Papers by Keyword: Proton Conductivity

Abstract: This research reported on the preparation of proton exchange membranes from electronic and food packaging waste composed of Styrofoam. Polymeric Solution of 25 wt. % Styrofoam dissolved in an acidic mixture (DMF: THF at 70:30 volumetric ratio) were prepared. Polymeric membranes were fabricated by electrospinning. The effect of MgO NPs addition to polymeric solution was studied. Before sulfonation reaction, SEM results showed a clear reduction in average fiber diameters from (1.5-2) µm to (0.5-1) µm after addition of 0.04 wt.% MgO NPs. After sulfonation reaction by 35% diluted sulfuric acid, SEM results show an increase in average fiber diameters from (0.5-1) µm to (2-2.5) µm. This increase may be correlated to hydrophilic behavior results from incorporation of (-SO₃H) to aromatic ring. FTIR analysis indicates the presence of new peaks related to sulfonic acid group (SO₃H) attachment to polymeric chain. Proton conductivity as well as water uptake in membranes increased with increasing MgO NPs percentage.

Abstract: The wide applicability of proton exchange membrane fuel cells (PEMFCs) is hindered by their dependency on the Nafion membrane as a state-of-the-art electrolyte. Nafion membranes can only operate at relatively low temperatures, up to 80°C. Therefore, any application of the fuel cell above this temperature would cause the PEMFC to lose its proton conductivity and mechanical integrity. For this reason, the development of Nafion-free membranes for PEMFCs has been studied extensively through the corporation of several additives over polymer substrates. The charge transfer abilities of metal-organic frameworks (MOFs), among other properties, make them one of the possible additives. The objective of this work is to synthesize Nafion-free membranes based on graphene oxide, MOFs, ionic liquids, polyethylene glycol, and zirconium phosphate over PTTFE membrane as an alternative to Nafion membranes. The preliminary results gave proton conductivities in the range of 10^-4 S/cm up to 150°C with graphene oxide MOF addition to all samples.

Abstract: The breakdown mechanism of a number of crystal materials with hydrogen bonds is investigated. The contribution of the proton component is considered and it is shown that the formation of an avalanche-streamer discharge is characteristic of multilayer electrical insulation materials. As a result of the breakdown, a discharge channel is formed, along which the protons that form the reverse proton conductivity will move in the opposite direction. In the process of directed translational diffusion of protons, the formation and decay of H₃O⁺ and OH^- ions occur, which move in opposite directions, resulting in the formation of a reverse positive streamer from the anode to the cathode. For layered samples of phlogopite, muscovite, and magnesium hydrosilicate, it is shown that for thin samples, a volume charge is formed as a result of a multi-avalanche-streamer discharge that significantly exceeds the volume charge that occurs in thick samples, which is determined by the value of high temperature maximum of the spectrum of thermally stimulated depolarization currents. The field of the volume charge reduces the external electric field, as a result of which the breakdown field strength in thin samples increases. That is, the material is electrically strengthened. Based on the results of the research, a non-destructive method of electrical hardening of electrical insulation materials was developed, which was confirmed by the patent.

Abstract: Proton-conducting membranes were fabricated from a new short-side chain ionomer Inion (Russian analogue of Aquivion) by solution casting method. A series of temperature treatment experiments was conducted to show that annealing of Inion membranes at the temperature range from 160 °C to 170 °C leads to a significant increase of specific proton conductivity to values even higher than those of commercial membrane Nafion NR212. An explanation of this fact can be given by considering the membranes’ proton transport mechanism and water behavior models in nanopores. Matching the proton conductivity mechanism of the membranes, which is realized in nanostructured channels with the diameter of about several nanometers according to the Grotthuss proton hopping mechanism, and the model of water and ice states in nanopores leads to the comprehensive understanding for the further optimization of the membranes to achieve high transport characteristic. For example, it can be improved by increasing the number of side-chain branches of the polymer.

Abstract: The complex oxide BaLaIn_0.9Nb_0.1O_4.1 with Ruddlesden-Popper structure was obtained for the first time. It was found that the introduction of niobium into indium sublattice leads to the increase in the cell volume. Hydration processes and electrical properties have been investigated. For BaLaIn_0.9Nb_0.1O_4.1 it was proved the capability for water uptake and the appearance of proton current carriers. It was established that niobium doping leads to the increase of conductivity compared to undoped composition BaLaInO₄ at ~1 order of magnitude in whole temperature range.

