Preparation method of cerium oxide and nitrogen-doped carbon composite material
By using low eutectic solvents to prepare cerium oxide and nitrogen-doped carbon composites, the problems of poor conductivity of cerium oxide nanomaterials and complex nitrogen-doped carbon process were solved, achieving efficient and green electrocatalytic activity improvement.
Patent Information
- Application Number
- CN202511055746.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-30
- Publication Date
- 2025-09-09
AI Technical Summary
Existing cerium oxide nanomaterials have problems such as poor conductivity, large size and uneven distribution, which limit their application in electrochemical biosensors. In addition, the preparation process of traditional nitrogen-doped carbon is complex and harmful to the environment.
Dicyandiamide, choline chloride and glucose are used as components of the low eutectic solvent and as nitrogen and carbon sources. Cerium oxide and nitrogen-doped carbon composites are prepared by direct carbonization of self-templated precursors. Combining the advantages of both, a composite material with large specific surface area and good conductivity is prepared.
The prepared composite material has excellent electrocatalytic activity, a large contact area, and many catalytic active sites. The preparation method is simple, efficient, and green.
Smart Images
Figure CN120607271A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of nanoenzyme materials, and in particular to a method for preparing a cerium oxide and nitrogen-doped carbon composite material. Background Art
[0002] With the rapid development of society and the significant improvement in people's living standards, attention to health and safety is increasing. As an efficient and sensitive detection tool, electrochemical biosensors play an irreplaceable role in environmental pollution monitoring, early disease diagnosis, food safety testing, and other fields, providing important support for safeguarding human health and ecological safety. Electrochemical biosensors rely on biological target recognition elements and electrochemical signal transduction elements to achieve high-sensitivity detection. Enzymes are the recognition elements used because of their high efficiency, high resolution, and strong specificity. However, the inherent shortcomings of enzymes, such as poor stability, high cost, inability to tolerate harsh environments, and difficulty in storage, have greatly limited their further application in electrochemical biosensors. To overcome these problems, scientists have developed artificial enzymes that mimic enzyme activity, particularly nanozymes. Due to their low cost, high stability, and easy storage, they are considered ideal alternatives to natural enzymes and can improve the performance of electrochemical biosensors. Cerium, the most abundant rare earth element, has a unique outer electron structure, resulting in variable valence states. Its oxide, cerium oxide (CeO2), has many oxygen vacancies in its crystal structure, and the formation and elimination of oxygen vacancies lead to reversible conversion between tetravalent cerium and trivalent cerium, thus having excellent redox properties. In addition, cerium oxide also has a variety of enzyme activities and has been widely used in the field of nanoenzyme materials. However, pure cerium oxide nanomaterials have problems such as poor conductivity, large size and uneven distribution, which limit their application in electrochemical biosensors. Therefore, it is necessary to seek a cerium oxide-based nanomaterial with small size, uniform distribution, good conductivity and good catalytic activity.
[0003] Nitrogen-doped carbons (NCs) have attracted widespread attention in recent years due to their high specific surface area, good electrical conductivity, and tunable surface chemical properties. Combining cerium oxide with nitrogen-doped carbon effectively combines the advantages of both materials, overcoming the shortcomings of either material alone and resulting in a composite material with superior performance. However, the traditional preparation process for nitrogen-doped carbon is complex and often involves chemical activation, which has adverse environmental impacts. Therefore, directly carbonizing self-templated precursors into NCs is a more attractive and feasible approach. For example, nitrogen-containing ionic liquids can be used. However, the high cost, toxicity, and low biodegradability of ionic liquids limit their application as nitrogen-doped carbon precursors. Deep eutectic solvents (DESs), analogs of ionic liquids, offer advantages over ionic liquids, such as low cost, simple synthesis, non-toxicity, and biodegradability. The components in DESs can act as both hydrogen bond donors / acceptors and nitrogen / carbon sources. They act as self-templates, allowing in situ nitrogen doping during the carbonization process, making it possible to synthesize specialized carbon materials with controllable structure and properties.
[0004] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a cerium oxide and nitrogen-doped carbon composite material. The method is simple, efficient, and green, and the prepared composite material has a large specific surface area, which makes the contact area between the electrolyte and the material larger, and there are more active sites involved in catalysis. In addition, due to the good conductivity of the nitrogen-doped carbon material itself, the composite material exhibits excellent electrocatalytic activity. Summary of the Invention
[0005] The object of the present invention is to provide a method for preparing a cerium oxide and nitrogen-doped carbon composite material to solve the problems raised in the above background technology.
