Method for producing an electrolyte solution or water containing ethylidine

Abstract

To provide an electrolyte with mass production ability in water splitting.SOLUTION: The present invention provides an electrolyte or water containing ethylidyne which has a redox function effective for water splitting. The electrolyte is an aqueous solution containing various salts that ionize in water, with its examples including seawater containing various salts.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention provides Method for producing an electrolyte solution or water containing ethylidine Regarding. [Background technology]

[0002] If hydrogen gas or electrical energy could be obtained through water splitting, it would eliminate pollution and create a more environmentally friendly planet. Therefore, photovoltaic water splitting systems that utilize solar energy as the energy source for water splitting have been proposed. One such system uses an optical semiconductor electrode, and the old method, known as the Honda-Fujishima effect, utilizes titanium oxide (TiO2). However, perhaps due to the low utilization rate of visible light energy, a method using a semiconductor layer with an absorption wavelength longer than 450 nm and a reflectivity-enhancing layer selected from the group consisting of Ag and Al in contact with this semiconductor layer has recently been proposed (Patent Document 1). On the other hand, a metal complex containing three ruthenium centers in its molecule was employed as a light-harvesting molecule, and a hydrogen generation reaction using near-infrared light was successfully reported (Non-Patent Document 1). This solar energy-utilizing system requires various metals, such as platinum, and photocatalytic semiconductors, making it expensive and limiting its use to daytime hours.

[0003] In addition, focusing on the four-electron reduction reaction of water in photosynthesis, alloyed catalysts using iron-cobalt phosphide (Non-Patent Document 2) and artificial manganese catalysts (Non-Patent Document 3) have been proposed as water-splitting catalysts that can perform water splitting without using solar energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-23940 [Non-patent literature]

[0005] [Non-Patent Document 1] Angewandte Chemie International Edition, October 16, 2017 [Non-patent document 2] Published in Nature on December 26, 2016: Assistant Professor Tan et al., Tohoku University [Non-patent document 3] Published in the Journal of the American Chemical Society on January 17, 2017: Nakamura et al., RIKEN Summary of the Invention [Problem to be solved by the invention]

[0006] Although many photocatalysts and water splitting catalysts have been proposed, with the exception of titanium oxide, they are not mass-producible, are expensive, and are far from practical for mass hydrogen production. Therefore, the present invention provides a novel, inexpensive hydrogen supply system that can perform water splitting or hydrogen gas generation at low cost without using solar energy or external power. Manufacturing method of electrolyte or water used The objective is to provide the following. [Means for solving the problem]

[0007] The inventors discovered that various carbon electrodes are available as carbon-based electrodes, but that when the carbon electrode is immersed in an electrolyte, hydrogen gas is generated from the water, while when it is used as a counter electrode with various adsorbed active materials, hydrogen gas is generated from the metal surface, possibly because the active material is released into the water (Figs. 2A and 2B). Then, through careful examination using a hydrogen microscope using TOF-ESD (time-of-flight electron stimulated ion desorption), the inventors discovered that a hydrocarbon-based active material is being released from the carbon electrode. After careful examination, the inventors discovered that this hydrocarbon-based active material is an ethylidyne chemical species that is generated on the surface of a platinum catalyst in the hydrogenation reaction of ethylene, and that it also promotes water decomposition. Based on this, the inventors have developed a method for producing an ethylidyne active material for use in an inexpensive and efficient hydrogen supply system. A method for producing electrolyte or water was discovered. .

[0008] The present invention relates to a hydrogen supply system comprising a carbon electrode containing ethylidine and a metal electrode, wherein the two electrodes are placed opposite or in contact with each other in an electrolyte, and hydrogen gas is generated by the interaction of metal ions from the metal electrode and ethylidine from the carbon electrode. Methods for producing usable electrolytes and water is located.

