One-compartment aqueous fuel cell with metallic copper as the cathode

Abstract

To provide a fuel cell in one-compartment.SOLUTION: In a fuel cell, a cathode electrode made of metallic copper and a metal anode having a lower electrode potential than copper are opposed to each other in an electrolytic solution containing hydrogen peroxide, hydrogen gas is generated on the surface of the copper cathode in an electrolyte containing hydrogen peroxide, and reacts with oxygen supplied from hydrogen peroxide, and causes power generation reaction without supplying hydrogen from the outside. The configuration of the present invention can provide a novel and useful configuration as a one-compartment hydrogen fuel cell or a hydrogen peroxide fuel cell.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a novel fuel cell that uses metallic copper as a cathode electrode and generates electricity in a single compartment in an aqueous electrolyte tank without separating the positive and negative electrodes with an ion separation membrane wall. [Background technology]

[0002] Voltaic cells, which are chemical cells that use metallic copper as the cathode electrode and metallic zinc as the counter electrode, and use the dissolution of metals and the accumulation of metal ions in a dilute sulfuric acid electrolyte as energy, are well known as batteries that use metallic copper as the cathode electrode, but metal-air batteries and fuel cells that use copper as the cathode electrode have not been developed. This is because metal-air batteries that use oxygen as the active material at the cathode and a metal electrode as the anode adopt a system in which the reactant between oxygen, which is the positive electrode active material, and the metal, which is the negative electrode active material, is stored on the cathode side, so it is necessary to use carbon electrodes or ceramic electrodes other than metals to store the reactant, which is a metal oxide, and there are no metal-air batteries that use copper as the cathode electrode. As for fuel cells, hydrogen fuel cells have been attracting attention, and typically hydrogen is sent to an electrode sandwiching a solid electrolyte, and oxygen is sent to the other electrode to react with hydrogen and oxygen to generate electricity, which requires a hydrogen supply source and a solid electrolyte that reacts hydrogen and oxygen to be sandwiched between both electrodes, and there are no hydrogen fuel cells that use copper as the cathode electrode.

[0003] In recent years, hydrogen peroxide fuel cells, which use aqueous solutions and have a single compartment structure, have been expected to be a promising energy conversion platform because, unlike hydrogen fuel cells, they can be easily supplied with fuel and can operate in a single compartment structure without a membrane separating the cathode and anode chambers. However, because hydrogen peroxide is a high-energy-density liquid that functions as both fuel and oxidant, most metal electrodes are required to separate the H2O and O2 fart No hydrogen peroxide fuel cells exist that use metal cathodes because they catalyze the disproportionation reaction of 1,2-dinitrophenyl ether (HO) and thus represent a significant loss mechanism in peroxide fuel cells.

[0004] In the past, a peroxide fuel cell was announced that uses a conductive polymer poly(3,4-ethylenedioxythiophene (PEDOT) as a cathode electrode and a nickel mesh as an anode electrode, and shows an open circuit potential in the range of 0.5 to 0.6 V at a power density of 0.20 to 0.30 mW cm without generating losses due to disproportionation reactions (Non-Patent Document 1: “Single-Compartment hydrogen peroxide fuel cell with poly(3,4-ethylenedioxythiophene) cathodes” Chemical Communications, 2018, Vol. 54, Pages 11873-11876). On the other hand, a hydrogen peroxide fuel cell that uses copper hexacyanoferrate (CuHCF) as a cathode material and a Ni grid as an anode material has also been announced (Non-Patent Document 2: “Copper hexacyanoferrate as cathode material for hydrogen peroxide fuel cell” International Journal of Hydrogen Energy, ELSEVIER, Vol. 45, Issue 47, 25 September 2018). 2020,Pages 25708-25718). [Prior art documents]

[0005] [Non-Patent Document 1] Chemical Communications,2018,Vol.54,Pages 11873-11876 [Non-Patent Document 2] Journal of Hydrogen Energy,ELSEVIER,Vol.45,Issue 47,25 September 2020,Pages 25708-25718 Summary of the Invention Problem to be solved by the invention

