Combustion method for hydrogen peroxide fuel cell using cathode electrode made of copper or copper alloy

Abstract

To provide a hydrogen peroxide fuel cell reaction fueled by hydrogen peroxide.SOLUTION: In a novel combustion method for a hydrogen peroxide fuel cell, a cathode electrode consisting of metallic copper or an alloy thereof in an aqueous electrolyte containing hydrogen peroxide and an anode electrode made of a metal or an alloy thereof that has an electrode potential lower than that of the cathode electrode and forms an electrode potential difference equal to or higher than the decomposition voltage of hydrogen peroxide are immersed, and 4OH-→2O2+2H2+4e- electromotive force is obtained by decomposing hydroxyl ions formed on the cathode electrode surface into oxygen and hydrogen.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion method for a hydrogen peroxide fuel cell using a cathode electrode made of copper or a copper alloy. [Background technology]

[0002] In fuel cells, hydrogen peroxide has attracted attention as a fuel source that is easier to supply than hydrogen. In recent years, hydrogen peroxide fuel cells have been expected to be a promising energy conversion platform because, unlike hydrogen fuel cells, their single-compartment structure using an aqueous solution makes fuel supply easy and they can operate without a membrane separating the cathode and anode chambers.

[0003] However, because hydrogen peroxide is a high-energy-density liquid that functions as both a fuel and an oxidant, most metal electrodes catalyze the disproportionation of H2O2 to H2O and O2. As a result, this heterogeneous reaction represents a significant loss mechanism in peroxide fuel cells, and no hydrogen peroxide fuel cells with metal cathodes exist. Specifically, a hydrogen peroxide fuel cell has been reported that uses a conductive polymer, poly(3,4-ethylenedioxythiophene (PEDOT)) as the cathode electrode and a nickel mesh as the anode electrode to prevent losses due to disproportionation reactions, and that exhibits 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 (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 has also been reported that uses copper hexacyanoferrate (CuHCF) as the cathode material and a Ni grid as the anode material (Non-Patent Document 2: "Copper hexacyanoferrate as cathode material for hydrogen peroxide fuel cell," International Journal of Hydrogen Energy, ELSEVIER, Vol. 45, Issue 47, September 25, 2018). 2020, Pages 25708-25718). [Prior art documents] [Non-patent literature]

[0004] [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 [Non-patent document 3] Eiji Mizuto: Progress in Physical Chemistry (1936), 10(3): 154-165 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional cathode electrodes for hydrogen peroxide fuel cells, such as poly(3,4-ethylenedioxythiophene) (PEDOT) and copper hexacyanoferrate (CuHCF), are complex and difficult to mass-produce. Therefore, the present inventors have conducted extensive research to provide a new electrode that can be used as a cathode electrode for hydrogen peroxide fuel cells.

[0006] As a result, hydrogen peroxide solution is alkaline and contains many hydroxy ions along with oxygen. When copper or a copper alloy is immersed in hydrogen peroxide solution, gas is generated. Under normal conditions, this gas is oxygen resulting from the decomposition of hydrogen peroxide, but it was discovered that it contains not only oxygen but also hydrogen. While a photocatalyst would decompose water when exposed to sunlight, copper and copper alloys remain unaffected by sunlight. The decomposition of water in hydrogen peroxide solution results in a loss of electromotive force. Therefore, a battery configuration with a magnesium or aluminum anode and a copper or copper alloy cathode constitutes a voltaic cell, generating electricity by generating hydrogen from the anode side in the acidic range of the electrolyte, but no reaction occurs in the neutral range. When placed in an alkaline electrolyte containing hydrogen peroxide solution, both relatively large and fine particles of gas are generated from the copper cathode side, and electricity is generated as oxygen and hydrogen are generated from the copper electrode side. As a result, the copper electrode reacts with the OH atoms present near the electrode. - It is thought to catalyze the decomposition of hydroxy ions, and - The reaction of hydroxyl ion decomposing to form oxygen and hydrogen is 4OH - → 2O2+2H2+4e- Therefore, an object of the present invention is to provide a novel method for burning copper or its alloy in a hydrogen peroxide fuel cell. [Means for solving the problem]

