Preparation method of iron-cobalt bimetal-derived carbon thin film electrode for electrocatalytic reduction of nitrate

Abstract

The present invention discloses a method for preparing an iron-cobalt bimetallic derived carbon film electrode for electrocatalytic reduction of nitrate in the field of environmental nanomaterial technology, comprising the following steps: step 1, adding polyacrylonitrile and polyvinyl pyrrolidone to an FC-PBA dispersion, stirring the mixture under water bath heating until uniformly mixed, and obtaining an electrospinning precursor solution; step 2, regulating the humidity and temperature of the electrospinning environment, and electrospinning the electrospinning precursor solution to obtain FC-PBA / PAN-PVP fibers, flattening and compacting the FC-PBA / PAN-PVP fibers, and cutting the fibers; step 3, carbonizing the FC-PBA / PAN-PVP fibers at 600-1000°C under an N2 atmosphere to obtain an iron-cobalt bimetallic derived carbon film electrode. The iron-cobalt bimetallic derived carbon film prepared by the present invention can be attached to an electrode substrate such as nickel foam without relying on an adhesive and can be used directly as a working electrode. The synergistic effect of the iron-cobalt bimetallic and the freedom from the influence of the adhesive enable the material to exhibit excellent nitrate removal rate and ammonium selectivity during the electrocatalytic reduction of nitrate.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental nanomaterials, and in particular is a method for preparing an iron-cobalt bimetallic derived carbon film electrode for electrocatalytic reduction of nitrates. Background Art

[0002] The nitrogen cycle is crucial for maintaining ecosystem balance and stability. With the advent of large-scale industrial ammonia synthesis in the early 20th century, global food production and population grew exponentially. Simultaneously, excess nitrogen fertilizer and industrial nitrogen-containing wastewater entered the environment, ultimately leading to eutrophication of surface waters and posing a threat to human health. Nitrates that enter the human body through drinking water and other sources are converted to nitrites by the reduction action of specific bacteria. Nitrites can hinder oxygen transport in the blood, leading to methemoglobinemia and even inducing various cancers, including gastric and esophageal cancer. Consequently, countries and regions around the world have established strict concentration limits for nitrates in drinking water and have made nitrate removal a key component of water pollution control.

[0003] Traditional methods for removing nitrates from water bodies mainly include physical and chemical methods and biological methods. Physical methods such as membrane separation can only enrich nitrates in a certain medium and transfer them, while the additional chemicals added by chemical methods will also produce additional toxic byproducts. In other words, physical and chemical methods will not completely remove nitrates and will cause secondary pollution after treatment. As the mainstream denitrification method in industrialization, biological methods also have problems such as slow reduction rate, high reactor cost, long sludge acclimatization time, and the need for deep treatment of effluent. This also limits its development prospects for reducing and removing nitrate from water. In the context of promoting sustainable development and ecological construction, it is of great significance to efficiently reduce nitrates in wastewater to harmless or even high value-added products.

[0004] Electrocatalytic reduction of nitrate, due to its low energy consumption, high efficiency, and strong controllability, has attracted increasing research in environmental and energy applications such as wastewater denitrification, nitrate reduction to ammonia, and energy storage. Platinum-group metals, with their excellent electrochemical properties, are excellent electrocatalytic materials, but their scarcity and high cost hinder their large-scale industrial application. Iron, a metal element with high reserves, strong reducing properties, and low toxicity, can significantly reduce the cost of electrocatalytic materials. However, its susceptibility to corrosion leads to poor electrode stability, and its high surface energy hinders the reaction of reactants at its surface active sites. The introduction of cobalt can modulate its conductivity and electronic band structure, creating new active sites and enhancing electrocatalytic activity. Carbon-coated iron-cobalt bimetallics also exhibit low aggregation tendency during the carbonization process, further enhancing the synergistic effect of the bimetallics and increasing the accessible area of active sites. Therefore, the search for one or more transition metals with high electrocatalytic activity, abundant reserves, low cost, and non-toxicity to replace precious metals and the exploration of synergistic effects between multicomponent alloys have become a hot topic of research. Summary of the Invention

