DUAL-CATHODE FUEL BIOCELL

Abstract

A biocell having an electrochemical cell. The electrochemical cell includes an anode, a first cathode and a second cathode, and first and second porous separator membranes, wherein the first membrane is placed between a first contact surface of the anode and a first surface of the first cathode, and wherein the second membrane is placed between a second contact surface of the anode and a first surface of the second cathode.

Claims

1-10. (canceled)

11. A comprising an electrochemical cell, said electrochemical cell comprising: an anode consisting of a solid agglomerate having a first contact surface and a second contact surface, said first and second contact surfaces being opposite each other and intended to be brought into contact with a liquid medium, said liquid medium optionally comprising a fuel, said anode comprising a conductive material mixed with a first enzyme capable of catalyzing the oxidation of a fuel and, optionally, a mediator allowing the transfer of electrons; a first cathode and a second cathode each consisting of a solid agglomerate and each having a first contact surface and a second contact surface, said first and second contact surfaces being opposite each other, said first contact surfaces being intended to be brought into contact with a liquid medium and said second contact surfaces being intended to be brought into contact with a gas comprising an oxidant, said first and second cathodes comprising a conductive material, optionally mixed with a second enzyme capable of catalyzing the reduction of said oxidant; and a first and a second porous separator membrane, each electrically insulating, and permeable to a liquid medium, said first membrane being placed between the first contact surface of the anode and the first surface of the first cathode and said second membrane being placed between the second contact surface of the anode and the first surface of the second cathode; said biocell further comprising means for electrically switching on said biocell with an electrical receiver, said electric switching means allowing current to flow between the anode and the first and second cathodes.

12. The biocell according to claim 11, wherein said electrochemical cell comprises a series of layers, forming a multilayer stack, these layers comprising said anode, cathodes, separator layers and circuitry means.

13. The biocell according to claim 11, wherein said fuel is selected from the group consisting of sugar, methanol, starch and mixtures thereof.

14. The biocell according to claim 11, wherein the oxidant is selected from the group consisting of carbon dioxide, sulfur or nitrogen oxides and mixtures thereof.

15. The biocell according to claim 11, wherein said first and, optionally, second membranes are based on cellulose.

16. The biocell according to claim 11, wherein said circuitry means comprise a conductive element in contact with the anode and a conductive element in contact with the first and the second cathode, said conductive element in contact with the first and the second cathode comprising a material also allowing gaseous diffusion at the cathodes of said oxidant.

17. The biocell according to claim 11, wherein said separating and porous membranes, electrically insulating, and permeable to the liquid medium, are also a means for storing said fuel and making the liquid available.

18. The biocell according to claim 11, wherein said biocell comprises an external coating, preferably flexible, insulating and/or impermeable to liquid, comprising openings positioned and dimensioned so as to allow access of said liquid to the anode and/or of said gas to the cathodes.

19. An apparatus comprising the biocell according to claim 11, and an electrical receiver, said biocell being electrically connected to said electrical receiver.

20. A method of generating a current, comprising: electrically switching on the biocell according to claim 11 or an apparatus comprising the biocell and an electrical receiver, said biocell of said apparatus being electrically connected to said electrical receiver.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0077] The invention will be better understood on reading the description that follows, given solely by way of example and with reference to the appended drawings, in which:

[0078] FIG. 1 is a diagram showing the conventional configuration of a single cathode cell (SC) and a single air cathode cell (SABC) as well as the configuration of the dual air cathode cell (DABC) according to the principle of the invention.

[0079] FIG. 2 is an exploded front perspective view of the structure of a fuel cell according to the invention.

[0080] FIG. 3 is an illustration of the device of FIG. 2 in top view.

[0081] FIG. 4 is an illustration of the device of FIG. 2 in top view.

[0082] FIG. 5 is a bias diagram showing the peak power for the dual air cathode (DABC) device of FIG. 2.

[0083] FIG. 6 is a bias diagram showing the peak power for a single air cathode (SABC) device.

[0084] FIG. 7 shows the power curves as a function of the current of the DABC and SABC biocells as well as of a cell comprising two SABCs in series (2×2.5 mg enzymes).

EXAMPLE EMBODIMENTS

[0085] The traditional configuration of a cell (SC) is also shown in FIG. 1. In this figure, the cathode 2 is positioned in a conventional manner between an anode 4 and a support 6. FIG. 1 also shows an air cathode cell (SABC) where the support 8 is permeable to air and allows the penetration of oxygen.

[0086] The partial schematic configuration of a cell according to the invention (DABC), for its part, comprises two cathodes 2 positioned on each side of the anode 4. An air-permeable support, or protective layers, 8, is positioned on the external face of each cathode 2. Thus, the surface footprint remains the same while the power density is increased.

[0087] An example of the electrical energy production device has been provided, and its structure is shown in FIG. 2. The device is a fuel cell 10 that comprises a series of layers of constituent materials stacked on top of each other. Obviously, such a device can be positioned during its construction, or its use, in any desired position, and the terms “lower” and “upper” are used only to clarify the relative position of the elements of the device according to the invention in context and in association with the figures.