[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a cerium oxide and nitrogen-doped carbon composite material, comprising the following steps:
[0007] Step 1: stirring dicyandiamide, choline chloride and glucose at a certain temperature until a clear and transparent deep eutectic solvent is formed;
[0008] Step 2: After freeze-drying the deep eutectic solvent, the solution is placed in a tube furnace and calcined at high temperature under a protective gas atmosphere to obtain a black nitrogen-doped carbon material;
[0009] Step 3: a certain amount of the carbon material obtained in step 2 is dispersed in a certain volume of deionized water and stirred for a certain period of time, and then a certain amount of Ce(NO3)3·6H2O and dopamine hydrochloride powder are dispersed in the uniform solution under magnetic stirring until they are completely dissolved;
[0010] Step 4: NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution. The system was then transferred to a polytetrafluoroethylene-lined autoclave. After reacting at a certain temperature for a certain time and then naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven.
[0011] Step 5: The dark brown product formed in step 4 is placed in a tube furnace and calcined at high temperature under a protective gas atmosphere to obtain a cerium oxide and nitrogen-doped carbon composite material.
[0012] Furthermore, in the step 1, the molar ratio of dicyandiamide, choline chloride and glucose is 1:1:1, 1:2:2, 1:3:3, 2:2:3, 2:3:1, 3:2:2, and the temperature of heating and stirring is 90°C.
[0013] Furthermore, in step 2, the freeze-drying treatment time is 48 hours.
[0014] Furthermore, in step 2, the protective gas is one of nitrogen, argon or argon / hydrogen gas.
[0015] Furthermore, in the step 2, the calcination temperature is between 700° C. and 900° C., the heating rate is 5° C. / min, and the holding time is 2 h.
[0016] Furthermore, in step three, the concentration of the nitrogen-doped carbon material dispersion was 3.335 mg / mL, and the stirring time was 10 min.
[0017] Furthermore, in step 3, the molar amount of Ce(NO3)3·6H2O added is in the range of 0.2 to 1.0 mmol, and the amount of dopamine hydrochloride added is in the range of 50 to 150 mg.
[0018] Furthermore, in step 4, the pH value of the solution is 8.5.
[0019] Furthermore, in step 4, the reaction temperature in the reactor is 160° C. and the reaction time is 12 h.
[0020] Furthermore, in step 4, the oven drying temperature is 80°C.
[0021] Furthermore, in step five, the protective gas is one of nitrogen, argon or argon / hydrogen gas.
[0022] Furthermore, in the step 5, the calcination temperature is 500° C., the heating rate is 5° C. / min, and the holding time is 1 h.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] The present invention is the first to design and synthesize a low eutectic solvent with dicyandiamide and glucose as hydrogen bond donors and choline chloride as a hydrogen bond acceptor. In the low eutectic solvent, dicyandiamide and glucose serve as nitrogen and carbon sources, respectively, and are directly carbonized as self-templated precursors to form nitrogen-doped carbon materials. Due to the good conductivity and high specific surface area of the nitrogen-doped carbon material, the composite material with cerium oxide exhibits excellent electrocatalytic activity. The preparation method is simple, efficient, and green, and the prepared composite material has a large specific surface area, which increases the contact area between the electrolyte and the material and increases the number of active sites involved in catalysis. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 The X-ray diffraction pattern of the product obtained according to Example 1 of the present invention is shown in FIG.
[0026] Figure 2 The scanning electron microscope photograph of the product obtained according to Example 1 of the present invention is shown in FIG.
[0027] Figure 3 Cyclic voltammograms of a glassy carbon electrode modified with the product obtained in Example 1 of the present invention in the absence and presence of 5 mM H2O2 in 0.1 M PBS (pH = 7.0) containing 0.3 M KCl, and cyclic voltammograms of a bare electrode under the same conditions.
[0028] Figure 4 The current response and corresponding calibration curve of the glassy carbon electrode modified with the product obtained in Example 1 of the present invention in 0.1 M PBS (pH = 7.0) containing 0.3 M KCl and continuous addition of H2O2 at an applied potential of 0.6 V.