[0005] In order to solve the problems in the background technology, the purpose of the present invention is to provide a method for preparing an iron-cobalt bimetallic derived carbon thin film electrode for the electrocatalytic reduction of nitrates, so as to prepare one or more transition metals with high electrocatalytic activity, abundant storage, low cost and non-toxicity to replace precious metals.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for preparing an iron-cobalt bimetallic derived carbon thin film electrode for electrocatalytic reduction of nitrates comprises the following steps:

[0008] Step 1: adding polyacrylonitrile and polyvinyl pyrrolidone to the FC-PBA dispersion, stirring the mixture in a water bath until uniformly mixed, to obtain an electrospinning precursor solution;

[0009] Step 2: Control the humidity and temperature of the electrospinning environment, electrospin the electrospinning precursor solution to obtain FC-PBA / PAN-PVP fibers, and then flatten, compact, and cut the FC-PBA / PAN-PVP fibers;

[0010] Step 3: Carbonize the cut FC-PBA / PAN-PVP fibers at 600-1000° C. in a N 2 atmosphere to obtain an iron-cobalt bimetallic carbon thin film electrode.

[0011] Iron-cobalt bimetallic derived carbon thin film electrode for electrocatalytic reduction of nitrate.

[0012] Furthermore, the mass ratio of FC-PBA, polyacrylonitrile and polyvinyl pyrrolidone is 3:2:2.

[0013] Furthermore, in step 1, the concentration of the FC-PBA dispersion is 0.06-0.12 g / mL, and the solvent is N,N-dimethylformamide.

[0014] Furthermore, in step 1, the temperature of the water bath heating is: 50-70°C.

[0015] Furthermore, in step 2, the positive pressure of the electrospinning voltage is set to 12-14 kV, the negative pressure is set to 1-3 kV, and the injection rate is set to 0.06-0.08 mm / min.

[0016] Furthermore, in step 2, the humidity of the electrospinning environment is controlled at 10-30%, and the temperature is controlled at 30-50°C.

[0017] Furthermore, in step 2, the weight of the weight used for compaction is 5-10 kg, the compaction time is 12-24 hours, and the cutting size is 4-10 cm in length and 1.5-2 cm in width.

[0018] Furthermore, in step 3, the heating rate is 3-8°C / min.

[0019] The above scheme achieves the following beneficial effects: The preparation process of the present invention is simple, and has the advantages of low energy consumption, high efficiency and strong controllability. The obtained iron-cobalt bimetallic derived carbon fiber film is directly used as a working electrode without relying on an adhesive. It not only solves the problem that the adhesive causes poor conductivity and covers the active sites on the surface of the material, but also solves the problem that the nanopowder is easy to agglomerate and difficult to recycle. At the same time, the synergistic effect of the iron-cobalt bimetallic still has excellent nitrate removal rate and ammonium selectivity. Therefore, it has great application potential in water treatment and energy fields such as electrocatalytic removal of nitrate and reduction to produce ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the preparation of iron-cobalt bimetallic derived carbon thin film electrode;

[0021] Figure 2 is the scanning electron microscopy image of FC-PBA;

[0022] Figure 3 Schematic diagram of the electrocatalytic reduction of nitrate by the iron-cobalt bimetallic carbon fiber film of Example 1;

[0023] Figure 4 Schematic diagram of the device for using the electrode of iron-cobalt bimetallic derived carbon fiber film in Example 1. DETAILED DESCRIPTION

[0024] The following is further described in detail through specific implementation methods:

[0025] Example 1:

[0026] The present application provides a method for preparing an iron-cobalt bimetallic-derived carbon thin film electrode for electrocatalytic reduction of nitrates, comprising the following steps:

[0027] Step 1: Add polyacrylonitrile and polyvinyl pyrrolidone to the FC-PBA dispersion in a mass ratio of 3:2:2. Stir the mixture in a water bath heated at 50-70°C until uniformly mixed, to obtain an electrospinning precursor. The FC-PBA dispersion is prepared by dissolving FC-PBA powder in N,N-dimethylformamide to a concentration of 0.06-0.12 g / mL. The FC-PBA powder is an iron-cobalt Prussian blue analog.

