Selenium-nitrogen modified stainless steel material and preparation method and application thereof

Abstract

The invention discloses a preparation method of a selenium-nitrogen modified stainless steel material, which comprises the following steps: calcining a stainless steel material, a selenium source and a nitrogen source in a closed container to obtain the selenium-nitrogen modified stainless steel material, wherein the selenium source comprises at least one of selenium powder, selenate and selenium oxide, and the nitrogen source comprises at least one of melamine, ammonia water, ammonia gas, alanine and glycine; the calcining temperature is 550-600 DEG C, and the calcining time is 1-2 hours. The invention further discloses the selenium-nitrogen modified stainless steel material prepared through the method and application of the selenium-nitrogen modified stainless steel material. The selenium-nitrogen modified stainless steel material prepared through the method is simple, environmentally friendly and low in cost, the effect of reducing nitrate to produce ammonia is excellent, and when clean electric energy is used for conducting electro-catalysis nitrate reduction to produce ammonia under the normal-temperature and normal-pressure conditions, the excellent ammonia production Faraday efficiency and the ammonia yield are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrate reduction to produce ammonia, and particularly relates to a selenium-nitrogen modified stainless steel material, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of industrial and agricultural production, there are varying degrees of nitrogen pollution problems in the groundwater of rural and urban areas. The content of nitrate nitrogen in surface water and groundwater in many parts of the world is increasing continuously, which has endangered the quality and safety of the vadose zone soil and groundwater, and the nitrate pollution is becoming increasingly serious. Nitrate (NO 3 - ) is the most stable form of nitrogen-containing compound in an aerobic environment and is also the final product of the decomposition of nitrogen-containing organic matter through mineralization. The exceeding standard of nitrate nitrogen has become a limiting factor for the difficult discharge of TN up to the standard. Therefore, the efficient and harmless removal of NO 3 - has become the key. At present, the main treatment methods for nitrate include biological method, ion exchange method, membrane separation method, and electrochemical reduction method. Among them, the biological denitrification cycle is relatively long, and it is necessary to monitor the system parameters in real time (such as the influence of adding carbon source, controlling pH and temperature, etc. on the microbial activity). The ion exchange method and the membrane separation method are costly, and only concentrate or transfer the nitrate, and do not fundamentally eliminate the nitrate pollution problem. The electrochemical reduction method, which is easy to operate, automated, environmentally friendly, and has high efficiency, is considered the most promising denitrification method. Applying electrocatalytic technology to nitrate reduction to produce ammonia not only helps to solve environmental pollution problems but also is expected to realize the green synthesis of ammonia.

[0003] At present, in the research of electrocatalytic nitrate reduction to produce ammonia, it is important to obtain a cathode catalytic electrode with excellent performance. High-performance electrode materials such as Cu, Co, Ni, Fe and other alloys that have been reported have made good progress in electrochemical nitrate production of ammonia. However, high-performance self-supporting electrodes with simple process, low cost, and easy availability for industrialization are still scarce at present. Therefore, stainless steel, as a material containing iron and nickel, is simple to produce, low in price, and has been commercialized. Modifying it to improve its reduction catalytic performance provides an option for realizing efficient nitrate reduction to produce ammonia. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of a selenium-nitrogen modified stainless steel material, which is simple, environmentally friendly, and low in cost, and the prepared selenium-nitrogen modified stainless steel material has excellent effects in reducing nitrate to produce ammonia, has excellent Faraday efficiency of ammonia production and ammonia production rate, and its catalytic performance and industrialization ability greatly exceed most of the reported nitrate reduction catalysts.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] In the first aspect of the present invention, a method for preparing a selenium-nitrogen modified stainless steel material is provided, comprising: calcining a stainless steel material, a selenium source, and a nitrogen source in a closed container to obtain the selenium-nitrogen modified stainless steel material; wherein, the selenium source includes at least one of selenium powder, selenate, and selenium oxide, and the nitrogen source includes at least one of melamine, ammonia water, ammonia gas, alanine, and glycine; the temperature of the calcination is 550-600 °C, and the calcination time is 1-2 h.

