A catalyst, a method of preparation and use

Abstract

The application relates to the technical field of catalysts and discloses a preparation method of a catalyst, which comprises the following steps: mixing 25% ammonia water, ethanol and pure water by volume, performing first magnetic stirring, adding tetraethyl orthosilicate into the mixed solution, performing second magnetic stirring, and obtaining an A solution; uniformly mixing dopamine hydrochloride and pure water to obtain a B solution, adding the B solution into the A solution, stirring, and obtaining a mixed solution; centrifugally washing the mixed solution with pure water for 5 times, placing the mixed solution in a vacuum oven at 50 DEG C-70 DEG C for 12h-36h, drying the moisture, and obtaining a first intermediate product; calcining the first intermediate product in a nitrogen atmosphere for 1h-3h, and obtaining a second intermediate product; uniformly mixing the second intermediate product and ammonium fluoride according to a mass ratio of 1:(15-25), and calcining at high temperature at 800 DEG C-1000 DEG C for 1h-3h, so as to obtain an F@SiO2 catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a catalyst, a preparation method and application. BACKGROUND

[0002] Energy and environmental problems have become two of the ten serious problems facing mankind in the next 50 years, and are the main challenges facing mankind in the 21st century. Human beings are in the process of sustainable development and global industrialization, and the demand and consumption of energy are increasing year by year. The environmental and ecological problems caused by energy utilization are also deteriorating, and the green and low-carbon transformation of energy is imminent. Microbial fuel cells, as a new type of microbial electrochemical process, can produce electricity while degrading organic matter, and have the characteristics of cleanliness, energy saving and economy, and have become a research hotspot in the field of wastewater treatment, and are expected to improve energy and environmental problems.

[0003] In the anaerobic environment of the anode chamber of a microbial fuel cell (MFC), organic matter is catalytically degraded by microorganisms to produce electrons and protons. The electrons are transmitted to the cathode through an external circuit, and the protons are transmitted to the cathode chamber through a proton exchange membrane. The protons, O2 and electrons are reduced to form H2O in the aerobic environment of the cathode. MFC can produce electricity while degrading various pollutants, does not need to intake energy from the outside world, and does not cause secondary pollution. It has the characteristics of economy and cleanliness, and has broad application value.

[0004] Silicon dioxide is widely used in the field of electrochemistry due to its abundant reserves, low cost, good thermal stability, high specific surface area and other characteristics, and is often used as a MFC cathode material. In the process of preparing silicon dioxide, hydrogen fluoride solution is often used to etch silicon dioxide. After etching is completed, the material needs to be washed and baked. In addition, hydrogen fluoride solution is highly toxic, so this method is relatively cumbersome, not green and environmentally friendly, and has safety hazards. Therefore, we propose a catalyst, a preparation method and application. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the shortcomings of the prior art, the present application provides a catalyst, a preparation method and application, which solves the above problems.

[0007] (II) Technical solutions

[0008] To achieve the above purposes, the present application provides the following technical solutions: a catalyst comprising ammonium fluoride, an A solution and a B solution, the A solution comprising ammonia water, ethanol, pure water and tetraethyl silicate, and the B solution comprising dopamine hydrochloride and pure water.

[0009] The mass ratio of ammonia water, ethanol, pure water and tetraethyl silicate is: ammonia water: ethanol: pure water: tetraethyl silicate = (1-3): (47-49): (159-161): 1.

[0010] Preferably, the mass ratio of ammonia water, ethanol, pure water and tetraethyl silicate is: ammonia water: ethanol: pure water: tetraethyl silicate = 2:48:160:1.

[0011] A preparation method of a catalyst, comprising the following steps:

[0012] First step: mix 25% volume fraction of ammonia water, ethanol and pure water, perform first magnetic stirring, add tetraethyl silicate in the mixed solution, perform second magnetic stirring, and obtain A solution;

[0013] Second step: uniformly mix dopamine hydrochloride and pure water to obtain B solution, add B solution into A solution, and stir to obtain a mixed solution;

[0014] Third step: centrifugally wash the mixed solution with pure water for 5 times, place it in a vacuum oven at 50-70°C for 12-36h, and dry the moisture to obtain a first intermediate product;

[0015] Fourth step: burn the first intermediate product in a nitrogen atmosphere for 1-3h to obtain a second intermediate product;

[0016] Fifth step: uniformly mix the second intermediate product and ammonium fluoride according to a mass ratio of 1:(15-25), and burn at high temperature at 800-1000°C for 1-3h to obtain the F@SiO2 catalyst.