[0028] Step 2, regulate the humidity and temperature of the electrospinning environment, the humidity of the electrospinning environment is controlled at 10-30%, the temperature is controlled at 30-50 ° C, the positive pressure of the electrospinning voltage is set to 12-14 kV, the negative pressure is 1-3 kV, the injection rate is 0.06-0.08 mm / min, and the electrospinning precursor is electrospun to obtain FC-PBA / PAN-PVP fiber, and then the FC-PBA / PAN-PVP fiber is flattened, compacted and cut. The weight of the compaction weight is 5-10 kg, the compaction time is 12-24 h, and the cutting size is 4-10 cm long and 1.5-2 cm wide.

[0029] Step 3: Carbonize the cut FC-PBA / PAN-PVP fibers at 600-1000°C (heating rate of 3-8°C / min) under N2 atmosphere to obtain an iron-cobalt bimetallic derived carbon thin film electrode.

[0030] The experimental method is as follows:

[0031] Experiment 1,

[0032] A method for preparing an iron-cobalt bimetallic derived carbon thin film electrode for electrocatalytic reduction of nitrates comprises the following steps:

[0033] Step 1: Dissolve 0.6 g of FC-PBA powder in 5.5 mL of N,N-dimethylformamide and disperse it by ultrasonication to make it completely uniform. Then, add 0.4 g of polyacrylonitrile and 0.4 g of polyvinylpyrrolidone, and use magnetic stirring in a 60°C water bath to mix FC-PBA nanoparticles, PAN and PVP evenly.

[0034] Step 2: Transfer the mixed solution obtained in step 1 into a 5 mL syringe. Using electrospinning technology, adjust the voltage to a positive pressure of 12 kV, a negative pressure of 2 kV, and an injection rate of 0.08 mm / min to obtain FC-PBA / PAN-PVP fibers. Then, weigh and compact them for 12 hours and cut them into sizes of 4 cm long and 1.5 cm wide.

[0035] Step 3: In an inert atmosphere, the cut FC-PBA / PAN-PVP fibers are carbonized at 800° C. at a heating rate of 5° C. / min to obtain an iron-cobalt bimetallic derived carbon fiber thin film electrode.

[0036] Figure 1 It can be seen that the iron-cobalt bimetallic derived carbon fiber material has a clear one-dimensional structure, and the cubic structure on the fiber is formed by FC-PBA during the carbonization process. Figure 2 This is a scanning electron microscope image of the prepared FC-PBA. In the image, it can be seen that the synthesized FC-PBA nanoparticles have a cubic structure of uniform size.

[0037] As attached Figure 1 It can be seen that the iron-cobalt bimetallic derived carbon fiber material has a clear one-dimensional structure, and the cubic structure on the fiber is formed by FC-PBA during the carbonization process. Figure 2 This is a scanning electron microscope image of the prepared FC-PBA. In the image, it can be seen that the synthesized FC-PBA nanoparticles have a cubic structure of uniform size.

[0038] Experiment 2

[0039] A method for preparing an iron-cobalt bimetallic derived carbon thin film electrode for electrocatalytic reduction of nitrates comprises the following steps:

[0040] Step 1: Dissolve 0.3 g of FC-PBA powder in 3 mL of N,N-dimethylformamide and disperse it uniformly by ultrasonication. Then, add 0.2 g of polyacrylonitrile and 0.2 g of polyvinylpyrrolidone. In a 60°C water bath, use magnetic stirring to mix the FC-PBA nanoparticles, PAN, and PVP uniformly.

[0041] Step 2: Transfer the mixed solution obtained in step 1 into a 5 mL syringe. Using electrospinning technology, adjust the voltage to a positive pressure of 12 kV, a negative pressure of 2 kV, and an injection rate of 0.08 mm / min to obtain FC-PBA / PAN-PVP fibers. Then, compact them with a heavy object for 12 hours and cut them into sizes of 8 cm long and 1.5 cm wide.

[0042] Step 3: In an inert atmosphere, the cut FC-PBA / PAN-PVP fibers are carbonized at 800° C. at a heating rate of 5° C. / min to obtain an iron-cobalt bimetallic derived carbon fiber thin film electrode.

