Proton Conducting Polymer Membranes
Fig 1: Electrochemical cell testing an invention membrane
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Sr. Technology Licensing Officer
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Proton conducting polymer membranes are of general interest because such membranes can be used to conduct protons in fuel cells, which convert methanol into electrical energy and show promise as low emission power sources. Improved proton conducting polymer membranes (a/k/a polymer electrolyte membranes) have been developed, along with methods for the manufacture thereof.
Proton conducting polymer membranes are of general interest because such membranes can be used to conduct protons in fuel cells, which convert methanol into electrical energy and show promise as low emission power sources. Methanol-based fuel cells produce power through the electrochemical reaction of methanol and oxygen whereby oxygen is reduced at the cathode and methanol is oxidized at the anode. An appropriate polymer membrane is insoluble in water and methanol and is selectively permeable to hydrogen ions. Fluorocarbon based resins, such as NAFION™ and its derivatives, are the most common materials used in the manufacture of solid-polymer electrolyte membranes in methanol fuel cells. The membranes are stable and conduct protons. However, the membranes are permeable to methanol and allow significant amounts of methanol to diffuse through the membrane and crossover from the anode to cathode resulting in oxidation of methanol at the cathode. This oxidation depletes fuel from the cell and results in a loss of energy and efficiency. It would be advantageous to develop alternative membrane materials that are more resistant to methanol diffusion (and thus crossover).
Improved proton conducting polymer membranes (a/k/a polymer electrolyte membranes) have been developed, along with methods for the manufacture thereof. These proton conducting membranes exhibit excellent proton conductivity (comparable to standard commercially available membranes) and yet have increased resistance to methanol diffusion. The polymer membranes are formed by combining a polymer, an oxyacid (such as phosphorus oxyacid), and water. In a preferred embodiment, the polymeric membranes are formed by (a) dissolving a polymer, preferably a polyphosphazene, in an organic solvent to form a polymer solution; (b) adding an oxyacid to the polymer solution; (c) optionally, adding water to the polymer solution, preferably in a molar ratio equivalent to the oxyacid; (d) optionally, concentrating the polymer solution; (e) casting the polymer solution on a casting surface, such as one formed of or coated with TEFLON™.; and (f) removing the organic solvent, so as to form the polymeric membrane. A particularly useful application for these polymeric membranes is in fuel cells, such as those wherein methanol and oxygen are converted into electrical energy.
- Polymer electrolyte membranes with excellent proton conductivity
- Resistance to methanol diffusion and thus useful in methanol fuel cells