Water-splitting system using waste aluminum with crushed natural graphite ore as catalyst

Abstract

To provide a water-splitting system using short-chain Calvin species as a redox catalyst.SOLUTION: The present invention provides a water-splitting system using aluminum, characterized by adding crushed natural graphite ore as a water-splitting catalyst to generate hydrogen by immersing crushed waste aluminum in an alkaline solution.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a water splitting system using waste aluminum, in which crushed natural graphite ore is used as a catalyst. [Background technology]

[0002] Hydrogen is generally produced by electrolysis of water, but a cheap hydrogen production method that uses recycled aluminum cans as a raw material has been proposed as a method for decomposing water without using electricity (Patent Document 1). In this method, the typical reaction is as follows: aluminum reacts with an alkaline aqueous solution to generate hydrogen. 2Al+2NaOH+6H2O→2Na[Al(OH)4]+3H2↑ For this reaction, the use of a water-soluble catalyst such as Fe2(SO4)3 is recommended. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-2557 A [Non-patent literature]

[0004] [Non-Patent Document 1] YPKudryavtsev and S.Evsyukov Carbon 30(1992)213-221 [Non-Patent Document 2] VVKorshak and YPKudryavtsev, Makromol, Chem, Rapid Commun.9 (1988)135-140 [Non-Patent Document 3] K. Akagi, M. Nishiguchi and H. Shirakawa, synth. Met. 17 (1987) 557-562 [Non-Patent Document 4] Synthesis and structure of carbyne: Carbon TANSO 1997 [No. 178] 122-127 [Non-Patent Document 5] Physical properties of quasi-one-dimensional carbon crystal, carbolite (KAKEN 1996 research report) Representative: Professor Seiichi Tanuma, Iwaki Meisei University Summary of the Invention [Problem to be solved by the invention]

[0005] In examining the decomposition catalysts conventionally used for the reaction of aluminum with an alkaline aqueous solution, it was found that the decomposition reaction was accelerated by adding crushed natural graphite ore. Therefore, an object of the present invention is to provide a water decomposition system that uses crushed natural graphite ore as a decomposition catalyst instead of the water-soluble catalyst that has been conventionally used. [Means for solving the problem]

[0006] In considering the reason why the ground material of natural graphite ore promotes the reaction between aluminum and caustic soda, the components contained in natural graphite ore were analyzed, and it was found that the carbyne species (carbinoid or graphyne) containing fullerene in natural graphite contains a solid-state linear sp hybridized carbon chain in which carbon atoms are linked by either conjugated triple bonds (polyyne type isomers) or cumulant double bonds (polycumulene type isomers), and that such carbon structure species have superior functions to conventional water-soluble catalysts. Based on this, the present invention was completed. That is, the present invention is a water splitting system using waste aluminum, characterized in that crushed natural graphite ore is added as a water splitting catalyst when crushed waste aluminum is immersed in an alkaline aqueous solution to generate hydrogen. Here, crushed waste aluminum includes crushed and powdered waste aluminum used in canned beer, etc. Since the surface is usually painted, it is preferable to use waste aluminum cans that have been immersed in a glycol-based solvent including ethylene glycol EG, diethylene glycol DEG, and triethylene glycol TEG, or a ketone-based solvent such as cyclohexanone CHN or methyl isobutyl ketone MIBK, and heated at normal pressure to remove the surface resin coating. The active components of the water splitting catalyst in natural graphite ore are short-chain carbyne species (RC:·, where R is C n H 2n-1 where n is an integer of 3 or less, and :· represents three unpaired electrons). As the alkaline aqueous solution, an alkaline agent such as caustic soda or caustic potash is used to determine the reactivity with aluminum. In the present invention, since a reaction with carbyne species is required, it is preferable to add an electrolyte as necessary, and seawater can be used. Effect of the Invention

[0007] According to the system of the present invention, since waste aluminum cans and inexpensive crushed natural graphite ore are used as raw materials, hydrogen can be produced more cheaply and simply. [Brief description of the drawings]