[0043] Experiment 3

[0044] A method for preparing an iron-cobalt bimetallic derived carbon thin film electrode for electrocatalytic reduction of nitrates comprises the following steps:

[0045] Step 1: Dissolve 0.6 g of FC-PBA powder in 5 mL of N,N-dimethylformamide and disperse it by ultrasonication to make it completely uniform. Then, add 0.4 g of polyacrylonitrile and 0.4 g of polyvinylpyrrolidone, and use magnetic stirring in a 60°C water bath to mix FC-PBA nanoparticles, PAN and PVP evenly.

[0046] Step 2: Transfer the mixed solution obtained in step 1 into a 5 mL syringe. Using electrospinning technology, adjust the voltage to 14 kV positive pressure, 2 kV negative pressure, and 0.08 mm / min push rate to obtain FC-PBA / PAN-PVP fiber. Then, compact it with a heavy object for 12 hours and cut it into a size of 8 cm long and 1.5 cm wide.

[0047] Step 3: In an inert atmosphere, the cut FC-PBA / PAN-PVP fibers are carbonized at 600° C. with a heating rate of 5° C. / min to obtain an iron-cobalt bimetallic derived carbon fiber thin film electrode.

[0048] The three-electrode system was provided by the CHI660E electrochemical workstation produced by Shanghai Chenhua Company, and the performance of the electrocatalytic reduction of nitrate was tested using the UV-1800PC UV-visible spectrophotometer produced by Shanghai Meipu Instrument Co., Ltd. First, 80 mL of a solution containing 0.1 M NaSO4 and 100 mg / L NaNO3 was prepared. A platinum electrode was used as the counter electrode and a silver-silver chloride electrode was used as the reference electrode. The electrocatalytic reduction of nitrate was carried out at a voltage of -1.3 V. Figure 3 As shown in the figure, the removal rate of nitrate ions in the solution was nearly 90% within 240 minutes, and the reduction product was almost ammonium ions.

[0049] like Figure 4 As shown, the iron-cobalt bimetallic derived carbon fiber film in Experiment 1 was used as the working electrode in the three-electrode system. After continuous electrocatalytic reduction of nitrate in the solution for 12 hours, it can still maintain its original morphology and can be recovered relatively completely from the cathode.

[0050] The above is only an embodiment of the present invention, and common knowledge such as the specific structure and / or characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. An application of an iron-cobalt bimetallic derived carbon thin film electrode, characterized by: Applied to the electrocatalytic reduction of nitrates, the preparation method of the iron-cobalt bimetallic derived carbon thin film electrode comprises the following steps: Step 1: Add polyacrylonitrile and polyvinyl pyrrolidone to the FC-PBA dispersion, respectively, with the mass ratio of FC-PBA, polyacrylonitrile, and polyvinyl pyrrolidone being 3:2:2; stir until uniformly mixed under heating in a water bath at a temperature of 50-70° C. to obtain an electrospinning precursor solution; wherein the concentration of the FC-PBA dispersion is 0.06-0.12 g / mL, and the solvent is N,N-dimethylformamide; Step 2: Regulating the humidity and temperature of the electrospinning environment, electrospinning the electrospinning precursor solution to obtain FC-PBA / PAN-PVP fibers, and then flattening, compacting, and cutting the FC-PBA / PAN-PVP fibers; wherein the electrospinning voltage is set to a positive voltage of 12-14 kV, a negative voltage of 1-3 kV, a push rate of 0.06-0.08 mm / min, and the humidity and temperature of the electrospinning environment are controlled at 10-30%. In step 3, the cut FC-PBA / PAN-PVP fibers are carbonized at 600-1000°C in a nitrogen atmosphere to obtain an iron-cobalt bimetallic carbon thin film electrode.

2. The use according to claim 1, characterized in that: In step 2, the weight of the compaction weight is 5-10 kg, the compaction time is 12-24 hours, and the cutting size is 4-10 cm in length and 1.5-2 cm in width.

3. The use according to claim 1, characterized in that: In step 3, the heating rate is 3-8°C / min.

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