A method to improve the nanostructure stability of titanium dioxide in molten salt environment and during electrolysis

Abstract

This invention discloses a method for improving the nanostructure stability of titanium dioxide in molten salt environments and during electrolysis. The method includes: 1. preparing a glucose solution by dissolving glucose in deionized water; 2. immersing nano-TiO2 in the glucose solution for surface treatment; 3. subjecting the surface-treated nano-TiO2 to heat treatment under an inert atmosphere to form a carbon-coated nano-TiO2. This invention significantly inhibits the destruction of the nanostructure during molten salt environments and electrolysis by pre-synthesizing a protective carbon film on the surface of nano-TiO2, ensuring the stable inheritance of the nanomorphology during the conversion of TiO2 to TiC, thus maintaining its original morphology. It has advantages such as low cost, simple operation, low equipment investment, and significantly improved nanomorphological stability, making it suitable for large-scale industrial conversion of nano-TiO2 to nano-TiC.

Description

Technical Field

[0001] This invention belongs to the field of molten salt electrochemistry technology, specifically relating to a method for improving the stability of the nanostructure of titanium dioxide in molten salt environment and during electrolysis. Background Technology

[0002] Nano-titanium carbide possesses excellent electrical conductivity, corrosion resistance, chemical stability, and mechanical stability, making it widely applicable in the fields of energy storage and conversion.

[0003] However, due to the limitations of thermodynamic and kinetic conditions in carbothermic reduction reactions, the traditional preparation temperature of nano-TiC is usually above 1200℃, or requires a long period of mechanically induced self-propagating reaction to ensure sufficient diffusion rate and reaction uniformity. In contrast, molten salt electrochemistry, through the unique convection diffusion and reactant dissolution and migration mechanisms of the molten salt medium, can significantly enhance mass transfer efficiency and improve the kinetic conditions of the carbide reaction, thereby greatly reducing the carbide synthesis temperature to 600℃~900℃. However, most of the metal carbides prepared by existing molten salt electrochemistry methods are nanoparticles, and research involving the directional synthesis of ordered nanostructures remains challenging.

[0004] Using nano-TiO2 as a structural template and precursor to prepare TiC with corresponding nanostructures is a feasible molten salt electrochemical directional synthesis technique. However, studies have found that nano-TiO2 is highly sensitive to trace amounts of CaO impurities in molten salt. When the TiO2 precursor is immersed in molten salt for a short time, CaO reacts rapidly, causing deformation of the nanostructure, and even forming CaTiO3, completely destroying the nanostructure. While molten salt purification strategies can reduce the concentration of CaO impurities in the molten salt and mitigate its impact on the TiO2 precursor to some extent, maintaining an extremely low CaO impurity concentration during long-term operation remains a challenge. Therefore, without the need for extreme molten salt purification, effectively reducing the influence of CaO and maintaining the integrity of the nanostructure during electrolysis becomes the core issue for broadening the stable conversion window of TiO2→TiC, and a key breakthrough for promoting the industrialization of this technology. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for improving the nanostructure stability of titanium dioxide in molten salt environments and during electrolysis. This method significantly inhibits the destruction of the nanostructure during molten salt environments and electrolysis by pre-synthesizing a protective carbon film on the surface of nano-TiO2, ensuring the stable inheritance of the nanomorphology during the conversion of TiO2 to TiC, thereby maintaining its original morphology. This solves the problem of impurities in molten salt affecting and making it difficult to maintain the structural integrity of nano-titanium carbide in molten salt electrolysis processes.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for improving the nanostructure stability of titanium dioxide in molten salt environment and during electrolysis, characterized in that the method includes the following steps:

[0007] Step 1: Dissolve glucose in deionized water to prepare a glucose solution;

[0008] Step 2: The nano-TiO2 is immersed in the glucose solution prepared in Step 1 for surface treatment;

[0009] Step 3: The nano-TiO2 that has undergone surface treatment in Step 2 is heat-treated in an inert atmosphere to form nano-TiO2 coated with a carbon film.