Abstract: Polymer electrolyte membranes (PEM) with good properties are essential for the improvement of electrochemical operations. The increase in properties of polymer electrolyte membranes will develop the performance of polymer electrolyte membranes in the fuel cells. The importance of polymer electrolyte membranes is increasing recently due to its activity and simplicity in energy associated applications like automobiles and various portable applications. PEM has various properties like proton conductivity, chemical stability, mechanical properties, thermal stability and so on. These properties are enhanced and influenced by various factors like morphology, the molecular weight of the membranes, chemical structures, cross linkages etc. The present chapter attempts to summarize about the properties of polymer electrolyte membrane involved in the different types of electrochemical utilizations. Keywords: Polymer electrolyte membrane, fuel cells, morphology, proton conductivity, chemical structure.

Abstract: The chlorine-doped complex oxide Ba₂CaNbO_5.475Cl_0.05 based on barium calcium niobate was synthesized using the solid state method. It was found that the introduction of chloride ions leads to the increase of the cell volume. Structure and electrical properties have been investigated. Electrical conductivities were measured by varying the temperature in dry (pH₂O=3.5·10^-5 atm) and wet (pH₂O=2·10^-2 atm) air. The composition Ba₂CaNbO_5.475Cl_0.05 is capable to dissociative dissolution of water vapor and can exhibit proton transport. Chlorine doping increases the conductivity of matrix compound Ba₂CaNbO_5.5, the difference between un-and chlorine-doped samples is up to one order of magnitude at low temperatures.

Abstract: Ceramic samples of tungstoantimonic acid (TAA) were obtained by ion exchange of sintered potassium tungstoantimonate, KWSbO₆, in acid solution. The ac conductivity of these samples is by 2 orders of magnitude higher than the conductivity of pressed powder of tungstoantimonic acid. The conduction mechanism in this material seems similar to the one in polyantimonic acid (PAA), though the conductivity of TAA is by 1.5 orders of magnitude lower than that of PAA. Based on these results and literature data on the conductivity of PAA and its derivatives, the directions for the search for materials with improved proton-conducting properties in this family of compounds are discussed.

Abstract: The amino functionalized magnesium phyllosilicate clay (AC) intercalated over PVA-Nafion hybrid nanocomposite membranes were prepared by sol-gel method. The free standing membranes were obtained by solution recasting. The composition of clay materials such as AC and montmorillonite (MMT) was varied between 2-10 wt.% with respect to PVA-Nafion content. The molecular interactions and surface morphology of nanocomposite membranes were investigated by FT-IR and SEM analyses respectively. The thermal and mechanical stabilities of nanocomposite membranes were studied using TGA and Nanoindentation techniques. For 6 wt. % AC/PVA-Nafion, TGA results showed no appreciable mass change up to 380 °C and hardness calculated from nanoindentation studies was nearly 30 % higher than the other compositions. An improved conductivity was obtained for 6 wt. % AC/PVA-Nafion (1.4×10^-2 S/cm) compared to pure Nafion (1.2×10^-2 S/cm) and PVA-Nafion and MMT/PVA-Nafion composite membranes. From these studies, we observed that 6 wt. % AC/PVA-Nafion membrane possessed a good conductivity with higher thermal and mechanical stabilities.

Abstract: Linear and kinked bulky monomers were incorporated into the main chain of a polyimide in order to investigate the effect of kinked versus linear polymers on membrane properties such as water uptake and proton conductivity. Polymers prepared using linear 1,4-bis (4-aminophenoxy)-naphthyl-2,7-disulfonic acid (BAPNDS), SPI-N, and using kinked 2,2’-bis (p-aminophenoxy)-1,1’-binaphthyl-6,6’-disulfonic acid (BNDADS), SPI-BN, were cast into membranes. All the copolymers showed excellent solubility and good film-forming capability. Membranes are thermally stable up to 300 °C under air. For SPI-BN, the nonplanar binaphthyl group result in polymer chain relaxation and produce large water uptake. However, the conductivity of kinked, SPI-BN membranes is lower than those prepared from SPI-N for a given IEC but water uptakes are higher. This might be related to substitution position of the sulfonic acid groups and the microstructure. Sulfonic acid group were located at the same side of the main chain will be favorable for forming hydrophilic clusters, thus better proton conductivity performance would be achieved.