[0088] The cell 10 comprises, as electrodes, an anode 14, an upper cathode 12 and a lower cathode 12′. The electrodes 14, 12 and 12′ are in the form of thin sheets of MWCNT “Multi Walled Carbon Nanotube” nanotubes. Sheets of nanotubes suitable for this use are commercially available or can be easily manufactured using a suspension of nanotubes in a solvent such as DMF, sonication (e.g. 30 minutes) and filtration (PTFE filter from the company Millipore PTFE (JHWP, pore size 0.45 μm, Ø=46 mm). This method is described in detail in Gross et al (2017) “A High Power Buckypaper Biofuel Cell: Exploiting 1,10-Phenanthroline-5,6-dione with FAD-Dependent Dehydrogenase for Catalytically-Powerful Glucose Oxidation” ACS Catal. 2017, 7, 4408-4416. These sheets were modified by depositing (pipette) a solution of the mediator (phenanthrolinequinone, 10 mmol/L in acetonitrile) in an amount of 40 μL/0.785 cm.sup.2 on each face of the anode 14 and of the promoter (protoporphyrin IX, 10 mmol/L in water) with a volume of 40 μL/0.785 cm.sup.2 for each cathode 12 and 12′. After drying the electrodes and the mediator, the enzymes are added to these sheets by depositing (pipette) a solution thereof. At the anode 14, a solution of 5 mg/L FAD-GDH is used and a volume of 40 μL/0.785 cm.sup.2 is deposited on each of the faces of the anode. For the cathodes 12 and 12′, a 5 mg/L Bilirubin oxidase solution is used and a volume of 40 μL/0.785 cm.sup.2. Each sheet/electrode 12, 12′ and 14 was then left to dry overnight at room temperature.

[0089] Liquid diffusion and electrically insulating layers (12×18 mm) are positioned between the anode 14 on the one hand and the cathodes 12 and 12′ on the other hand. The upper diffusion layer 16 is positioned between the anode and the upper cathode 12. The lower diffusion layer 16′ is positioned between the anode 14 and the lower cathode 12′. The diffusion layers are made of Whatman filter paper-type blotting paper. They are cut to meet the configuration of the desired biocell and have a thickness of 190 μm and a weight of 97 g.Math.m.sup.−2. The upper diffusion layer 16 has a different shape from the lower layer 16′. The latter comprises a cutout portion (6×6 mm) in one of its corners, that is to say, a recess 17, which allows access from outside the device 10 to an electrical conductor 18 in contact with the anode 14 and which is positioned between the anode 14 and the diffusion layer 16′.

[0090] The electrical conductor 18 consists of a PANASONIC brand flexible graphite sheet sold by the company TOYO TANSO FRANCE SA—ZA du Buisson de la Couldre—9-10 rue Eugene Hénaff—78190 Trappes—France and described in patent JP 3691836. The use of graphite is advantageous because it combines stability, lightness and electrical and thermal conductivity. The electrical conductor sheet 18 measuring (10×18 mm) is positioned between the liquid diffusion layer 16′ and the anode 14 so as to be in direct contact with the latter and partly facing: [0091] 1) the recess 17 of the diffusion layer 16′; and [0092] 2) the opening 24′ of the support layer 22′.

[0093] A conductive and gas diffusion layer 20, also made of carbon, and allowing gas diffusion (here, air) is placed in contact with the upper cathode 12. More particularly, it is placed opposite the face of the cathode 12 that is not in contact with the upper diffusion layer 16. The latter, measuring (10×18 mm), allows the supply of oxygen to the cathode 12. This layer comprises a layer of carbon fiber covered with a layer of carbon black and polytetrafluoroethylene (PTFE) of the SIGRACET® type (marketed by the company SGL CARBON GmbH, Werner-von Siemens Strasse 18, 86405 Meitingen, Germany). The diffusion of the gas is carried out through an opening 23 in particular allowing the passage of the gas toward the cathode 12. A lower conductive and gas diffusion layer 20′ identical to the upper layer 20 is positioned symmetrically and is in contact with the cathode 12′ and facing the opening 23′.

[0094] Finally, the cell 12 comprises an upper support sheet, or support, 22, of fiberglass coated with PTFE adhesive (ref. 208AP sold by TECHNIFLON EUROPE, 3, rue du bicentenaire de la Révolution, 91220 LE PLESSIS PATE, FR). The upper support 22 measures 18×28 mm and comprises a central opening 23 measuring 8×8 mm and two circular openings 24 and 26 measuring 4 mm in diameter. The support sheet 22 covers the upper conductive and gas diffusion layer 20. The circular opening 24 allows access of a liquid to the elements of the cell. A lower support sheet 22′ forms the underside of the cell and may be of the same composition and size as the upper support sheet 22. In this example, however, the sheet 22 is a sheet of the non-woven adhesive tape type comprising a layer of polyester/rayon fibers and an acrylate-based pressure-sensitive adhesive layer sold by the company 3M. This type of material, generally for medical use, is well suited as an external coating.