[0007] Further, the stainless steel material includes at least one of 304 stainless steel, 316 stainless steel, and 316L stainless steel.

[0008] Further, the stainless steel material is at least one of sheet-like, net-like, and felt-like.

[0009] Further, it further includes a step of pre-treating the stainless steel material before calcination; the pre-treatment is: placing the stainless steel material in an alkali solution, soaking it at 70-100 °C for 2-6 h; then taking it out, washing it with water and drying it.

[0010] In the present invention, the purpose of pre-treating the stainless steel material with an alkali solution is to activate the stainless steel material, thereby improving the activity of subsequent reactions. Among them, the alkali solution includes, but is not limited to, potassium hydroxide solution, sodium hydroxide solution, ammonia water, etc.

[0011] Further, the ratio of the selenium source to the stainless steel material is 1-50 mg·cm -2 , and the ratio of the nitrogen source to the stainless steel material is 1-50 mg·cm -2 .

[0012] Further, the ratio of the selenium source to the stainless steel material is 17 mg·cm -2 , and the ratio of the nitrogen source to the stainless steel material is 2 mg·cm -2 .

[0013] Further, the sealing is specifically: sealing with a graphite plate or sealing with a vacuum sealing tube machine under liquid nitrogen protection.

[0014] In the second aspect of the present invention, a selenium-nitrogen modified stainless steel material prepared by the above-mentioned preparation method is provided.

[0015] In the third aspect of the present invention, the application of the selenium-nitrogen modified stainless steel material as a nitrate reduction catalyst is provided.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. Compared with the prior art, the present invention uses a sealed method for calcination, which has high processing efficiency, greatly saves selenium sources and nitrogen sources, reduces costs, is both efficient and economical, and is easy to industrialize.

[0018] 2. The catalyst prepared by the present invention has a self-supporting network or sheet structure, with uniform element distribution, large specific surface area, high stability, strong conductivity and mechanical strength. Excellent nitrate conversion rate and ammonia production Faraday efficiency can be achieved by adjusting the surface element composition.

[0019] 3. The selenium-nitrogen modified stainless steel electrode prepared by the present invention has much better catalytic performance and industrialization ability than most of the reported nitrate reduction catalysts. After experimental verification, using a 5 cm×10 cm 2 stainless steel sheet added with 850 mg of selenium powder and 100 mg of melamine, the obtained selenium-nitrogen modified stainless steel electrode can obtain a high NH 3 production rate of 11122.86 μg·h -1 ·cm -2 at -1.35 V voltage in a 1M KOH + 0.1M KNO 4 + solution, with an ammonia Faraday efficiency of 83.48%, an NH 4 + selectivity of 78.38% and a NO 3 - -N conversion rate of 83.48%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Product diagrams of stainless steel (SS) and selenium-nitrogen modified stainless steel (SeN-SS) from left to right;

[0021] Figure 2 SEM image of the selenium-nitrogen modified stainless steel material prepared in Example 1;

[0022] Figure 3 XRD pattern of the selenium-nitrogen modified stainless steel material prepared in Example 1;

[0023] Figure 4 XPS spectrum of the selenium-nitrogen modified stainless steel material prepared in Example 1;

[0024] Figure 5 Schematic diagram of the electrolytic cell reaction device for electrocatalytic nitrate reduction to ammonia;

[0025] Figure 6 LSV comparison diagram of unselenized stainless steel, selenium modified stainless steel prepared in Comparative Example 1 and selenium-nitrogen modified stainless steel prepared in Example 1 as electrocatalytic materials;

[0026] Figure 7 Comparison chart of nitrate reduction performance of non-selenized stainless steel, selenium-modified stainless steel prepared in Comparative Example 1, and selenium-nitrogen modified stainless steel prepared in Example 1 as electrocatalytic materials;