[0009] In the present invention, the carbon electrode preferably contains ethylidine and is made of graphite. On the other hand, the metal electrode must serve as a source of electrons for ionization in the electrolytic bath. Typical metals with high ionization tendency, such as Al and Zn, are selected, but transition metals such as Cu may also be selected due to their synergistic effect with ethylidine. The electrolyte may be acidic or alkaline. When using alkaline electrolyte, it is preferable to add 5 to 30% by volume, preferably 15 to 20% by volume, of a 50% caustic soda solution to water or saltwater. Seawater is preferred because of its concentration at which chlorine generation is suppressed, but saltwater containing 1 mol or more of sodium chloride may also be used. [Effects of the Invention]

[0010] According to the present invention, the layered, expanded graphite layers in the carbon electrode contain ethylidine, a representative carbyne radical. When a copper electrode is used as the counter electrode in water, hydrogen is initially generated slowly from the carbon electrode (Fig. 2A). However, the carbon electrode releases ethylidine into the water, and when it comes into contact with the copper electrode, it begins to violently decompose water, producing gas containing hydrogen (Fig. 2B). As a result, it is believed that the leaching of ethylidine from the carbon electrode into the electrolyte and the formation of metal ions from the metal electrode are involved in the hydrogen gas generation as follows: Ethylidyne CH3C reacts with oxygen in water, CH3C+O→CH3CO + +e - And Reaction with H2O: CH3CO + +e - +H2O → CH3COOH +H2↑ is thought to form acetic acid CH3COOH and generate hydrogen gas H2. Also, metals react with ethylidine in water, CH3C+Me→CH3CMe + +e - And Reaction with H2O: CH3CMe + +e - +H2O → CH3COMe + H2↑ is thought to form acetic acid CH3COMe and generate hydrogen gas H2. and the intermediate CH3CO + and CH3CMe + is reduced by receiving electrons from the metal ion formed at the metal electrode, and is reduced to ethylidine via an intermediate, and this reaction is thought to be repeated until the metal ion disappears. On the other hand, the following phenomenon in the nanospace within the carbon electrode containing ethylidine is also thought to be involved (Figure 8). Metal ion Me + When the carbon nanotube penetrates into the nanospace of the graphite intercalation compound, it forms a The electrolytic cell adheres to the graphite layer, forming a microcell due to the contact potential difference with the counter electrode, and the resulting electromotive force is stored in the microcapacitor between the graphite layers adjacent to the microcell. When this electromotive force causes the microcell to generate hydrogen gas in the nanospace, the pressure in the nanospace with a minute volume V rises rapidly, resulting in a sudden increase in temperature in the nanospace. According to the gas equation of state PV=nRT, boiling occurs. This is thought to be the cause of the boiling of the electrolytic cell in this hydrogen supply system. Furthermore, as the storage capacity of the microcapacitor increases, the metal is electrolytically evaporated, moving and adhering to the adjacent graphite layer, resulting in the movement of the microcell. This is thought to be the cause of the gradual change in the position of hydrogen generation on the carbon electrode.

[0011] The carbon electrodes used in this invention are preferably made from graphite. Graphite undergoes rapid thermal decomposition at high temperatures, and the gasification pressure of the resulting decomposition products causes the interlayers of the graphite to expand in a direction perpendicular to the layer plane (hexagonal mesh plane), resulting in bulky expanded graphite. Furthermore, if the carbon electrode is an intercalation compound used as a positive electrode or air electrode in which ethylidine acts, metal ions penetrate into the intercalation compound and form microcells due to the difference in contact potential between the intercalation compound and the carbon layer serving as the counter electrode. This is thought to form a microcapacitor between the intercalation compound and the adjacent carbon layer (Figure 8).

