Organic fuel cell methods and apparatus

• US 6,248,460 B1
• Filed: 06/07/1995
• Issued: 06/19/2001
• Est. Priority Date: 10/12/1993
• Status: Expired due to Term

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Olah, George A., Prakash, G. K. Surya, Narayanan, Sekharipuram R., Vamos, Eugene, Frank, Harvey A., Surampudi, Subbarao, Halpert, Gerald
• Primary Examiner(s): KALAFUT, STEPHEN J
• Application Number:
  US08/478,801
• Time in Patent Office: 2,204 Days
• Field of Search: 429/15, 429/33, 429/42, 502/101, 427/115, 427/220, 427/221, 427/443.2
• US Class Current: 429/415
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 4/8605 Porous electrodes
• CPC Class Codes: H01M 4/8807 Gas diffusion layers
• CPC Class Codes: H01M 4/8853 Electrodeposition
• CPC Class Codes: H01M 4/921 Alloys or mixtures with metallic elements
• CPC Class Codes: H01M 4/926 on carbon or graphite
• CPC Class Codes: H01M 8/0234 Carbonaceous material
• CPC Class Codes: H01M 8/0239 Organic resins; Organic polymers
• CPC Class Codes: H01M 8/0243 in the form of mixtures
• CPC Class Codes: H01M 8/04186 of liquid-charged or electrolyte-charged reactants
• CPC Class Codes: H01M 8/1004 characterised by membrane-electrode assemblies [MEA] H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1009 with one of the reactants being liquid, solid or liquid-charged H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: H01M 8/1023 having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
• CPC Class Codes: H01M 8/1039 halogenated, e.g. sulfonated polyvinylidene fluorides
• CPC Class Codes: H01M 8/1053 consisting of layers of polymers with at least one layer being ionically conductive
• CPC Class Codes: H01M 8/22 Fuel cells in which the fuel is based on materials comprising carbon or oxygen or hydrogen and other elements; Fuel cells in which the fuel is based on materials comprising only elements other than carbon, oxygen or hydrogen
• CPC Class Codes: H01M 8/2455 with liquid, solid or electrolyte-charged reactants
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A liquid organic fuel cell is provided which employs a solid electrolyte membrane. An organic fuel, such as a methanol/water mixture, is circulated past an anode of a cell while oxygen or air is circulated past a cathode of the cell. The cell solid electrolyte membrane is preferably fabricated from Nafion™. Additionally, a method for improving the performance of carbon electrode structures for use in organic fuel cells is provided wherein a high surface-area carbon particle/Teflon™-binder structure is immersed within a Nafion™/methanol bath to impregnate the electrode with Nafion™. A method for fabricating an anode for use in a organic fuel cell is described wherein metal alloys are deposited onto the electrode in an electro-deposition solution containing perfluorooctanesulfonic acid. A fuel additive containing perfluorooctanesulfonic acid for use with fuel cells employing a sulfuric acid electrolyte is also disclosed. New organic fuels, namely, trimethoxymethane, dimethoxymethane, and trioxane are also described for use with either conventional or improved fuel cells.

Claims

1. An aqueous methanol operating fuel cell, comprising:

an anode formed with particles of catalyst of material which are effective to catalyze methanol,

said anode including a first surface that has a layer of liquid perfluorooctanesulfonic applied thereto, and said first surface with said liquid perfluorooctanesulfonic thereon being exposed to a fuel solution including said methanol, and a second surface of said anode, opposite said first surface;

a proton conducting electrolyte and membrane, said proton conducting electrolyte and membrane coupled to said second surface of said anode; and

a cathode, coupled to a second surface of said proton conducting electrolyte and membrane, said cathode effective to reduce particles which are applied thereto.

2. A fuel cell as in claim 1 wherein said methanol is substantially free of any liquid acid electrolyte therein.

3. A method of operating a fuel cell, comprising:

preparing a first electrode to operate as a first polarity electrode, said first electrode having a first surface exposed to the fuel;

modifying said first electrode in a way to bring the fuel into better contact with the first electrode by its wetting of the first electrode;

circulating an organic fuel which is substantially free of any acid electrolyte into contact with said first surface of said first electrode, said organic fuel having a component which is capable of electro-oxidation;

preparing a second electrode which operates as a second polarity electrode, said second polarity being different than the first polarity, said second electrode having a second surface;

preparing an electrolyte which includes a proton conducting membrane;

circulating a second reactive component into contact with said second surface of said second electrode, said second reactive component including a component capable of electro-reduction to form a reaction wherein said wetting comprises adding a superacid to the organic fuel.