[0010] The method described above for improving the nanostructure stability of titanium dioxide in a molten salt environment and during electrolysis is characterized in that the concentration of the glucose solution in step one is 1 mol / L to 2 mol / L. By controlling the concentration of the glucose solution, a uniform carbon film is formed on the surface of the nano-TiO2, avoiding both insufficient concentration (making it difficult to form a protective carbon film) and excessively thick carbon film (causing the nano-TiO2 to be completely embedded, thus affecting the subsequent molten salt electrolysis process).

[0011] The method described above for improving the nanostructure stability of titanium dioxide in a molten salt environment and during electrolysis is characterized in that, in step two, the temperature of the glucose solution during surface treatment is 30℃~50℃, and the immersion time is 1h~3h. By controlling the temperature of the glucose solution and the immersion time, uniform coating is achieved, resulting in a protective carbon film. This avoids situations where excessively low temperature or insufficient immersion time hinders the formation of a uniform carbon film, while excessively high temperature or excessively long immersion time leads to the carbon film completely covering the nano-TiO2, affecting the exposure of its nano-morphology.

[0012] The method described above for improving the nanostructure stability of titanium dioxide in a molten salt environment and during electrolysis is characterized in that the heat treatment temperature in step three is 400℃~500℃, the holding time is 1h~3h, and the inert atmosphere is argon. By controlling the temperature and time of the heat treatment, the glucose on the surface of the nano-TiO2 is pyrolyzed to form a carbon film, while the use of an inert atmosphere avoids the oxidation and combustion of the carbon film.

[0013] The method described above for improving the nanostructure stability of titanium dioxide in molten salt environments and during electrolysis is characterized in that the carbon coating layer in the nano-TiO2 coated with carbon film in step three is a continuous carbon film with a thickness of 10 nm to 30 nm. This thickness of continuous carbon film can provide stable protection for the TiO2 nanostructure without affecting it.

[0014] The above-mentioned method for improving the nanostructure stability of titanium dioxide in molten salt environment and during electrolysis is characterized in that the nano-TiO2 coated with carbon film in step three is converted into nano-titanium carbide through molten salt electrolysis.

[0015] The aforementioned method for improving the nanostructure stability of titanium dioxide in a molten salt environment and during electrolysis is characterized in that the molten salt system used in the molten salt electrolysis is a CaCl2-LiCl mixed molten salt, the electrolysis voltage is 3.2V, and the electrolysis temperature is 600℃. By controlling the parameters of the molten salt electrolysis, the transformation of TiO2@C (i.e., carbon film-coated nano-TiO2) to TiC can be achieved without changing the nanostructure.

[0016] The above-mentioned method for improving the nanostructure stability of titanium dioxide in molten salt environment and during electrolysis is characterized in that the nano-TiO2 in step two has a tubular structure with a tube diameter of 80 nm to 100 nm; the nano-titanium carbide maintains the same tube diameter and morphology as the nano-TiO2 in step two. Typical TiO2 nanotubes are selected as nano-TiO2, and TiO2 nanotube arrays are usually formed on the surface of titanium fiber felt through anodic oxidation.

[0017] The above-mentioned method for improving the nanostructure stability of titanium dioxide in molten salt environment and electrolysis process is characterized in that the nano-titanium carbide in step four is transformed from nano-TiO2 coated with carbon film, and the microstructure of nano-TiO2 is maintained.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. This invention uses inexpensive glucose solution as a carbon source and pre-treats the surface of nano-TiO2 to form a protective carbon film, which effectively isolates the damage of trace CaO impurities in molten salt to the morphology of nano-TiO2, and achieves the morphological and structural stability of nano-TiO2 in molten salt environment under non-extreme purification molten salt conditions, thereby reducing the difficulty of preparing nano-titanium carbide and saving preparation costs.

[0020] 2. In this invention, a protective carbon film is pre-formed on the surface of nano-TiO2, and the high-melting-point carbon film effectively suppresses Ca during molten salt electrolysis. 2+ The incorporation of TiO2 and the sintering between nano-TiO2 alleviate the volume expansion and agglomeration problems during molten salt electrolysis, ensuring the stable inheritance of nano-morphology during the conversion of TiO2 to TiC.