[0012] Carbon electrodes are preferable because when they are expanded so that the interlayer spacing is uniformly enlarged, the ion insertion capacity of the intercalation compound can be increased, thereby increasing the battery capacity. In the present invention, CH3C+O→CH3CO + +e - In addition to the formation of hydrogen gas by ethylidine (CH3COO- + H2↑), the following phenomenon in the nanospace within the carbon electrode is thought to be involved: + When penetrates the nanospace of a graphite intercalation compound, it adheres to the graphite layer and forms a microcell due to the contact potential difference with the counter electrode. The electromotive force is stored in the microcapacitor between the graphite layers adjacent to the microcell. When this electromotive force causes the microcell to generate hydrogen gas in the nanospace, the pressure in the nanospace with a minute volume V rises rapidly, causing a sudden rise in temperature in the nanospace and resulting in boiling. This is thought to be the cause of heat generation. Furthermore, as the storage capacity of the microcapacitor increases, the metal is electrolytically evaporated, moving and adhering to the adjacent graphite layer, resulting in the movement of the microcell.

[0013] (Mass analysis of ions in a carbon electrode) Mass analysis was performed using a hydrogen microscope (time-of-flight electron-stimulated desorption: TOF-ESD) at TF Giken, located on the second floor of the Keihanna Plaza Laboratory in Kyoto, Japan. The hydrogen microscope used here is called a scanning electron-stimulated desorption ion microscope (SESDIK). As shown in Figure 3, when a sample is irradiated with pulses of slow electrons of 100–500 eV, hydrogen, oxygen, and other adsorbed species adsorbed on the solid surface are ionized and released into the vacuum. These ions are detected and amplified to produce signals. Because the electron beam is irradiated as a pulse, ions are detected using the time-of-flight (TOF) method, which calculates the time of flight using a formula. Displaying this signal as a TOF spectrum allows for localized mass analysis, yielding a two-dimensional distribution of hydrogen, oxygen, and other adsorbed species. Not only can hydrogen and oxygen be detected, but differences in bonding and adsorption states can also be projected onto the desorption kinetic energy, allowing for selective detection of adsorbed species, enabling chemical mass analysis.

[0014] (Ion mass spectrometry in carbon electrodes) For hydrogen analysis, the unused carbon electrode and the carbon electrode after water electrolysis, each measuring 10 mm x 8 mm, were set in a sample holder equipped with a heater. Measurement examples are shown in Figures 5A and 5B. Figure 5A shows the thermal desorption of impurities released from the surface into vacuum when the sample temperature was raised to 200°C. Figure 5B shows the thermal desorption spectrum of impurities released from the surface into vacuum when the sample was heated to a temperature of 290°C. The bar graph on the right shows the final amount of each mass released, and the bar on the left shows the heating state. Figure 5A shows the heating up to 200°C, while Figure 5B shows the state after saturating at 200°C, then heating by another 90°C, and then cooling after stopping heating at the peak. Figures 6A, B, and C show the states after the heating up to 290°C was repeated six times with time intervals. Figure 6A shows the gas released from the third sample (4 minutes) with little change from the second measurement taken one hour earlier. Figure 6B shows the ion pump turned on during the gas released from the fourth sample, then turned off again after a while and gas from the sample was introduced, with the final value clearly displayed. Figure 6C shows the gas released from the sixth sample. From these results, attention is drawn to the spectra of the impurities with masses 27 and 28, and the measurement data indicates that both ethylidine and ethylene are being released from the sample. [Brief explanation of the drawings]