[0029] Figure 5 The amperometric response of the glassy carbon electrode modified according to the product obtained in Example 1 of the present invention when 5 μM H2O2, ascorbic acid, KCl, NaCl, glucose and CaCl2 are successively added in 0.1 M PBS (pH = 7.0) containing 0.3 M KCl, and the long-term amperometric response graph when 50 μM H2O2 is added. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0031] Example 1
[0032] (1) Accurately weigh 1681.6 mg of dicyandiamide, 4188.6 mg of choline chloride, and 1801.6 mg of glucose solids, mix the three solids, and stir at 90°C until a clear and transparent deep eutectic solvent is formed.
[0033] (2) The low eutectic solvent obtained in the above step 1 was freeze-dried for 48 hours, placed in a tube furnace, and calcined at 800° C. for 2 hours under a protective gas atmosphere to obtain a black nitrogen-doped carbon material.
[0034] (3) Accurately weigh 66.7 mg of the nitrogen-doped carbon material obtained in step 2, disperse it into 20 mL of deionized water and continue stirring for 10 min. Then, 86.8 mg of Ce(NO3)3·6H2O and 125 mg of dopamine hydrochloride powder were dispersed in the uniform solution under magnetic stirring until they were completely dissolved.
[0035] (4) NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution to 8.5. The system was then transferred to a polytetrafluoroethylene-lined autoclave and reacted at 160°C for 12 h. After naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven at 80°C.
[0036] (5) The dark brown product formed in step 4 was placed in a tube furnace and calcined at 500° C. for 1 h under a protective gas atmosphere to obtain a cerium oxide and nitrogen-doped carbon composite material.
[0037] Figure 1 Figure 2 is the X-ray diffraction pattern of the product obtained according to Example 1 of the present invention. Two broad peaks are observed at approximately 25° and 43° for the nitrogen-doped carbon material (NC), cerium oxide, and nitrogen-doped carbon composite material (CeO2 / NC), which are attributed to the (002) and (100) crystal planes of amorphous carbon, respectively. The X-ray diffraction peaks of pure cerium oxide (CeO2) synthesized by the same synthesis method at 2θ = 28.5°, 33.1°, 47.5°, 56.3°, 69.4°, 76.7° and 79.1° are consistent with the (111), (200), (220), (311), (400), (331) and (420) crystal planes of cubic fluorite CeO2, indicating that although the XRD spectrum of the composite material does not show the diffraction peak of cerium oxide, cerium oxide is present in the composite material, and due to the presence of a large amount of carbon, CeO2 / NC exhibits weak crystallinity.
[0038] Figure 2This is a scanning electron micrograph of the product obtained according to Example 1 of the present invention. As can be seen from the image, the nitrogen-doped carbon (NC) material is an irregular, block-like structure stacked together, with lengths ranging from 1 to 10 μm. Numerous cerium oxide nanoparticles approximately 10 nm in size are loaded on the surface of the NC material.
[0039] Figure 3 Cyclic voltammograms of a glassy carbon electrode modified with the product obtained in Example 1 of the present invention in 0.1M PBS (pH 7.0) containing 0.3M KCl, in the absence and presence of 5mM H₂O₂, are shown, along with cyclic voltammograms of a bare electrode under the same conditions. The graphs show that the onset potential for electrocatalytic H₂O₂ oxidation over CeO₂ / NC is approximately 0.28V, with a current corresponding to 58.48μA at 0.8V. In contrast, the onset potential for electrocatalytic H₂O₂ over the bare electrode is approximately 0.45V, with a current corresponding to 1.342μA at 0.8V. This comparison demonstrates that CeO₂ / NC exhibits excellent electrocatalytic H₂O₂ oxidation performance.
[0040] Figure 4 The current and corresponding calibration curve of the glassy carbon electrode modified with the product obtained in Example 1 of the present invention in 0.1M PBS (pH=7.0) containing 0.3M KCl and continuously adding H2O2 at an applied potential of 0.6V are shown. As shown in Figure A, a significant increase in current can be observed with the continuous addition of H2O2. As shown in Figure B, the current response is linearly related to concentration in the two concentration ranges of 0.05-60μM and 60-300μM, and the corresponding linear equations are: I(μA)=0.0186c(μM)+0.200(R 2 =0.990) and I(μA)=0.00968c(μM)+0.727(R 2 =0.994). In addition, the sensitivity of CeO2 / NC / GCE to H2O2 oxidation is 0.0948μAμM -1 cm -2 and 0.0493 μA μM -1 cm -2 , the limit of detection (LOD) was 0.036 μM.