[0021] 3. This invention provides a simple and low-cost method for synthesizing carbon films to improve the stability of TiO2 nanostructures. A uniform carbon film can be formed on the surface of nano-TiO2 by solution impregnation under normal pressure combined with medium-temperature heat treatment. It does not require complex equipment investment or a high-pressure special environment. The equipment investment is small, the cost is low, and it is easy to implement.

[0022] 4. This invention broadens the molten salt condition window for the stable transformation of TiO2 to TiC by synthesizing a protective carbon film on the surface of nano-TiO2, reduces the influence of CaO impurity concentration fluctuations in molten salt on the stable inheritance of nano-morphology, which is conducive to promoting the industrial application of this method, and provides a reliable technical solution for the stable preparation of nano-metal carbides by molten salt electrolysis.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 Transmission electron microscope image of titanium fiber felt with carbon film coated with TiO2 nanotubes prepared in Example 1 of the present invention.

[0025] Figure 2 This is a scanning electron microscope image of the titanium fiber felt coated with TiO2 nanotubes by carbon film in Example 1 of the present invention after immersion.

[0026] Figure 3 This is a scanning electron microscope image of the nano-titanium carbide prepared in Example 2 of the present invention.

[0027] Figure 4 This is a scanning electron microscope image of the nano-titanium carbide prepared in Example 3 of the present invention.

[0028] Figure 5 This is a scanning electron microscope image of the nano-titanium carbide prepared in Example 4 of the present invention.

[0029] Figure 6 This is a scanning electron microscope image of the nano-titanium carbide prepared in Example 5 of the present invention.

[0030] Figure 7 This is a scanning electron microscope image of the nano-titanium carbide prepared in Comparative Example 1 of this invention.

[0031] Figure 8 This is a scanning electron microscope image of the nano-titanium carbide prepared in Comparative Example 2 of this invention.

[0032] Figure 9 This is a scanning electron microscope image of the nano-titanium carbide prepared in Comparative Example 3 of this invention.

[0033] Figure 10 This is a scanning electron microscope image of the nano-titanium carbide prepared in Comparative Example 4 of this invention. Detailed Implementation

[0034] Example 1

[0035] This embodiment includes the following steps:

[0036] Step 1: Dissolve glucose in deionized water and stir magnetically for 30 minutes to ensure complete dissolution of glucose, thus preparing a 2 mol / L glucose solution.

[0037] Step 2: Add NH4F, HF, and H2O to a diethylene glycol solution at a mass ratio of 0.3wt%, 0.6wt%, and 6wt%, respectively, to form an electrolyte. Then, using titanium fiber felt as the anode and platinum sheet as the cathode, oxidize at 50°C and 60V for 2 hours to form an interstitial TiO2 nanotube array (s-TiO2NTAs) coating with a tube diameter of 80nm~100nm.

[0038] The glucose solution prepared in step one is heated to 50°C and kept at that temperature for 30 minutes. After the solution temperature stabilizes, the titanium fiber felt with the s-TiO2NTAs coating is immersed in the stable glucose solution for 3 hours for surface treatment.

[0039] Step 3: Immerse the titanium fiber felt with s-TiO2NTAs coating that has undergone surface treatment in Step 2 in an argon atmosphere and heat it to 500℃ for 2 hours. Then, let it cool naturally to room temperature to form a titanium fiber felt with a carbon film coating TiO2 nanotubes.

[0040] Step 4: Add the CaCl2-LiCl mixed molten salt (molar ratio 1:1) to the corundum crucible and place it in the electrolytic furnace. After evacuation, continuously introduce high-purity argon to ensure a good inert atmosphere in the furnace. Then, heat the CaCl2-LiCl mixed molten salt to 600℃, using a graphite rod as the anode and a stainless steel rod as the cathode, and electrolyze it at 3V for 3 hours to initially remove impurities from the mixed molten salt. Next, add 0.1mol% Li2CO3 to the mixed molten salt and immerse the titanium fiber felt coated with TiO2 nanotubes from Step 3 in it for 5 minutes. After immersion, slowly remove the cathode from the molten salt and cool it. Repeatedly wash the titanium fiber felt coated with TiO2 nanotubes with 0.5mol / L dilute hydrochloric acid and deionized water to remove residual molten salt on the surface, and then vacuum dry it.

