Graphite material capable of releasing short-chain carbyne species as redox catalyst, and use thereof

Abstract

[Problem] To provide a graphite material capable of releasing a short-chain carbyne species as a redox catalyst. [Configuration] Provided are a natural graphite material, and water and an electrolytic solution containing the same. The natural graphite material has a C≡C polyyne (α-carbyne) structure and / or a C=C cumulene (β-carbyne) structure forming a linear sp hybrid carbon chain, and can leach out a short-chain carbyne species (RC:·, wherein R represents CnH2n-1, n represents an integer of 3 or less, and :· represents 3 unpaired electrons) as a redox catalyst when being immersed in water or an electrolytic solution.

Description

Graphite material capable of releasing short-chain carbyne species as an oxidation-reduction catalyst and its use

[0001] The present invention relates to short chain hydrocarbons, particularly carbyne species (represented by the formula: RC: ., where R is C ｎ H ２ｎ－１ wherein n is an integer of 3 or less, and . represents three unpaired electrons) into water as an oxidation-reduction catalyst, and the present invention relates to water and an electrolyte solution containing short-chain carbyne species.

[0002] Chemical bonds between carbon electrons can have three types of hybrid orbitals. They can be classified into diamond species, which have a three-dimensional structure with an sp3 hybrid orbital and one σ bond; graphite species, which have a two-dimensional structure with an sp2 hybrid orbital and one σ bond and one π bond; carbyne species, which have a one-dimensional structure with an sp hybrid orbital and one σ bond and two π bonds; and fullerene species, which have a zero-dimensional structure with one quasi-σ bond and one quasi-π bond forming a quasi-sp2 hybrid orbital, as shown in the three-dimensional correlation diagram in Figure 3. Of these, carbyne species (Carbynoid or Graphyne), including fullerenes, are particularly suggested to be solid-state linear sp hybridized carbon chains in which carbon atoms are connected by either conjugated triple bonds (polyyne-type isomers) or cumulant double bonds (polycumulene-type isomers). Many researchers have attempted to synthesize these carbyne species. Representative physical methods include laser irradiation or ion sputtering of graphite (Non-Patent Document 1), and representative chemical methods include dehalogenating polyvinylidene halide in a tetrahydrofuran solution of potassium ethylide (Non-Patent Document 2), and pre-chlorinating polyacetylene followed by dechlorination oxidation (Non-Patent Document 3). However, mass production has not been successful (Non-Patent Document 4), and industrial use of carbynes is still a long way off. Furthermore, research on newly created quasi-one-dimensional carbon crystals named carbolites has only focused on their electrical properties (Non-Patent Document 5), and their properties and applications, including their crystal structures, remain largely a mystery.

[0003] Y.P. Kudryavtsev and S.Evsyukov Carbon 30 (1992) 213-221 V.V.Korshak and Y.P. Kudryavtsev, Makromol, Chem, Rapid Commun.9 (1988) 135-140 K.Akagi, M.Nishiguchi and H.Shirakawa, synth.Met.17 (1987) 557-562 Synthesis and structure of carbyne: Carbon TANSO 1997 [No.178] 122-127 Physical properties of quasi-one-dimensional carbon crystal carbolite (KAKEN 1996 research report) Representative: Professor Tanuma Seiichi, Iwaki Meisei University Physical meaning of electrode potential: Materia Vol. 33 No. 11 (1994)

[0004] The inventors have confirmed through chromatography analysis that natural graphite extracted from natural graphite ore contains not only graphite but also carbynoid and graphyne structures, as well as polyyne (α-carbyne) and cumulene (β-carbyne) carbon structures, as shown in Figure 3. The one-dimensional carbon structure between carbon atoms is easily dissociated, and due to the presence of carbon-carbon bonds, many hydrocarbons are exuded into the water simply by immersing the graphite in water or boiling it in hot water. To determine the hydrocarbon structure, the inventors examined the graphite fragments using temperature-programmed ion desorption (TOF-ESD: time-of-flight electron-stimulated ion desorption) and confirmed that various hydrocarbon ions, including short-chain carbyne species, were desorbed in addition to oxygen, hydrogen, and carbon dioxide. These short-chain carbyne species are active due to the three unpaired electrons at the end of the carbyne structure, which makes them particularly short in 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 this graphite material is placed opposite or in contact with a metal electrode, it has the function of promoting water splitting through the ionization of the metal electrode. These phenomena are caused by 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) in water.