4. A fuel cell system with water recycling, comprising:

a methanol storage tank, including inner surfaces adapted for storing a quantity of liquid methanol containing fuel, and an output port;

a circulation tank, receiving said methanol from said methanol storage tank, and to receive water therein, and having inner surfaces which contain said methanol and water, said circulation tank also including a recycling port receiving at least one source of recycled fuel material;

a fuel pump, connected to said circulation tank, and pumping said methanol and water from said circulation tank to an output port;

a fuel cell stack, including a plurality of fuel cell elements therein, each fuel cell element of a type which electrochemically reacts with methanol and water, and with an oxidant, to produce electricity, carbon dioxide, and water and output products, said fuel cell stack having a first side which receives said methanol and water containing fuel from said output port of said fuel pump, and a second side which receives oxidant material; and

a first water recovery unit, connected to an output of said fuel cell stack on the first side that receives the methanol and water containing fuel to receive used fuel material that has reacted with said fuel cell stack, said first water recovery unit operating to cool the sued fuel material, and to extract usable parts of the used fuel material, and connecting said usable parts into said recycling port of said circulation tank as recycled fuel material.

5. A system as in claim 4, further comprising a second water recovery unit, connected to an output of said fuel cell stack on the second side that receives the oxidant, operating to recover water from used oxidant that has passed through the stack, and coupling said recovered water to the recycling port of said circulation tank.

6. A system as in claim 5 wherein said recycling port receives both fuel and water as the recycled fuel material.

7. A system as in claim 5 wherein said methanol storage tank stores concentrated methanol, and wherein there is an aqueous solution of methanol in said methanol circulation tank, said aqueous solution of methanol being substantially free of any acid electrolyte.

8. A system as in claim 4 wherein said stack elements include:

an anode electrode on the first side, having a structure to react with the methanol and water containing fuel;

a cathode electrode on the second side, having a structure to react with the oxidant; and

an electrolyte, comprising a proton-conducting membrane which is coupled between, and to both of, said first and second electrodes.

9. A system as in claim 4 wherein said first water recovery unit also includes an element for removing carbon dioxide from said used fuel.

10. A system as in claim 9 wherein said element includes a carbon dioxide port on the circulation tank which allows carbon dioxide gas to be vented.

11. A system as in claim 9 wherein said carbon dioxide removing element comprises a microporous material which allows gases to be released when they are passed therethrough.

12. A methanol based fuel cell system with water recycling, comprising:

a fuel cell stack, including a plurality of fuel cell elements therein, each fuel cell element of a type which electrochemically reacts with methanol and water, and with an oxidant, to produce electricity, carbon dioxide, and water and output products, said fuel cell stack having;

a) an anode electrode on a first side of the stack, having a structure to react with a methanol and water containing fuel;

b) a cathode electrode on a second side of the stack, having a structure to react with the oxidant;

c) an electrolyte, comprising a proton-conducting membrane which is coupled between, and to both of, said first and second electrodes; and

d) a casing, holding said anode electrode, said cathode electrode, and said electrolyte, and having first, and second ports on said first side, said first port allowing fuel to enter, and bringing said fuel into contact with said anode electrode, fuel being exhausted through said second port after contacting said anode electrode, and having third and fourth ports on said second side, said third port allowing oxidant to enter, and said fourth port exhausting oxidant after contacting said cathode electrode;

a methanol storage tank, including inner surfaces adapted for storing a quantity of liquid methanol containing fuel, and an output port;

a circulation tank, receiving said methanol from said methanol storage tank, and receiving water therein, and having inner surfaces which contain said methanol and water, said circulation tank also including a recycling port receiving at least one source of recycled fuel material;

a fuel pump, connected to said circulation tank, and pumping said methanol and water from said circulation tank to said first port of said fuel cell stack;

a first water recovery unit, connected to said second port of said fuel cell stack on the first side that receives the methanol and water containing fuel to receive used fuel material that has reacted with said fuel cell stack, said first water recovery unit operating to extract usable parts of the used fuel material, and to connect said usable parts into said recycling port of said circulation tank as recycled fuel material; and

a second water recover unit, connected to said fourth port of said fuel cell stack on the second side that receives the oxidant, operating to recover water from used oxidant that has passed through the stack, and coupling said recovered water to the recycling port of said circulation tank.

13. A method of operating a methanol-based fuel cell system with water recycling, comprising:

forming a fuel cell stack by providing;

a) an anode electrode on a first side of the stack, having a structure to react with a methanol and water containing fuel;

b) a cathode electrode on a second side of the stack, having a structure to react with the oxidant;

c) an electrolyte, comprising a proton-conducting membrane which is coupled between, and to both of, said first and second electrodes; and

d) a casing, holding said anode electrode, said cathode electrode, and said electrolyte, and having first, and second ports on said first side, said first port allowing fuel to enter, and bringing said fuel into contact with said anode electrode, fuel being exhausted through said second port after contacting said anode electrode, and having third and fourth ports on said second side, said third port allowing oxidant to enter, and said fourth port exhausting oxidant after contacting said cathode electrode;

storing a quantity of liquid methanol containing fuel;

supplying said liquid methanol containing fuel from said circulation tank to said first port of said fuel cell stack;

recovering water from said second port of said fuel cell stack on the first side that receives the methanol and water containing fuel to receive used fuel material that has reacted with said fuel cell stack, and to mix usable parts with said liquid methanol containing fuel; and

recovering water from said fourth port of said fuel cell stack on the second side that receives the oxidant, and to mix usable parts with said liquid methanol containing fuel.