[0041] Figure 1 This is a transmission electron microscope (TEM) image of the titanium fiber felt with carbon film-coated TiO2 nanotubes prepared in this embodiment. Figure 1 It can be seen that the carbon film is continuous and has a thickness of approximately 10nm~30nm.

[0042] Figure 2This is a scanning electron microscope (SEM) image of the titanium fiber felt coated with TiO2 nanotubes by carbon film after immersion in this embodiment. Figure 2 It can be seen that after being soaked in mixed molten salt, the titanium fiber felt coated with carbon film still maintains the structure of TiO2 nanotubes before surface treatment, with the same tube diameter and microstructure. This indicates that the carbon film prepared in advance in this invention effectively reduces the influence of CaO impurities in molten salt on TiO2 nanotubes.

[0043] Example 2

[0044] This embodiment includes the following steps:

[0045] Step 1: Dissolve glucose in deionized water and stir magnetically for 30 minutes to ensure complete dissolution of glucose, thus preparing a 2 mol / L glucose solution.

[0046] Step 2: Add NH4F, HF, and H2O to a diethylene glycol solution at a mass ratio of 0.3wt%, 0.6wt%, and 6wt%, respectively, to form an electrolyte. Then, using titanium fiber felt as the anode and platinum sheet as the cathode, oxidize at 50°C and 60V for 2 hours to form an interstitial TiO2 nanotube array (s-TiO2NTAs) coating with a tube diameter of 80nm~100nm.

[0047] The glucose solution prepared in step one is heated to 50°C and kept at that temperature for 30 minutes. After the solution temperature stabilizes, the titanium fiber felt with the s-TiO2NTAs coating is immersed in the stable glucose solution for 3 hours for surface treatment.

[0048] Step 3: Immerse the titanium fiber felt with s-TiO2NTAs coating that has undergone surface treatment in Step 2 in an argon atmosphere and heat it to 500℃ for 3 hours. Then, let it cool naturally to room temperature to form a titanium fiber felt with a carbon film coating TiO2 nanotubes.

[0049] Step 4: Add the CaCl2-LiCl mixed molten salt (molar ratio 1:1) to the corundum crucible and place it in the electrolytic furnace. After evacuation, continuously introduce high-purity argon to ensure a good inert atmosphere in the furnace. Then, heat the CaCl2-LiCl mixed molten salt to 600℃, using a graphite rod as the anode and a stainless steel rod as the cathode, and electrolyze at 3V for 3 hours to initially remove impurities from the mixed molten salt. Next, add 0.1mol% Li2CO3 to the mixed molten salt and place the titanium fiber felt coated with TiO2 nanotubes from Step 3 into it. Electrolyze at 3.2V for 5 minutes. After electrolysis, slowly remove the cathode from the molten salt and cool it. Wash the titanium fiber felt coated with TiO2 nanotubes after molten salt electrolysis repeatedly with 0.5mol / L dilute hydrochloric acid and deionized water to remove residual molten salt on the surface, and then vacuum dry to obtain nano-titanium carbide.

[0050] Figure 3 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this embodiment. Figure 3 It can be seen that the nano-titanium carbide prepared after 5 minutes of electrolysis still maintains the structure of the TiO2 nanotubes before surface treatment, with the same tube diameter and microstructure, indicating that the carbon film prepared in advance in this invention is beneficial to improving the stability of the nanostructure during electrolysis.

[0051] Example 3

[0052] This embodiment includes the following steps:

[0053] Step 1: Dissolve glucose in deionized water and stir magnetically for 30 minutes to ensure complete dissolution of glucose, thus preparing a 2 mol / L glucose solution.