[0007] The present invention is based on the decomposition reaction of hydroxy ions in a hydrogen peroxide fuel cell using copper or its alloy as a cathode electrode, and is provided with an aqueous electrolyte containing hydrogen peroxide, a cathode electrode made of metallic copper or its alloy immersed in the electrolyte, and an anode electrode made of a metal or its alloy that has an electrode potential lower than that of the cathode electrode and that forms an electrode potential difference equal to or greater than the decomposition voltage of hydrogen peroxide, Hydroxy ions generated on the surface of the cathode electrode made of metallic copper or its alloy are decomposed by the following catalytic action to generate oxygen and hydrogen, thereby generating electricity. 4OH - →2O2+2H2+4e - The present invention relates to a method for burning hydrogen peroxide in a fuel cell. [Effects of the Invention]

[0008] In the past, hydrogen peroxide fuel cells have been used in acidic regions, as shown in Non-Patent Document 1. Cathode: H2O2+ 2H++ 2e - → 2H2O (1.78 V vs. NHE)(1) Anode: H2O2 → O2+ 2H + + 2e - (0.682 V vs. NHE)(2) The total electrochemical reaction is: 2H2O2 → 2H2O + O2 (1.09 V) (3). In the alkaline region where hydrogen peroxide is added in the present invention, Cathode: H2O2+ 2e - → 2H2O+2OH - (1) Anode: H2O2+2OH - → O2 + 2H2O + 2e - (2) In the present invention, however, a catalytic reaction occurs on the copper cathode surface, and the decomposition of hydrogen peroxide leads to the decomposition of hydroxy ions, generating oxygen and hydrogen. 2H2O2→ ·4OH→ 2O2+ 2H2+ 4e - Power generation reaction or 4OH by direct decomposition of hydroxyl ion - →O2+2H2O+4e - This is accompanied by the power generation reaction. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a conceptual diagram of a hydrogen peroxide fuel cell using copper or its alloy of the present invention as a cathode electrode. [Figure 2A] FIG. 1 is a perspective view of a first cathode electrode configuration of the present invention; [Figure 2B] FIG. 1 is an assembly diagram of a first cathode electrode configuration of the present invention with an anode. [Figure 3A] FIG. 1 is a perspective view of a second cathode electrode configuration of the present invention; [Figure 3B] FIG. 11 is an assembly diagram of a second cathode electrode configuration of the present invention with an anode. [Figure 4A] FIG. 3 is a conceptual diagram of a capacitor having the electrode configuration of FIG. 2. [Figure 4B] FIG. 4 is a conceptual diagram of a capacitor having the electrode configuration of FIG. 3. [Figure 5] 4 is a conceptual diagram of the microcapacitor effect occurring on the cathode electrode surface of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the present invention, a fuel cell is constructed by arranging an Al or Mg anode electrode and a Cu cathode electrode facing each other and immersing them in an alkaline electrolyte containing hydrogen peroxide, as shown in Figure 1. The electromotive force in the anode electrode / alkaline electrolyte containing hydrogen peroxide / cathode electrode configuration is as follows: The oxidation reaction on the anode side is Me → Me n+ + ne- and On the other hand, the reduction reaction on the cathode side is O2 + H2O + 4e - →4OH - This becomes: In the present invention, hydrogen peroxide is added to the electrolyte to promote the reduction reaction on the cathode side, thereby improving the cause of the slower ionization rate at the cathode side positive electrode compared to the anode side negative electrode. That is, metallic copper is Cu+2H2O2→Cu 2+ +2OH+2OH - and Cu+2OH→Cu 2+ +2OH - and partially dissolves in hydrogen peroxide, but Cu 2+ +2HO2 - →Cu+2HO2, and the HO2 group is thought to promote the decomposition of hydrogen peroxide via a Haber-Willstatter chain reaction (Non-Patent Document 3).

