Composite material, preparation method thereof and application of composite material in heat-assisted electro-catalysis

Abstract

The invention discloses a composite material as well as a preparation method and application thereof in heat-assisted electro-catalysis, and belongs to the technical field of oxygen preparation and electro-catalysis. The preparation method of the composite material comprises the following steps: stirring and mixing nickel sulfate, ferric nitrate, urea, ammonium fluoride, cesium tungsten bronze and water to obtain a precursor solution; the precursor solution is subjected to a hydrothermal reaction at the temperature of 100-110 DEG C, and the composite material is obtained. In addition, the invention also provides the composite material which is prepared by the preparation method. The composite material prepared by the preparation method provided by the invention has excellent photo-thermal performance and good electro-catalytic activity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oxygen preparation and electrocatalysis, and in particular to a composite material, a preparation method thereof and application thereof in thermal-assisted electrocatalysis. BACKGROUND

[0002] Hydrogen energy, as an excellent clean and renewable energy, has an extremely important strategic position in the face of energy shortage and ecological environment deterioration. Electrolysis of water to produce hydrogen is an important way to obtain high-purity hydrogen, but the catalytic efficiency of one of the half-reactions, oxygen evolution reaction (OER), directly affects the entire reaction. Although traditional noble metal materials such as IrO2 and RuO2 are of great concern due to their excellent catalytic activity, they are high in cost and extremely scarce, which limits their further application in industry.

[0003] Nickel-iron layered double hydroxide (NiFe-LDH) is a kind of non-noble metal electrocatalyst with wide application prospects. It is of great concern due to its low cost, abundant resources and excellent electrocatalytic activity. Although this material has great application potential, the problems of high overpotential and kinetic sluggishness still need to be solved by modification strategies.

[0004] In recent years, photo-thermal assisted electrocatalysis technology, as a new emerging catalytic enhancement strategy, has developed rapidly. This strategy is to composite photo-thermal materials and electrocatalysts together, and use the thermal effect brought by light to improve the temperature of the material, and then improve the kinetics and activity of the electrocatalytic process. Cesium tungsten bronze (Cs x WO3) is a kind of efficient near-infrared photo-thermal conversion material, which has excellent near-infrared light absorption capacity and energy conversion efficiency, and has important application prospects and research significance in photo-thermal catalysis.

[0005] Therefore, it is of great significance to prepare a composite material combining the excellent electrocatalytic performance of NiFe-LDH and the high-efficiency photo-thermal conversion capability of Cs x WO3 to improve the electrocatalytic efficiency of oxygen evolution reaction (OER). SUMMARY

[0006] The present application aims to overcome the above technical deficiencies, and provides a composite material, a preparation method thereof and application thereof in thermal-assisted electrocatalysis, to solve the technical problem of how to improve the electrocatalytic efficiency of oxygen evolution reaction (OER) in the prior art.

[0007] To achieve the above technical purpose, the technical scheme of the present application provides a preparation method of a composite material, comprising the following steps: stirring and mixing nickel sulfate, iron nitrate, urea, ammonium fluoride, cesium tungsten bronze and water to obtain a precursor solution; and hydrothermally reacting the precursor solution at 100-110 DEG C to obtain the composite material.

[0008] In any embodiment, the molar ratio of the nickel nitrate and the iron nitrate is (2-2.5):1; and / or, the molar ratio of the urea and the iron nitrate is (70-72):1; and / or, the molar ratio of the ammonium chloride and the iron nitrate is (15-16):1.

[0009] In any embodiment, the material ratio of the cesium tungsten bronze and the iron nitrate is (20-25) mg:1 mmol.

[0010] In any embodiment, the hydrothermal reaction time is 10-14 h.

[0011] In any embodiment, the stirring and mixing time is 2-3 h.

[0012] In any embodiment, the cesium tungsten bronze is prepared by the following steps: dispersing cesium hydroxide and tungsten hexoxide in an ethanol solvent, then adding glacial acetic acid to obtain a mixed solution, and then performing hydrothermal reaction at 220-240 DEG C to obtain the cesium tungsten bronze.

[0013] In any embodiment, the hydrothermal reaction time at 220-240 DEG C is 24-26 h.

[0014] In any embodiment, the mass ratio of the cesium hydroxide and the tungsten hexoxide is 1:(7-7.5).