[0008] [Figure 1] 1 is a photograph showing the state in which water is decomposed by immersing crushed natural graphite ore containing short-chain carbyne species in water in a beaker. [Diagram 2] This is a photograph showing the state in which water is decomposed by immersing crushed natural graphite ore containing short-chain carbyne species and pieces of aluminum cans, which are a typical metal, in water in a beaker. [Diagram 3] FIG. 1 is a classification diagram showing the correlation of carbon configurations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Chemical bonds between carbon electrons have the possibility of three types of hybrid orbitals, and can be classified into diamond species with a three-dimensional structure consisting of one σ bond and sp3 hybrid orbitals, graphite species with a two-dimensional structure consisting of one σ bond and one π bond and sp2 hybrid orbitals, carbyne species with a one-dimensional structure consisting of one σ bond and two π bonds and sp hybrid orbitals, and fullerene species with a zero-dimensional structure that forms a quasi-sp2 hybrid orbital from one quasi-σ bond and one quasi-π bond, as shown in the three-dimensional correlation diagram in Figure 3. Of these, carbyne species (Carbinoid or Graphyne), including fullerene, in particular, are suggested to be solid-state linear sp hybridized carbon chains in which carbon atoms are linked by either conjugated triple bonds (polyyne type isomers) or cumulative double bonds (polycumulene type isomers), and many researchers are attempting to synthesize these carbyne species. A representative physical method is to generate carbyne by irradiating graphite with a laser or by ion sputtering (Non-Patent Document 1), and a representative chemical method is to dehalogenate polyvinylidene in a tetrahydrofuran solution of potassium ethylide (Non-Patent Document 2), and a method is to chlorinate polyacetylene in advance and then oxidize it by dechlorination (Non-Patent Document 3). However, mass production has not been successful (Non-Patent Document 4), and industrial use of carbyne is still a long way off. In addition, only the electrical properties of newly created carbon crystals named carbolites as quasi-one-dimensional carbon crystals have been studied (Non-Patent Document 5), and many of their properties and uses, including their crystal structures, remain a mystery.

[0010] The inventors have confirmed by chromatography that natural graphite extracted from natural graphite ore contains not only graphite but also carbinoid and graphyne structures, and has polyyne (α-carbyne) and cumulene (β-carbyne) carbon structures, and that the one-dimensional carbon structure between carbons is in a form that is easily dissociated, and that due to the presence of carbon-carbon bonds, many hydrocarbons are exuded into the water by simply immersing the graphite piece in water or boiling it in hot water. In order to determine the structure of the hydrocarbons, the inventors have confirmed that various hydrocarbon ions, including short-chain carbyne species, are desorbed in addition to oxygen, hydrogen, and carbon dioxide, when the graphite piece is examined by temperature-programmed ion desorption spectroscopy (TOF-ESD: time-of-flight electron stimulated ion desorption spectroscopy). This short-chain carbyne is active because the end of the carbyne structure has three unpaired electrons, and therefore has a particularly short carbon chain (RC:·, where R is C n H 2n-1 where n is an integer of 3 or less, and :· represents three unpaired electrons) and its reactivity is predicted to be very high (Non-Patent Document 4), and it has been discovered that it has a catalytic function of reacting with water to release hydrogen. Furthermore, it has been discovered that when a metal electrode is placed opposite or in contact with this graphite material, it has the function of promoting water splitting through the ionization of the metal electrode. These phenomena occur when short-chain carbyne species (RC:·, where R is C n H 2n-1 where n is an integer of 3 or less, and :· represents three unpaired electrons) in water. Therefore, it is believed that the short-chain carbyne species generates the carbyne ion RC:· in water, which promotes the redox reaction and thus catalyzes water splitting.

[0011] Therefore, the short-chain carbyne species (RC:·, where R is C n H 2n-1 where n is an integer of 3 or less, and :· represents three unpaired electrons), the short-chain carbyne species (RC:·, where R represents C n H 2n-1 where n is an integer of 3 or less, and :· represents three unpaired electrons) serves as an oxidation-reduction catalyst to promote the hydrolysis of waste aluminum and generate large amounts of hydrogen.

[0012] Presence of short-chain carbyne species Short-chain carbyne species can be identified by searching for C≡C polyyne (α-carbyne) structures and / or C=C cumulene (β-carbyne) structures that form linear sp hybridized carbon chains. Carbon double and triple bonds can be identified by temperature-programmed ion desorption (TOF-ESD) spectroscopy, which identifies short-chain carbyne species (RC:·, where R is C n H 2n-1 (n is an integer of 3 or less, :· indicates three unpaired electrons) and the emission of ethylidine of the minimum n=1 CH3C:· has been confirmed. In addition, carbon triple bonds are usually observed in infrared spectroscopy at 2260-2100 cm due to the C≡C stretching. -1 , ≡CH stretching 3340~3270cm -1 Or ≡CH bending angle 700~600cm -1 While the absorption spectrum is said to be specific to the acetylene, chemical detection is also used.

