Catalyst for nitrate reduction to produce ammonia, preparation method and application thereof

Abstract

The present invention discloses a catalyst for nitrate reduction to ammonia, its preparation method, and application. The preparation method comprises: (i) pretreating a substrate surface; (ii) preparing a growth copper solution; (iii) electrodepositing and growing copper atoms; (iv) preparing a growth polypyrrole solution; and (v) electrodepositing and growing polypyrrole. The catalyst prepared by the present invention contains copper nanoparticles and polypyrrole. By growing a conductive polymer polypyrrole film layer on the copper nanoparticles and forming connections between the copper nanoparticles, the performance of the electrocatalytic reduction of nitrate can be improved, achieving efficient electrocatalytic reduction of nitrate to ammonia. Furthermore, the catalyst has a fast reaction rate, high Faradaic efficiency, high ammonia yield, high conversion rate, and other characteristics, can effectively reduce energy consumption, and has the advantages of low cost, simple process, and environmental protection and no pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of ammonia synthesis catalysts, and in particular relates to a catalyst for nitrate reduction ammonia production, and a preparation method and application thereof. Background Art

[0002] Nitrate is a naturally occurring ion. Large amounts of nitrate and nitrite enter surface and groundwater, causing numerous problems. Nitrate in water systems can have significant adverse effects on humans, such as birth defects and cancer. Worse still, nitrate can be converted by bacteria into nitrite, which is even more harmful. High concentrations of nitrite in drinking water can cause congenital malformations, goiter, methemoglobinemia in infants, and cancer. Therefore, there is an urgent need to develop low-cost and efficient methods to convert large amounts of nitrate and nitrite contamination into harmless products, or ideally, energy sources such as ammonia, which is in high demand.

[0003] Ammonia is an important raw material for fertilizer production, a clean energy carrier, and a potential fuel, offering enormous potential for addressing the energy crisis. Electrochemical nitrate reduction to ammonia (NRA) utilizes water and nitrate in an electrolyte as hydrogen and nitrogen sources, achieving room-temperature ammonia synthesis through an electrochemical reduction strategy while simultaneously removing nitrate contaminants.

[0004] Therefore, there is an urgent need for a catalyst that can improve the efficiency of the electrocatalytic reduction reaction. Summary of the Invention

[0005] The object of the present invention is to provide a catalyst for nitrate reduction to ammonia production and its preparation method and application, so as to solve one or more of the above-mentioned technical problems.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a catalyst for reducing ammonia containing nitrates comprises the following steps:

[0008] (i) pre-treating the substrate surface;

[0009] (ii) preparing a growth copper solution;

[0010] (iii) growing copper onto the substrate using an electrodeposition method;

[0011] (iv) preparing a growth polypyrrole solution;

[0012] (v) Pyrrole is polymerized onto a copper-containing substrate by an electrodeposition method to obtain a nitrate-containing catalyst for reducing ammonia supported on the substrate.

[0013] In the above technical solution, in step (i), the carbon cloth is ultrasonically cleaned with 0.1 M hydrochloric acid aqueous solution, anhydrous ethanol and deionized water in sequence; the time for each ultrasonic cleaning step is 10 minutes;

[0014] In the above technical solution, the copper growth solution in step (ii) is an acid solution of copper sulfate pentahydrate and an additive; the additive is 3,5-diamino-1,2,4-triazole, 1,2,4-triazole or 3-amino-1,2,4-triazole; and the acid is sulfuric acid or hydrochloric acid.

[0015] In the above technical solution, the concentration of the acid in the growth copper solution is 0.05 M to 0.5 M;

[0016] The concentration of copper sulfate pentahydrate in the growth copper solution is 0.05 M to 0.5 M;

[0017] The concentration of the additive in the growth copper solution is 0.5 mM to 50 mM.

[0018] In the above technical solution, the electrodeposition method in step (iii) is a constant current method with a current density of 15 mA / cm 2 , the electrodeposition time is 600 s.

[0019] In the above technical solution, the polypyrrole growing solution in step (iv) is an aqueous solution of sodium dihydrogen phosphate, sodium perchlorate and pyrrole.

[0020] In the above technical solution, the concentration of the sodium dihydrogen phosphate is 0.05 M ~ 0.5 M;

[0021] The concentration of the sodium perchlorate is 0.5 M ~ 50 mM;

[0022] The concentration of pyrrole is 0.05 M to 0.5 M;

[0023] The ratio of the added amounts of sodium dihydrogen phosphate, sodium perchlorate and pyrrole is 1:0.1:1.