[0041] Figure 5The amperometric response of a glassy carbon electrode modified with the product obtained in Example 1 of the present invention to the sequential addition of 5μM H2O2, ascorbic acid, KCl, NaCl, glucose, and CaCl2 to 0.1M PBS (pH 7.0) containing 0.3M KCl, as well as the long-term amperometric response after the addition of 50μM H2O2, are shown. As shown in Figure A, a clear current response is observed after the addition of 5μM H2O2, while the effect of 5μM interfering substances on the current response is negligible, demonstrating that the proposed sensor can be used to selectively detect H2O2. Figure B shows that the sensor maintains high catalytic activity and exhibits no material shedding over extended periods of continuous detection.
[0042] Example 2
[0043] (1) Accurately weigh 840.8 mg of dicyandiamide, 2792.4 mg of choline chloride, and 3603.2 mg of glucose solids, mix the three solids, and stir at 90°C until a clear and transparent deep eutectic solvent is formed.
[0044] (2) The low eutectic solvent obtained in step 1 was freeze-dried for 48 hours, placed in a tube furnace, and calcined at 700° C. for 2 hours under a protective gas atmosphere to obtain a black nitrogen-doped carbon material.
[0045] (3) Accurately weigh 66.7 mg of the nitrogen-doped carbon material obtained in step 2, disperse it into 20 mL of deionized water and continue stirring for 10 min. Then, 260.5 mg of Ce(NO3)3·6H2O and 50 mg of dopamine hydrochloride powder were dispersed in the uniform solution under magnetic stirring until they were completely dissolved.
[0046] (4) NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution to 8.5. The system was then transferred to a polytetrafluoroethylene-lined autoclave and reacted at 160°C for 12 h. After naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven at 80°C.
[0047] (5) The dark brown product formed in step 4 was placed in a tube furnace and calcined at 500° C. for 1 h under a protective gas atmosphere to obtain a cerium oxide and nitrogen-doped carbon composite material.
[0048] Example 3
[0049] (1) Accurately weigh 1681.6 mg of dicyandiamide, 2792.4 mg of choline chloride, and 5404.8 mg of glucose solids, mix the three solids, and stir at 90°C until a clear and transparent deep eutectic solvent is formed.
[0050] (2) The low eutectic solvent obtained in step 1 was freeze-dried for 48 hours, placed in a tube furnace, and calcined at 750° C. for 2 hours under a protective gas atmosphere to obtain a black nitrogen-doped carbon material.
[0051] (3) Accurately weigh 66.7 mg of the nitrogen-doped carbon material obtained in step 2, disperse it into 20 mL of deionized water and continue stirring for 10 min. Then, 173.7 mg of Ce(NO3)3·6H2O and 75 mg of dopamine hydrochloride powder were dispersed in the uniform solution under magnetic stirring until they were completely dissolved.
[0052] (4) NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution to 8.5. The system was then transferred to a polytetrafluoroethylene-lined autoclave and reacted at 160°C for 12 h. After naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven at 80°C.
[0053] (5) The dark brown product formed in step 4 was placed in a tube furnace and calcined at 500° C. for 1 h under a protective gas atmosphere to obtain a cerium oxide and nitrogen-doped carbon composite material.
[0054] Example 4
[0055] (1) Accurately weigh 840.8 mg of dicyandiamide, 4188.6 mg of choline chloride, and 5404.8 mg of glucose solids, mix the three solids, and stir at 90°C until a clear and transparent deep eutectic solvent is formed.
[0056] (2) The low eutectic solvent obtained in step 1 was freeze-dried for 48 hours, placed in a tube furnace, and calcined at 850° C. for 2 hours under a protective gas atmosphere to obtain a black nitrogen-doped carbon material.
[0057] (3) Accurately weigh 66.7 mg of the nitrogen-doped carbon material obtained in step 2, disperse it into 20 mL of deionized water and continue stirring for 10 min. Then, 347.4 mg of Ce(NO3)3·6H2O and 100 mg of dopamine hydrochloride powder were dispersed in the uniform solution under magnetic stirring until they were completely dissolved.