[0017] Preferably, the first magnetic stirring in the first step is performed at 20-30°C for 30min.

[0018] The second magnetic stirring time is 15min.

[0019] Preferably, the stirring condition in the second step is stirring at 20-30°C for 24h.

[0020] Preferably, the centrifugal rotation speed in the third step is 7000-9000r / min, the centrifugal time is 5min, the vacuum drying temperature is 60°C, and the time is 24h.

[0021] Preferably, the burning temperature in the fourth step is 1000°C, the burning time is 2h, and the temperature rising speed is 5°C / min.

[0022] Preferably, the mass ratio of the second intermediate product and ammonium fluoride in the fifth step is 1:20, the burning temperature is 900°C, the burning time is 2h, and the temperature rising speed is 5°C / min.

[0023] The application of a catalyst, F@SiO2 catalyst is applied in a microbial fuel cell.

[0024] (III) beneficial effects

[0025] Compared with the prior art, the application provides a catalyst, a preparation method and application, and has the following beneficial effects:

[0026] 1. The catalyst is more green, clean and reduces environmental hazards. Silica is used as a precursor, and hydrogen fluoride gas is used for etching to achieve doping. Ammonium fluoride is pyrolyzed at high temperature to generate hydrogen fluoride and ammonia gas, which can achieve etching and F doping, and promote oxygen reduction activity by promoting mass transfer and regulating material electronic structure.

[0027] 2. When the catalyst is applied in a microbial fuel cell, it has strong stability, low operating cost and high cathode electron transfer rate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a microbial fuel cell reactor diagram;

[0029] Figure 2 is a cyclic voltammetry curve diagram of different materials;

[0030] Figure 3 is an electrochemical linear polarization curve diagram of different materials;

[0031] Figure 4 is a pore size distribution diagram of different materials;

[0032] Figure 5 is a N2 adsorption and desorption diagram of different materials;

[0033] Figure 6 is a voltage output diagram of the catalyst obtained in Example 3 and Pt / C as MFC cathode catalysts, respectively. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0035] A preparation method of a catalyst, refer to the following Examples 1-4.

[0036] Example 1: The preparation process of SiO2 catalyst includes the following steps:

[0037] (1) mixed ammonia water, ethanol, pure water and tetraethyl orthosilicate in a certain mass ratio, and stirred magnetically at 20-30°C for 30 min; then added dopamine hydrochloride and pure water in a certain mass ratio to obtain a clear and transparent B solution; added the B solution into the A solution, and stirred at 20-30°C for 24 h to obtain a first mixed solution; wherein the mass ratio of ammonia water, ethanol, pure water and tetraethyl orthosilicate was ammonia water: ethanol: pure water: tetraethyl orthosilicate = 2:48:160:1;

[0038] (2) centrifuged the first mixed solution in step (1) with pure water for 5 times, and placed in a 60°C oven for 24 h to dry the moisture to obtain a first intermediate product;

[0039] (3) calcined the first intermediate product obtained in step (2) at 1000°C for 2 h with a temperature rising speed of 5°C / min to obtain a second intermediate product;

[0040] (4) calcined the second intermediate product in step (3) at 900°C for 2 h with a temperature rising speed of 5°C / min to obtain a catalyst.

[0041] Example 2: Preparation process of F@SiO2-800 catalyst, including the following steps:

[0042] (1) mixed ammonia water, ethanol, pure water and tetraethyl orthosilicate in a certain mass ratio, and stirred magnetically at 20-30°C for 30 min; then added dopamine hydrochloride and pure water in a certain mass ratio to obtain a clear and transparent B solution; added the B solution into the A solution, and stirred at 20-30°C for 24 h to obtain a first mixed solution; wherein the mass ratio of ammonia water, ethanol, pure water and tetraethyl orthosilicate was ammonia water: ethanol: pure water: tetraethyl orthosilicate = 2:48:160:1;

[0043] (2) centrifuged the first mixed solution in step (1) with pure water for 5 times, and placed in a 60°C oven for 24 h to dry the moisture to obtain a first intermediate product;

[0044] (3) calcined the first intermediate product obtained in step (2) at 1000°C for 2 h with a temperature rising speed of 5°C / min to obtain a second intermediate product;

[0045] (4) mixed the second intermediate product in step (3) and ammonium fluoride in a mass ratio of 1:20, and calcined at 800°C for 2 h with a temperature rising speed of 5°C / min to obtain a F@SiO2-800 catalyst.

