Novel composite Zr/PBI-O-PhT membranes for HT-PEFC applications

Abstract

SummaryNovel composite membranes for high temperature polymer-electrolyte fuel cells (HT-PEFC) based on a poly[oxy-3,3-bis(4′-benzimidazol-2″-ylphenyl)phtalide-5″(6″)-diyl] (PBI-O-PhT) polymer with small amounts of added Zr were prepared. It was shown in a model reaction between zirconium acetylacetonate (Zr(acac)4) and benzimidazole (BI) that Zr-atoms are capable to form chemical bonds with BI. Thus, Zr may be used as a crosslinking agent for PBI membranes. The obtained Zr/PBI-O-PhT composite membranes were examined by means of SAXS, thermomechanical analysis (TMA), and were tested in operating fuel cells by means of stationary voltammetry and impedance spectroscopy. The new membranes showed excellent stability in a 2000-hour fuel cell (FC) durability test. The modification of the PBI-O-PhT films with Zr facilitated an increase of the phosphoric acid (PA) uptake by the membranes, which resulted in an up to 2.5 times increased proton conductivity. The existence of an optimal amount of Zr content in the modified PBI-O-PhT film was shown. Larger amounts of Zr lead to a lower PA doping level and a reduced conductivity due to an excessively high degree of crosslinking.

Self-supported phase-pure Ni3S2 sheet-on-rod nanoarrays with enhanced pseudocapacitive properties and high energy density

“…as the frequency extends to zero hertz the Warburg element adopts the behaviour of a capacitor in series with a resistor and is thus now modelled as an open-circuit terminus Warburg impedance. The theory behind the different varieties of the Warburg impedance is based on the use of transmission lines first developed by de Levie [44,45] and is well documented in the literature [46,47]. Usually supercapacitors and lithium batteries display a Warburg element with an open-circuit terminus, as there is no flux of species at the secondary boundary layer, that is to say, the diffusion occurs into the diffusion zone not across it as in the case for a Warburg element with a short-circuit terminus.…”

Novel concept of polymer electrolyte membranes for high-temperature fuel cells based on ETFE grafted with neutral acrylic monomers

“…According to literature for PBI/acid systems one PA molecule is bound to the protonated N-atom and additional PA molecules are retained due to hydrogen bonds [77]. In the case of grafted HEMA-HEA copolymer phosphoric acid ester groups may be formed upon condensation of PA with OH-groups of the monomer units [60], which is illustrated for HEA units of the grafted polymer in Scheme 1.…”

Carbon Nanofiber Paper Electrodes Based on Heterocyclic Polymers for High Temperature Polymer Electrolyte Membrane Fuel Cell

“…Testing of the electrodes with 5 cm 2 active surface in fuel cells was performed in standard “Arbin Instruments” cells with PBI‐O‐Pht membrane, developed and synthesized by our group, modified by zirconium acetylacetonate and doped by phosphoric acid (350–400%, up to 25 phosphoric acid molecules per polymer unit). Transmission electron microscopy (TEM) was performed on Tecnai G 2 30 ST. Porosity and specific surface area data for pyrolyzed materials was obtained by using the method of standard contact porosimetry.…”

“…After thermal oxidation (stabilization) at 250–280 °C and pyrolysis (carbonization) at 900–1200 °C, carbon nanofibers (CNF) were obtained in a form of a carbon nanofiber paper (CNFP) . The CNFP was suitable for Pt deposition and the obtained nanocomposite materials were effectively used as gas diffusion electrodes (GDE) which possess macro‐ and microporosity, as anodes and cathodes, for HT‐PEMFC on PBI‐O‐Pht (PBI‐type polymer) membrane, also developed by our group . The choice of PAN nanofibers was based on the fact that they are among the most common easily produced nanofibers which are obtained by the electrospinning method .…”