Patent Application
20250026641
The present disclosure relates to a carbon nitride crystal with a cubic crystal structure, a method for producing the carbon nitride crystal, and a device for producing the carbon nitride crystal.
In Non Patent Literature 1, carbon nitride represented by C3N4, especially carbon nitride with a cubic crystal structure (c-C3N4), is predicted to be present. Carbon nitride with a cubic crystal structure is calculated to have a hardness exceeding that of diamond. In addition to such high-hardness properties, cubic carbon nitride is also expected to have tribological, phosphor, and photocatalytic properties, thus making it a next-generation functional material.
Meanwhile, methods for producing carbon nitride (CNx), which have been reported, includes a production method utilizing an unbalanced magnetron sputtering method (Non Patent Literatures 2 and 3) and a production method of subjecting a mixture of a graphitic substance and a metal powder to an explosion treatment under high temperature and high pressure, for example.
Carbon nitride represented by a C3N4 crystal with a cubic crystal structure (hereinafter also referred to as “cubic C3N4 crystal” or “c-C3N4”) is theoretically expected to exist, but there is no example of actual synthesis. In the production methods of Patent Literature 1 and Non Patent Literatures 2 and 3, the formation of carbon nitride has been confirmed, but the formation of carbon nitride having a stoichiometric ratio of C3N4, especially, c-C3N4 has not been confirmed. Specifically, crystalline carbon nitride is formed in Patent Literature 1, but there is no disclosure of data that identifies it as c-C3N4, and the stoichiometric ratio of carbon to nitrogen is 1:1 or 1:1.1. In Non Patent Literatures 1 and 2, the resulting carbon nitride is amorphous.
An object of the present disclosure is to provide c-C3N4 and a method for producing the same.
The present disclosure includes aspects as described below.
A C3N4 crystal with a cubic crystal structure.
The production method according to any one of [5] to [9] above, wherein a potential during a pause of potential application in the pulse electrolysis is an open circuit potential.
The production method according to any one of [5] to above, wherein a pause time of potential application is 1.0 seconds or more in the pulse electrolysis.
The production method according to any one of [5] to above, wherein the pulse electrolysis is performed under a nitrogen atmosphere or rare gas atmosphere.
The production method according to above, wherein the rare gas atmosphere is an argon atmosphere.
The production method according to any one of [5] to above, wherein an anode is an electrode of a noble metal, a conductive metal oxide, glassy carbon, natural graphite, isotropic graphite, pyrolytic graphite, plastic formed carbon, or boron doped diamond.
The production method according to any one of [5] to above, wherein the anode is a Pt electrode.
The production method according to any one of [5] to above, wherein a cathode is an electrode of Ag, Cu, Ni, Pb, Hg, TI, Bi, In, Sn, Cd, Au, Zn, Pd, Ga, Ge, Ni, Fe, Pt, Pd, Ru, Ti, Cr, Mo, W, V, Nb, Ta, Zr, or an alloy thereof, glassy carbon, natural graphite, isotropic graphite, pyrolytic graphite, plastic formed carbon, conductive diamond, or nitrogen.
The production method according to any one of [5] to above, wherein the cathode is a glassy carbon electrode.
The production method according to any one of [5] to above, wherein the molten salt is a molten salt of one or more salts selected from alkali metal or alkaline earth metal halides.
The production method according to any one of [5] to above, wherein a carbon anion source is CaC2.
The production method according to any one of [5] to above, wherein a nitrogen anion source is Li3N.
An electrolyzer comprising an anode, a cathode, and an electrolytic cell, wherein
The electrolyzer according to above, further comprising a reference electrode.
According to the present disclosure, a molten salt containing carbon and nitrogen anions is subjected to pulse electrolysis to oxidize the carbon and nitrogen anions, thereby forming carbon nitride represented by C3N4, particularly c-C3N4.
Hereinafter, the present disclosure is described in detail. Note that the following description is intended to embody a technical concept of the invention according to the present disclosure and not to limit the invention of the present disclosure to those described below, unless otherwise specifically stated.