[0046] Example 3: Preparation process of F@SiO2-900 catalyst, comprising the following steps:

[0047] (1) Mix ammonia water with a volume fraction of 25%, ethanol, pure water and according to a certain mass ratio, magnetically stir for 30 min at 20-30°C, add tetraethyl orthosilicate to the above solution, magnetically stir for 15 min to obtain a clear and transparent A solution; mix dopamine hydrochloride and pure water uniformly according to a certain mass ratio to obtain a clear and transparent B solution; add the above B solution to the A solution, stir at 20-30°C for 24 h to obtain a first mixed solution which is dark brown; wherein the mass ratio of ammonia water, ethanol, pure water and tetraethyl orthosilicate is: ammonia water: ethanol: pure water: tetraethyl orthosilicate = 2:48:160:1;

[0048] (2) Centrifugal water wash the first mixed solution in step (1) with pure water for 5 times, place in a 60°C oven for 24 h, dry the moisture to obtain a first intermediate product;

[0049] (3) High-temperature calcination of the first intermediate product obtained in step (2) at 1000°C for 2 h with a temperature rising speed of 5°C / min to obtain a second intermediate product;

[0050] (4) Mix the second intermediate product in step (3) and ammonium fluoride uniformly according to a mass ratio of 1:20, high-temperature calcination at 900°C for 2 h with a temperature rising speed of 5°C / min to obtain the F@SiO2-900 catalyst.

[0051] Example 4: Preparation process of F@SiO2-1000 catalyst, comprising the following steps:

[0052] (1) Mix ammonia water with a volume fraction of 25%, ethanol, pure water and according to a certain mass ratio, magnetically stir for 30 min at 20-30°C, add tetraethyl orthosilicate to the above solution, magnetically stir for 15 min to obtain a clear and transparent A solution; mix dopamine hydrochloride and pure water uniformly according to a certain mass ratio to obtain a clear and transparent B solution; add the above B solution to the A solution, stir at 20-30°C for 24 h to obtain a first mixed solution which is dark brown; wherein the mass ratio of ammonia water, ethanol, pure water and tetraethyl orthosilicate is: ammonia water: ethanol: pure water: tetraethyl orthosilicate = 2:48:160:1;

[0053] (2) Centrifugal water wash the first mixed solution in step (1) with pure water for 5 times, place in a 60°C oven for 24 h, dry the moisture to obtain a first intermediate product;

[0054] (3) High-temperature calcination of the first intermediate product obtained in step (2) at 1000°C for 2 h with a temperature rising speed of 5°C / min to obtain a second intermediate product;

[0055] (4) The second intermediate product from step (3) and ammonium fluoride are mixed evenly at a mass ratio of 1:20 and calcined at 1000℃ for 2 hours with a heating rate of 5℃ / min to obtain the F@SiO2-1000 catalyst.

[0056] Performance testing:

[0057] Figure 2 The cyclic voltammetry curves show the oxygen reduction activity of the catalyst. By observing the oxygen reduction peak potential, the oxygen reduction activity of the catalyst can be understood. A larger peak value indicates a smaller overpotential, making the reaction easier to occur and resulting in better catalyst performance. The oxygen reduction peak potentials of Examples 1-4 are 0.41, 0.43, 0.57, and 0.49 V, respectively. It can be seen that the catalyst obtained in Example 3 has the best performance.

[0058] Figure 3 Table 1 shows the electrochemical linear polarization curves of different materials and the corresponding three important parameters: onset potential, half-wave potential, and limiting current density. It can be seen that after ammonium fluoride pyrolysis, the removal of silica and fluorine doping significantly improve the material's performance. Compared with the catalyst obtained in Example 1, the performance of Examples 2-4 is significantly better, with Example 3 exhibiting the best electrochemical performance compared to the other examples.