[0013] Changes in water In addition, carbyne ions are thought to form short-chain carbynes containing propylidines of n=2 or more that couple with each other in water, and then bind to metal ions in water to form carbyne metal complexes. + or RCMe + is reduced by receiving electrons through the formation of metal ions, then reduced to carbyne via an intermediate, and this reaction is repeated until the metal ions disappear as ions. As a result, as shown in Figure 1, it is believed that this promotes the redox reaction that splits water when immersed in water.

[0014] The ground natural graphite of the present invention may be a graphite sheet prepared from graphite extracted from ground natural graphite ore. It is believed that some of the graphite sheets retain a C≡C polyyne (α-carbyne) structure and / or a C=C cumulene (β-carbyne) structure that form linear sp hybridized carbon chains, and are immersed in water or an electrolyte to produce short-chain carbyne species (RC:·, where R is C n H 2n-1where n is an integer of 3 or less, and :· represents three unpaired electrons).

[0015] (Mass analysis of ions in natural graphite) The time-of-flight electron-stimulated desorption ion microscope (TOF-ESD) can be used to perform mass analysis of the electronically excited ions released from natural graphite. This device, called a scanning type electron-stimulated desorption ion microscope (SESDIK), irradiates a sample with a pulse of low-speed electrons of 100 to 500 eV, causing hydrogen, oxygen, and other adsorbed species adsorbed on the solid surface to be ionized and fly out into the vacuum. These are detected and amplified to produce a signal. Since the electron beam is irradiated as a pulse, the ions are detected by the time-of-flight method (TOF), which uses a formula to calculate the flight time. If this signal is displayed as a TOF spectrum, mass analysis according to the local field can be performed, and a two-dimensional distribution of ions of hydrogen, oxygen, and other adsorbed species can be obtained. Not only can hydrogen and oxygen be detected, but differences in bonds and adsorption states can be projected onto the kinetic energy of desorption to select and detect the adsorbed object, allowing chemical mass analysis. When the substances leached from the natural graphite into the solution were examined using a liquid chromatograph, a large amount of hydrocarbons was confirmed. A slice of the natural graphite was then cut out and analyzed using a method in which the surface of a solid is irradiated with pulsed electrons to detect the protons that are released (electron stimulated ion desorption, TOF-ESD). In addition to hydrogen, oxygen, and carbon monoxide, ethylidine (CH3C·), with a molecular weight of 27, and ethylene (C2H4), with a molecular weight of 28, were detected.

[0016] Water splitting at graphite electrodes containing short-chain carbynes. When powder or crushed material of a slightly larger particle size obtained from natural graphite ore was added as an oxidation-reduction catalyst to an electrolyte containing 1 mole of sodium chloride, the water splitting action shown in Figure 1 was observed.

[0017] Water splitting by crushed natural graphite ore containing short-chain carbynes and a metallic aluminum plate A 100mm x 100mm sheet of 1 to 2mm thickness was made from natural graphite powder obtained from natural graphite ore, while a 100mm x 100mm piece cut from a 1mm thick used aluminum can with the paint removed was used as the counter electrode. When these were immersed in an electrolyte containing 1 mol of sodium chloride and 0.5 to 1.0 mol of caustic soda, a strong water splitting effect was observed, as shown in Figure 2.

[0018] Although the present invention has been specifically described with reference to the above examples, the present invention is not limited to these specific examples, and an alkaline aqueous solution may be prepared by adding 0.5 to 1.0 mol of an alkaline agent such as caustic soda or caustic potash to seawater.

Claims

1. A water splitting system that uses aluminum, characterized in that crushed waste aluminum is immersed in an alkaline aqueous solution to generate hydrogen, and crushed natural graphite ore is added as a water splitting catalyst.

2. The active ingredient of the water splitting catalyst in natural graphite ore is a short-chain carbyne species (RC: , where R is C ｎ H ２ｎ－１ The water splitting system according to claim 1, wherein n is an integer of 3 or less, and . represents three unpaired electrons.

3. 2. The water decomposition system according to claim 1, wherein the crushed waste aluminum is obtained by immersing waste aluminum cans in a glycol solvent or a ketone solvent and heating the can at normal pressure to remove the resin coating on the surface.

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