The present disclosure provides a C3N4 crystal with a cubic crystal structure.
The c-C3N4 crystal of the present disclosure preferably has peaks at 40.9°, 47.6°, and 69.6° (2θ) in an XRD (X-ray diffraction) pattern. 40.9°, 47.6°, and 69.6° are peaks of the (211), (220), and (400) planes, respectively. The C3N4 crystal of the present disclosure may further have a peak of 84.0° in an XRD (X-ray diffraction) pattern, where such a peak is the peak of the (332) plane.
In the present disclosure, X-ray diffraction analysis is performed using Cu—Kα radiation.
In the present disclosure, X-ray diffraction analysis is typically performed under the following measurement conditions:
The c-C3N4 crystal of the present disclosure preferably has a regular octahedral structure.
In a preferred aspect, the c-C3N4 crystal of the present disclosure may have a regular octahedral structure with an edge length of 0.3 μm or more, preferably 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1.0 μm or more, for example, 2.0 μm or more, 3.0 μm or more, or 5.0 μm or more. The upper limit of the edge length of the c-C3N4 crystal of the present disclosure may be, but is not particularly limited to, 100 μm or less, 50 μm or less, 10 μm or less, or 5 μm or less, for example.
The edge length of the c-C3N4 crystal above means an edge length of the regular octahedral structure of the crystal structure. The edge length of a c-C3N4 crystal can be measured by acquiring an image of the c-C3N4 crystal with a scanning electron microscope (SEM) to analyze such an image.
The c-C3N4 crystal of the present disclosure preferably has a bulk modulus of 200 GPa or more, more preferably 240 GPa or more.
In the present disclosure, the bulk modulus can be measured by a nanoindentation method.
The C3N4 content (i.e., purity) in the c-C3N4 crystal of the present disclosure is preferably 99.0% by mass or more, more preferably 99.5% by mass or more, and even more preferably 99.9% by mass or more.
In the present disclosure, the C3N4 content in the c-C3N4 crystal above can be measured using a glow discharge optical emission spectrometer.
The impurity content in the c-C3N4 crystal above may be preferably 0.1 at % or less, more preferably 0.01 at % or less. Examples of such impurities include atoms derived from the molten salt, such as metal atoms, oxygen atoms, and halogen atoms.
The c-C3N4 crystal of the present disclosure may have high hardness properties, tribological properties, phosphor properties, or photocatalytic properties and thus can be used in various applications as a functional material, for example, as an electronic material and an engineering material. Specifically, the c-C3N4 crystal can be used as a protective film on the surface of tools and as a solid lubricant due to its high hardness and tribological properties. Due to its excellent field electron emission properties, the c-C3N4 crystal can be used as an electron emitting material. Due to its photocatalytic properties, the c-C3N4 crystal can be used as an optical semiconductor material in an optoelectronic device. Due to its low dielectric properties, the c-C3N4 crystal can be used for an interlayer insulating film and a heavy particle ion detector.
The present disclosure provides a method for producing carbon nitride.
The method for producing carbon nitride according to the present disclosure includes subjecting a molten salt containing carbon and nitrogen anions, typically C22− and N3−, to pulse electrolysis to oxidize the carbon and nitrogen anions, thereby forming carbon nitride represented by C3N4. The resulting C3N4 may have a cubic crystal structure. As used herein, the pulse electrolysis means an electrolysis method of alternately repeating the application of a potential and a pause.
The pulse electrolysis of the present disclosure is usually performed in an electrolyzer having an anode, a cathode, and an electrolytic cell. Accordingly, the present disclosure also provides an electrolyzer for performing the pulse electrolysis of the present disclosure.
An electrolyzer 1 of the present disclosure includes an anode 2, a cathode 3, and an electrolytic cell 4. In the electrolytic cell 4, there is a molten salt 12 containing C22− and N3−. The electrolyzer 1 may also include a reference electrode 5, a gas injection member 6, a gas exhaust member 7, a lower sealed container 8, an upper sealed container 9, and a heater 10. In the electrolyzer 1, a pulse potential is applied between the anode 2 and the cathode 3 to oxidize C22− and N3− to C3N4.