[0005] Therefore, the present invention provides a method for producing a short-chain hydrocarbon (having 3 or less carbon atoms), especially a short-chain carbyne species (RC: ·, where R is C ｎ H ２ｎ－１ The first objective is to provide a natural graphite material capable of releasing a redox catalyst (where n is an integer of 3 or less, and . represents three unpaired electrons). The second objective is to study the applications of water containing short-chain carbyne species and to provide applications for drinking water or electrolyzed water that can utilize the redox catalytic function of the short-chain carbyne species without using solar energy or external electricity.

[0006] The present invention has a C≡C polyyne (α-carbyne) structure and / or a C═C cumulene (β-carbyne) structure that form a linear sp hybridized carbon chain, and by immersing it in water or an electrolyte, it is possible to form a short-chain hydrocarbon (having 3 or less carbon atoms), particularly a short-chain carbyne species (RC: ·, where R is C ｎ H ２ｎ－１ wherein n is an integer of 3 or less, and . represents three unpaired electrons) as an oxidation-reduction catalyst.

[0007] Natural graphite has a C≡C polyyne (α-carbyne) structure and / or a C≡C cumulene (β-carbyne) structure that form linear sp hybridized carbon chains. When these structures are broken, 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) are exuded into water or electrolytes as carbyne ions RC:·. Surprisingly, these exhibit high reactivity in water and catalyze redox reactions. That is, the carbyne ions RC:· are thought to couple with each other in water, or to combine with water molecules or metal ions to form complexes, or to re-separate. Therefore, it is thought that short-chain carbyne species generate carbyne ions RC:· in water, which promote redox reactions and thus catalyze water splitting.

[0008] Therefore, 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), the short-chain carbyne species (RC:·, where R represents C ｎ H ２ｎ－１ wherein n is an integer of 3 or less; and · represents three unpaired electrons) as an oxidation-reduction catalyst.

[0009] In other words, water containing short-chain carbyne species can capture active oxygen in the body due to the high redox catalytic ability of the carbyne ion RC:. Hydrogen ion water, which is said to capture and reduce active oxygen in the body, is valuable as this type of drinking water, but it is surprising that short-chain carbyne species can remain in water for a longer period of time than hydrogen ions and have a much greater effect of capturing active oxygen in the body than hydrogen ions. Furthermore, when short-chain carbyne species are included in an electrolyte, their high redox catalytic ability results in promoting electrochemical reactions.

[0010] This is a photograph showing the state of water decomposition by immersing a natural graphite material containing short-chain carbyne species in water in a beaker. This is a photograph showing the state of water decomposition by immersing a natural graphite material containing short-chain carbyne species and an aluminum plate, a typical metal, in water in a beaker. This is a classification diagram showing the correlation between carbon structures. This is a schematic diagram of a hydrogen microscope TOF-ESD device for detecting graphite containing hydrocarbons with carbyne groups in a natural graphite sheet according to the present invention. This is a photograph of a 10 mm x 8 mm natural graphite sheet set in a sample holder equipped with a heater for hydrogen analysis after water electrolysis. This is a photograph of a 10 mm x 8 mm natural graphite sheet set in a sample holder equipped with a heater for hydrogen analysis after water electrolysis. This shows the thermal desorption spectrum of impurities released from the sample surface into a vacuum by heating the sample to a temperature of 200°C. This shows the thermal desorption spectrum of impurities released from the sample surface into a vacuum by heating the sample to a temperature of 290°C. This is the thermal desorption spectrum of the third time of heating the sample to 290°C, which was repeated six times with time intervals. The sample temperature was increased to 290°C six times with time intervals, and the fourth thermal desorption spectrum is shown. The sample temperature was increased to 290°C six times with time intervals, and the sixth thermal desorption spectrum is shown.

