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Tolmachev Yu.V.,Ftorion Inc.
Russian Journal of Electrochemistry

Described herein are established and emerging applications of hydrogen-halogen direct and regenerative fuel cells such as energy recovery from excess H2 and Cl2 products of chloro-alkali electrolysis as well as stationary and on-board energy storage. Due to significant similarities between hydrogen-halogen fuel cells and electrolyzers, the latter are also discussed. This is followed by a more detailed description of various designs classified on the basis of their electrolytes: aqueous solutions, ionomers, phosphoric acid doped polybenzimidazole, halide melts and others. It is concluded that hydrogen-chlorine and hydrogen-bromine cells may present competitive options for on-board and grid energy storage. However, the choice of the most suitable electrolyte for such cells cannot be made at present and more studies of complete systems, particularly with ionomers and solid acid electrolytes, would be desirable. © 2014 Pleiades Publishing, Ltd. Source

Tolmachev Y.V.,Ftorion Inc.
Russian Journal of Electrochemistry

A polymer electrolyte fuel cell with Pt grid electrodes employing acidic lithium bromate as the oxidant and alkaline sodium borohydride as the reducer is demonstrated. Such system provides simultaneously high energy (over 1000 A h/L and 660 A h/kg in the tanks) and high power (0.5 W/cm2 at 60°C) densities on discharge. A regenerative fuel cell cycle employing hydrogen as the reducer is also discussed. © 2015, Pleiades Publishing, Ltd. Source

Vorotyntsev M.A.,CNRS Molecular Chemistry Institute of Burgundy University | Vorotyntsev M.A.,Moscow State University | Konev D.V.,RAS Institute of Problems of Chemical Physics | Lange U.,University of Regensburg | And 2 more authors.
Electrochimica Acta

Polypyrrole (PPy) films of different thicknesses (within the range from 200 nm to 2.5 μm) were electrodeposited on two types of inhomogeneous substrates, single band and double-band Pt electrodes. Topographic images of the polymer layers were obtained by means of ex situ large-scale AFM technique to demonstrate how the propagation rates of the film growth above the electrode (in the normal direction to the electrode surface) and along the insulating surface surrounding the single- or double-band electrodes (in the horizontal direction) change with the deposition charge. It is proved that variations in the film thickness over the double band electrodes and progressive changes of the PPy morphology from compact thin film to rough thick layers represents an obstacle for reliable determination of the specific conductivity of the deposited polymer film from conductance/resistance data for such coated microband electrodes. Advantages and shortcomings of other methods of specific conductivity measurements of the polymer films are also discussed. © SIA M. V. Lomonosov Moscow State University Russia. Source

Tolmachev Y.V.,Ftorion Inc. | Piatkivskyi A.,Northern Illinois University | Ryzhov V.V.,Northern Illinois University | Konev D.V.,Mendeleev University of Chemical Technology | Vorotyntsev M.A.,CNRS Molecular Chemistry Institute of Burgundy University
Journal of Solid State Electrochemistry

A flow battery employing H2 as the fuel and one or more of highly soluble halate salts (such as 50 % w/w LiBrO3 aq.) as the oxidant presents a viable opportunity as a power source for fully electric vehicles which meets the specific energy, specific power, energy efficiency, cost, safety, and refill time requirements. We further disclose a process of regeneration of the fuel and the oxidant from the discharged halide salt and water using electric (or solar) energy as the only input and generating no chemical waste. The cycle of discharge and regeneration takes advantage of pH-driven comproportionation and disproportionation reactions, respectively, and of pH manipulation using an orthogonal ion migration across laminar flow (OIMALF™) reactor. © 2015, Springer-Verlag Berlin Heidelberg. Source

Vorotyntsev M.A.,University of Burgundy | Vorotyntsev M.A.,Moscow State University | Konev D.V.,RAS Institute of Problems of Chemical Physics | Tolmachev Y.V.,Ftorion Inc.
Electrochimica Acta

Abstract Theoretical analysis of the system with coupled electrochemical and chemical steps has been carried out where bulk solution contains non-electroactive halogen oxoanions, XOn-, with a very small addition of halogen molecules, X2. The latter are electroreduced rapidly at the electrode surface, generating halide anions, X-, which diffuse towards solution, wherein they comproportionate with the principal oxidant, XOn-, yielding electroactive halogen. Unlike the well-known catalytic EC' mechanism where both the electrochemical reaction and the chemical step retain the total amount of the mediating redox couple, the passage of the electroreduction cycle in the system under our study results in an increase of the total content of its components, halogen and halide anion, via the consumption of halate anions. We propose to denote this new autocatalytic EC mechanism as EC". Approximate analytical formulas have been derived for all characteristics of this system under steady state conditions at the uniformly accessible electrode surface. We found that the behavior of the system depends crucially on the relation between the diffusion layer thickness, zd, and the kinetic layer thickness, zk (determined by the rate of the homogeneous reaction). For a very thin diffusion layers: zd < zk, halide anions leave the diffusion layer and react with XOn- anions only in the bulk solution. Both the polarization curve and the maximal current correspond to the electrode reaction of halogen molecules from the bulk solution, without a significant contribution due to the comproportionation reaction. In the intermediate range of the diffusion layer thickness: zk < zd < 2n zk, the halide anions generated at the electrode are consumed mostly by this homogeneous reaction within a thin kinetic layer (located deeply inside the diffusion layer) while the halogen molecules produced by this reaction diffuse partially to the electrode, generating again halide anions. This combination of the chemical and electrochemical steps results in an autocatalytic cycle, based on the X-/X2 mediating redox couple, which consumes a significant amount of XOn- anions. The maximal current becomes much higher than the mass-transport of halogen from the bulk can sustain, depending essentially on the kinetic layer thickness. In the third range of the diffusion layer thickness: 2n zk < zd, the amounts of the accumulated redox-couple components are so high that the principal (but non-electroactive) oxidant, XOn- is consumed within the external part of the kinetic layer with the maximal rate determined by the XOn- anion diffusion across the diffusion layer, which results in a very high maximal current proportional to the bulk concentration of XOn- anions. The theory predicts a complicated behavior of the maximal current as a function of the diffusion layer thickness (or the disk rotation rate for the RDE technique), with a maximum and a minimum separated by the range with an anomalous variation: increase of the maximal current with increase of the diffusion layer thickness ("autocatalytic interval"). © 2015 Elsevier Ltd. Source

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