The anode 2, the cathode 3, and the reference electrode 5 are at least partially located in the molten salt 12. In other words, the anode 2, the cathode 3, and the reference electrode 5 are arranged such that at least a portion of them is in contact with the molten salt 12. The anode 2, the cathode 3, and the reference electrode 5 are connected by a conducting wire 11 to a device to apply a pulse potential, for example, a potentiostat (not shown). The molten salt 12 in the electrolytic cell 4 is heated to a predetermined temperature or higher by the heater 10. The anode 2, the cathode 3, the reference electrode 5, and the electrolytic cell 4 are arranged inside the lower sealed container 8, and sealed by the upper sealed container 9 to be kept under a sealed condition.
The gas injection member 6 is used to introduce inert gas into the sealed container from the outside. The tip of the gas injection member 6 may be located inside or above the molten salt 12. The gas exhaust member 7 is used to discharge gas inside the sealed container to the outside of the sealed container.
The material of the anode is not particularly limited. Examples of anode materials include noble metals (e.g., Au, Ag, and Pt), conductive metal oxides, glassy carbon, natural graphite, isotropic graphite, pyrolytic graphite, plastic formed carbon, and boron doped diamond. Examples of an electrode made of the conductive metal oxides include a transparent conductive electrode obtained by forming a film of a mixed oxide of indium and tin on glass, which is called an ITO electrode, and an electrode obtained by forming a film of an oxide of a platinum-group metal, such as ruthenium or iridium, on a base material such as titanium, which is called a DSA electrode (trademark of De Nora Permelec Ltd).
In a preferred aspect, the anode can be a noble metal electrode, preferably an Au, Ag, or Pt electrode, more preferably a Pt electrode. The use of a noble metal electrode as the anode increases reduction resistance of the electrode and enables a stable electrolysis reaction for a long time.
The material of the cathode is not particularly limited. Examples of cathode materials include metals such as Ag, Cu, Ni, Pb, Hg, TI, Bi, In, Sn, Cd, Au, Zn, Pd, Ga, Ge, Ni, Fe, Pt, Pd, Ru, Ti, Cr, Mo, W, V, Nb, Ta, Zr, alloys thereof, and carbon materials such as glassy carbon, natural graphite, isotropic graphite, pyrolytic graphite, plastic formed carbon, and conductive diamond. Alternatively, the cathode may be a nitrogen electrode.
In a preferred aspect, the cathode can be a glassy carbon electrode or a transition metal (e.g., Fe, Cu, and Ni), preferably a glassy carbon electrode. The use of the electrode above as the cathode, especially, a glassy carbon electrode, enables the electrode to be excellent in conductivity and resistant to high temperature.
In a more preferred aspect, the anode can be a Pt electrode while the cathode can be a glassy carbon electrode. The use of a Pt electrode as the anode and a glassy carbon electrode as the cathode makes it possible to carry out the electrolysis reaction at a high temperature and more efficiently.
In a preferred aspect, the electrolyzer has a reference electrode. The reference electrode is preferably an Ag+/Ag electrode.
In one aspect, the electrolyzer includes a gas injection member for injecting gas into the electrolytic cell or into the molten salt. Furthermore, the electrolyzer includes a gas exhaust member for exhausting the gas in the electrolytic cell.
First, a molten salt containing carbon and nitrogen anions, typically C22− and N3−, is prepared. A preparation method of such a molten salt is not particularly limited as long as the carbon and nitrogen anions can be made to be in the molten salt.
In the present disclosure, the molten salt refers to a liquid obtained by heating and melting a metal salt or metal oxide as a raw material. The molten salt contains cations and anions derived from the metal salt or metal oxide as a raw material.