[0015] In any embodiment, the volume ratio of the glacial acetic acid and the ethanol solvent is 1:(8-9); and the material ratio of the cesium hydroxide and the ethanol solution is 1 g:(32-35) mL.

[0016] In addition, the present application also provides a composite material prepared by the above preparation method.

[0017] In addition, the present application also provides the application of the composite material prepared by the above preparation method or the above composite material in thermal-assisted electrocatalysis.

[0018] Compared with the prior art, the present application has the following beneficial effects: the composite material prepared by the preparation method of the present application has the Cs x WO3 excellent photo-thermal performance and NiFe-LDH good electrocatalytic activity; at 1.579 V, the prepared composite material can reach 10 mA cm -2The current density is 10 mA / cm2, and the performance of the pure NiFe-LDH material at 1.661 V is compared, and the overpotential is significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The NiFe-LDH prepared for the present application Comparative Example 1, the Cs x WO3 and NiFe-LDH / Cs x X-ray diffraction patterns of WO3 and NiFe-LDH / Cs

[0020] Figure 2 Scanning electron microscope images of different materials, wherein (a), (b) are Cs x WO3 prepared for Comparative Example 2, (c), (d) are NiFe-LDH prepared for Comparative Example 1, (e), (f) are NiFe-LDH / Cs prepared for Example 1 x WO3.

[0021] Figure 3 Infrared thermal imaging images of four materials under light, wherein A1-A5 are Cs x WO3 prepared for Comparative Example 2, B1-B5 are NiFe-LDH prepared for Comparative Example 1, C1-C5 are NiFe-LDH / Cs prepared for Example 1 x WO3 material, D1-D5 are PM-NiFe-LDH / Cs prepared for Comparative Example 3 x Temperature distribution of the WO3 material after 1, 3, 5, 7, 9 minutes of light irradiation.

[0022] Figure 4 The material prepared for Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 is a curve graph of the relationship between light irradiation time and material temperature change.

[0023] Figure 5 The material prepared for Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 is a linear sweep voltammetry curve graph.

[0024] Figure 6 NiFe-LDH / Cs prepared for Example 1 x WO3 material and PM-NiFe-LDH / Cs prepared for Comparative Example 3 x Linear sweep voltammetry curve comparison of the WO3 material before and after photo-thermal assistance. DETAILED DESCRIPTION

[0025] "RANGES" disclosed herein are defined, for each specific range by a lower and an upper limit, the lower and upper limit defining the boundaries of a particular range. Ranges defined by these methodologies can either be inclusive or exclusive of the endpoints, and are arbitrarily combinable, i.e., any lower limit can be combined with any upper limit to define a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that a range of 60-110 and 80-120 is also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" indicates a range of any combination of the numbers between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, "0-5" is merely a shorthand for listing all of these numerical combinations. Also, when a parameter is stated to be an integer > 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise indicated, "including" and "comprising" in this application are open-ended, and also include the other components listed in the application. For example, "including" and "comprising" can mean that other components can also be included or comprised.

[0027] Unless otherwise indicated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0028] The specific embodiment provides a preparation method of a composite material, comprising the following steps: stirring and mixing nickel sulfate, iron nitrate, urea, ammonium fluoride, cesium tungsten bronze and water for 2-3 h to obtain a precursor solution; hydrothermally reacting the precursor solution at 100-110 °C for 10-14 h to obtain the composite material; the molar ratio of the nickel sulfate and the iron nitrate is (2-2.5): 1; the molar ratio of the urea and the iron nitrate is (70-72): 1; the molar ratio of the ammonium chloride and the iron nitrate is (15-16): 1; the material ratio of the cesium tungsten bronze and the iron nitrate is (20-25) mg: 1 mmol.

[0029] In some embodiments, the cesium tungsten bronze is prepared by the following steps: dispersing cesium hydroxide and tungsten trioxide in an ethanol solvent, then adding glacial acetic acid to obtain a mixed solution, and then performing a hydrothermal reaction at 220-240 ℃ for 24-26 h to obtain the cesium tungsten bronze; the mass ratio of the cesium hydroxide to the tungsten trioxide is 1:(7-7.5); the volume ratio of the glacial acetic acid to the ethanol solvent is 1:(8-9); and the material ratio of the cesium hydroxide to the ethanol solution is 1 g:(32-35) mL. The cesium tungsten bronze is Cs x WO3, x is a decimal between 0.1 and 0.5, most commonly x is approximately 0.33.