[0059] Figure 4 , Figure 5 The figures show pore size distribution diagrams and N2 adsorption / desorption diagrams for different materials. Porosity and specific surface area are important factors affecting the electrocatalytic oxygen reduction performance of the catalysts. As shown in the figures, the curves for Examples 1-4 exhibit type IV isotherms with hysteresis loops, indicating that the materials possess a hierarchical porous structure with both micropores and mesopores. This facilitates the transport of substances between the three-phase interfaces, exposes more active sites, and further promotes the oxygen reduction reaction. Example 3 showed the best performance.

[0060] The data above shows that the best material is the catalyst obtained in Example 3. The catalyst obtained in Example 3 was used as the cathode catalyst in a microbial fuel cell, and its voltage was tested. Figure 6 The output voltage diagrams are shown for the catalyst obtained in Example 3 and Pt / C, respectively, when used as MFC cathode catalysts. From... Figure 6 It can be seen that the average voltage of the Pt / C material is approximately 0.383V, while the average voltage of the catalyst obtained in Example 3 is approximately 0.583V, with a maximum voltage reaching 0.652V, which is much greater than that of the Pt / C material. In summary, this demonstrates that the catalyst obtained in the embodiments of the present invention can replace the Pt / C material as a catalyst supported on the cathode for application in microbial fuel cells.

[0061] Table 1 shows the onset potential, half-wave potential, and limiting current density parameters of different materials in neutral media:

[0062]

[0063] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the embodiments described, since numerous changes, modifications, substitutions and variations can be made thereto without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A method for preparing a catalyst, characterized in that, Includes the following steps: Step 1: Mix 25% ammonia, ethanol and pure water, and perform the first magnetic stirring. Add tetraethyl silicate to the mixed solution and perform the second magnetic stirring to obtain solution A. Step 2: Mix dopamine hydrochloride and pure water evenly to obtain solution B. Add solution B to solution A and stir to obtain a mixture. Step 3: Wash the mixture five times with pure water by centrifugation, place it in a vacuum oven at 50℃-70℃ for 12h-36h to dry the moisture, and obtain the first intermediate product. Step 4: The first intermediate product is ignited in a nitrogen atmosphere for 1-3 hours to obtain the second intermediate product; Step 5: Mix the second intermediate product and ammonium fluoride at a mass ratio of 1:(15-25) and calcine at 800℃-1000℃ for 1-3 hours to obtain the catalyst.

2. The method for preparing a catalyst according to claim 1, characterized in that, In the first step, the mass ratio of ammonia, ethanol, pure water and tetraethyl silicate is: ammonia: ethanol: pure water: tetraethyl silicate = (1-3): (47-49): (159-161):

1.

3. The method for preparing a catalyst according to claim 2, characterized in that: The mass ratio of ammonia, ethanol, pure water and tetraethyl silicate is: ammonia: ethanol: pure water: tetraethyl silicate = 2:48:160:

1.

4. The method for preparing a catalyst according to claim 1, characterized in that: The first magnetic stirring condition in the first step is to magnetically stir for 30 minutes at 20℃-30℃. The second magnetic stirring time is 15 minutes.

5. The method for preparing a catalyst according to claim 1, characterized in that: The stirring conditions in the second step are 20℃-30℃ and stirring for 24 hours.

6. The method for preparing a catalyst according to claim 1, characterized in that: In the third step, the centrifugation speed is 7000-9000 r / min, the centrifugation time is 5 min, the vacuum drying temperature is 60℃, and the time is 24 h.

7. The method for preparing a catalyst according to claim 1, characterized in that: The burning temperature in the fourth step is 1000℃, the burning time is 2 hours, and the heating rate is 5℃ / min.

8. The method for preparing a catalyst according to claim 1, characterized in that: In the fifth step, the mass ratio of the second intermediate product to ammonium fluoride is 1:20, the calcination temperature is 900℃, the calcination time is 2h, and the heating rate is 5℃ / min.

9. The application of the catalyst according to claim 1, characterized in that, Applications in microbial fuel cells.

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