[0015] [Figure 1A] This is a schematic diagram of the hydrogen supply system according to the present invention, showing the state in which a 3 mm thick aluminum metal plate and a carbon electrode expanded to a thickness of 15 mm are combined and placed in a saline solution containing 50% caustic soda and 20% by volume of the solution. [Figure 1B] 1B is a photograph of the hydrogen supply system of FIG. 1A during hydrogen generation. [Figure 2A] 1 is a photograph showing hydrogen generation in water from a carbon electrode according to the present invention. [Figure 2B] 1 is a photograph showing the state of hydrogen generation from an ethylidine metal complex formed when ethylidine released from a carbon electrode into water adheres to the electrode according to the present invention. [Figure 3] FIG. 1 is a schematic diagram of a hydrogen microscope TOF-ESD device for detecting ethylidine in a carbon electrode according to the present invention. [Figure 4A] This is a photograph of an unused carbon electrode (10mm x 8mm) set in a sample holder with a heater for hydrogen analysis. [Figure 4B] This photograph shows a 10mm x 8mm carbon electrode set in a sample holder with a heater for hydrogen analysis after water electrolysis. [Figure 5A] The thermal desorption spectrum of impurities released from the sample surface into vacuum when the sample temperature was increased to 200°C is shown. [Figure 5B] The thermal desorption spectrum of impurities released from the sample surface into vacuum when the sample was heated to a temperature of 290°C is shown. [Figure 6A] The sample temperature was raised to 290°C six times at intervals, and the third thermal desorption spectrum is shown. [Figure 6B] The sample temperature was raised to 290°C six times at intervals, and the fourth thermal desorption spectrum is shown. [Figure 6C] The sample temperature was raised to 290°C six times at intervals, and the sixth thermal desorption spectrum is shown. [Figure 7] FIG. 1 is a conceptual diagram showing the state in which electrons are extracted from oxygen by Na+ in expanded FGS. [Figure 8] This is a conceptual diagram of the microcells and microcapacitors formed by metal ions in expanded FGS. [Figure 9] This is an EDS elemental composition table of a carbon electrode obtained by electrolysis in saline solution. [Figure 10] 1 is a micrograph of a carbon electrode that has absorbed hydrogen through water electrolysis. [Figure 11] This shows a micrograph and EDS elemental composition table of a carbon electrode that has absorbed hydrogen through a water splitting power generation process in saline solution and has been subjected to an expansion treatment. [Figure 12A] 1 is a graph showing a microscopic Raman spectrum of a carbon electrode before expansion treatment. [Figure 12B] 1 is a graph showing the microscopic Raman spectrum of the carbon electrode (B) after expansion treatment. [Figure 12C] 10 is a graph showing the microscopic Raman spectrum of a carbon electrode after swelling treatment and after immersion treatment in concentrated nitric acid (C). DETAILED DESCRIPTION OF THE INVENTION

[0016] (Production of carbon electrodes containing ethylidine) As shown in Figure 10, the carbon electrode of the present invention must form a microcell with a graphite layer that serves as a counter electrode through the penetration of metal ions, and a microcapacitor must be formed between adjacent graphite layers. Therefore, a graphite sheet is immersed in water or the like overnight and then expanded by flame heating using a burner or the like. To facilitate flame expansion, it is recommended to prepare an immersion solution by dissolving 50 ml of concentrated nitric acid, 0.5 to 1.0 mol of glucose, and 1.0 to 1.5 mol of NaCl in 1 liter of water.

[0017] When a carbon electrode manufactured using the following method is immersed in 1M salt water for about 30 seconds, the generation of small bubbles is gradually observed from all over the surface of the carbon electrode, especially from the sides. When the substances seeping out of the carbon sheet into the solution are examined using liquid chromatography, a large amount of hydrocarbons is confirmed. A slice of the expanded carbon sheet is then cut out and analyzed at the TF Technology Research Institute in the Keihanshin Nagoya Laboratory Building using a method of irradiating the surface of the solid with pulsed electrons to detect the desorbed protons (electron stimulated ion desorption, TOF-ESD). This reveals that in addition to hydrogen, oxygen, and carbon monoxide, ethylidine (CH3C) with a molecular weight of 27 is also present. · ) and ethylene (C2H4) with a molecular weight of 28 were detected. When this ethylidine is released into water, it is thought to separate water molecules into hydrogen ions and hydroxide ions, and then reduce the hydrogen ions to generate hydrogen gas. Furthermore, when it combines with metal ions, it forms an ethylidine metal complex, which is thought to function as a water splitting catalyst. Not only typical metals such as Al, Zn, and Fe, but also transition metals such as Cu are particularly likely to form complexes.

