Layer-by-layer deposition of open-pore mesoporous TiO 2- Nafion® film electrodes

The formation of variable thickness TiO2 nanoparticle-Nafion® composite films with open pores is demonstrated via a layer-by-layer deposition process. Films of about 6 nm diameter TiO2 nanoparticles grow in the presence of Nafion® by “clustering” of nanoparticles into bigger aggregates, and the resulting hierarchical structure thickens with about 25 nm per deposition cycle. Film growth is characterized by electron microscopy, atomic force microscopy, and quartz crystal microbalance techniques. Simultaneous small-angle X-ray scattering and wide-angle X-ray scattering measurements for films before and after calcination demonstrate the effect of Nafion® binder causing aggregation. Electrochemical methods are employed to characterize the electrical conductivity and diffusivity of charge through the TiO2-Nafion® composite films. Characteristic electrochemical responses are observed for cationic redox systems (diheptylviologen2+/+, Ru(NH3)3+/2+6, and ferrocenylmethyl-trimethylammonium2+/+) immobilized into the TiO2-Nafion® nanocomposite material. Charge conduction is dependent on the type of redox system and is proposed to occur either via direct conduction through the TiO2 backbone (at sufficiently negative potentials) or via redox-center-based diffusion/electron hopping (at more positive potentials)

«The Car Is Not a Luxury, but a Means of Transportation». The Analysis of Trends in the Development of the Car Market

Рынок легковых автомобилей России – один из крупных секторов и входит в число драйверов развития экономики страны. Целью данной работы является анализ тенденций развития легкого автомобильного рынка. Нами были рассмотрены основные игроки рынка продаж легковых автомобилей, с помощью анализа, основанного на четырехсекторной модели: производители – посредники – государство – потребители, где в каждом секторе рассмотрены основные факторы, определяющие динамику продаж. Авторы рассматривали потребительские практики, где с помощью статистических тестов проанализирована и выявлена зависимость доходов населения и объема рынка легковых автомобилей. Проанализирована структура рынка, его состояние, рассмотрены основные барьеры входа для новых игроков. Государство выступает активным игроком, регулируя отрасль, используя различные рыночные и нерыночные инструменты. Рассмотрены реализуемые и планируемые государственные программы поддержки развития автомобильного рынка России. Далее авторами рассмотрен более узкий, региональный сегмент рынка. Выявлена специфика потребления в регионе, и описаны перспективы автомобильного рынка Тюмени.The Russian car market is one of the largest sectors and one of the drivers of the country’s economic development. The purpose of this paper is to analyze the development trends of the light car market. The authors have reviewed the main players in the car sales market, using analysis based on the four-sector model: intermediary – producer – state – consumers. In each sector, the main factors determining the dynamics of sales are considered. The authors have analyzed consumer practices, where statistical tests were used to analyze and determine the dependence of household incomes and the volume of the car market. They have analyzed the structure of the market, its condition, and the main barriers to entry for new players. As the state is an active participant, regulating the industry (using various market and non-market instruments), attention is paid to the implemented and planned state programs to support the development of the automotive market in Russia. Furthermore, the authors have considered a narrower, regional segment of the market. They have revealed the specificity of consumption in the region, and described the prospects of the Tyumen automobile market

High temperature transport properties of polyphosphazene membranes for direct methanol fuel cells

Experimental methods for studying the conductivity and methanol permeability of proton conductive polymers over a wide range of temperatures have been developed. The proton conductivity and methanol permeability of several polymer electrolyte membranes including sulfonated and phosphonated poly[(aryloxy)phosphazenes] was determined at temperatures up to 120 °C. Nafion 117 membranes were tested using the same methods in order to determine the reliability of the methods. Although the conductivities of the polyphosphazene membranes were either similar to or lower than that of the Nafion 117 membranes, they continue to hold promise for fuel cell applications. We observed similar activation energies of proton conduction for Nafion 117, and for sulfonated and phosphonated polyphosphazene membranes. However, the methanol permeability of a sulfonated membrane was about 8 times lower than that of the Nafion 117 membrane at room temperature although the values were comparable at 120 °C. The permeability of a phosphonated phosphazene derivative was about 40 times lower than that of the Nafion 117 membrane at room temperature and about 9 times lower at 120 °C. This is a significant improvement over the behavior of Nafion 117

Phenyl phosphonic acid functionalized poly[aryloxyphosphazenes] as proton-conducting membranes for direct methanol fuel cells

A method for the synthesis of phenyl phosphonic acid functionalized poly[aryloxyphosphazene] membranes is described. Membranes of polymers with total ion-exchange capacities between 1.17 and 1.43 meq. g −1 were cast from N, N-dimethyl-formamide and found to have proton conductivities between 10 −2 and 10 −1 S cm −1. Equilibrium water swelling values were determined to be between 11 and 32% depending on the polymer structure. Methanol diffusion coefficients for both radiation cross-linked and non-cross-linked membranes in 3 M aqueous methanol at 80 °C and 2.8 bar were found to be at least 12 times lower than for Nafion 117, and 6 times lower than for a radiation cross-linked sulfonated polyphosphazene membrane

Polyvinyl alcohol nanofiber reinforced Nafion membranes for fuel cell applications

This work has been focused on the preparation and characterization of composite membranes with thickness between 19 and 97 mu m and containing Nafion(R) infiltrated into a porous mat obtained by electrospinning of an aqueous solution of Poly vinyl alcohol (PVA). The mat was composed of PVA nanofibers with diameters between 200 and 300 nm, which were functionalized on their external surface with sulfonic acid groups in order to cooperate in the proton conductivity of Nafione(R). The proton conductivity of a composite membrane (47 mu m thick) measured by impedance spectroscopy reached 0.022 S/cm at 70 degrees C and fully hydrated. This value is lower than the conductivity measured in the same conditions for a pristine Nafion(R) cast membrane (46 mu m), 0.032 S/cm. However, the performance of both membranes in Direct Methanol Fuel Cell tests was evaluated and showed comparable results. The proton conductivity of a series of cast Nafion(R) membranes with thickness similar to those of the composite membranes was found to behave linearly thickness-dependent, while NAF/PVA composite membranes do not show such a linear behavior due to their heterogeneous composition. Nevertheless, the composite membrane presenting a thickness of 47 mu m records the maximum peak conductivities at the whole temperature range. An intrinsic value for the activation energy of our cast Nafion(R) membranes at fully hydrated conditions was estimated to be 7 kJ/mol.This work has been supported by the Valencian Institute of Small and Medium-Sized Enterprises (IMPIVA) and the European Regional Development Funds, through the project IMIDIC/2009/155.Mollá Romano, S.; Compañ Moreno, V. (2011). Polyvinyl alcohol nanofiber reinforced Nafion membranes for fuel cell applications. Journal of Membrane Science. 372(1-2):191-200. https://doi.org/10.1016/j.memsci.2011.02.001S1912003721-

Evaluation of methanol crossover in proton-conducting polyphosphazene membranes

A diffusion cell was developed to evaluate the methanol crossover for a novel class of polyphosphazene electrolyte membranes. It was found that the methanol diffusion coefficients of phenyl phosphonic acid functionalized poly[aryloxyphosphazene] membranes in an aqueous methanol solution (50% v/v) were ∼40 times lower than for Nafion 117, and ∼10–20 times lower than for sulfonated polyphosphazene membranes