A hydroxystannate perovskite electrocatalyst Cu 1-x Co x Sn(OH)6, its preparation methods, and applications

Abstract

This invention discloses a hydroxystannate perovskite electrocatalyst Cu 1‑x Co x Sn(OH)6, its preparation method, and applications involve dissolving stannate in deionized water to obtain a stannate solution; dissolving soluble copper and cobalt salts in deionized water to obtain a copper-cobalt mixed solution; then directly mixing and stirring the stannate solution and the copper-cobalt mixed solution to produce a precipitate, followed by solid-liquid separation and freeze-drying to obtain Cu. 1‑x Co x Sn(OH)6 was used for the electrocatalytic reduction of nitrate to ammonia. The hydroxystannate perovskite electrocatalyst of this invention has a nanocubic particle morphology and abundant reaction sites. When used for the electrocatalytic reduction of nitrate, the ammonia production rate is higher than 1 mmol / cm². ‑2 h ‑1 The ammonia production faradaic efficiency remains above 90%, demonstrating excellent ammonia production faradaic efficiency and ammonia yield.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials technology, specifically relating to a hydroxystannate perovskite electrocatalyst Cu. 1-x Co x Sn(OH)6, its preparation methods, and applications. Background Technology

[0002] nitrate anion (NO3) - It is widely present in industrial and agricultural wastewater, posing a threat to human health and ecological balance.

[0003] Traditionally, NO3 - The conversion and removal mainly proceed in two directions: (1) reduction to nitrogen (N2) through the denitrification process in wastewater treatment plants; (2) reduction to ammonia (NH3) through nitrate / nitrite reductases secreted by microorganisms (such as Shewanella oneidensis cytochrome c nitrite reductase). Among them, NO3 - The reduction to NH3 is of greater concern from an industrial perspective because NH3 is a crucial industrial chemical widely used in the synthesis of pharmaceuticals, fertilizers, dyes, and plastics, and is also used as a hydrocarbon-free hydrogen storage / release carrier. However, to date, the industrial synthesis of NH3 heavily relies on the unsustainable and environmentally unfriendly Haber-Bosch route, which requires harsh conditions of high temperature (400-600°C) and high pressure (200-350 atm), and the source of hydrogen as a feedstock is heavily dependent on fossil fuels. In fact, the total carbon dioxide generated during the Haber-Bosch process accounts for approximately 1.2% of global annual carbon dioxide emissions.

[0004] By utilizing denitrifying microorganisms in the natural environment, NO3 in wastewater can be removed under mild environmental conditions. - Biocatalytic reduction to NH3 (bio-NRA) is an emerging, sustainable, and environmentally friendly technology that can convert recalcitrant nitrate pollutants into high-value products. These high-value products can then be precipitated as NH3 through physicochemical methods such as ion exchange adsorption and struvite precipitation for further industrial applications. However, the bio-NRA biocatalytic system is time-consuming and yields low NH3 production, significantly lower than the Haber-Bosch route, making it difficult to meet practical industrial needs. Furthermore, bio-NRA is highly sensitive to the environmental conditions of the wastewater being treated, such as NO3 in mining wastewater. - High concentration (over 2500 mg / L) -1Furthermore, the low organic matter content limits the reproduction and growth of microorganisms. Therefore, in order to fill the gap between the limitations of natural biocatalysis and the high demand for environmental remediation, scientists have begun to incorporate the functions of microbial enzymes into artificially synthesized chemical materials that are easy to prepare in large quantities, and use renewable electricity for reduction-driven production to achieve low-carbon, environmentally friendly, and efficient ammonia production from nitrate reduction.