[0011] The present invention has a C≡C polyyne (α-carbyne) structure and / or a C═C cumulene (β-carbyne) structure that form a linear sp hybridized carbon chain, and by immersing it in water or an electrolyte, it is possible to form hydrocarbons, particularly short-chain carbyne species (RC: ·, where R is C ｎ H ２ｎ－１ The present invention also provides natural graphite that can exude a short-chain carbyne species (RC:·, where R is C, where n is an integer of 3 or less, and :· represents three unpaired electrons) as a redox catalyst. The present invention also provides a natural graphite that has a C≡C polyyne (α-carbyne) structure and / or a C═C cumulene (β-carbyne) structure that form a linear sp hybridized carbon chain, and that can exude a short-chain carbyne species (RC:·, where R is C ｎ H ２ｎ－１ wherein n is an integer of 3 or less; and * represents three unpaired electrons) as an oxidation-reduction catalyst.

[0012] The water from which the short-chain carbyne species of the present invention can be exuded can be pure water or electrolyzed water to which an electrolyte has been added. The amount of electrolyte added can be adjusted depending on the application. Drinking water can also contain other nutrients or various inorganic and organic components.

[0013] Presence of short-chain carbyne species Short-chain carbyne species can be confirmed 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 or triple bonds can be detected by temperature-programmed ion desorption (TOF-ESD) spectroscopy, where R is C. ｎ H ２ｎ－１ (where n is an integer of 3 or less, and : represents three unpaired electrons) and the minimum n = 1, CH3C: : , has been confirmed to emit ethylidine. Also, carbon triple bonds are usually detected by infrared spectroscopy at 2260-2100 cm of the C≡C stretching. －１ , ≡C-H stretching 3340-3270 cm －１ Or ≡C-H bending angle 700 to 600 cm －１ While the absorption spectrum is characteristic of acetylides, chemical detection is also possible.

[0014] Changes in water: Carbyne ions are thought to couple with each other in water to form short chain carbynes containing propylidines of n=2 or more, and then to combine with metal ions in water to form carbyne metal complexes. + and RCMe + is reduced by receiving electrons through the formation of metal ions, and is then reduced to carbyne via an intermediate. This reaction is repeated until the metal ions disappear as ions, and as a result, it is thought that immersion in water promotes the redox reaction that splits water, as shown in Figure 1.

[0015] The natural graphite material of the present invention may be a graphite sheet prepared from graphite extracted from natural graphite ore. It is believed that some of the natural graphite materials retain a C≡C polyyne (α-carbyne) structure and / or a C═C cumulene (β-carbyne) structure that form linear sp hybridized carbon chains. By immersing the graphite sheet in water or an electrolyte, it is possible to obtain 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).

[0016] Graphite Material Production from Natural Graphite Ore Industrially, natural graphite powder is immersed in a 100°C mixed acid solution of 90% concentrated sulfuric acid (95-98%) and 10% concentrated nitric acid (specific gravity 1.33) to produce sulfuric acid-graphite intercalation compounds (HSO-GICs), which are then washed with water, dried, and rapidly heated for final production. Other methods include the use of hydrogen peroxide to reduce the heavy metal content in the vapor generated during heat treatment, and the electrochemical method of electrolytically oxidizing graphite powder in a formic acid solution to produce formic acid-graphite intercalation compounds (HCOOH-GICs). Any graphite material can be used in the present invention as long as it has a C≡C polyyne (α-carbyne) structure and / or a C═C cumulene (β-carbyne) structure that form a linear sp hybridized carbon chain. Graphite oxide can be subjected to rapid heat treatment to produce expanded graphite, in which the graphite layers are expanded, and this can also be used as the graphite material of the present invention. Expanded graphite powder is supplied from a hopper to a pre-pressure roll by a vibrating belt and preformed into a plate, which is then subjected to a heat treatment process for degassing and purification, and then formed into a sheet in a roll molding process.