In one aspect, the molten salt containing carbon and nitrogen anions can be obtained by dissolving a carbon anion source and a nitrogen anion source in a liquid obtained by heating and melting the metal salt and/or metal oxide, or by melting a carbon anion source and a nitrogen anion source together with the metal salt and/or metal oxide. Alternatively, one of the carbon anion source and the nitrogen anion source may be dissolved first, and the other may be separately dissolved. Hereinafter, the “carbon anion source” and the “nitrogen anion source” are also simply referred to as a “C source” and an “N source”, respectively.
The metal salt and metal oxide as a raw material of the molten salt is preferably alkali metal, alkaline earth metal, or other metal, more preferably alkali metal or alkaline earth metal salt and oxide. In a preferred aspect, the raw material of the molten salt is a metal salt, preferably an alkali metal salt or an alkaline earth metal salt, more preferably an alkali metal salt. The molten salt can be prepared at a relatively low temperature by using the metal salt as a raw material.
Examples of the alkali metal include at least one selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The alkali metal is preferably at least one selected from the group consisting of Li, Na, K, Rb, and Cs, more preferably at least one selected from the group consisting of Li, Na, and K, particularly preferably Li or K.
Examples of the alkaline earth metal include at least one selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The alkaline earth metal is preferably at least one selected from the group consisting of Mg. Ca, Sr, and Ba, more preferably Mg or Ca, particularly preferably Ca.
Examples of the other metal include at least one selected from the group consisting of aluminum (Al), gallium (Ga), indium (In), thallium (Tl), zinc (Zn), cadmium (Cd), gold (Au), silver (Ag), copper (Cu), and rare earth metals such as scandium (Sc), yttrium (Y), lanthanoid elements, and actinoid elements. The other metal is preferably at least one selected from the group consisting of Al and rare earth metals, and more preferably Al.
Examples of the anion of the metal salt include a halogen ion, a carbonate ion, a sulfate ion, a phosphate ion, a nitrate ion, and a carbonate ion. The anion of the metal salt is preferably a halogen ion. The halogen ion has a wide electrochemical window; allowing the reaction to proceed without bath decomposition.
The halogen may be at least one selected from the group consisting of fluoride (F), chloride (Cl), bromide (Br), iodine (I), and astatine (At). The halogen is preferably at least one selected from the group consisting of F, Cl, Br, and I, more preferably at least one of F or Cl. In one aspect, halogen is Cl. In another aspect, halogen is F.
Specific examples of the raw material of the molten salt include an alkali metal halide such as LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI; an alkaline earth metal halide such as MgF2, CaF2, SrF2, BaF2, MgCl2, CaCl2, SrCl2, BaCl2, MgBr2, CaBr2, SrBr2, BaBr2, MgI2, CaI2, SrI2, and BaI2; an aluminum halide such as AlCl3; a metal carbonate such as Li2CO3, Na2CO3, and K2CO3; a metal nitrate such as LiNO3, NaNO3, and KNO3; and an oxide of metals such as Li2O and CaO. The raw material of the molten salt is preferably at least one selected from the group consisting of a lithium salt, a sodium salt, and a potassium salt. The raw material of the molten salt is more preferably a chloride or fluoride, preferably a chloride, of at least one selected from the group consisting of Li, Na, and K.
The metal salt and metal oxide above may be used alone or in combination of two or more. It is preferable to use two or more metal salts and metal oxides in combination from the viewpoint that the melting temperature is easily lowered. For example, a combination of a plurality of chlorides, a combination of a plurality of fluorides, and a combination of one or more chlorides and one or more fluorides may be used. Specific examples of such combinations include combinations of LiCl with KCl, LiCl and KCl with CaCl2, LiF and NaF with KF, NaF with NaCl, and NaCl and KCl with AlCl3.
In a preferred aspect, the molten salt is prepared from at least one and preferably two or more metal salts selected from the group consisting of LiF, NaF, KF, RbF, CsF, LiCl, NaCl, and KCl. Such a metal salt may preferably be a combination of LiCl and KCl.