[0005] In bio-NRA, nitrate reductase accepts electrons from quinones to convert NO3- into NO3-. - Reduced to NO2 - The NO2 produced - Nitrite is further converted to NH3 by nitrite reductase (NIR). Among various NIRs, the copper-type NIR (Cu-NIR), widely found in rhizobia, has been extensively studied by scientists. Cu-NIR consists of a trimeric protein composed of three identical subunits, with each enzyme monomer containing two types of copper atoms, acting as an electron donor center (T1Cu) and a catalytic center (T2Cu), respectively. Its mechanism of action is *NO2 - (Where * represents the adsorbed substance) binds to T2Cu in a bidentate configuration via two oxygen atoms, electrons are transferred from T1Cu to T2Cu, and the oxidation state of T2Cu decreases from (II) to (I), promoting the growth of *NO2. - It binds to T2Cu via a bridging nitro group. Simultaneously, the aspartic acid adjacent to T2Cu is NO2. - One of the oxygen atoms in the NO bond provides a proton, causing the NO bond to elongate and break.

[0006] Although Cu-NIR possesses a unique composition and structure and excellent catalytic activity, its Faradaic efficiency for ammonia production is around 70%, and the ammonia production rate is less than 1 mmol / cm². -2 h -1 Although many researchers have modified Cu-NIR in existing technologies to increase the Faraday efficiency of nitrate reduction to ammonia production to over 90%, the ammonia production rate still cannot meet the needs of practical applications. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a hydroxystannate perovskite electrocatalyst Cu. 1-x Co x Sn(OH)6, its preparation method, and its application in the electrocatalytic reduction of nitrate: This hydroxystannate perovskite electrocatalyst has a nanocubic particle morphology and abundant reaction sites. When used for the electrocatalytic reduction of nitrate, the ammonia production rate is higher than 1 mmol / cm². -2 h -1 The ammonia production faradaic efficiency remains above 90%, demonstrating excellent ammonia production faradaic efficiency and ammonia yield.

[0008] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0009] A hydroxystannate perovskite electrocatalyst Cu 1-x Co x The preparation method of Sn(OH)6 involves dissolving stannate in deionized water to obtain a stannate solution; dissolving soluble copper and cobalt salts in deionized water to obtain a copper-cobalt mixed solution; then directly mixing and stirring the stannate solution and the copper-cobalt mixed solution to produce a precipitate, followed by solid-liquid separation and freeze-drying to obtain Cu. 1-x Co x Sn(OH)6, where x = 0.15 to 0.3.

[0010] Preferably, x = 0.2.

[0011] Preferably, the stannate is sodium stannate, and the concentration of the stannate solution is 10-50 g / L.

[0012] Preferably, the soluble copper salt and cobalt salt are selected from their respective nitrates, sulfates, acetates and chlorides, and the concentrations of the soluble copper salt and cobalt salt in the copper-cobalt mixed solution are both 10-50 g / L.

[0013] Preferably, the stirring reaction conditions are: a speed of 600-900 r / min, a temperature of 5-40℃, and a time of not less than 3 hours.

[0014] Preferably, the freeze-drying temperature is -30 to -70°C and the pressure is 8 to 50 Pa.

[0015] This invention also provides a Cu hydroxystannate perovskite electrocatalyst prepared by the above method. 1-x Co x Sn(OH)6.

[0016] This invention also provides the above-mentioned hydroxystannate perovskite electrocatalyst Cu. 1-x Co x Sn(OH)6 is used for the electrocatalytic reduction of nitrate to produce ammonia.

[0017] The beneficial effects of this invention are:

[0018] The hydroxystannate perovskite electrocatalyst of this invention has a nanocubic particle morphology and abundant reaction sites. When used for the electrocatalytic reduction of nitrate, its ammonia production Faradaic efficiency can be maintained above 90% over a wide potential range of -0.8 to 1.0 V vs. RHE, while remaining within the range of 40-200 mmol / L. -1 The width of NO3 -Within the concentration range, the ammonia production Faradaic efficiency remained above 90% at -0.8V vs. RHE, demonstrating adaptability to various wastewater environments, and ammonia production rates consistently exceeded 1 mmol / cm². -2 h -1 Maintain good NO3 - Recycling capacity. Attached Figure Description

[0019] Figure 1 Cu prepared in Example 2 0.8 Co 0.2 Scanning electron microscope image of Sn(OH)6.

[0020] Figure 2 Cu prepared in Example 2 0.8 Co 0.2 XRD pattern of Sn(OH)6.