[0017] Graphite sheets produced from natural graphite can increase ion insertion capacity and can be used as the graphite material of the present invention. On the other hand, charcoal blocks, carbon materials bound with nanocarbon binders, and carbon fiber sheets have not been observed to exude short-chain carbyne species even when these carbon materials are calcined and expanded. Therefore, it is believed that natural graphite is formed by water exuding short-chain carbyne species due to crustal movements, resulting in the formation of C≡C polyyne (α-carbyne) structures and / or C═C cumulene (β-carbyne) structures in the graphite, which form linear sp hybridized carbon chains.

[0018] (Mass Analysis of Ions from Natural Graphite Sheets) Mass analysis of electron-excited ions emitted from natural graphite can be performed using time-of-flight electron-stimulated ion desorption (TOF-ESD) spectroscopy. This instrument, called a scanning electron-stimulated desorption ion microscope (SESDIK), irradiates a sample with pulses of slow electrons of 100-500 eV, ionizing hydrogen, oxygen, and other adsorbed species on the solid surface and releasing them 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 ions of hydrogen, oxygen, and other adsorbed species. Not only can hydrogen and oxygen be detected, but differences in bonding and adsorption states can be projected onto the desorption kinetic energy, allowing for selective detection of adsorbed species, enabling chemical mass analysis. Liquid chromatography of the substances that leached from the natural graphite into the solution confirmed the presence of large amounts of hydrocarbons. A slice of the natural graphite was then cut out and analyzed using a method of detecting desorbed protons by irradiating the surface of the solid with pulsed electrons (electron stimulated ion desorption, TOF-ESD). In addition to hydrogen, oxygen, and carbon monoxide, ethylidyne (CH3C·), with a molecular weight of 27, and ethylene (C2H4), with a molecular weight of 28, were detected.

[0019] Water splitting using a graphite electrode containing short-chain carbynes. Natural graphite obtained from natural graphite ore was acid-treated to form a graphite raw material, which was then expanded and rolled to form a 1-2 mm thick porous graphite sheet (100 mm x 100 mm). This was flame-expanded to a thickness of 1 cm, and immersed in an electrolyte containing 1 mol of sodium chloride as an oxidation-reduction catalyst. The water splitting action shown in Figure 1 was observed.

[0020] Water splitting using a graphite electrode containing short-chain carbynes and a metal aluminum plate. A graphite raw material, made by acid-treating natural graphite obtained from natural graphite ore, was expanded and then rolled to form a 1-2 mm thick porous graphite sheet (100 mm x 100 mm). This was then flame-expanded to a thickness of 1 cm, while a 1 mm thick metal aluminum plate (100 mm x 100 mm) was used as the counter electrode. When these were immersed in an electrolyte containing 1 mole of sodium chloride as a composite redox catalyst, the water splitting action shown in Figure 2 was observed. In the configuration shown in Figure 2, not only is the reaction on the electrode surface caused by carbynes mentioned above, but the following phenomenon in the nanospace between the graphite layers containing carbynes is also thought to be involved. Aluminum metal ions Al ３+ does not only react on the metal surface, but also penetrates into the nanospace between the layers of the porous graphite sheet, attaches to the graphite layer, and forms a microcell due to the contact potential difference with the counter electrode. The electromotive force is accumulated in the microcapacitor between the graphite layers adjacent to the microcell, and as a result, it is thought to cause water decomposition more vigorously than in the case of only the graphite sheet in Figure 1 (see Figure 2).