[0027] Figure 8 LSV comparison chart of selenium-nitrogen modified stainless steel prepared in Example 1 as an electrocatalytic material in the presence and absence of nitrate ions;

[0028] Figure 9 Faraday efficiency and nitrate conversion rate chart of selenium-nitrogen modified stainless steel material prepared in Example 1 at 5 different voltages;

[0029] Figure 10 Ammonia selectivity and ammonia production rate chart of selenium-nitrogen modified stainless steel material prepared in Example 1 for electrocatalytic nitrate reduction to synthesize ammonia at 5 different voltages;

[0030] Figure 11 Ammonia production rate and Faraday efficiency chart of selenium-nitrogen modified stainless steel material after 5 cycles of electrocatalytic nitrate reduction to synthesize ammonia;

[0031] Figure 12 For selenium-nitrogen modified stainless steel material after 5 cycles of electrocatalytic nitrate reduction to synthesize ammonia, NH 4 + --N, NO 2 - --N, NO 3 - --N concentration and Faraday efficiency chart. Detailed implementation manners

[0032] The present invention will be further described below in conjunction with specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited are not intended to limit the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0034] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0035] Example 1

[0036] This embodiment provides a method for preparing a selenium-nitrogen modified stainless steel material, which includes the following steps: Place 1 piece of 304 stainless steel material with an area of 5 cm × 10 cm 2 together with 850 mg of selenium powder and 100 mg of melamine in a quartz boat, and completely seal it with a graphite plate; then place the quartz boat in a muffle furnace, heat it to 575 °C at a rate of 5 °C / min, and calcine for 1.5 hours to obtain the selenium-nitrogen modified stainless steel material.

[0037] Example 2

[0038] This embodiment provides a method for preparing a selenium-nitrogen modified stainless steel material, which includes the following steps: Place 1 piece of 304 stainless steel material with an area of 5 cm × 10 cm 2 together with 850 mg of selenium powder and 100 mg of melamine in a quartz boat, and completely seal it with a graphite plate; then place the quartz boat in a muffle furnace, heat it to 550 °C at a rate of 5 °C / min, and calcine for 1.5 hours to obtain the selenium-nitrogen modified stainless steel material.

[0039] Example 3

[0040] This embodiment provides a method for preparing a selenium-nitrogen modified stainless steel material, which includes the following steps: Place 1 piece of 304 stainless steel material with an area of 5 cm × 10 cm 2 together with 850 mg of selenium powder and 100 mg of melamine in a quartz boat, and completely seal it with a graphite plate; then place the quartz boat in a muffle furnace, heat it to 600 °C at a rate of 5 °C / min, and calcine for 1.5 hours to obtain the selenium-nitrogen modified stainless steel material.

[0041] Example 4

[0042] This embodiment provides a method for preparing a selenium-nitrogen modified stainless steel material, which includes the following steps: Place 1 piece of 304 stainless steel material with an area of 5 cm × 10 cm 2 together with 500 mg of selenium powder and 50 mg of glycine in a quartz boat, and completely seal it with a graphite plate; then place the quartz boat in a muffle furnace, heat it to 575 °C at a rate of 5 °C / min, and calcine for 1.5 hours to obtain the selenium-nitrogen modified stainless steel material.

[0043] Example 5

[0044] This embodiment provides a method for preparing a selenium-nitrogen modified stainless steel material, which includes the following steps: Place 1 piece of 304 stainless steel material with an area of 5 cm × 10 cm 2A 304 stainless steel material, 1000 mg of selenium dioxide, and 200 mg of ammonia water were placed in a quartz boat and completely sealed with a graphite plate. Then, the quartz boat was placed in a muffle furnace and heated to 575 °C at a rate of 5 °C / min and calcined for 1.5 hours to obtain a selenium-nitrogen modified stainless steel material.