[0006] Under these circumstances, metal-air batteries or fuel cells that use oxygen from the air as the active material at the cathode, rather than chemical batteries, are preferable as sources of electrical energy. However, hydrogen fuel cells require a solid electrolyte that forms a hydrogen-oxygen reaction tank and an external supply of hydrogen, and hydrogen stations limit the effective use of hydrogen fuel cells in automobiles. In contrast, fuel cells that use hydrogen peroxide as fuel are promising for compacting battery systems, as the reaction takes place within a single compartment. However, they require the use of conductive polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) or copper hexacyanoferrate (CuHCF) as the cathode electrode material, which makes them less versatile.

[0007] In various experiments, the inventors have focused on the phenomenon that a large amount of hydrogen is generated from the copper surface when metallic copper is used and an aqueous solution containing sodium chloride and hydrogen peroxide or sodium percarbonate is used (Fig. 2). As a result of intensive research, the inventors have come to the conclusion that if the hydrogen generated on the electrode surface can be utilized, it is possible to eliminate the need for an excessively large hydrogen supply system, which is the biggest problem in hydrogen fuel cells. On the other hand, in hydrogen peroxide fuel cells, since it is easy to provide a fuel cell that can generate electricity by supplying oxygen in an aqueous solution in one compartment, the inventors have focused on the fact that a simple fuel cell can be provided even if a versatile metal electrode is used, as long as the disproportionation of hydrogen peroxide at the cathode electrode is eliminated. In view of this point, the inventors have focused on the purpose of providing a fuel cell configuration that utilizes a system that can supply hydrogen within the cell, while supplying oxygen to the cathode and reacting the oxygen and hydrogen in an aqueous solution in one compartment to generate electricity, without dividing the electrolytic layer into two with a solid electrolyte as in conventional hydrogen fuel cells. Means for achieving the object

[0008] As shown in Fig. 1, the present invention is a one-compartment fuel cell comprising an aqueous electrolyte solution containing at least an electrolyte for imparting electrical conductivity and hydrogen peroxide, a cathode electrode made of metallic copper immersed in the electrolyte solution, and an anode electrode made of metallic aluminum or magnesium metal or an alloy thereof, which has an electrode potential lower than that of metallic copper, and the metallic copper cathode electrode and the anode electrode are disposed opposite each other by being immersed in the electrolyte solution. In the present invention, in order to utilize the generation of hydrogen ions or hydrogen gas on the surface of metallic copper serving as the cathode electrode, it is preferable to provide at least one electrode configuration in which the anode electrode is plate-shaped and metallic copper plates are disposed on both sides of the anode electrode at a distance from each other. Effects of the invention

[0009] According to the present invention, hydrogen and oxygen are generated and react on the metallic copper surface of the cathode electrode, and a boiling phenomenon that generates heat, which is specific to the reaction, is observed (Fig. 3). On the other hand, since the aqueous electrolyte solution containing the electrolyte and hydrogen peroxide is in a nearly neutral range, the aluminum or magnesium constituting the anode electrode only dissolves and loses 1-5% in about one day, which is much smaller than the case of a Volta cell, which is a chemical cell that uses dilute sulfuric acid as the electrolyte. In addition, while the copper surface of a Volta cell becomes passivated and power generation stops in less than one hour, in the present invention, power generation continues for one day and night as long as hydrogen peroxide is present in the electrolyte, so the anode electrode is not dissolved in the chemical cell, and the electrolyte is heated between the anode electrode and the cathode electrode, probably because oxygen and hydrogen formed from hydrogen peroxide react on the copper electrode surface and generate heat, and the boiling phenomenon gradually occurs. Therefore, the cell configuration of the present invention is recognized to have a phenomenon specific to a hydrogen fuel cell in which hydrogen reacts with oxygen to generate reaction heat. Therefore, in the present invention, a power generation amount of 5 wh / g or more per gram of electrode weight reduction is observed, which has never been seen in conventional chemical batteries. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram showing a battery configuration of the present invention. [Diagram 2] 1 is a photograph showing the generation of hydrogen from the surface of metallic copper in an electrolyte containing hydrogen peroxide. [Diagram 3] 1 is a photograph showing that the boiling phenomenon of the electrolyte sandwiched between the electrodes is observed in the configuration of the present invention. [Figure 4] 4 is a photograph showing the power generation state in a specific battery configuration of the present invention. EMBODIMENTS OF THE PRESENTINVENTION