[0021] Figure 3 Cu prepared in Example 2 0.8 Co 0.2 Figures showing the electrochemical water splitting performance and electrochemical nitrate reduction performance of Sn(OH)6.

[0022] Figure 4 The graph shows the electrocatalytic hydrogen production performance of the catalysts prepared in Examples 1-2 and Comparative Examples 1-4. Detailed Implementation

[0023] The technical solution of the present invention will be described below through specific embodiments, but the technical solution of the present invention is not limited to the specific embodiments.

[0024] Performance testing:

[0025] (1) Reagent preparation:

[0026] A. Preparation of nitrate reducing electrolyte: Weigh 6.601 g of KOH solid into a beaker and dissolve it in water. After the solution cools to room temperature, transfer it to a 1000 mL flask and make up to volume to obtain 100 mmol / L. -1 KOH solution. Weigh 5.055 g KNO3 and 6.601 g KOH into a beaker and dissolve in water. After the solution cools to room temperature, transfer it to a 1000 mL flask and make up to volume to obtain 100 mmol L. -1 KNO3 and 100 mmol L -1 A mixed solution of KOH. Weigh 10.110 g KNO3 and 6.601 g KOH into a beaker and dissolve in water. After the solution cools to room temperature, transfer it to a 1000 mL flask and make up to volume to obtain 200 mmol L. - 1 KNO3 and 100 mmol L-1 A mixed solution of KOH. Similarly, by adjusting the ratio, 100 mmol / L is obtained. -1 KOH and 20, 40, 60, 80, 300, 400, 500, 1000 mmol / L -1 A mixed solution of KNO3.

[0027] (2) Specific test conditions:

[0028] A. All electrochemical tests in this invention were performed on a Biologic electrochemical workstation using a three-electrode system in an H-type electrolytic cell. A catalyst-loaded carbon paper electrode was used as the working electrode, a platinum sheet as the counter electrode, and a mercury / mercuric chloride electrode (filled with 1 mol / L...) was used. -1 Using KCl solution as the reference electrode, at 5 mV s -1 The scan rate was used to obtain electrochemical linear voltammetry curves in an H-type electrolytic cell (working electrode area: 1.0*1.0 cm²). 2 A constant-voltage electrocatalytic reduction experiment of nitrate reduction was conducted in an H-type electrolytic cell using 0.1 mol L⁻¹ KOH aqueous solutions with different potassium nitrate concentrations (20 and 200 mmol L⁻¹) as the electrolyte (working electrode area: 1.0 * 1.0 cm²). 2 ).

[0029] B. Disperse each catalyst separately using ultrasonication in a solvent containing a binder (225 μL anhydrous ethanol: 225 μL deionized water: 50 μL 5% Nafion solution) to form a uniform ink (10 mg / mL). -1 40 μL of ink was uniformly loaded onto clean carbon paper. The carbon paper electrode, platinum electrode, and mercury / mercuric chloride electrode loaded with the above catalyst were used as the working electrode, counter electrode, and reference electrode, respectively. In an H-type electrolytic cell, a solution containing 200 mmol L... -1 0.1 mol / L of potassium nitrate -1 KOH aqueous solution was used as the electrolyte at 5 mV s -1 Linear voltammetric curves were obtained by adjusting the scan rate. Before all electrochemical tests, the electrolyte was purged to saturation with argon gas to remove dissolved oxygen.

[0030] C. Catalyst stability testing was conducted in an H-type electrolytic cell. The catalyst was supported on Cu. 0.8 Co 0.2 Sn(OH) 6-δ The catalyst uses a carbon paper electrode as the working electrode, a platinum sheet as the counter electrode, and a mercury / mercuric chloride electrode (filled with 1 mol L⁻¹) as the working electrode. -1 Using KCl solution as the reference electrode, at 100 mmol / L... -1 KNO3 + 1 mol L -1In a KOH electrolyte solution, electrolysis reduction was performed at a constant potential of -0.8V vs. RHE for 10 hours. The anode and cathode chambers were separated by a Nafion 117 membrane.