[0011] Furthermore, in the present invention, hydrogen and oxygen gases are generated from the cathode side, so that the present invention constitutes a normal hydrogen peroxide fuel cell (see Non-Patent Document 1). Cathode: H2O2+ 2H + + 2e- → 2H2O (1.78 V vs. NHE)(1) Anode: H2O2 → O2+ 2H++ 2e- (0.682 V vs. NHE)(2) Total: 2H2O2→ 2H2O + O2(1.09 V)(3) In the present invention, hydrogen peroxide 2H2O2 decomposes to 4OH, accompanied by a catalytic reaction on the copper cathode surface, and 4OH → H2 + O2 + 4e - ↑ and oxygen and hydrogen are generated or hydroxyl ion 4OH - →2H2+2O2+4e - It is thought that the compound directly decomposes to generate oxygen and hydrogen, simultaneously releasing electrons.

[0012] Furthermore, according to the present invention, the electric double layer formed on the surface of the cathode electrode contains hydrogen peroxide and has a dipole function, so that even when the counter anode electrode is combined with the cathode electrode (FIG. 2A) and brought into contact with it (FIG. 2B), a dipole electric double layer capacitor is formed as shown in the figure and no short circuit occurs (FIG. 4A). On the other hand, even when the counter anode electrode is combined with the cathode electrode (FIG. 3A) and brought into contact with it (FIG. 3B), if it is formed with protrusions or the like arranged in a dot pattern at regular intervals, the tips of the dot-like protrusions have a dipole electric double layer microcapacitor structure (FIG. 4B). Although this has the same configuration as the dipole electric double layer capacitor of FIG. 4A, a large number of microcapacitors are dotted on the electrode surface, resulting in a microcapacitor effect (FIG. 5), and the capacitor of FIG. 3 exhibits more than twice the power generation capacity of the capacitor of FIG. 2. In the present invention, hydrogen peroxide is added to the electrolyte as an oxidizing agent for the cathode electrode surface. However, a person skilled in the art will understand from the description in this specification that any oxidizing agent that oxidizes a metal surface and has the function of forming an electric double layer can be used together with hydrogen peroxide to achieve the same functions and effects.

[0013] In the present invention, it is preferable to supply part or all of the hydrogen peroxide to the aqueous electrolyte solution by sodium percarbonate. Specifically, it is preferable to add several to several tens of percent of aqueous hydrogen peroxide (volume %) or sodium percarbonate (weight %) to a neutral or alkaline aqueous solution containing 0.5 to 2.0 moles of an alkali metal or alkaline earth metal halide salt, particularly sodium chloride.

[0014] The anode electrode is made of magnesium or its alloy, and the battery configuration is (-)Mg / NaCl+H2O2 / Cu(+), which provides the decomposition voltage required to decompose hydrogen peroxide or the hydroxyl radicals produced by its decomposition between the anode electrode and the copper cathode electrode.

[0015] The cathode electrodes (Figure 2A) and anode electrodes are alternately arranged facing each other at a fixed interval via spacers, and an electric double layer capacitor is formed at the contact point between the anode and cathode electrodes using an aqueous electrolyte containing hydrogen peroxide (Figure 4A).However, if the spacer is made of the same metal, copper or copper alloy, as the cathode electrodes and has dot-like protrusions spaced at regular intervals on the surface of the counter electrode (Figure 3A), the combination of electrodes (Figure 3B) will form multiple microcapacitors (Figure 4B), and will have an avalanche amplification effect (Figure 5) as a microcapacitor effect. [Industrial Applicability]

