Fuel battery

• US 20050053825A1
• Filed: 07/25/2003
• Published: 03/10/2005
• Est. Priority Date: 07/26/2002
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Takagi, Kyosuke, Tomita, Takashi, Suzuki, Yusuke, Sakai, Hideki, Hatazawa, Tsuyonobu
• Granted Patent: US 8,076,035 B2
• Time in Patent Office: Days
• US Class Current: 429/401
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 8/16 Biochemical fuel cells, i.e. cells in which microorganisms function as catalysts
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell which utilizes the biogenic metabolism to produce a high current density is provided. The fuel cell generates electric power in such a way that the fuel is decomposed stepwise by a plurality of enzymes and those electrons formed by oxidation are transferred to the electrode. The enzymes work such that the enzyme activity of the enzyme involved in decomposition in the early stage is smaller than the sum of the enzyme activities of the enzymes involved in decomposition in the later stage. In the case where a coenzyme is involved, the enzyme activity of the oxidase that oxidizes the coenzyme is greater than the sum of the enzyme activities of the enzymes involved in the formation of the reductant of the coenzyme, out of the enzymes involved in the stepwise decomposition of the fuel.

Claims

1-14. -14. (canceled).

15. A fuel cell comprising, the fuel cell capable of decomposing fuel with a plurality of enzymes in one or more stepwise reactions and transfers of electrons produced by oxidation reaction to an electrode of the fuel cell, wherein the reactions occur such that U(E1)≦

U(E2), where U(E1) denotes the enzyme activity of enzyme-1 to produce decomposition product-1 through its decomposition reaction and U(E2) denotes the sum of the enzyme activity of enzyme group-2 to decompose the decomposition product-1.

16. The fuel cell as defined in claim 15, wherein the enzyme-1 includes an oxidase.

17. The fuel cell as defined in claim 15, wherein the decomposition reaction by the enzyme-1 includes an oxidation reaction which transfers electrons to a coenzyme.

18. The fuel cell as defined in claim 17, which further includes a coenzyme oxidase to produce an oxidant of the coenzyme such that U(Co)≧

U(E), where U(Co) denotes the enzyme activity of the coenzyme oxidase and U(E) denotes the sum of the enzyme activity of a group of enzymes associated with the plurality of enzymes that are involved in a production of reductant of the coenzyme.

19. The fuel cell as defined in claim 17, wherein the coenzyme produces an oxidant that includes NAD⁺ and a reductant that includes NADH.

20. The fuel cell as defined in claim 18, wherein the oxidant of the coenzyme is formed by a coenzyme oxidase that includes diaphorase.

21. The fuel cell as defined in claim 17, wherein the coenzyme transfers electrons further to an electron mediator.

22. The fuel cell as defined in claim 21, wherein the electron mediator includes vitamin K₃.

23. The fuel cell as defined in claim 16, wherein the fuel is at least one species selected from the group consisting of alcohols, saccharides, fats, proteins, and organic acids.

24. The fuel cell as defined in claim 22, wherein the fuel is at least one species selected from the group consisting of methanol, ethanol, and glucose.

25. The fuel cell as defined in claim 16, wherein the fuel includes methanol and the enzymes that decompose the fuel stepwise are selected from the group consisting of alcohol dehydrogenase, formaldehyde dehydrogenase, formate dehydrogenase and mixtures thereof.

26. The fuel cell as defined in claim 16, wherein the fuel includes ethanol and the enzymes that decompose the fuel stepwise are alcohol dehydrogenase and aldehyde dehydrogenase.

27. The fuel cell as defined in claim 16, wherein the fuel is glucose and the enzymes that decompose the fuel stepwise are selected from the group consisting of glucose dehydrogenase, gluconokinase, phosphogluconate dehydrogenase and mixtures thereof.

28. The fuel cell as defined in claim 18, wherein the fuel includes methanol, the enzymes that decompose the fuel stepwise are selected from the group consisting of alcohol dehydrogenase, formaldehyde dehydrogenase, formate dehydrogenase and combinations thereof, the coenzyme oxidase that oxidizes the coenzyme includes diaphorase, and the conditions specified by equations (1) and (2) below are satisfied and defined as follows:

0<

U(ADH)≦

U(FalDH)≦

U(FateDH) 

 

(1)
U(ADH)+U(FalDH)+U(FateDH)≦

U(DI) 

 

(2)

where U(ADH) denotes an enzyme activity of the alcohol dehydrogenase, U(FalDH) denotes an enzyme activity of the formaldehyde dehydrogenase, U(FateDH) denotes an enzyme activity of the formate dehydrogenase, and U(DI) denotes an enzyme activity of the diaphorase.