Pore-filling electrolyte membranes

Navarro, A., del Rio, C. and Acosta, J.L. 2008. Pore-filling electrolyte membranes based on microporous polyethylene matrices activated with plasma and sulfonated hydrogenated styrene butadiene block copolymer. Synthesis, microstructural and electrical characterization. J. Pohm. Sci. B Polvm. Phvs. 46 1684-1695. 

Fig. 16.2 The concept of a pore-filling electrolyte membrane. The real substrate matrix has an isotropic structure, and the pores are not cylindrical and they are interconnected...

We fabricated an MEA using pore-filling electrolyte membranes and measured their fuel cell performance in PEMFC operation using pure hydrogen gas as a fuel. The membrane was prepared using a cross-linked polyethylene (CLPE) film as Ihe porous substrate and poly(aciylamide J rJ-butyl sulfonic acid) (AXES) as Ihe filling electrolyte. 

The pore-filling membranes can reduce methanol crossover in wide range of methanol concentrations due to the suppression effect of the substrate matrix. A membrane-electrode assembly using pore-filling electrolyte membranes... 

T. Yamaguchi, H. Hayashi, S. Kasahara and S. Nakao, Plasma-graft pore-filling electrolyte membranes using a porous poly(tetrafluoroethylene) substrate. Electrochemistry, 70(12), 950-952 (2002). 

In this process, the first network generally determines the morphology of the final material. In addition, the composition range is limited by the maximum swelling capacity of the first network by the second network of precursors. It is important to note that the pore-filling electrolyte membranes can be considered as IPNs depending on whether or not the polymer substrate is crosslinked. Indeed, the pores of a porous polymer substrate are filled with polyelectrolyte precursors and the linear or network polyelectrolyte is synthesized within the porous substrate [69]. Ihis is shown in Figure 15.4. 

S. Alwin, S.D. Bhat, A.K. Sahu, A. Jalajakshi, P. Sridhar, S. Pitchumani, A.K. Shukla, Modified-pore-filled-PVDF-membrane electrolytes for direct methanol fuel cells, /. Electrochem. Soc., 158 (2011) B91-B98. 

This theory will be demonstrated on a membrane with fixed univalent negative charges, with a concentration in the membrane, cx. The pores of the membrane are filled with the same solvent as the solutions with which the membrane is in contact that contain the same uni-univalent electrolyte with concentrations cx and c2. Conditions at the membrane-solution interface are analogous to those described by the Donnan equilibrium theory, where the fixed ion X acts as a non-diffusible ion. The Donnan potentials A0D 4 = 0p — 0(1) and A0D 2 = 0(2) — 0q are established at both surfaces of the membranes (x = p and jc = q). A liquid junction potential, A0l = 0q — 0P, due to ion diffusion is formed within the membrane. Thus... 

The conductivity of membranes that do not contain dissolved ionophores or lipophilic ions is often affected by cracking and impurities. The value for a completely compact membrane under reproducible conditions excluding these effects varies from 10-8 to 10 10 Q 1 cm-2. The conductivity of these simple unmodified membranes is probably statistical in nature (as a result of thermal motion), due to stochastically formed pores filled with water for an instant and thus accessible for the electrolytes in the solution with which the membrane is in contact. Various active (natural or synthetic) substances... 

The first one makes use of the pores of membranes as templates for the electrolytic growth of metal nanorods. This technique consists of coating one side of a membrane with a metal electrode (such as gold or platinum) and then elec-trodepositing a metal or conducting polymer within the pores of the membrane [90]. This method controls more closely the filling of the pores compared to other... 

When used in different kinds of electrochemical equipment the membranes are in contact with aqueous solutions of the low molecular weight electrolytes in which they swell. Moreover, a certain amount of the ambient solution penetrates the voids or pores in the membrane. So the swollen membrane is a multiphase system composed of an ion containing component appearing in a gel state, an inert partly crystalline polymer, and the electrolyte filling any voids or nonselec-tive domains, all of them in varying amounts. For such a system it is possible to calculate the approximate phase composition based on the conductivity and the multilayer electrochemical model. We presented such a model at the First Italian-Polish Seminar on Multi-component Polymeric Systems in 1979. 

Nasef, M.M., Zubir, N.A., Ismail, A.F., Dahlan, K.Z.M., Saidi, H. and Khayet, M. 2005. Preparation of radiochemically pore-filled polymer electrolyte membranes for direct methanol fuel cells. 166 200-210. 

Within the alternative approach, the film is considered a porous medium [54, 94,114,119,121,122,127-129,148], Physically, it represents a porous membrane that includes a matrix formed by the conducting polymer and pores filled with an electrolyte. Mathematically, in this approach the film is modeled as a macroscop-ically homogeneous two-phase system consisting of an electronically conducting sohd phase and an ionically conducting electrolyte phase. Considering a planar geometry, each layer perpendicular to the electrode smface contains these two phases, and it can therefore be described at any point by two potentials that depend on the time and the spatial coordinates. 

M.M. Nasef, N.A. Zubir, A.F. Ismail, K.Z.M. Dahlan, H. Saidi and M. Khayet, Preparation of radiochemicaUy pore-filled polymer electrolyte membranes for direct methanol fuel cell, J. Power Sources 156, 200 (2006). 

Systematic Design of Polymer Electrolyte Membranes for Fuel Cells Using a Pore-Filling Membrane Concept... 

To develop polymer electrolyte membrane for fuel cells, our conceptual approach is a pore-filling membrane. 

T. Yamaguchi, F. Miyata and S. Nakao, Polymer electrolyte membranes with pore-filling structure for a direct methanol fuel ceU,Adv. Mater., 15(14), 1198-1201 (2003). 

T. Yamaguchi, H. Kuroki and F. Miyata, DMFC performances using a pore-filling polymer electrolyte membrane for portable usages, Electrochem. Common., 7(7), 730-734 (2005). 

During the preparation of a gel copolymer P(VDF-HFP) electrolyte membrane by the phase inversion method, using different solvents such as NMP and NAf-dimethylformamide) (DMF) and nonsolvents such as dibutyl phthalate (DBF) and di-(2-ethylhexyl phthalate) (DEHP) will result in different pore sizes and different porosities. As a result, they are called porous polymer electrolytes, hi fact, they are gel electrolytes. The micromorphology of e membrane is related to the preparation conditions, but the solvents and nonsolvents used do not affect the ionic conductivity much, under certain conditions. After adding a certain amount of plasticizer, the pores will be filled by the plasticizer, and the ionic conductivity is 4.07 x 10 S/cm, with an electrochemical window of 4.5 V. 

The subsequent investigations are focused on the filling state of the micropores in the PMMA membrane, whereas the preceding chapter referred to residues at the bottom of the micropores. Micropores have to be filled by electrolyte for their intended application as ion channel biosensor. The available imaging techniques revealed variations among the pore volumes after admission of electrolyte, but... 

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