[0018] Next, a copper plate (1 mm thick, 5×15 cm) and the carbon electrode of the present invention are bonded together using a rubber band or the like, or are arranged facing each other, and the resulting mixture is immersed in 1 M saline solution. First, hydrogen generation was observed from the carbon electrode, then from the copper plate (Fig. 2A), and even when the carbon electrode was removed from the salt water, hydrogen gas generation from the copper plate was observed. When an aluminum plate was immersed in this solution, hydrogen gas generation from the aluminum plate was also observed (Fig. 2B). It is speculated that the generation of hydrogen from the copper plate and the aluminum plate is due to the water decomposition effect of the ethylidyne copper complex formed between the copper plate and the aluminum plate. In more detail, when water is decomposed, as shown in Fig. 1, In the hydrogen evolution reaction, 4H + +2e - →2H2 is shown, This phenomenon is somewhat complicated, but it is as follows: First, the material is placed in the electrolyte. A chemical reaction occurs between the electrode materials, resulting in the release of metal ions from the metal electrode and the release of ethylidine from the carbon into the electrolyte. Therefore, on the metal side, the attachment of ethylidine to the electrode forms an ethylidine-metal complex. Meanwhile, on the carbon material side, a battery action occurs due to the difference in contact potential between the localized metal ion-coated area and the counter-electrode carbon material. This generates hydrogen through electrolysis, while the capacitor section stores electricity, forming a battery. Focusing on this carbon electrode, it is thought to have a multilayer structure that locally forms sub-nanometer spaces. While the battery structure formed in the nanocells on the surface gradually disappears, the internal multilayer structure generates a similar battery action, while the electrolyzed hydrogen atoms become hydrogen molecules, increasing the volume of the material and gradually becoming active as a battery cell. These power generation and hydrogen generation mechanisms are understood as phenomena occurring between metal and carbon. It is speculated that the ethylidine or its metal complex formed between the metal and carbon on the metal side promotes the power generation and hydrogen generation mechanisms.

[0019] Reaction with various metals When the carbon electrode of the present invention is immersed in 1M salt water together with a copper plate, it exhibits a water-splitting action, reacts violently, and generates a large amount of hydrogen gas, including hydrogen, and the copper plate is decomposed into various parts. The reaction proceeded until the reaction temperature reached 1000°C. Furthermore, even when a zinc plate was used instead of a copper plate, the entire zinc plate became zinc oxide, and the water splitting reaction slowed, but the reaction continued. Aluminum plates were found to be durable in saline solution and to have a longer hydrogen production capacity than copper or zinc. In particular, in a battery configuration of aluminum plate / 1M NaCl+H2O2 / carbon electrode, translucent crystals formed around the carbon electrode. These crystals had a high oxygen content and were highly conductive. Furthermore, perhaps because the aluminum hydroxide or sodium aluminate contained ethylidine, they formed a semi-solid electrolyte, which intervened between the aluminum / copper, zinc / copper, aluminum / carbon electrode, and carbon / carbon electrode to form a battery.

[0020] Preparation of carbon electrodes containing ethylidine In the method for producing a carbon electrode of the present invention, it is preferable to use the carbon electrode as one or both electrodes in an electrolytic solution and apply a voltage to cause a water electrolysis reaction or to form a battery with a metal to cause a power generation reaction, in order to absorb hydrogen during electrolysis.

[0021] The process of separating and expanding the graphite layers is intended to separate and expand the carbon electrode to a specific gravity of 0.1 to 0.5 g / cm3. If the specific gravity is less than 0.1, the shape retention after expansion is poor, and if it is more than 0.5, the separation of the layers after expansion is insufficient.

[0022] Concentrated nitric acid may be used as an oxidizing agent for the carbon electrode, as this may improve the catalytic function through the pickling effect or oxidation. Furthermore, the carbon electrode of the present invention can maintain its catalytic function for a long period of time by mixing it with radium ore powder that has gamma-ray radioactivity.