[0030] The present embodiment also provides a composite material prepared by the above preparation method.

[0031] The present embodiment also provides the use of the composite material prepared by the above preparation method or the above composite material in heat-assisted electrocatalysis.

[0032] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0033] In the present application, "some embodiments", "the present embodiment" and the like are described, which describe a subset of all possible embodiments, but it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0034] If the application file contains similar descriptions such as "first / second", the following description is added: in the following description, the terms "first\second\third" involved only distinguish similar objects, and do not represent a specific order of the objects. It can be understood that "first\second\third" can be interchanged in a specific order or sequence as allowed, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0035] In the present embodiment, the term "and / or" only describes the association relationship between the associated objects, which means that there can be three relationships, for example, object A and / or object B, which means that there can be three cases: object A exists alone, object A and object B exist together, and object B exists alone.

[0036] Hereinafter, the examples of the present application will be described. The examples described below are illustrative and are intended to be purely exemplary of the application and are not intended to limit the application. Unless otherwise indicated, technical or conditions not specified in the examples are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments used are not specified by the manufacturer, but are conventional products that can be obtained commercially.

[0037] Example 1 This example proposes a composite material, which is prepared by the following steps: Step 1: Cs x Preparation of WO3 photo-thermal material A clean beaker was taken, 0.18 g of cesium hydroxide monohydrate and 1.28 g of tungsten trioxide were weighed, 32 mL of anhydrous ethanol was added as a solvent, and a magnetic stirrer was used to stir at room temperature until the solids were dispersed. After the mixture was uniformly mixed, 8 mL of glacial acetic acid was slowly added dropwise and continued to stir until uniform to obtain a mixed solution. Then, the above mixed solution was transferred into a 100 mL polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, sealed and placed in a 230 °C oven for hydrothermal reaction for 24 h. After the reaction was completed, the reaction kettle was allowed to cool to room temperature, and then transferred to a centrifuge tube. Deionized water and ethanol were used to clean alternately for three times, the purpose was to remove the unreacted raw materials and by-products, and finally the sample was placed in a vacuum oven at 60 °C for drying for 12 hours. Finally, Cs x WO3 powder was obtained.

[0038] Step 2: NiFe-LDH / Cs x Preparation of WO3 composite catalyst 1.8 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.9 mmol of iron nitrate nonahydrate (Fe(NO3)3·9H2O), 64 mmol of urea (CO(NH2)2) and 13.5 mmol of ammonium fluoride (NH4F) were accurately weighed. Then, 20 mg of Cs x WO3 powder obtained in step 1 was accurately weighed, and then placed in 50 mL of deionized water together with other required reagents, and stirred with a magnetic stirrer for 2 h to mix the various substances uniformly. The prepared precursor solution was poured into a 100 mL polytetrafluoroethylene-lined reaction kettle, and then the reaction kettle was placed in an oven for hydrothermal reaction treatment at a temperature of 105 °C for 12 h. After the hydrothermal reaction was completed, the reaction kettle was allowed to cool naturally to room temperature, and then the sample was taken out and washed with deionized water and anhydrous ethanol alternately for three times. The washed product was transferred to a vacuum drying oven with a preset temperature of 60 °C, and dried for 12 h. Finally, NiFe-LDH / Cs x WO3 composite catalyst powder sample was obtained.

[0039] Example 2 The difference between the preparation method of the composite material proposed in this example and that of Example 1 is that in Step 1, the temperature of the hydrothermal reaction is 220 °C, and the time is 26 h; the other steps and conditions are the same as those of Example 1.

[0040] Example 3 The difference between the preparation method of the composite material proposed in this example and that of Example 1 is that in Step 1, the temperature of the hydrothermal reaction is 240 °C, and the time is 25 h; the other steps and conditions are the same as those of Example 1.

[0041] Example 4 The difference between the preparation method of the composite material proposed in this example and that of Example 1 is that in Step 2, the temperature of the hydrothermal reaction is 110 °C, and the time is 14 h; the other steps and conditions are the same as those of Example 1.

[0042] Example 5 The difference between the preparation method of the composite material proposed in this example and that of Example 1 is that in Step 2, the temperature of the hydrothermal reaction is 100 °C, and the time is 13 h; the other steps and conditions are the same as those of Example 1.