[0054] Step 2: Add NH4F, HF, and H2O to a diethylene glycol solution at a mass ratio of 0.3wt%, 0.6wt%, and 6wt%, respectively, to form an electrolyte. Then, using titanium fiber felt as the anode and platinum sheet as the cathode, oxidize at 50°C and 60V for 2 hours to form an interstitial TiO2 nanotube array (s-TiO2NTAs) coating with a tube diameter of 80nm~100nm.

[0055] The glucose solution prepared in step one is heated to 50°C and kept at that temperature for 30 minutes. After the solution temperature stabilizes, the titanium fiber felt with the s-TiO2NTAs coating is immersed in the stable glucose solution for 3 hours for surface treatment.

[0056] Step 3: Immerse the titanium fiber felt with s-TiO2NTAs coating that has undergone surface treatment in Step 2 in an argon atmosphere and heat it to 500℃ for 3 hours. Then, let it cool naturally to room temperature to form a titanium fiber felt with a carbon film coating TiO2 nanotubes.

[0057] Step 4: Add the CaCl2-LiCl mixed molten salt (molar ratio 1:1) to the corundum crucible and place it in the electrolysis furnace. After evacuation, continuously introduce high-purity argon to ensure a good inert atmosphere in the furnace. Then, heat the CaCl2-LiCl mixed molten salt to 600℃, using a graphite rod as the anode and a stainless steel rod as the cathode, and electrolyze at 3V for 3 hours to initially remove impurities from the mixed molten salt. Next, add 0.1mol% Li2CO3 to the mixed molten salt, and place the titanium fiber felt coated with TiO2 nanotubes from Step 3 into it. Electrolyze at 3.2V for 10 minutes. After electrolysis, slowly remove the cathode from the molten salt and cool it. Wash the titanium fiber felt coated with TiO2 nanotubes after molten salt electrolysis repeatedly with 0.5mol / L dilute hydrochloric acid and deionized water to remove residual molten salt on the surface, and then vacuum dry to obtain nano-titanium carbide.

[0058] Figure 4 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this embodiment. Figure 4 It can be seen that the nano-titanium carbide prepared after 10 min of electrolysis still maintains the structure of TiO2 nanotubes before surface treatment, with the same tube diameter and microstructure, indicating that the carbon film prepared in advance in this invention is beneficial to improving the stability of the nanostructure during electrolysis.

[0059] Example 4

[0060] This embodiment includes the following steps:

[0061] Step 1: Dissolve glucose in deionized water and stir magnetically for 30 minutes to ensure complete dissolution of glucose, thus preparing a 2 mol / L glucose solution.

[0062] Step 2: Add NH4F, HF, and H2O to a diethylene glycol solution at a mass ratio of 0.3wt%, 0.6wt%, and 6wt%, respectively, to form an electrolyte. Then, using titanium fiber felt as the anode and platinum sheet as the cathode, oxidize at 50°C and 60V for 2 hours to form an interstitial TiO2 nanotube array (s-TiO2NTAs) coating with a tube diameter of 80nm~100nm.

[0063] The glucose solution prepared in step one is heated to 50°C and kept at that temperature for 30 minutes. After the solution temperature stabilizes, the titanium fiber felt with the s-TiO2NTAs coating is immersed in the stable glucose solution for 3 hours for surface treatment.

[0064] Step 3: Immerse the titanium fiber felt with s-TiO2NTAs coating that has undergone surface treatment in Step 2 in an argon atmosphere and heat it to 500℃ for 3 hours. Then, let it cool naturally to room temperature to form a titanium fiber felt with a carbon film coating TiO2 nanotubes.