[0021] (Mass analysis of ions in natural graphite sheets) Using a hydrogen microscope at TF Giken, located on the second floor of the Keihanna Plaza Laboratory in Kyoto Prefecture, mass analysis was performed using electron-stimulated ion desorption (TOF-ESD) from the sample. The hydrogen microscope used here is called a scanning-type electron-stimulated desorption ion microscope (SESDIK). As shown in Figure 4, 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 formula. Displaying this signal as a TOF spectrum allows for mass analysis, enabling the two-dimensional distribution of hydrogen, oxygen, and other adsorbed species ions to be obtained. Not only can hydrogen and oxygen be detected, but differences in bonding and adsorption state can be projected onto the kinetic energy of desorption, allowing for selective detection of adsorption targets, enabling chemical mass analysis.

[0022] (Ion Mass Analysis in Natural Graphite Sheet) A natural graphite sheet and a 10 mm x 8 mm carbon film (flexible graphite sheet FGS) after water electrolysis were placed in a sample holder equipped with a heater for hydrogen analysis. Measurement examples are shown in Figures 5A and 5B. Figure 6A shows the thermal desorption spectrum of impurities released from the surface into a vacuum upon heating to a sample temperature of 200°C. Figure 6B shows the thermal desorption spectrum of impurities released from the surface into a vacuum upon heating to a sample temperature of 290°C. The bar graph on the right indicates the final amount of release for each mass, while the bar graph on the left indicates the temperature rise. Figure 6A shows the temperature rise up to 200°C, while Figure 6B shows the temperature rise after saturating at 200°C, then increasing by another 90°C, at which point heating was stopped and the sample cooled. Figures 7A, 7B, and 7C show the third, fourth, and sixth cycles of a six-time heating cycle to 290°C. Figure 7A shows the gas released from the third sample (4 minutes) with little change from the second measurement taken one hour earlier. Figure 7B shows the ion pump turned on during the gas released from the fourth sample, then turned off again after a while. The gas from the sample is introduced and the final value is displayed for easy understanding. Figure 7C shows the gas released from the sixth sample. From these results, the spectra of impurities with masses 27 and 28 are noteworthy, and the measurement data indicates that both graphite containing hydrocarbons with carbyne groups and ethylene are being released from the sample.

[0023] The electromotive force in a battery reaction is governed by the electrode potential difference between the anode and cathode in the electrolyte. This electrode potential is usually calculated as the relative value of the potential difference at the electrode interface (electrode / electrolyte interface) and is introduced through the Nernst relation. However, according to Non-Patent Document 6 (The Physical Meaning of Electrode Potential by Norio Sato), the electrode potential is considered to be divided into the electrode potential inherent to the electrode and the ionic electrode potential of the electrolyte. The inventors found that in an Al / 1N nitric acid aqueous solution / Cu battery configuration, the electrode potential difference of 0.98 V increased by 0.5 V when half the amount of a solution prepared by soaking natural graphite ore overnight in 1M NaCl solution was added. This improvement in the electrode potential difference indicates an improvement in the ionic electrode potential due to the addition of the electrolyte. Although it is unclear which function of the short-chain carbyne is responsible for this improvement, it is presumed to be due to its ability to enhance the redox reaction and / or the formation of a dipole electric double layer at the electrode / electrolyte interface.

Claims

1. A natural graphite material having a C≡C polyyne (α-carbyne) structure and / or a C≡C cumulene (β-carbyne) structure that form a linear sp hybridized carbon chain, and capable of exuding short-chain hydrocarbons (having 3 or less carbon atoms) as an oxidation-reduction catalyst when immersed in water or an electrolyte.

2. The short-chain hydrocarbon is a short-chain carbyne species (RC: , where R is C ｎ H ２ｎ－１ 2. The natural graphite material according to claim 1, wherein n is an integer of 3 or less, and . represents three unpaired electrons.

3. Short-chain carbyne species (RC: , where R is C ｎ H ２ｎ－１ wherein n is an integer of 3 or less, and . represents three unpaired electrons) as an oxidation-reduction catalyst; and an electrolyte solution.

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