[0011] The amount of power generated was measured using the battery configuration shown in Figure 4. Electrodes were placed at equal intervals in a 1200 ml open-top rectangular plastic container with corrugated walls. Three 10 x 20 cm, 0.5 mm thick copper plates and two 10 x 20 cm, 0.5 mm thick aluminum plates were placed in an alternating copper / aluminum / copper / aluminum / copper arrangement from left to right. 750 ml of tap water was mixed with salt to a concentration of 0.5 to 2.0 mol / l, and 250 ml of hydrogen peroxide (30% concentration, manufactured by Wako Pure Chemical Industries) or an equivalent amount of sodium percarbonate, or 250 ml of hydrogen peroxide and 0.5 mol / l of sodium percarbonate were mixed, and the amount of electricity generated was measured.

[0012] As a result, it was found that, although it depends on the amount of hydrogen peroxide supplied, the amount of electricity generated is small with saline solution of 0.5 mol / l or less, while with saline solution of a concentration of 1.5 mol / l to 2.0 mol / l, the reaction becomes so great that the electrolyte boils and spills out of the container, so a salt concentration of 1.0 mol / l to 1.5 mol / l, preferably around 1.2 mol / l, is preferable.

[0013] The amount of hydrogen peroxide to be supplied is preferably 1 / 10 to 1 / 4 of the electrolyte solution, with 30% hydrogen peroxide solution (mass / mass), and 10 to 30 ml is added at regular intervals, preferably every 2 to 3 hours. However, sodium percarbonate can be used instead of hydrogen peroxide solution. The use of sodium percarbonate is preferable for reaction control of the battery of the present invention, since hydrogen peroxide is gradually released. Furthermore, since sodium carbonate serves as an electrolyte, the reaction proceeds without adding salt. However, the simultaneous use of hydrogen peroxide solution, sodium percarbonate, and salt, allows the power generation reaction to start up quickly, and is currently the most preferable combination.

[0014] Considering the above experiments, in the present invention, when metallic copper is used as a cathode electrode and opposed to a metal anode with a lower electrode potential than copper in an electrolyte containing hydrogen peroxide, hydrogen gas is generated on the surface of the copper cathode in the electrolyte containing hydrogen peroxide, where it reacts with oxygen supplied from the hydrogen peroxide solution to generate electricity, as seen in hydrogen fuel cells. This is a phenomenon that has not been discovered until now. Therefore, the configuration of the present invention is revolutionary because it can provide a new and useful configuration for a one-compartment hydrogen fuel cell or hydrogen peroxide fuel cell.

Claims

1. A one-compartment fuel cell comprising: an aqueous electrolyte solution containing at least sodium percarbonate and / or sodium chloride and hydrogen peroxide; a cathode electrode made of metallic copper immersed in the electrolyte solution; and an anode electrode made of metallic aluminum or magnesium metal or an alloy thereof, the electrode potential of which is lower than that of metallic copper; the metallic copper cathode electrode and the anode electrode are disposed in the electrolyte solution facing each other without being separated by an ion separation membrane wall, and hydrogen and oxygen are reacted on the surface of the cathode.

2. 2. The fuel cell according to claim 1, comprising at least one electrode configuration in which the anode and cathode electrodes are in the form of plates, and cathode electrodes made of metallic copper are disposed on both sides of the anode plate so as to face each other at a distance in the electrolyte.

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