[0016] (Performance comparison) Using the copper electrodes shown in Figures 2A and 3A, we compared the performance of batteries with and without the microcapacitor shown in Figure 4B. A 3000 ml open-top rectangular plastic container was used. In Figure 3, a 1 mm thick, 100 x 100 mm copper cathode electrode plate 10 was provided with numerous 50 mm high triangular protrusions 11 cut into it at 150 mm to 200 mm intervals (Figure 3A). As shown in Figure 3B, the copper plates 10 were attached back-to-back to each other at both ends, with the protrusions 11 facing inward. A 2 mm thick, 100 x 100 mm magnesium anode electrode plate 20 was sandwiched between the copper electrodes 10. Using this combined electrode, a microcapacitor could be formed on the surface of the copper cathode electrode, as shown in Figure 4B. On the other hand, a copper cathode electrode plate 10 (1 mm thick, 100 × 100 mm long and wide) is cut into a T-shape and fitted with a spacer S (see Figure 2A). A 2 mm thick, 100 × 100 mm long and wide magnesium anode electrode plate 20 is sandwiched between the cathode electrode plate and the spacer S. Two magnesium anode electrode plates 20 are alternately sandwiched between three copper cathode electrode plates 10, resulting in the top end view shown in Figure 2B. Using this combined electrode, a bipolar electric double layer capacitor (see Figure 4A) is constructed, but a microcapacitor (see Figure 4B) is not formed.

[0017] Prepare an electrolyte solution of 0.5 mol / L or more, preferably 1.5 mol / L or more to 2 mol / L, of sodium chloride in approximately 1500 ml of pure water in a plastic container, and add 50-100 g of sodium percarbonate and 50 ml of 30% hydrogen peroxide. After a certain amount of time has passed, the hydrogen peroxide will be consumed and the bulb will decrease, so add 10 ml of 30% hydrogen peroxide every 2-3 hours.

[0018] In this example, the performance of the electrode configurations of FIGS. 2A and 2B and 3A and 3B was compared by forming a normal capacitor and a microcapacitor on the surface of a copper cathode electrode. Since the conditions were the same except for the electrode configuration, the hydrogen peroxide fuel cell reaction in alkaline electrolyzed water was accompanied by a magnesium-air battery reaction. Hydrogen peroxide is H2O2+2H2O+2e - →2H2O+2OH - On the cathode side, H2O2 + 2OH- → O2 + 2H2O + 2e - Not only does it cause an oxidation reaction of The metal oxidation reaction in alkaline electrolyte is Mg → Mg 2+ +2e - The reaction of reducing and ionizing oxygen on the cathode side is O2 + 2H2O + 4e- → 4OH - A typical metal-air battery reaction occurs. However, while it is understood that oxygen gas is generated in a hydrogen peroxide fuel cell, the above configuration generates not only oxygen gas but also hydrogen gas. This suggests that, as suggested in Non-Patent Document 3 (Mizuto Eiji, Advances in Physical Chemistry (1936), 10(3): pp. 154-165), catalytic function operates on the surface of the copper cathode electrode, causing the decomposition of hydrogen peroxide or hydroxy ions, leading to a power generation reaction. 2H2O2 → 4 OH → H2 + O2 + 4e - 4OH- → H2 + O2 + 4e -

[0019] Considering the above experimental results, it was found that, depending on the configuration of the microcapacitor, a fuel cell having a microcapacitor as shown in Figure 3 exhibits an increase in current value of more than twice that of one having a simple capacitor as shown in Figure 2.

Claims

1. A fuel cell using hydrogen peroxide as fuel, comprising: an alkaline electrolyte containing hydrogen peroxide; a cathode electrode made of metallic copper or an alloy thereof immersed in the electrolyte; and an anode electrode made of a metal or alloy thereof that has an electrode potential lower than that of the cathode electrode and that forms an electrode potential difference equal to or greater than the decomposition voltage of hydrogen peroxide, The cathode electrode made of metallic copper or its alloy has a plurality of dot-like protrusions made of metallic copper or its alloy on its surface, and the protrusions face the anode electrode to form an electric double layer capacitor. The generated hydroxy ions are decomposed by the following catalytic action to generate oxygen and hydrogen, thereby generating electricity. 4OH - →2O 2 +2H 2 +4e - A method for burning hydrogen peroxide in a fuel cell.

2. 2. The method for combustion in a hydrogen peroxide fuel cell according to claim 1, wherein part or all of the hydrogen peroxide in said alkaline electrolyte is supplied by sodium percarbonate.

3. 2. The method of claim 1, wherein the anode electrode is made of magnesium, aluminum, or an alloy thereof. Hydrogen peroxide fuel cell combustion method.

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