[0023] (Micrograph of electrode) Figure 12 shows SEM photographs (a) and (b) of the carbon electrode after expansion and oxidation treatment at 10,000 magnifications. The oxidized graphite structure has a porous structure, with triangular cutaways inside, and each layer is translucent. Figures 12(c) and (d) show the white areas at the cutaway tips, which are thought to have Na+ attached. When the irradiation energy was concentrated, they appeared to partially decompose. This resulted in the accumulation of thin flakes of graphite or graphene. Based on the carbon-oxygen atomic ratio shown in Figure 11, a structure in which an oxygen atom is bonded to each carbon atom (carbon-oxygen atomic ratio is approximately 1:1) is observed between each layer. The function of this structure suggests the formation of a new "carbon-oxygen" structure that functions as a catalyst for the redox reaction between peroxide and oxide within the positive electrode.

[0024] The microscopic Raman spectra of the carbon electrodes A, B, and C were measured. A near-field optical microspectrometer (NFS-230HKG) manufactured by JASCO Corporation was used to obtain the microscopic Raman spectra shown in Figures 14A, 14B, and 14C under the following conditions: excitation wavelength: 532 nm, laser intensity: approximately 6.4 mW, slit width: diameter 100 μm, aperture: diameter 4000 μm, objective lens: ×20 (analysis diameter: approximately 4 μm), exposure time × number of integrations: 10 sec × 2. The upper part of the solid was peeled off from samples B and C to be measured. The D band of sample A changed from sample C, and the spectral peak shifted from 1349.99 to 1356.11 cm. -1 A Raman shift phenomenon was observed.

[0025] (Example) As shown in Figure 1A, a 3 mm thick, 100 cm2 Al metal plate 10 and a 15 mm thick, 100 cm2 carbon electrode 20, which had been immersed overnight in a 1 liter solution of water containing 1 to 1.5 mol NaCl and 0.5 to 1.0 mol glucose, and then swelled by flame irradiation on both sides, were secured with a rubber band. A 30°C electrolyte 30, which was a 0.5 mol sodium chloride solution with 15 to 20% by volume of 50% caustic soda added, was placed in a 1 liter beaker. As hydrogen gas was generated, heat was generated, reaching 90°C within 5 minutes, and the electrolyte's boiling point of 106°C was reached immediately thereafter and continued boiling. Therefore, water vapor was released from the beaker outlet along with the hydrogen gas. The amount of electrolyzed water was rapidly and drastically reduced. Figure 1B is a photograph showing the state of electrolyzed water boiling. From this, it can be seen that the hydrogen gas supply system of the present invention can easily provide a large amount of hydrogen gas. In this case, a large amount of water vapor is generated along with the hydrogen gas, and these can be temporarily collected underwater or cooled to collect only the hydrogen gas. [Industrial Applicability]

[0026] According to the hydrogen supply system of the present invention, by placing a carbon electrode and a metal electrode opposite or in contact with each other, electrolytic water such as seawater can be decomposed to easily generate and supply hydrogen gas, making it very useful for the hydrogen society of the future. [Explanation of symbols]

[0027] 10 copper plates, 20 carbon electrodes, 30 1 molar salt electrolyte

Claims

1. A method for producing electrolyte or water, which comprises immersing a graphite sheet in neutral or acidic water or electrolyte, heating it to release water vapor, causing interlayer separation and expansion, and then immersing it in electrolyte or water to produce a hydrocarbon-based active material with a mass of 27, the active material containing ethylidine, which has an oxidation-reduction function that decomposes water.

2. 2. The method for producing an electrolytic solution or water according to claim 1, wherein the hydrocarbon-based active material is a substance whose mass can be confirmed to be 27 by TOF spectroscopy using a TOF-ESD (time-of-flight electron stimulated ion desorption) method.

3. A method for producing an electrolyte or water according to claim 1, wherein the electrolyte is seawater.

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