In the combination of a plurality of salts, a compounding ratio thereof is not particularly limited. In the combination of LiCl with KCl, for example, the number of moles of LiCl may be 10 mol % or more, 30 mol % or more, 45 mol % or more, or 50 mol % or more with respect to the total number of moles of LiCl and KCl. The number of moles of LiCl may be 90 mol % or less, 70 mol % or less, or 65 mol % or less with respect to the total number of moles of LiCl and KCl. In one aspect, the number of moles of LiCl may be 10 mol % or more and 90 mol % or less, preferably 45 mol % or more and 70 mol % or less with respect to the total number of moles of LiCl and KCl.
The C source is preferably a metal carbide, more preferably an alkali metal or alkaline earth metal carbide, and even more preferably an alkaline earth metal carbide. Such alkali metals and alkaline earth metals include the same as those described above.
Specific examples of the C source include Li2C2, Na2C2, K2C2, Rb2C2, BeC2, MgC2, CaC2, and SrC2. The C source is preferably Li2C2, Na2C2, or CaC2, more preferably CaC2. The use of Li2C2, Na2C2, or CaC2, especially CaC2, allows the metal carbide to be easily dissolved by the molten salt.
The metal carbide can be used as M1C2 or M22C2 (M1 is an alkaline earth metal and M2 is an alkali metal) obtained by reducing CO2 at the cathode. In other words, CO2 can also be a C source.
The N source can be preferably a metal nitride or nitrogen gas. The N source is preferably a metal nitride, more preferably an alkali metal or alkaline earth metal nitride, and even more preferably an alkali metal nitride. Such alkali metals and alkaline earth metals include the same as those described above.
Specific examples of the N source include N2, Li3N, Na3N, K3N, Rb3N, Be3N2, Mg3N2, Ca3N2, and Sr3N2. The N source is preferably Li3N, Na3N, Mg3N2, and Ca3N2, more preferably Li3N. The use of Li3N, Na3N, Mg3N2, and Ca3N2, especially Li3N allows the metal nitride to be easily dissolved by the molten salt.
The compounding ratio of the C source to the N source is not particularly limited. The C atoms in the C source can be, for example, 5 mol % or more, preferably 10 mol % or more, more preferably 20 mol % or more, and even more preferably 30 mol % or more, with respect to the total number of moles of C atoms in the C source and N atoms in the N source. The C atoms in the C source can be, for example, 95 mol % or less, preferably 70 mol % or less, more preferably 50 mol % or less, with respect to the total number of moles of C atoms in the C source and N atoms in the N source. In one aspect, the C atoms in the C source can be 5 mol % or more and 95 mol % or less, preferably 20 mol % or more and 70 mol % or less, more preferably 30 mol % or more and 50 mol % or less, with respect to the total number of moles of C atoms in the C source and N atoms in the N source.
The concentrations of the carbon anion (e.g., C22−) and nitrogen anion (e.g., N3−) in the molten salt are not particularly limited as long as they are contained in amounts at which the electrolysis reaction occurs. The concentration of the carbon anion in the molten salt can be preferably 0.1 mol % or more, more preferably 0.3 mol % or more, and even more preferably 0.5 mol % or more, for example 1.0 mol % or more. The upper limit of the concentration of the carbon anion in the above molten salt may be, but is not particularly limited to, 20 mol % or less, 10 mol % or less, 5.0 mol % or less, or 2.0 mol % or less, for example. The concentration of the carbon anion in the molten salt can be preferably 0.1 to 10.0 mol %, more preferably 0.2 to 5.0 mol %, and even more preferably 0.3 to 2.0 mol %. The concentration of the nitrogen anion can be preferably 0.1 mol % or more, more preferably 0.5 mol % or more, and even more preferably 0.8 mol % or more, for example 1.0 mol % or more. The upper limit of the concentration of the nitrogen anion in the above molten salt may be, but is not particularly limited to, 20 mol % or less, 10 mol % or less, 8.0 mol % or less, or 3.0 mol % or less, for example. The concentration of the nitrogen anion can be preferably 0.1 to 10.0 mol %, more preferably 0.5 to 8.0 mol %, and even more preferably 0.8 to 3.0 mol %. Higher concentrations of carbon and nitrogen anions result in more efficient formation of C3N4.
