adding zirconium phosphate. Such additions have also been successful in increasing the mechanical strength of materials [26, 27]. 

He et al. investigated the use of zirconium phosphate (ZrP) in a PA/PBI system [49]. The conductivity of m-PBI with a doping level of 5.6 PA/PRU increased from 0.068 S cm to 0.096 S cm with the addition of 15 wt% ZrP at 200°C and at 5% relative humidity. As seen in Fig. 13.11, the conductivity of the membrane increased as the relative humidity and temperature of its environment increased. Conductivities of other inorganic fillers, such as phosphotungstic acid, sUicotungstic acid, and tricarboxylbutylphosphonate, are comparable or lower than that of ZrP. Unfortunately, there have been no fuel cell performance tests published on these systems. Overall, these inorganic fillers improved the conductivity of m-PBI membranes. 

The primary drawbacks of the Nafion membranes are poor conductivity at low relative humidities (and consequently at temperatures >100 C and ambient pressure) and large crossover of methanol in direct methanol fuel ceU (DMFC) applications. As a result, considerable efforts have been made in recent years to overcome these drawbacks. Peihaps the most widely employed approach is the addition of inorganic additives to Nafion m branes to yield organic/inorganic composite membranes. Three major types of inorganic additives that have been studied (zirconium phosphates, heteropolyadds, metal hydrogen sulfates and metal oxides) are reviewed in the following. 

To improve proton transport of PFSA membranes at high temperatures and in order to operate PFSA membranes at temperatures above 100°C, inorganic compounds such as Si02 and Ti02 were employed as additives to retain water in the Naflon membranes for an acceptable proton conductivity. Proton conductors such as zirconium phosphate, heteropolyacid/ and heterocycle compounds including imidazole,benzimidazole, triazole, and polyfunctional phosphonic acid were also added in the Naflon membrane. In addition, ionic liquids were applied to fabricate composite Naflon membranes due to their anhydrous high conductivity and good thermal stability. Besides, Naflon/Naflon-functionalized multiwalled carbon nanotube composite membrane exhibits a remarkable improvement in proton conductivity compared to the pristine Naflon membrane. ... 

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