[0024] In the above technical solution, the electrodeposition method in step (v) is a constant voltage method, the voltage is 0.9 V, and the electrodeposition time is 100 s.

[0025] A catalyst for reducing ammonia to nitrate is disclosed. The catalyst is prepared by first growing copper nanoparticles on a conductive substrate and then connecting the nanoparticles through a ribbon-like structure formed by polypyrrole. This not only improves the stability of the catalyst, but also enhances the reduction performance of the catalyst.

[0026] The invention discloses an application of a catalyst for nitrate reduction ammonia production in electrochemical nitrate reduction ammonia production.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides an electrochemical nitrate-to-ammonia conversion catalyst, a preparation method, and an application thereof. The prepared catalyst contains copper nanoparticles and polypyrrole. The connection between the copper nanoparticles is effectively improved by growing a polymer, thereby improving the efficiency of the electrocatalytic reduction reaction and achieving efficient conversion of nitrate into ammonia. At the same time, the catalyst has a fast reaction rate, high Faradaic efficiency, high ammonia yield, high conversion rate, etc., can effectively reduce energy consumption, and has the advantages of low cost, simple process, and environmental protection and no pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 and 2 are SEM images of the products in Example 1 of the present invention (a. carbon cloth loaded with copper; b. carbon cloth loaded with copper and polypyrrole).

[0030] Figure 2 The nitrate reduction performance comparison data are shown using the products of each stage in Example 1 of the present invention as catalysts.

[0031] Figure 3 1 is a graph showing the Faradaic efficiency and ammonia production performance of the polypyrrole-copper nanocatalyst prepared in Example 1 of the present invention in the electrocatalytic reduction of nitrate to synthesize ammonia in 0.5M sulfuric acid and 0.1M nitrate electrolyte.

[0032] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the catalyst for ammonia production by nitrate reduction, its preparation method and application will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

[0034] Example 1

[0035] A method for preparing a catalyst for reducing ammonia containing nitrates comprises the following steps:

[0036] (i) pre-treating the substrate surface;

[0037] The substrate was ultrasonically cleaned with 0.1M hydrochloric acid solution, anhydrous ethanol and deionized water in sequence; each ultrasonic cleaning step lasted 10 minutes; the substrate in this embodiment was made of carbon cloth;

[0038] (ii) preparing a growth copper solution;

[0039] First, a 0.1 M sulfuric acid solution was prepared and stirred for 10 minutes. Then, 0.1 M copper sulfate pentahydrate and 10 mM 3,5-diamino-1,2,4-triazole were added to the 0.1 M sulfuric acid solution and stirred for 10 minutes to obtain a growth copper solution.

[0040] (iii) growing copper nanoparticles by electrodeposition;

[0041] Copper was grown onto the carbon cloth substrate using an electrodeposition method using a constant current method with a current density of 15 mA / cm 2 , the electrodeposition time was 600 s;

[0042] SEM images of copper nanoparticles on carbon cloth substrate Figure 1 As shown in (a), it can be seen from the figure that copper nanoparticles are evenly dispersed on the carbon cloth, and each copper nanoparticle exhibits a nanoflower morphology when observed under high magnification.

[0043] (iv) preparing a growth polypyrrole solution;

[0044] Add 0.1 M sodium dihydrogen phosphate to 70 mL of deionized water while stirring. After it is fully dissolved, add 10 mM sodium perchlorate. Finally, add 0.1 M pyrrole to the solution and stir for 30 minutes to obtain the growth polypyrrole solution.

[0045] (v) Pyrrole is polymerized onto copper-containing carbon cloth by an electrodeposition method to obtain a catalyst for nitrate reduction to ammonia; the electrodeposition method is a constant voltage method with a voltage of 0.9 V and an electrodeposition time of 100 s.

[0046] SEM of copper-polypyrrole Figure 1 (b) is a SEM image of the catalyst for ammonia production by nitrate reduction obtained in the present invention. Figure 1 As can be seen in (b), the polypyrrole film layer is coated on the copper nanoparticles and forms a connecting belt between the copper nanoparticles, connecting the dispersed copper nanoparticles.

[0047] In order to further verify the catalytic performance of the catalyst for nitrate reduction to ammonia of the present invention, carbon cloth substrate, carbon cloth substrate loaded copper, carbon cloth substrate loaded polypyrrole, carbon cloth substrate loaded copper and polypyrrole were immersed in a nitrate solution as catalysts, and linear sweep voltammetry test was performed by electrochemical device to test the catalytic reduction effect of nitrate. The results are as follows: Figure 2 As shown, it can be seen that compared with pure copper nanoparticle catalysts, the copper-polypyrrole composite catalyst promotes the reduction effect of nitrate, the reduction potential of nitrate is reduced to 0.05V vs.RHE, and the current density is increased by more than 2 times.