The molten salt containing the carbon and nitrogen anions is then subjected to pulse electrolysis. In the method of the present disclosure, a high current density is applied only for a short time by subjecting the molten salt containing carbon and nitrogen anions to pulse electrolysis, and a nonequilibrium field is induced to produce C3N4, which is a nonequilibrium substance. According to the method of the present disclosure, C3N4 can be produced on a base material with an arbitrary shape.
The pulse electrolysis is performed in the electrolyzer of the present disclosure above.
When a pulse potential is applied between the anode and the cathode in the electrolyzer, an oxidation reaction of carbon anions (e.g., C22−) and nitrogen anions (e.g., N3) occurs at the anode to produce C3N4 (reaction formula (1)). On the other hand, at the cathode, for example, a reduction reaction of a metal ion (e.g., Ca2+) occurs to produce a metal (e.g., Ca) (reaction formula (2)).
3/2C22−+4N3−→C3N4+14e− (1)
Ca2++2e−→Ca (2)
The potential-time graph in the pulse electrolysis of the present disclosure shows a rectangle. In other words, from the potential application pausing state, a cycle is repeated in which a predetermined potential is applied, the potential is held for a predetermined time, and then the potential application is paused, resulting in the potential application pausing state.
In the pulse electrolysis of the present disclosure, the potential during potential application (hereinafter also referred to as the pulse potential) may be preferably 0.10 to 5.00 V, more preferably 0.30 to 3.20 V, and even more preferably 1.00 to 3.00 V, for example, 1.80 to 2.60 V or 2.00 to 2.50 V. The pulse potential can be set to such a range, for example, to suppress the formation of by-products derived from the molten salt and to more efficiently produce C3N4, where the potential is a potential of the working electrode (i.e., anode) with respect to the Ag+/Ag electrode, which is a reference electrode.
In the pulse electrolysis of the present disclosure, the potential application time (Ton in
In the pulse electrolysis of the present disclosure, the potential during the pause of potential application is an open circuit potential, where the potential in a circuit is a potential of the working electrode (i.e., anode) with respect to the Ag+/Ag electrode, which is a reference electrode, in the non-energized state.
In the pulse electrolysis of the present disclosure, the pause time of the potential application (Toff in
The duty cycle (Ton/(Ton+Toff)) in the pulse electrolysis of the present disclosure may be preferably 0.001 to 0.5, more preferably 0.01 to 0.1. By setting the duty ratio to such a range, C3N4 is produced more efficiently.
The number of pulse cycles in the pulse electrolysis of the present disclosure is not particularly limited. The number of pulse cycles may be, for example, 1 cycle or more, preferably 10 cycles or more, more preferably 20 cycles or more. An increase in the number of cycles can increase the yield (weight and number) of C3N4, resulting in formation of larger C3N4 crystals. The number of pulse cycles may be, for example, 1000 cycles or less, preferably 500 cycles or less, more preferably 100 cycles or less, for example, 50 cycles or less. A reduced number of cycles can suppress a decrease in the reaction rate.
The temperature of the molten salt in the pulse electrolysis of the present disclosure is not particularly limited but may be, for example, 200 to 1000° C., more preferably 300 to 800° C., and even more preferably 400 to 600° C. The pulse electrolysis of the present disclosure has high energy efficiency because the reaction proceeds at a relatively low temperature.
The pulse electrolysis of the present disclosure is preferably performed under a nitrogen or rare gas atmosphere, preferably under a rare gas atmosphere. When the pulse electrolysis is performed under a nitrogen or rare gas atmosphere, side reactions can be suppressed, thereby forming C3N4 with higher purity.
Examples of the rare gas include helium, neon, and argon, and argon is preferable.
In one aspect, the pulse electrolysis of the present disclosure is performed under an argon atmosphere.
In one aspect, the pulse electrolysis of the present disclosure is performed under a nitrogen atmosphere.