[0031] Comparative Example 1

[0032] Dissolve 2.0 g of sodium stannate trihydrate in 100 ml of deionized water to obtain 75 mmol / L. -1 A stannate solution was prepared by dissolving 1.9 g of copper sulfate pentahydrate in 100 ml of deionized water to obtain 75 mmol / L. -1 The copper salt solution was prepared by adding the copper sulfate solution to the stannate solution and stirring the mixture at 20°C for 3 hours. The mixture was then washed five times with deionized water and freeze-dried under vacuum at -56°C to obtain solid powder CuSn(OH)6.

[0033] The electrocatalytic nitrate reduction ammonia production performance of the above samples under constant pressure was tested, and the ammonia production yield and Faraday efficiency are shown in the figure. Figure 4 The ammonia yield was 0.66 mmol / h. -1 mg cat -1 This corresponds to a Faraday efficiency of 39.4%.

[0034] Comparative Example 2

[0035] Dissolve 2.0 g of sodium stannate trihydrate in 100 ml of deionized water to obtain 75 mmol / L. -1 The stannate solution was prepared by dissolving 2.2 g of cobalt nitrate hexahydrate in 100 ml of deionized water to obtain 75 mmol / L. -1 The cobalt salt solution was prepared by adding the cobalt nitrate solution to the stannate solution and stirring the mixture at 20°C for 3 hours. The mixture was then washed five times with deionized water and freeze-dried under vacuum at -56°C to obtain solid powder CoSn(OH)6.

[0036] The electrocatalytic nitrate reduction ammonia production performance of the above samples under constant pressure was tested, and the ammonia production yield and Faraday efficiency are shown in the figure. Figure 4 The ammonia yield was 0.87 mmol / h. -1 mg cat -1 This corresponds to a Faraday efficiency of 90.6%.

[0037] Example 1

[0038] Dissolve 2.0 g of sodium stannate trihydrate in 100 ml of deionized water to obtain 75 mmol / L. -1A stannate solution was prepared by dissolving copper sulfate pentahydrate and cobalt nitrate hexahydrate in 100 ml of deionized water. The mass of the solution was adjusted so that the sum of the amounts of copper and cobalt salts was equal to the amount of stannate, and the molar ratio of Cu to Co was 7:3. The mixture was stirred at 20°C for 3 hours, washed five times with deionized water, and then freeze-dried under vacuum at -56°C to obtain a solid Cu powder. 0.7 Co 0.3 Sn(OH)6.

[0039] The electrocatalytic nitrate reduction ammonia production performance of the above samples under constant pressure was tested, and the ammonia production yield and Faraday efficiency are shown in the figure. Figure 4 The ammonia yield was 1.36 mmol / h. -1 mg cat -1 This corresponds to a Faraday efficiency of 94.3%.

[0040] Example 2

[0041] Dissolve 2.0 g of sodium stannate trihydrate in 100 ml of deionized water to obtain 75 mmol / L. -1 A stannate solution was prepared by dissolving copper sulfate pentahydrate and cobalt nitrate hexahydrate in 100 ml of deionized water. The mass of the solution was adjusted so that the sum of the amounts of copper and cobalt salts was equal to the amount of stannate, and the molar ratio of Cu to Co was 8:2. The mixture was stirred at 20°C for 3 hours, washed five times with deionized water, and then freeze-dried under vacuum at -56°C to obtain a solid Cu powder. 0.8 Co 0.2 Sn(OH)6.

[0042] For the prepared Cu 0.8 Co 0.2 Morphological analysis of the Sn(OH)6 sample was performed, and its scanning electron microscope (SEM) images are shown below. Figure 1 .Depend on Figure 1 As can be seen, the above samples have a nanocubic particle morphology and abundant reaction sites.

[0043] The phase composition of the above samples was analyzed, and their X-ray diffraction patterns are as follows: Figure 2 .Depend on Figure 2 Characteristic diffraction peaks of CuSn(OH)6 and CoSn(OH)6 can be observed, and Cu 0.8 Co 0.2 The characteristic diffraction peaks of Sn(OH)6 are obtained by superimposing the characteristic diffraction peaks of CuSn(OH)6 and CoSn(OH)6, indicating that the two phases coexist in the catalyst.