[0058] (4) NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution to 8.5. The system was then transferred to a polytetrafluoroethylene-lined autoclave and reacted at 160°C for 12 h. After naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven at 80°C.
[0059] (5) The dark brown product formed in step 4 was placed in a tube furnace and calcined at 500° C. for 1 h under a protective gas atmosphere to obtain a cerium oxide / nitrogen-doped carbon composite material.
[0060] Example 5
[0061] (1) Accurately weigh 2522.4 mg of dicyandiamide, 4188.6 mg of choline chloride, and 3603.2 mg of glucose solids, mix the three solids, and stir at 90°C until a clear and transparent deep eutectic solvent is formed.
[0062] (2) The low eutectic solvent obtained in step 1 was freeze-dried for 48 hours, placed in a tube furnace, and calcined at 900° C. for 2 hours under a protective gas atmosphere to obtain a black nitrogen-doped carbon material.
[0063] (3) Accurately weigh 66.7 mg of the nitrogen-doped carbon material obtained in step 2, disperse it into 20 mL of deionized water and continue stirring for 10 min. Then, 434.2 mg of Ce(NO3)3·6H2O and 150 mg of dopamine hydrochloride powder were dispersed in the uniform solution under magnetic stirring until they were completely dissolved.
[0064] (4) NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution to 8.5. The system was then transferred to a polytetrafluoroethylene-lined autoclave and reacted at 160°C for 12 h. After naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven at 80°C.
[0065] (5) The dark brown product formed in step 4 was placed in a tube furnace and calcined at 500° C. for 1 h under a protective gas atmosphere to obtain a cerium oxide and nitrogen-doped carbon composite material.
Claims
1. A method for preparing a cerium oxide and nitrogen-doped carbon composite material, characterized in that: The steps include: Step 1: stirring dicyandiamide, choline chloride and glucose at a certain temperature until a clear and transparent deep eutectic solvent is formed; Step 2: After freeze-drying the deep eutectic solvent, the solution is placed in a tube furnace and calcined at high temperature under a protective gas atmosphere to obtain a black nitrogen-doped carbon material; Step 3: a certain amount of the carbon material obtained in step 2 is dispersed in a certain volume of deionized water and stirred for a certain period of time, and then a certain amount of Ce(NO3)3·6H2O and dopamine hydrochloride powder are dispersed in the uniform solution under magnetic stirring until they are completely dissolved; Step 4: NH3·H2O (25 wt.% to 28 wt.%) was added dropwise to the homogeneous solution obtained in step 3 to adjust the pH value of the solution. The system was then transferred to a polytetrafluoroethylene-lined autoclave. After reacting at a certain temperature for a certain time and then naturally cooling to room temperature, the prepared sample was washed with deionized water and ethanol and dried in an oven. Step 5: The dark brown product formed in step 4 is placed in a tube furnace and calcined at high temperature under a protective gas atmosphere to obtain a cerium oxide and nitrogen-doped carbon composite material.
2. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 1, the molar ratios of dicyandiamide, choline chloride and glucose are 1:1:1, 1:2:2, 1:3:3, 2:2:3, 2:3:1 and 3:2:2, and the heating and stirring temperature is 90°C.
3. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 2, the freeze-drying treatment time is 48 hours.
4. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 2, the protective gas is one of nitrogen, argon or argon / hydrogen gas.
5. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 2, the calcination temperature is between 700° C. and 900° C., the heating rate is 5° C. / min, and the holding time is 2 h.
6. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 3, the concentration of the nitrogen-doped carbon material dispersion is 3.335 mg / mL, and the stirring time is 10 min.
7. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 3, the molar amount of Ce(NO3)3·6H2O added is in the range of 0.2 to 1.0 mmol, and the amount of dopamine hydrochloride added is in the range of 50 to 150 mg.
8. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 4, the pH value of the solution is 8.
5.
9. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 4, the reaction temperature in the reactor is 160° C. and the reaction time is 12 h.
10. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 4, the oven drying temperature is 80°C.
11. The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1, wherein: In the step 5, the protective gas is one of nitrogen, argon or argon / hydrogen gas. 12 . The method for preparing a cerium oxide and nitrogen-doped carbon composite material according to claim 1 , wherein in step 5, the calcination temperature is 500° C., the heating rate is 5° C. / min, and the holding time is 1 hour.