The nitrogen and rare gas are preferably continuously injected into the system during the pulse electrolysis. In other words, it is preferable to keep purging the system with these gases. Side reactions can be further suppressed by continuous injection of nitrogen gas and rare gas into the system.
The nitrogen and rare gases may be directly injected into the molten salt or may be injected into a space above the molten salt inside the electrolytic cell. In a preferred aspect, the nitrogen and rare gases are injected directly into the molten salt. The nitrogen gas or rare gas can be directly injected into the molten salt to efficiently remove gas contained as an impurity in the molten salt, thereby further suppressing the side reactions.
When nitrogen is used, such nitrogen is ionized in the molten salt to N3−, which can serve as an N source.
A nitrogen atmosphere may be generated by using a nitrogen electrode as a cathode. In this case, since nitrogen is supplied from the nitrogen electrode, the gas injection member need not be installed.
Thus, the carbon nitride and the method for producing carbon nitride according to the present disclosure have been described in detail. Note that the applications of the carbon nitride of the present disclosure are not limited to those exemplified above.
Hereinafter, the present disclosure is described in Examples, but the present disclosure is not limited to the following Examples.
LiCl and KCl were mixed to make LiCl/KCl=59.0 mol %/41.0 mol %, and the mixture was vacuum dried at 200° C. and 100 Pa or less for 24 hours or more to form a mixed salt of LiCl and KCl. 0.5 mol % of CaC2 and 1.8 mol % of Li3N, with respect to the total number of moles of LiCl and KCl, were added to the resulting mixed salt to obtain a raw material mixture of molten salts. The raw material mixture was added to an electrolytic cell in a Pyrex holder (corresponding to the lower closed container in
The Pyrex holder was then sealed with a lid (corresponding to the upper sealed container in
Then, the oxidation behavior of the molten salt was observed by measuring the current density through application of a potential between the working electrode and the counter electrode at a scanning speed of 100 mV/s by cyclic voltammetry.
The oxidation behavior of the molten salt was observed in the same manner as in Example 1 except that no Li3N was added to the molten salt.
A molten salt of LiCl—KCl—CaC2—Li3N was obtained in the same manner as in Experimental Example 1. The Pyrex holder was then sealed with a lid (corresponding to the upper sealed container in
Then, a pulse potential with a potential application time (Ton) of 0.5 seconds and a pause time (Toff) of 10 seconds was applied for 10 cycles using a potentiostat/galvanostat with the potential of the working electrode with respect to the reference electrode during potential application being set at 2.00 V.
After the pulse potential was applied, electrodeposits were observed on the surface of the working electrode.
Pulse electrolysis was performed in the same manner as in Example 1 except that the potential of the working electrode with respect to the reference electrode during potential application was set to 2.28 V.
After the pulse potential was applied, electrodeposits were observed on the surface of the working electrode.
Pulse electrolysis was performed in the same manner as in Example 1 except that the potential of the working electrode with respect to the reference electrode during potential application was set to 2.50 V.
After the pulse potential was applied, electrodeposits were observed on the surface of the working electrode.
Pulse electrolysis was performed in the same manner as in Example 3 except that the number of cycles was changed to 20.
After the pulse potential was applied, electrodeposits were observed on the surface of the working electrode.
Pulse electrolysis was performed in the same manner as in Example 1 except that the potential of the working electrode with respect to the reference electrode during potential application was set to 1.70 V.
The electrodeposits obtained in Example 1 to 5 were subjected to XRD analysis using MultiFlex (manufactured by Rigaku Corporation) under the following measurement conditions.
The results of
The electrodeposits obtained in Examples 2 and 5 were observed using JSM-7001 FD (manufactured by JEOL Ltd.) under the following measurement conditions.
The image of
Nanoindentation hardness was measured on the electrodeposit obtained in Example 5. As a result, the c-C3N4 hardness was 240 GPa.
The carbon nitride of the present disclosure can be used in various applications as a next-generation functional material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-185715 | Nov 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/042271 | 11/14/2022 | WO |
