Redox membrane-based flow fuel cell

a fuel cell and membrane technology, applied in the direction of fuel cells, indirect fuel cells, electrical equipment, etc., can solve the problems of low internal electric resistance of the cell, the need for a catalyst, and the use of oxygen reduction reaction, etc., to achieve the effect of increasing the complexity of the problem, slowing down the reaction speed, and reducing the resistance of the cell

Inactive Publication Date: 2011-08-18
THE BOARD OF TRUSTEES OF THE UNIV OF ILLINOIS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Positive and small H′ ions have the highest diffusion coefficient and can present in high concentrations, leading to low internal electric resistance of the cell.
The problem with proton exchange membrane-based fuel cells, including direct methanol fuel cells, is that usually used oxygen reduction reaction, occurring at the cathode, is very slow and a catalyst is needed.
The problem becomes even more complicated because exchange currents for anode and cathode reactions on Pt can be limited by both ion transport in solutions and interface electron transfer, thus leading to the current-overpotential, i.e. it is necessary to use voltage higher than its thermodynamic equilibrium value to start and conduct fast electrochemical reaction.
Application of fuel cells in underwater vehicles has another problem.
Unlike ground and air transportation, these vehicles must carry both the fuel and the oxygen source because the oxygen concentration in water is insufficient to meet the vehicle power requirements.
Gaseous oxygen storage does not provide adequate storage densities, while liquid oxygen storage introduces challenges with handling and storage.
Solid-state oxygen sources such as sodium chlorate (NaClO3) and lithium perchlorate (LiClO4) possess high oxygen contents and are stable under ambient conditions; however, decomposition of these materials to gaseous oxygen typically employs thermal methods that are often difficult to start, stop, and control.
They can be used in submarine applications to accumulate, to store and to use electric energy when necessary, but have the major challenge, which is nonselective ionic and water migration through the ion-exchange membrane.
An electric organ of an eel Electrophorus electricus is a battery of biological membranes, which during excitation can generate voltages up to 1000V and currents up to 1 A. After purification these membranes are not stable and can not be used as a electrochemical power source in everyday life.
These electrochemical cells are called concentration elements, but they did not find practical applications because of the low generated voltage.

Method used

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Examples

Experimental program
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example 3

[0071]This example demonstrates that it is possible to use not only inorganic but also organic reducing agents. Ascorbic acid, NADH and NADPH, redox active dyes Neutral red, Nile blue and N-phenylanthranilic acid can be used as reducing agents reacting with PANI. The membrane had a good response to redox active substances, which normally do not have satisfactory response on Pt electrode, i.e. ascorbic acid. The slope for ascorbic acid was near 26 mV for ten times concentration changes, corresponding to the redox mechanism with two electrons transferred through the membrane from one molecule of ascorbic acid. The lower concentration limit when these substances start changing transmembrane potential is near 0.2 mM in 0.01M phosphate buffer, pH 6.4.

example 4

[0072]Combination of the membrane together with many different redox agents, which can easily react with PANI and have different redox potentials can be used as a source of electric energy. This example demonstrates that using strong oxidizing agents at higher concentrations leads to higher and practically important transmembrane voltage. PANI can electro-catalyze the reduction of O2 in sulfuric acid in fuel cell operations with H2O2 as the product:

LEB+2A−+2H++O2→ES+H2O2  (1)

Here LEB and ES refer to leucoemeraldine base and emeraldine salt, respectively; A− is the anion from solution, which is then incorporated into ES as the counter ion. Freshly made polyaniline in acidic solutions in contacts with air can easily change its color from green to dark blue and then to black even without electrodes because of redox processes. Mechanism of possible continuous H2O2 formation and PANI regeneration using reducing potential is presented in the Scheme 1.

[0073]Thermodynamic electrode potentia...

example 5

[0075]This example demonstrates that transmembrane potential can be additionally influenced 425 by changes of chloride anion concentration. Addition of potassium chlorides into the reducing solution makes increases the transmembrane voltage and makes it even more negative. Addition of KCl into the opposite solution makes decreases the value of transmembrane voltage.

[0076]The transmembrane electric potential difference across the doped PANI membrane is a mixed potential due to both electron transport in redox processes and simultaneous Cl− ion transport. When the first reversible pare of redox agents is present in one of the solutions and the second in another, transmembrane voltage is described by the equation

V=ΔE0-2.3RTnFLogred1+αCl1-ox1-βCl1-+2.3RTnFLogred2+αCl2-ox2-βCl2-

Here red, ox and Cl− are activity of corresponding species; subscripts 1 and 2 correspond to the two solutions separated by the membrane; and α and β characterize membrane selectivity for pares red / Cl− and ox / Cl−....

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Abstract

A flow fuel cell for use as a source of electrochemical energy with the membrane separating two flowing aqueous solutions with dissolved redox active components and electrodes of the second kind, wherein the membrane is made of a redox active synthetic metal polymer.

Description

RELATED US PATENT DOCUMENTS[0001]L. H. Thaller, Electrically rechargeable redox flow cell, U.S. Pat. No. 3,996,064, 1976.[0002]M. S. Kazacos, M. Kazacos, Stabilized vanadium electrolyte solutions for all-vanadium redox cells and batteries, U.S. Pat. No. 6,562,514, 2003.[0003]L. Nagels, H. Bohets, M. Jimidar, Potentiometric electrode, gradient polymer, uses and method of preparation thereof, US Patent 2008 / 0000290 A1[0004]J. H. Kim, D. G. Ryu, Y. L Yi, J. H. Park, Composition of polythiophenethiophene-based conductive polymers having high conductivity, transparency, waterproof property and a membrane prepared using the same, US patent US 2008 / 0293855 A1.[0005]C-H Hsu, F. P. Uckert, Water dispersible polyanilines made with polymeric acid colloids for electronics applications, US patent US 2008 / 0210910 A1.[0006]K. Asazawa, K. Yamada, H. Tanaka, Fuel Cell, US patent application publication US2010 / 0035111 A1[0007]N. Kocherginsky, Wang Zheng, Measurements of Redox Potential and Concentrat...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M8/22
CPCH01M8/103H01M8/1032Y02E60/528Y02E60/521H01M8/20Y02E60/50H01M2008/1095H01M2300/0082
Inventor KOCHERGINSKY, NIKOLAI M.
Owner THE BOARD OF TRUSTEES OF THE UNIV OF ILLINOIS
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