[0048] Figure 3 The Faraday efficiency and ammonia production performance of the copper-polypyrrole catalyst prepared in Example 1 of the present invention in the electrocatalytic reduction of nitrate to synthesize ammonia in 0.5M sulfuric acid and 0.1M nitrate electrolyte are shown. Figure 3 It can be seen that the copper-polypyrrole catalyst prepared in the embodiment of the present invention can achieve a synthetic ammonia yield of 13.1 mmol h in 0.5 M sulfuric acid and 0.1 M nitrate electrolyte. -1 cm -2 , the Faraday efficiency is 90.1%.

[0049] The present invention provides an electrochemical nitrate-to-ammonia conversion catalyst, a preparation method, and an application thereof. The prepared catalyst contains copper nanoparticles and polypyrrole. The connection between the copper nanoparticles is effectively improved by growing a polymer, thereby improving the efficiency of the electrocatalytic reduction reaction and achieving efficient conversion of nitrate into ammonia. At the same time, the catalyst has a fast reaction rate, high Faradaic efficiency, high yield, high conversion rate, and the like, can effectively reduce energy consumption, and has the advantages of low cost, simple process, and environmental protection and no pollution.

[0050] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0051] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a catalyst for reducing ammonia containing nitrates, characterized in that: The following steps are involved: (i) pre-treating the substrate surface; (ii) preparing a growth copper solution; The growth copper solution is an acid solution of copper sulfate pentahydrate and an additive; the additive is 3,5-diamino-1,2,4-triazole, 1,2,4-triazole or 3-amino-1,2,4-triazole; the acid is sulfuric acid or hydrochloric acid; the concentration of the acid in the growth copper solution is 0.05 M to 0.5 M; the concentration of copper sulfate pentahydrate in the growth copper solution is 0.05 M to 0.5 M; the concentration of the additive in the growth copper solution is 0.5 mM to 50 mM; (iii) growing copper onto the substrate using an electrodeposition method; (iv) preparing a growth polypyrrole solution; The polypyrrole growth solution is an aqueous solution of sodium dihydrogen phosphate, sodium perchlorate and pyrrole; the concentration of the sodium dihydrogen phosphate is 0.05 M to 0.5 M; the concentration of the sodium perchlorate is 0.05 M to 0.5 M; the concentration of the pyrrole is 0.05 M to 0.5 M; the ratio of the addition amounts of the sodium dihydrogen phosphate, sodium perchlorate and pyrrole is 1:0.1:1; (v) polymerizing pyrrole onto a copper-containing substrate by an electrodeposition method, thereby obtaining a nitrate-containing catalyst for reducing ammonia supported on the substrate; The prepared catalyst contains copper nanoparticles and polypyrrole. The polypyrrole film layer is coated on the copper nanoparticles and forms a connecting belt between the copper nanoparticles, connecting the dispersed copper nanoparticles and effectively improving the connection between the copper nanoparticles by growing polymers.

2. The method for preparing a catalyst for reducing ammonia containing nitrate according to claim 1, wherein: The method for substrate pretreatment in step (i) is: ultrasonically cleaning the substrate with an acidic solution, anhydrous ethanol and deionized water in sequence; the substrate is one of a conductive substrate such as carbon cloth, carbon paper, foam nickel, nickel foil, nickel sheet, foam copper, copper foil, or stainless steel mesh.

3. The method for preparing a catalyst for reducing ammonia containing nitrate according to claim 1, wherein: The electrodeposition method in step (iii) is a constant current method with a current density of 15 mA / cm 2 , the electrodeposition time is 600 s.

4. The method for preparing a catalyst for reducing ammonia containing nitrate according to claim 1, wherein: The electrodeposition method in step (v) is a constant voltage method with a voltage of 0.9 V and an electrodeposition time of 100 s.

5. A catalyst for reducing ammonia containing nitrates, characterized in that: Prepared by the method according to any one of claims 1 to 4; the catalyst comprises a substrate, copper nanoparticles are loaded on the substrate, and the copper nanoparticles are tightly connected by a ribbon-like structure formed by polypyrrole.

6. A use of the catalyst for reducing ammonia containing nitrates as claimed in claim 5, characterized in that: Applied to electrochemical nitrate reduction to ammonia.

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