[0043] Comparative Example 1 The synthesis method given in Example 1 was used to prepare a composite material without Cs x WO3 powder, and the preparation of pure NiFe-LDH was completed through constant temperature hydrothermal reaction at 105 °C for 12 h, followed by centrifugal cleaning, vacuum drying, etc. x WO3 powder, and the preparation of pure NiFe-LDH was completed through constant temperature hydrothermal reaction at 105 °C for 12 h, followed by centrifugal cleaning, vacuum drying, etc.

[0044] Comparative Example 2 The method of Example 1 was used to prepare a pure Cs x WO3 material.

[0045] Comparative Example 3 The method of Example 1 was used to prepare a physical mixing type composite catalyst PM-NiFe-LDH / Cs x WO3: Physical mixed material first prepared pure NiFe-LDH: according to the reagent ratio listed in step 2 of example 1 (1.8 mmol Ni (NO3) 2·6H2O, 0.9 mmol Fe (NO3) 3·9H2O, 64 mmol CO (NH2) 2, 13.5 mmol NH4F dissolved in 50 mL deionized water), without adding Cs x WO3 powder, constant temperature hydrothermal reaction at 105°C for 12 h, and then centrifugal washing, vacuum drying and other processes, to complete the preparation of pure NiFe-LDH, then take 20 mg of Cs x WO3 powder, put into the grinder, grind for 5 min at room temperature, so that the two components are fully mixed and uniformly dispersed, which is the physical mixed composite catalyst PM-NiFe-LDH / Cs x WO3, which is used as a control group, and the influence of the composite material synthesized by in-situ hydrothermal method in example 1 on the catalytic performance is compared.

[0046] Material characterization and performance test 1. X-ray diffraction (XRD) analysis Figure 1 is the XRD pattern of the three materials, the results show that, pure Cs x WO3 sample diffraction peak with Cs 0.32 WO3 standard card PDF #83-1334 completely match, which is a good proof of Cs x WO3 sample was successfully prepared; at the same time, the diffraction pattern of pure NiFe-LDH sample also shows the standard card (PDF #49-0188) of NiFe-LDH, which shows the characteristic peaks of nickel-iron layered double hydroxide. As for the NiFe-LDH / Cs x WO3 composite material, its XRD spectrum has the characteristic peaks of NiFe-LDH, and also appears at 27.3° and 27.8°, which are the characteristic peaks of Cs 0.32 WO3, respectively corresponding to (102) and (200) crystal face, which proves the successful preparation of the composite material NiFe-LDH / Cs x WO3.

[0047] 2. Scanning electron microscope (SEM) morphology analysis Figure 2 The scanning electron microscope (SEM) image in shows that, Cs xWO3 presents a block structure of about 200 nm in size, with a relatively smooth surface and a relatively compact structure, while NiFe-LDH exhibits typical layered double hydroxide characteristics, consisting of many layers of thin sheets stacked in an interlaced manner to form a unique petal-like three-dimensional structure. This structure greatly increases the specific surface area of ​​the material and provides a large number of active sites. x Among WO3 composite materials, Cs x WO3 particles are distributed on the surface of NiFe-LDH layered structure and in the interlayer gaps. In this structure, the excellent ion transport properties of NiFe-LDH are retained, and due to the Cs x The addition of WO3 will effectively optimize the electronic conductivity of the composite material.

[0048] 3. Photothermal performance test Depend on Figure 3 、 Figure 4 Analysis shows that pure Cs x WO3 material has good light-to-heat conversion effect. After 9 minutes of continuous illumination, its surface temperature rises from room temperature to 78.7 °C, while the temperature of pure NiFe-LDH only rises to 38.7 °C under the same illumination conditions. x The final temperature of the WO3 composite material is 47.8 ℃, which indicates that Cs x The addition of WO3 improves the photothermal conversion efficiency of NiFe-LDH. Figure 4 The time-temperature curve shows that Cs x WO3 has good fast photothermal response performance, and the photothermal performance of its composite material is between the two single-component materials.

