Proton conduction enhancing

Weber J, Kreuer KD, Maier J, Thranas A (2008) Proton conductivity enhancement by nanostructural control of poly(benzimidazole)-phosphoric acid adducts. Adv Mater... 

The catalyst layer is composed of multiple components, primarily Nafion ion-omer and carbon-supported catalyst particles. The composition governs the macro- and mesostructures of the CL, which in turn have a significant influence on the effective properties of the CL and consequently the overall fuel cell performance. There is a trade-off between ionomer and catalyst loadings for optimum performance. For example, increased Nafion ionomer confenf can improve proton conduction, but the porous channels for reactanf gas fransfer and water removal are reduced. On the other hand, increased Pt loading can enhance the electrochemical reaction rate, and also increase the catalyst layer thickness. 

Yang, Y. S., Shi, Z. Q. and Holdcroft, S. 2004. Synthesis of sulfonated polysul-fone-block-PVDF copolymers Enhancement of proton conductivity in low ion exchange capacity membranes. Macromolecules 37 1678-1681. 

For instance, the Dow experimental membrane and the recently introduced Hyflon Ion E83 membrane by Solvay-Solexis are "short side chain" (SSC) fluoropolymers, which exhibit increased water uptake, significantly enhanced proton conductivity, and better stability at T > 100°C due to higher glass transition temperatures in comparison to Nafion. The membrane morphology and the basic mechanisms of proton transport are, however, similar for all PFSA ionomers mentioned. The base polymer of Nation, depicted schematically in Figure 6.3, consists of a copolymer of tetrafluoro-ethylene, forming the backbone, and randomly attached pendant side chains of perfluorinated vinyl ethers, terminated by sulfonic acid head groups. °... 

Impregnating these layers with PFSA ionomer for enhanced proton conduction or hydrophobizing agents like Teflon for sufficient gas porosity is optional. However, ionomer impregnation is indispensable in CLs with thicknesses of > 1 ftm. Ultrathin CLs with - 100-200 nm, on the other hand, can operate well without these additional components, based on sufficiently high rates of transport of dissolved reactant molecules and protons in liquid water, which could ensure uniform reaction rate distributions over the entire thickness of the layer. 

A typical PEFC, shown schematically in Fig. 1, consists of the anode and cathode compartments, separated by a proton conducting polymeric membrane. The anode and cathode sides each comprises of gas channel, gas diffusion layer (GDL) and catalyst layer (CL). Despite tremendous recent progress in enhancing the overall cell performance, a pivotal performance/durability limitation in PEFCs centers on liquid water transport and resulting flooding in the constituent components.1,2 Liquid water blocks the porous pathways in the CL and GDL thus causing hindered oxygen transport to the... 

Keywords Compact fuel cell Proton conductive oxide Radiation induced conductivity Radiation enhanced diffusion... 

There are some reports on an enhanced ionic conductivity of nano-sized Z1O2 films whether this is due to mobility effects (core or elastic strain, in particular in epitaxial films) or to proton conductivity is to be clarified.291... 

This scale effect indicates that the electrical conductivity is nearly constant for the films varying in thickness from 60 to 2,000 nm. The measured resistance, however, decreased when the film thickness further reduced. Both DC and AC conductivity measurements indicated that there was an enhanced conductivity for film thickness of <60 nm. They further proposed three orders of magnitude larger conductivity in 1.6-nm-thick films than lattice conductivity. Since the grain size was not provided, it is unknown whether only the grain size plays a role when a film s thickness is less than 60 nm. Guo et al. deposited YSZ thin films by pulsed laser deposition on MgO substrates with thicknesses of 12 and 25 nm. The electrical conductivity was measured in both dry and humid O2. The electrical conductivity in thin films, however, was found to be four times lower than ionic conductivity in microcrystalline specimens, as shown in figure 10.8. Furthermore, they found that there is not any remarkable proton conduction in the nanostructured films when annealed in water vapor. 

ENHANCEMENT OF PROTONIC CONDUCTIVITY IN THE NEAR SURFACE REGIONS OF RADIATION INDUCED POLYMER ELECTROLYTE MEMBRANES ... 

It was also revealed by means of ultraviolet, visible and infrared optical absorption and hydrogen ion-exchange capacity measurements that the radiation induced defects such as fluorocarbon and peroxy radicals, and C=0 including in carbonyl groups were related to the new proton conduction processes. The modification of the hydrogen absorption characteristics due to the radiation induced defects in the near sttrface regions induces the enhancement of the proton conductivity. 

Enhancement of Protonic Conductivity in the Near Surface Regions of Radiation Induced Polymer Electrolyte Membranes B. Tsuchiya, S. Nagata, K. Saito, T. Shikama... 

There is a class of nonporous materials called proton conductors which are made from mixed oxides and do not involve transport of molecular or ionic species (other than proton) through the membrane. Conduction of protons can enhance the reaction rate and selectivity of the reaction involved. Unlike oxygen conductors, proton conductors used in a fuel cell configuration have the advantage of avoiding dilution of the fuel with the reaction products [Iwahara ct al., 1986]. Furthermore, by eliminating direct contact of fuel with oxygen, safety concern is reduced and selectivity of the chemical products can be improved. The subject, however, will not be covered in this book. 

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