[0095] The support 22′ comprises a central opening 23′ and first and second circular openings 24′ and 26′. This support 22′ is positioned so as to cover the lower conductive and gas diffusion layer 20′. The adhesive surface of the sheets 22 and 22′ facing each other and in view of their larger dimensions than the other elements of the cell 10, the edges of the sheets 22 and 22′ can come into contact and join securely.

[0096] Thus, the cathodes 12 and 12′ as well as their respective electrical contacts are located on both sides of the anode 14 and can be physically or electronically connected to each other.

[0097] To generate electricity, a phosphate-buffered saline solution, pH 7.4 at 20° C.) comprising 170 mmol of glucose was poured onto the upper diffusion layer 20 via the opening 24 (cf. FIG. 3) using a pipette. By capillarity, the liquid propagates in the device 12 and reaches the liquid diffusion layers and 16′, which allows the ionic exchange of protons between the cathodes 12 and 12′ and the anode 14 and therefore the production of current at the biocell terminals 10. As is apparent from FIGS. 3 and 4, these terminals are constituted by the part of the electrical conductor 18 that is accessible through the opening 24′, for the anode, and by the parts of the conductive and gas diffusion layers 20 and 20′ accessible through openings 26 and 26′, respectively. The bias diagram of the DABC device according to the invention is shown in FIG. 5. The air containing the oxidant (oxygen) reaches the cathodes through the central openings 23 and 23′.

[0098] To compare the efficiency of the device 10 according to the invention, a single air cathode device SABC was produced. This device differed from that of the invention only in that it does not comprise a lower cathode 12′ or a lower conductive and diffusion layer 20′. The SABC device was the same size as the device according to the invention previously described, and contained the same total mass of enzyme, mediator, glucose, buffered saline solution and insulator/transport layers. In the case of the SABC device, the enzyme mass was distributed on a single cathode (instead of two) and on a single face of the anode (instead of two). The thickness of the liquid diffusion layer was exactly twice that used in the device according to the invention.

[0099] The bias diagram of the SABC device was made is shown in FIG. 6.

[0100] These diagrams were obtained by measuring the open circuit voltage (OCV) after applying a constant discharge current for a period of 60 s. The value of the discharge current was constantly increased until the maximum power was determined and then until this power collapsed.

[0101] The power peak of the DABC device according to the invention is 63% higher than that of the SABC device. Peak operational power appears to occur over a slightly wider current range, suggesting that DABC devices may perform better over a wide range of discharge currents.

[0102] The optimum amount of enzyme at the cathode (BOD) for the devices tested is 2.5 mg/cm.sup.2.

[0103] Finally, the power curves according to the current of the devices [0104] SABC (curve A single cathode (2.5 mg enzymes/cm.sup.2)) and [0105] DABC (curve B—a double cathode according to the invention (2×1.25 mg enzymes/cm.sup.2));

[0106] have been plotted on the diagram of FIG. 7 as well as point C), which corresponds to the power of a biocell at 550 μA comprising two SABCs connected in series (2.5 mg/cm.sup.2 enzymes). Such a DABC cell allows a power 30% higher than that of the invention, but requires twice as many enzymes at the cathode.

[0107] With the same amount of enzymes, a potency increase of about 70% was obtained. With the device according to the invention. Such an increase was not foreseeable.

[0108] The invention is not limited to the embodiments described here, and other embodiments will become clearly apparent to a person skilled in the art.

[0109] It is of course possible to provide for the use of materials different from those mentioned above to form the various elements forming the device for producing electrical energy. The compounds making it possible to produce energy can also be different from those mentioned above, as well as the arrangement of the various elements (anode, cathodes, conduction and/or diffusion layers, terminals, etc.) with respect to each other.

LIST OF REFERENCE NUMBERS

[0110] 2: cathode. [0111] 4: anode. [0112] 6: support. [0113] 8: gas permeable support. [0114] 10: gas breathing enzymatic fuel cell. [0115] 12: upper cathode of cell 10. [0116] 12′: lower cathode of cell 10. [0117] 14: anode of cell 10. [0118] 16: upper electrically insulating liquid diffusion layer of cell 10. [0119] 16′: lower electrically insulating liquid diffusion layer of cell 10. [0120] 17: recess of layer 16′. [0121] 18: electrical conductor of cell 10. [0122] 20: upper conductive and gas diffusion layer of cell 10. [0123] 20′: lower conductive and gas diffusion layer of cell 10. [0124] 22: upper support sheet, or support, of cell 10. [0125] 22′: bottom support sheet, or support, of cell 10. [0126] 23: central opening of support 22. [0127] 23′: central opening of support 22′. [0128] 24: first circular opening of support 22 allowing the introduction of a liquid into the cell and the diffusion layers 16 and 16′ [0129] 24′: first circular opening of support 22′ for electrical contact (toward anode 14) [0130] 26: second circular opening of support 22 for electrical contact (toward cathode 12′) [0131] 26′: second circular opening of support 22′ for electrical contact (toward cathode 12).

LIST OF DOCUMENTARY REFERENCES

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