[0044] The electrochemical water splitting performance and electrochemical nitrate reduction performance of the above samples were tested, and their linear voltammetric curves are shown in the figure. Figure 3.Depend on Figure 3 Cu can be observed 0.8 Co 0.2 The current density of Sn(OH)6 in electrochemical nitrate reduction is much higher than that in electrochemical water splitting, indicating its excellent electrocatalytic nitrate reduction performance.

[0045] The electrocatalytic nitrate reduction ammonia production performance of the above samples under constant pressure was tested, and the ammonia production yield and Faraday efficiency are shown in the figure. Figure 4 The ammonia yield was 1.60 mmol / h. -1 mg cat -1 This corresponds to a Faraday efficiency of 91.4%.

[0046] Comparative Example 3

[0047] Dissolve 2.0 g of sodium stannate trihydrate in 100 ml of deionized water to obtain 75 mmol / L. -1 A stannate solution was prepared by dissolving copper sulfate pentahydrate and cobalt nitrate hexahydrate in 100 ml of deionized water. The mass was adjusted so that the sum of the amounts of copper and cobalt salts was equal to the amount of stannate, and the molar ratio of Cu to Co was 9:1. The mixture was stirred at 20°C for 3 hours, washed five times with deionized water, and then freeze-dried under vacuum at -56°C to obtain solid Cu powder. 0.9 Co 0.1 Sn(OH)6.

[0048] The electrocatalytic nitrate reduction ammonia production performance of the above samples under constant pressure was tested, and the ammonia production yield and Faraday efficiency are shown in the figure. Figure 4 The ammonia yield was 1.35 mmol / h. -1 mg cat -1 This corresponds to a Faraday efficiency of 77.0%.

[0049] Comparative Example 4

[0050] The CuSn(OH)6 prepared in Comparative Example 1 and the CoSn(OH)6 prepared in Comparative Example 2 were mechanically mixed at a molar ratio of 8:2 and thoroughly mixed in a mortar to obtain solid powder mech-Cu. 0.8 Co 0.2 Sn(OH)6.

[0051] The electrocatalytic nitrate reduction ammonia production performance of the above samples under constant pressure was tested, and the ammonia production yield and Faraday efficiency are shown in the figure. Figure 4 The ammonia yield was 0.90 mmol / h. -1 mg cat -1 This corresponds to a Faraday efficiency of 50.7%.

Claims

1. A hydroxystannate perovskite electrocatalyst Cu 1-x Co x The application of Sn(OH)6 is characterized by: It was used for the electrocatalytic reduction of nitrate to ammonia, in which the ammonia production rate was higher than 1 mmol / cm. -2 h -1 The ammonia production faradaic efficiency remains above 90%; The hydroxystannate perovskite electrocatalyst Cu 1-x Co x The preparation process of Sn(OH)6 is as follows: Stannate is dissolved in deionized water to obtain a stannate solution; soluble copper and cobalt salts are dissolved in deionized water to obtain a copper-cobalt mixed solution; the stannate solution and the copper-cobalt mixed solution are then directly mixed and stirred to produce a precipitate, which is then separated into solid and liquid phases and freeze-dried to obtain Cu. 1-x Co x Sn(OH)6, where x = 0.15~0.

3.

2. The application according to claim 1, characterized in that: x=0.2。 3. The application according to claim 1 or 2, characterized in that: The stannate is sodium stannate, and the concentration of the stannate solution is 10~50 g / L.

4. The application according to claim 1 or 2, characterized in that: The soluble copper salt and cobalt salt are selected from their respective nitrates, sulfates, acetates and chlorides, and the concentration of the soluble copper salt and cobalt salt in the copper-cobalt mixed solution is 10~50 g / L.

5. The application according to claim 1 or 2, characterized in that: The stirring reaction conditions are: speed of 600~900 r / min, temperature of 5~40℃, and time of not less than 3h.

6. The application according to claim 1 or 2, characterized in that: The freeze-drying temperature is -30 to -70°C, and the pressure is 8 to 50 Pa.

Images