[0049] 4. Electrochemical oxygen evolution performance test The electrochemical test was conducted using a Chenhua CHI660E electrochemical workstation in a three-electrode system. The working electrode was a 3 mm diameter glassy carbon electrode, the reference electrode was a saturated Hg / HgO electrode, and the counter electrode was a graphite rod. Figure 5 As shown, pure Cs x WO3 has no obvious electrocatalytic activity in the entire test potential range, and its main function is photothermal conversion. However, pure NiFe-LDH has certain catalytic performance in oxygen evolution reaction. When the current density reaches 10 mA / cm 2 When NiFe-LDH and Cs x The composite material composed of WO3 has good electrocatalytic performance. Under the same test conditions, its potential is only 1.579 V, which is 82 mV lower than that of pure NiFe-LDH. Figure 6It can be seen that the photothermal effect significantly improved the NiFe-LDH / Cs x The electrocatalytic performance of WO3 composite material was significantly improved under the photothermal assistance of 400 mw / cm2 at 10 mA / cm2. 2 The potential at the current density decreased from 1.579 V to 1.565 V, which indicates that photothermal assistance plays an important role in improving the electrocatalytic activity.

[0050] The pure NiFe-LDH material proposed in Comparative Example 1 is 2 The potential was 1.661 V under the current density of , and the photothermal response diagram Figure 3 It shows that the temperature of this material only rises to 38.7 ℃ after 9 minutes of light exposure, which fully reflects the addition of Cs x The necessity of WO3 material and its key role in improving catalytic activity.

[0051] Combine Figure 3 and Figure 4 , pure Cs prepared in Example 2 x WO3 material. Test results show that pure Cs x WO3 has excellent photothermal conversion performance, and the temperature can reach 78.7 ℃ after 9 minutes of illumination, but it is almost inactive in the electrochemical oxygen evolution test, verifying the importance of compounding with NiFe-LDH.

[0052] Combine Figure 3 , the produced Cs x The WO3 sample was subjected to temperature response tests and electrocatalytic performance tests. From the experimental data, it can be seen that when the light exposure lasts for 9 minutes, this material shows an extremely prominent temperature rise phenomenon of 78.7 ° C, but its catalytic activity in the electrochemical oxygen evolution reaction is extremely low.

[0053] Physical mixed composite catalyst PM-NiFe-LDH / Cs prepared in Comparative Example 3 x WO3: Combine Figure 3 The effects of the composite material synthesized using the in-situ hydrothermal method on catalytic performance were compared with those in Example 1. The test results showed that after 9 minutes of illumination, the temperature of this material only rose to 40.6°C, and its catalytic performance did not significantly improve after illumination. The composite material prepared by physical mixing did not show a significant improvement in temperature response after the photothermal effect, nor did it improve its electrocatalytic oxygen evolution performance.

[0054] The above description of the specific embodiments of the present application is not intended to limit the scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A method for preparing a composite material, characterized in that: The method comprises the following steps: stirring and mixing nickel sulfate, ferric nitrate, urea, ammonium fluoride, cesium tungsten bronze and water to obtain a precursor solution; and subjecting the precursor solution to a hydrothermal reaction at 100-110° C. to obtain the composite material.

2. The method for preparing a composite material according to claim 1, wherein: The molar ratio of the nickel nitrate to the ferric nitrate is (2-2.5):1; and / or the molar ratio of the urea to the ferric nitrate is (70-72):1; and / or the molar ratio of the ammonium chloride to the ferric nitrate is (15-16):

1.

3. The method for preparing a composite material according to claim 1, wherein: The material ratio of the cesium tungsten bronze to the ferric nitrate is (20-25) mg:1 mmol.

4. The method for preparing a composite material according to claim 1, wherein: The hydrothermal reaction time is 10-14 hours.

5. The method for preparing a composite material according to claim 1, wherein: The stirring and mixing time is 2-3 hours.

6. The method for preparing a composite material according to claim 1, wherein: The cesium tungsten bronze is prepared by the following steps: dispersing cesium hydroxide and tungsten hexaoxide in an ethanol solvent, then adding glacial acetic acid to obtain a mixed solution, and then performing a hydrothermal reaction at 220-240° C. to obtain the cesium tungsten bronze.

7. The method for preparing a composite material according to claim 6, characterized in that: The hydrothermal reaction is carried out at 220-240° C. for 24-26 hours; and / or the mass ratio of the cesium hydroxide to the tungsten hexaoxide is 1:(7-7.5).

8. The method for preparing a composite material according to claim 6, characterized in that: The volume ratio of the glacial acetic acid to the ethanol solvent is 1:(8-9); the material ratio of the cesium hydroxide to the ethanol solution is 1 g:(32-35) mL.

9. A composite material, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite material obtained by the preparation method according to any one of claims 1 to 8 or the composite material according to claim 9 in heat-assisted electrocatalysis.

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