[0065] Step 4: Add the CaCl2-LiCl mixed molten salt (molar ratio 1:1) to the corundum crucible and place it in the electrolytic furnace. After evacuation, continuously introduce high-purity argon to ensure a good inert atmosphere in the furnace. Then, heat the CaCl2-LiCl mixed molten salt to 600℃, using a graphite rod as the anode and a stainless steel rod as the cathode, and electrolyze it at 3V for 3 hours to initially remove impurities from the mixed molten salt. Next, add 0.1mol% Li2CO3 to the mixed molten salt and place the titanium fiber felt coated with TiO2 nanotubes from Step 3 into it. Electrolyze it at 3.2V for 20 minutes. After electrolysis, slowly remove the cathode from the molten salt and cool it. Wash the titanium fiber felt coated with TiO2 nanotubes after molten salt electrolysis repeatedly with 0.5mol / L dilute hydrochloric acid and deionized water to remove residual molten salt on the surface, and then vacuum dry it to obtain nano-titanium carbide.

[0066] Figure 5 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this embodiment. Figure 5 It can be seen that the nano-titanium carbide prepared after 20 min of electrolysis still maintains the structure of TiO2 nanotubes before surface treatment, with the same tube diameter and microstructure, indicating that the carbon film prepared in advance in this invention is beneficial to improving the stability of the nanostructure during electrolysis.

[0067] Example 5

[0068] This embodiment includes the following steps:

[0069] Step 1: Dissolve glucose in deionized water and stir magnetically for 30 minutes to ensure complete dissolution of glucose, thus preparing a 1 mol / L glucose solution.

[0070] Step 2: Add NH4F, HF, and H2O to a diethylene glycol solution at a mass ratio of 0.3wt%, 0.6wt%, and 6wt%, respectively, to form an electrolyte. Then, using titanium fiber felt as the anode and platinum sheet as the cathode, oxidize at 50°C and 60V for 2 hours to form an interstitial TiO2 nanotube array (s-TiO2NTAs) coating with a tube diameter of 80nm~100nm.

[0071] The glucose solution prepared in step one is heated to 30°C and kept at that temperature for 30 minutes. After the solution temperature stabilizes, the titanium fiber felt with the s-TiO2NTAs coating is immersed in the stable glucose solution for 1 hour for surface treatment.

[0072] Step 3: Immerse the titanium fiber felt with s-TiO2NTAs coating that has undergone surface treatment in Step 2 in an argon atmosphere and heat it to 400℃ for 1 hour, then let it cool naturally to room temperature to form a titanium fiber felt with a carbon film coating TiO2 nanotubes.

[0073] Step 4: Add the CaCl2-LiCl mixed molten salt (molar ratio 1:1) to the corundum crucible and place it in the electrolytic furnace. After evacuation, continuously introduce high-purity argon to ensure a good inert atmosphere in the furnace. Then, heat the CaCl2-LiCl mixed molten salt to 600℃, using a graphite rod as the anode and a stainless steel rod as the cathode, and electrolyze it at 3V for 3 hours to initially remove impurities from the mixed molten salt. Next, add 0.1mol% Li2CO3 to the mixed molten salt and place the titanium fiber felt coated with TiO2 nanotubes from Step 3 into it. Electrolyze it at 3.2V for 20 minutes. After electrolysis, slowly remove the cathode from the molten salt and cool it. Wash the titanium fiber felt coated with TiO2 nanotubes after molten salt electrolysis repeatedly with 0.5mol / L dilute hydrochloric acid and deionized water to remove residual molten salt on the surface, and then vacuum dry it to obtain nano-titanium carbide.

[0074] Figure 6 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this embodiment. Figure 6 It can be seen that the nano-titanium carbide prepared after 20 min of electrolysis still maintains the structure of TiO2 nanotubes before surface treatment, with the same tube diameter and microstructure, indicating that the carbon film prepared in advance in this invention is beneficial to improving the stability of the nanostructure during electrolysis.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that a carbon film was not synthesized on the surface of the titanium fiber felt with the s-TiO2NTAs coating, that is, the titanium fiber felt with the s-TiO2NTAs coating prepared in step two was directly subjected to the process in step three.

