Polymer-electrolyte fuel cells humidity

The Nafion membrane, for instance, has shown good performance in fuel cells but has certain limitations, i.e., it has poor ionic conductivity at low humidity and is available at an expensive rate of 500 /m. The costs for Nafion , for example, become attractive only at high production voliunes [3]. Consequently, the search for new membrane materials with low cost and the required electrochemical characteristics, along with performances matching those of Nafion , is continuing and has become the most focused research area in the design of polymer electrolyte fuel cells. 

Wang, Y. (2009) Porous-media flow fields for polymer electrolyte fuel cells, I. Low humidity operation. J. Electrochem. Soc., 156 (10), B1124-B1133. 

Inoue, G., Yoshimoto, T., Matsukuma, Y., Minemoto, M., Itoh, H., and Tsummaki, S. (2006) Numerical analysis of relative humidity distribution in polymer electrolyte fuel cell stack including cooling water. /. Power Sources, 162 (1), 81-93. 

Wang, Y. and Wang, C.Y. (2005) Simulations of flow and transport phenomena in a polymer electrolyte fuel cell under low-humidity operations. J. Power Source, 147, 148. 

Hydrocarbon Membranes for Polymer Electrolyte Fuel Cells, Fig. 3 Humidity dependence of the proton conductivity of SPESK block copolymer membrane (lEC = 1.62 meq/g) at 80 °C and 110 °C... 

Polymer Electrolyte Fuel Cells, Perfluorinated Membranes, Fig. 3 Decomposition mechanism of PFSA polymer under low humidity conditions. 

Lindstrom RW, Kortsdottir K, Wesselmark M et al (2010) Active area determination of porous Pt electrodes used in polymer electrolyte fuel cells temperature and humidity effects. J Electrochem Soc 157 B1795-B1801... 

FIGURE 11.2 Polarization curves at wirious periods in time (0, 500, 5348, 10,100, 15,000, 20,000, and 26,330 h) during the life test. Cell temperature 70°C. Air 2.0 stoichiometry, ambient pressure, 100% relative humidity. Hydrogen 1.2 stoichiometry, ambient pressure, and 100% relative humidity. (Reprinted from Journal of Power Sources, 158, Gleghorn, S.J.C. et al., A polymer electrolyte fuel cell life test 3 years of continuous operation, 446-454, Copyright (2006), with permission from Elsevier.)... 

Fig. 10 Comparison of voltage losses of low- and high-temperature fuel cells at 0.2 A cm (a) and 0.8 A cm (b). Experimental conditions for the low-temperature polymer electrolyte fuel cell (LT-PEFC) were as follows Pt/Ketjenblack, 0.4mgp cm , 80°C, ISOkPa, 66% relative humidity (inlet), residence time 1.3 s. Experimental conditions for the high-temperatmc polymer electrolyte fuel cell (HT-PEFC) were as follows platinum alloyA ulcan XC72, 0.7mgp, an 160°C, lOOkPa, dry gases, residence time 2.5 s. (The data for the LT-PEFC were extracted from Yu et al. 2006)...

Q. Dong, M. M. Mench, S. Cleghom and U. Beuscher, Distributed Performance of Polymer Electrolyte Fuel Cells under Low-Humidity Conditions, J. Electrochem. Soc., Vol. 152, pp. A2114-A2122, 2005. 

Bxtensive research is continuing to be conducted into ways to improve polymer membrane fuel cells (PBMFCs), as outlined in recent reviews. " One particular problem associated with PBMFCs is that the proton-conducting membranes require the use of aqueous electrolyte solutions to obtain high proton conductivity, which causes their proton conductivity to be affected by changes in temperature and humidity, limits their use to <100 °C, and requires the constant replacement of lost water. A potential benefit of using PILs as electrolytes in PBMFCs is that the solutions can be anhydrous and, hence, can be operated at temperatures in excess of 100 °C. 

The initial fuel cell response to changes in load show is rapid with a time constant 1 s this corresponds to the convective flow into the fuel cell and the diffusion across the gas diffusion layer, ti and T2. Diffusion across the polymer membrane from the cathode/electrolyte interface to the anode, T3, is evident in Figure 3.9B, where the relative humidity change at the anode lags the change at the cathode by 100 s. 

Park, K.T., Jnng, U.H., Choi, D.W., Chun, K., Lee, H.M. and Kim, S.H. 2008. ZrOj-SiOy Nafion composite membrane for polymer electrolyte membrane fuel cells operation at high temperature and low humidity. 177(2) 247—253. 

One of the frequently advertised advantages of the phosphoric acid imbibed polybenzimidazole systems is their zero water drag coefficient and their possibihty to operate with dry hydrogen and oxygen. However, a vast literature has been devoted to the study of the proton conduction and the effect of relative humidity on the conductivity of the PBl-phosphoric acid system. The promoting effect and the physicochemical interactions of water vapors with the polymer electrolyte and on the fuel cell performance have been explicitly shown for the PBl/PPy(50)coPSF 50/50 polymer blend imbibed with phosphoric acid under fuel cell conditions. ... 

T. Tran Duy, S.I. Sawada, S. Hasegawa, Y. Katsumura, Y. Maekawa, Poly(ethylene-co-tetrafluoroethylene)(ETFE)-based graft-type polymer electrolyte membranes with different ion exchange capacities relative humidity dependence for fuel cell applications, J. Membr. Sci. 447 (2013) 19-25. 

Xie D, Jiang YD, Pan W, Li D, Wu ZM, Li YR (2002) Fabrication and characterization of polyanUine-based gas sensor by ultra-thin film technology. Sens Actuators B 81 158-164 Yasuda A, Doi K, Yamaga N, Fujioka T, Kusanagi S (1992) Mechanism of the sensitivity of the planar CO sensor and its dependency on humidity. J Electrochem Soc 139 3224-3229 Zawodzinski TA, Springer TE, Uribe F, Gottesfeld S (1993) Characterization of polymer electrolytes for fuel cell applications. Solid State Ionics 60 199-211... 

The proton conductive polymer electrolyte used to separate the anode and cathode compartments of fuel cells. The membrane replaces the liquid electrolytes used in some fuel cells. The voltage produced by a fuel ceU stack at a defined current density. A performance or polarization curve refers to a plot of the cell potential (V) versus current density (1) under specified conditions of pressure, temperature, humidity, and reactant stoichiometry. 

Fig. 6.14 The corresponding partial pressures of water at different relative humidity in the temperature range relevant for high-temperature polymer electrolyte membrane fuel cells...

Hinds G, Stevens M, Wilkinson J, de Podesta M and Bell S (2009), Novel 7 situ measurements of relative humidity in a polymer electrolyte membrane fuel cell , J. Power Sources, 186, 52-57. 

FIGURE 8.14 Voltage versus time curves with various levels of toluene at different current densities. Cell temperature = 80°C, Relative humidity = 80%, 30 psi back pressure, stoichiometry 1.5/3.0 for Hj/air. (Reprinted from Journal of Power Sources, 185, Li, H. et al. Polymer electrolyte membrane fuel cell contamination Testing and diagnosis of toluene-induced cathode degradation, 272-279, Copyright (2008), with permission from Elsevier.)... 

FIGURE 10.28 Effect of RH on fuel cell internal resistances (RC = electrode resistance, RM = membrane resistance). (Reprinted from /. Power Sources, 184, L. A. M. Riascos. Relative humidity control in polymer electrolyte membrane fuel cells without extra humidification, 204-211, Copyright (2008), with permission from Elsevier.)... 

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