Proton conductive copolymers of 1H,1H,2H,2H-perfluorodecyl acrylate (PFDA) and methacrylic acid (MAA) have been synthesized by initiated chemical vapor deposition (iCVD). Detailed insights into the copolymers’ molecular organization were gained through an X-ray-based investigation to serve as a starting point for systematic studies on the relation among proton conductivity and polymer structure. The method of copolymerization, iCVD, facilitated the tuning of the ratio between acidic −COOH groups, coming from MAA, and the hydrophobic matrix from the PFDA components. It was demonstrated that the copolymers crystallize into a bilayer structure, formed by the perfluorinated pendant chains of PFDA, perpendicular to the substrate surface. The MAA molecules form COOH-enriched regions among the bilayersparallel to the substrate surfacewhich can act as ionic channels for proton conduction when the acid groups are deprotonated. The interplanar distance between the bilayer lamellar structures increases by the presence of MAA units from 3.19 to 3.56 nm for the MAA–PFDA copolymer with 41% MAA, therefore yielding to 0.4 nm wide channels. Proton conductivities as high as 55 mS/cm have been achieved for copolymers with 41% MAA fraction. Such ordered, layered nanostructures were never shown before for copolymers deposited from the vapor phase, and their anisotropy can be of inspiration for many applications beyond proton conduction. Moreover, the one-step copolymerization process has the potential to manufacture inexpensive, high quality membranes for proton exchange membrane fuel cells.

The study focuses on the influence of Ni and Bi on alkaline ethanol oxidation reaction (EOR) activities, stabilities and structure characteristics of carbon supported Pd-based nanocatalysts (Pd/C, Pd 60 Ni 40 /C, Pd 60 Bi 40 /C, Pd 60 Ni 20 Bi 20 /C) by cyclic voltammetry/chronoamperometry using rotating disk electrode and various physico-chemical methods such as X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry. Nickel generates more adsorbed OH on the Pd catalyst surface than Bi and promotes the oxidation of adsorbed ethanol species. This results in a low onset potential toward ethanol oxidation with high current density. The presence of Bi facilitates high tolerance toward various reaction intermediates resulting from the incomplete ethanol oxidation, but might also initiate the agglomeration of Pd nanoparticles. The novel Pd 60 Ni 20 Bi 20 /C nanocatalyst displays exceptional byproduct tolerance, but only satisfying catalytic activity toward ethanol oxidation in an alkaline medium. Therefore, the EOR performance of the novel carbon supported ternary Pd x Ni y Bi z anode catalyst with various atomic variations (Pd 70 Ni 25 Bi 5 /C, Pd 70 Ni 20 Bi 10 /C, Pd 80 Ni 10 Bi 10 /C and Pd 40 Ni 20 Bi 40 /C) using the common instant reduction synthesis method was further optimized for the alkaline direct ethanol fuel cell. The carbon supported Pd:Ni:Bi nanocatalyst with atomic ratio of 70:20:10 displays outstanding catalytic activity for the alkaline EOR compared to the other Pd x Ni y Bi z /C nanocatalysts as well as to the benchmarks Pd/C, Pd 60 Ni 40 /C and Pd 60 Bi 40 /C. The synergy and the optimal content in consideration of the oxide species of Pd, Ni and Bi are crucial for the EOR kinetic enhancement in alkaline medium.

A series of novel cross-linked highly quaternized chitosan and quaternized poly (vinyl alcohol) membranes were successfully synthesized to be applied in alkaline direct ethanol fuel cells. Cross-linking was accomplished using two different cross-linking agents and an additional thermal process to improve both chemical and thermal properties. Equivalent blends of chitosan and poly (vinyl alcohol) membranes with various degrees of cross-linking were prepared by using different amounts of glutaraldehyde and ethylene glycol diglycidyl ether as cross-linkers. To investigate their applicability in direct ethanol fuel cells, the membranes were characterized in terms of their structural properties, chemical, thermal and alkaline stability, ion transport and ionic properties using following methods: Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, thermogravimetric analysis, water uptake by mass change, ethanol permeability in the diffusion cell, back titration method (ion exchange capacity) and electrochemical impedance spectroscopy (anion conductivity). Despite the high degree of quaternization of the applied materials and regardless of the thin film thickness of the blend membranes, the novel cross-linked products displayed outstanding mechanical stability. The lower crosslinked membranes exhibited the best transport and ionic properties with a high anion conductivity of 0.016 S cm-1 and a high ion exchange capacity of 1.75 meq g-1 , whereas membranes with a higher degree of cross-linking performed superior in terms of reduced ethanol permeability of 3.30•10-7 cm 2 s-1 at 60°C. The blend membranes-chemically and thermally cross-linked-provide excellent thermal stability with an onset degradation temperature above 280°C and superb alkaline stability in 1.0 M KOH at 60°C for 650 h. Therefore, these composite membranes exhibit high potential for application as alkaline electrolytes in fuel cells.

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Membrane degradation is a severe factor limiting the lifetime of polymer electrolyte fuel cells. Therefore, obtaining a deeper knowledge is fundamental in order to establish fuel cells as competitive product. A segmented single cell was operated under open circuit voltage with alternating relative humidity. The influence of the catalyst layer on membrane degradation was evaluated by measuring a membrane without electrodes and a membrane-electrode-assembly under identical conditions. After 100 h of accelerated stress testing the proton conductivity of membrane samples near the anode and cathode was investigated by means of ex situ electrochemical impedance spectroscopy. The membrane sample near the cathode inlet exhibited twofold lower membrane resistance and a resulting twofold higher proton conductivity than the membrane sample near the anode inlet. The results from the fluoride ion analysis have shown that the presence of platinum reduces the fluoride emission rate; which supports conclusions drawn from the literature.