[0077] Figure 7 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this comparative example. Figure 7 It can be seen that the TiO2 nanotube morphology in this nano-titanium carbide completely disappears, and is replaced by a large number of cubic CaTiO3. This indicates that without a carbon film coating on the surface, TiO2 nanotubes can easily react with trace amounts of CaO in the mixed molten salt, resulting in the complete destruction of the nano-morphology.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 2 is that a carbon film was not synthesized on the surface of the titanium fiber felt with the s-TiO2NTAs coating. Instead, the titanium fiber felt with the s-TiO2NTAs coating prepared in step 2 was directly subjected to the processes in steps 3 and 4.

[0080] Figure 8 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this comparative example. Figure 8 It can be seen that the tubular morphology of the nano-titanium carbide is severely damaged.

[0081] Comparative Example 3

[0082] The difference between this comparative example and Example 3 is that a carbon film was not synthesized on the surface of the titanium fiber felt with the s-TiO2NTAs coating, that is, the titanium fiber felt with the s-TiO2NTAs coating prepared in step two was directly subjected to the processes in steps three and four.

[0083] Figure 9 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this comparative example. Figure 9 It can be seen that the tubular morphology of the nano-titanium carbide is severely damaged.

[0084] Comparative Example 4

[0085] The difference between this comparative example and Example 4 is that a carbon film was not synthesized on the surface of the titanium fiber felt with the s-TiO2NTAs coating. Instead, the titanium fiber felt with the s-TiO2NTAs coating prepared in step two was directly subjected to the processes in steps three and four.

[0086] Figure 10 Here is a scanning electron microscope image of the nano-titanium carbide prepared in this comparative example. Figure 10 It can be seen that the tubular morphology of the nano-titanium carbide is severely damaged.

[0087] In summary, this invention addresses the critical challenge of CaO impurities in the molten salt causing damage to the nanostructure of the TiO2 precursor during the existing molten salt electrochemical preparation of nanostructured TiC. It innovatively proposes a method for pre-constructing a protective carbon film on the surface of nano-TiO2 using a glucose solution. This method has a wide molten salt condition window, effectively suppressing the damage of CaO to the TiO2 nanostructure without extreme molten salt purification, and significantly improving the stability and heritability of the nanostructure during the TiO2→TiC conversion. This invention provides a reliable solution for the stable synthesis of nanostructured TiC via molten salt electrochemistry, strongly promoting the industrial application of this technology.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for improving the nanostructure stability of titanium dioxide in molten salt environments and electrolytic processes, characterized by, The method includes the following steps: Step 1: Dissolve glucose in deionized water to prepare a glucose solution; the concentration of the glucose solution is 1 mol / L to 2 mol / L. Step 2: The nano-TiO2 is immersed in the glucose solution prepared in Step 1 for surface treatment; the nano-TiO2 has a tubular structure; the temperature of the glucose solution during the surface treatment is 30℃~50℃, and the immersion time is 1h~3h. Step 3: Heat-treat the surface-treated nano-TiO2 from Step 2 under an inert atmosphere to form carbon-coated nano-TiO2. Step 4: The nano-TiO2 coated with carbon film in Step 3 is converted into nano-titanium carbide by molten salt electrolysis; the molten salt system used for the molten salt electrolysis is a CaCl2-LiCl mixed molten salt, and 0.1 mol% of Li2CO3 is added to the mixed molten salt.

2. The method of claim 1, wherein the method is characterized by, The heat treatment in step three is performed at a temperature of 400℃~500℃, with a holding time of 1h~3h, and the inert atmosphere is argon.

3. The method of claim 1, wherein the method is characterized by, In step three, the carbon coating layer in the nano-TiO2 coated with carbon film is a continuous carbon film with a thickness of 10 nm to 30 nm.

4. The method of claim 1, wherein the method is characterized by, The electrolysis voltage of the molten salt electrolysis is 3.2V, and the electrolysis temperature is 600℃.

5. The method of claim 1, wherein the method is characterized by: The diameter of the nano-TiO2 in step two is 80nm~100nm; the nano-titanium carbide has the same diameter and morphology as the nano-TiO2 in step two.

6. The method of claim 1, wherein the method is characterized by: The nano-titanium carbide is transformed from nano-TiO2 coated with a carbon film, and maintains the microstructure of nano-TiO2.

Images