Nafion membranes zirconium phosphates

Yang, C., Srinivasan, S., Bocarsly, A. B., Tulyani, S. and Benziger, J. B. 2004. A comparison of physical properties and fuel cell performance of Nafion and zirconium phosphate/Nafion composite membranes. Journal of Membrane Science 237 145-161. 

P. Costamagna, C. Yang, A.B. Bocarsly and S. Srinvasan, Nafion 115/zirconium phosphate composite membranes for operation of PEMFCs above 100 °C, Electrochim. Acta, 2002, 47, 1023-1033 C. Yang, S. Srinivasan, A.S. Arico, P. Creti, V Baglio and Y Antonucci, Electrochem. Solid-State Lett., 2001, 4, A31-A34. 

P. Costamagna, C. Yang, A. B. Bocarsly and S. Srinivasan, Nafion 115/zirconium phosphate coposite membranes for operation of PEMFC above 100°C, Electrochirru Acta 47,1023-1033 (2002). 

Chapter 11 also includes the polymer inorganic membranes consisting of Nafion and zirconium phosphates, heteropolyacids, metal hydrogen sulfates and metal oxides. Moreover, this chapter includes the design of thin film electrodes for MFA. 

Sahul, A.K., Pitchumani, S., Sridhar, P., and Shukla, A.K. (2009) Co-assembly of a Nafion-mesoporous zirconium phosphate composite membrane for PEM fuel cells. Fuel Cells, 9,139-147. 

Costamagna P, Yang C, Bocarsly A B, Srinivasan S (2002) Nafion 115 Zirconium phosphate composite membranes for operation of PEMFCs above 100 C. Electrochim Acta, 47, pp. 1023-1033. 

Particularly, in the case of proton-conducting zirconium phosphate prepared via in situ growth within the preformed membrane,the proton conductivity of the highly dispersed filler may have some significance at high temperature and low humidity, where the conductivity of pure Nafion strongly decreases. 

The crossover of methanol has caused problems in finding a suitable membrane material. On the positive electrode side, methanol combines with oxygen to form CO2. Among the alternatives to pure Nafion are Nafion filled with zirconium phosphate or grafted with styrene to inhibit methanol transport (Bauer and Willert-Porada, 2003 Sauk et al., 2004), as well as non-Nafion membrane materials such as sulfonated polyimide (Woo et al., 2003). None have achieved performance as good as the one shown in Fig. 3.53, which, however, has a substantial methanol crossover rate. 

FIGURE 21.45 Polarization curves of PEMFCs based on Nation 115 and Nafion 115-a-ZrP (123 wt%) at 130°C and 3 atm with reactants humidified at 130°C. (Reprinted from Electrochim. Acta, Nafion (R) 115/zirconium phosphate composite membranes for operation of PEMFCs above 100 degrees C., 47, 2002, 1023, Costamagna, R, Yang, C., Bocarsly, A.B., Srinivasan, S. With permission from Elsevier.)... 

Yang C, Srinivasan S, Aric6 AS, Creti P, Baglio V, Antonucci V (2001) Composite Nafion/ zirconium phosphate membranes for direct methanol fuel cell operation at high temperature. 

A few examples of Nafion composite membranes with polymers and inorganic compotmds has been reported, such as poly(ethylene glycol) (PEG)/Si02 [155], PTFE/S102 [156], chitosan/phosphotungstic acid [157], PVI/Pd [158], and PBI/zirconium phosphate [159]. 

In the case of Nafion/zirconium phosphate membranes an increase of the water and a decrease of the methanol uptakes is observed with increasing content of the inorganic phase. 

The preference of Nafion for up taking methanol over water is certainly an undesirable property for DMFC using this proton conducting membrane. It would be worth to review the effect of inorganic or organic Nafion composite membranes on the sorption of water-methanol from the liquid phase and on the partition constant. The few reported studies include Nafion/sulfonated organosilica [47] and Nafion/zirconium phosphate [78], where a reduction of the total liquid uptake is observed for the composites in methanol solutions up to 10 M, attributed to a reduction of the free volume in the ionic clusters. 

Figure 6.26 also shows the results of maximum overall efficiency obtained with reported results for Nafion 117/S102 [41], Nafion 117 and 115/zirconium phosphate [41, 78], Nafion 117/titanium phosphate [41], and Nafion 112/PVA [111] composites at different temperatures between 75 °C and 90 °C. We have chosen these membranes because the measured power densities exceed, or are close, to 100 mW.cm , which is a reasonable value for DMFC at temperatures between 70 °C and 90 °C. 

DMFC operated at temperatures above 100 °C exhibit the highest power densities, from 195 to 320 mW.cm at 110 °C up to 240-420 mW.cm at 145 °C, and they correspond to inorganic fillers such as Si02 and binary Si02/ hetropolyacids [30-32], zeolites [52, 53], montmorillonites [61], and zirconium phosphate [75], which prevent Nafion dehydration upon. All these membranes, whose methanol selectivity were not determined in most of the cases, exhibit moderated but systematic DMFC performance improvement (1.1 < RMPD < 1.4) compared to pristine Nafion in both, passive and active cells. 

Casciola M, Bagnasco G, Domiadio A, Micoli L, Pica M, Sganappa M, Turco M (2009) Conductivity and methanol permeability of Nafion-zirconium phosphate composite membranes containing high aspect ratio filler particles. Fuel Cells 9 394-400... 

Chen LC, Yu TL, Lin HL, Yeh SH (2008) Nafion/PTFE and zirconium phosphate modified Nafion/PTFE composite membranes for direct methanol fuel cells. J Membr Sci 307 10-20... 

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