[0045] Example 6

[0046] This example provides a method for preparing a selenium-nitrogen modified stainless steel material, which includes the following steps: One piece of 304 stainless steel material with an area of 5 cm × 10 cm 2 was placed in a quartz boat together with 850 mg of selenium powder and 100 mg of alanine, and completely sealed with a graphite plate. Then, the quartz boat was placed in a muffle furnace and heated to 575 °C at a rate of 5 °C / min and calcined for 1.5 hours to obtain a selenium-nitrogen modified stainless steel material.

[0047] Comparative Example 1

[0048] This example provides a method for preparing a selenium modified stainless steel material, which includes the following steps: One piece of 5 cm × 10 cm 2 304 stainless steel was placed in a quartz boat together with 850 mg of selenium powder. Then, the quartz boat was placed in a muffle furnace and heated to 575 °C at a rate of 5 °C / min and calcined for 1.5 hours to obtain a selenium modified stainless steel material.

[0049] Testing and Characterization

[0050] Figure 2 SEM image of the selenium-nitrogen modified stainless steel material prepared in Example 1. It can be seen from the figure that the prepared selenium-nitrogen modified stainless steel catalytic material is granular.

[0051] Figure 3 XPS spectra of the selenium-nitrogen treated stainless steel material prepared in Example 1 and ordinary 304 stainless steel. It can be seen from the figure that selenium and nitrogen reacted with the stainless steel, and the elemental composition on the stainless steel surface changed.

[0052] Figure 4 XRD spectra of the selenium-nitrogen modified stainless steel material prepared in Example 1, the selenium modified stainless steel prepared in Comparative Example 1, and ordinary 304 stainless steel. It can be seen from the figure that in Example 1, selenium and nitrogen reacted with the stainless steel to generate new substances and new characteristic peaks; at the same time, the skeleton structure of the stainless steel remained intact.

[0053] Electrochemical Performance Test

[0054] Please refer to Figure 5, the unselenized stainless steel, the selenium-modified stainless steel material prepared in Comparative Example 1, and the selenium-nitrogen modified stainless steel material prepared in Example 1 were used as the cathode working electrodes, a platinum sheet as the counter electrode, and a mercury / mercuric oxide electrode as the reference electrode. The nitrate reduction performance was evaluated in a three-electrode system in a H cell with 1M KOH + 0.1M KNO 3 in the cathode chamber.

[0055] The specific steps for the electrocatalytic nitrate reduction to ammonia test are as follows:

[0056] (1) Preparation of the electrode: Cut a 2 cm × 1 cm piece of the stainless steel material and ultrasonically treat it for about 3 min to remove surface impurities. Wrap it with a sealing film to isolate the contact interface, leaving an effective area of 1 cm × 1 cm 2 for the experiment. 2

[0057] (2) Electrochemical reduction of NO 3 - : The electrochemical performance test was carried out on a CHI660e Shanghai Chenhua electrochemical workstation using a three-electrode configuration in a H-type cell. The electrode prepared in step (1) was used as the working electrode, a mercuric oxide electrode as the reference electrode, and a platinum foil (1 cm × 1 cm) as the counter electrode. Add 30 mL of 1M KOH (containing 0.1M NO 3 - ) solution to the cathode chamber, and add 30 mL of 1M KOH solution to the anode chamber. A pretreated Nafion proton exchange membrane was used as the separator.

[0058] Before the electrochemical test, the Nafion membrane was heated in 5% H 2 O 2 aqueous solution at 80 °C for one hour, then soaked in deionized water for half an hour; then heated in 5% wt H 2 SO 4 at 80 °C for one hour, and then soaked in deionized water for half an hour. Before the test, cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements were first carried out at a scanning rate of 5 mV / s until the polarization curve was stable. Then, a 3-hour chronopotentiometric test was carried out at different potentials. As Figure 5 obtained the comparison of the Faraday efficiency, nitrate conversion rate, ammonia yield, and ammonia production selectivity at different potentials to obtain the optimal potential. To test its stability, 5 cyclic tests were carried out with the same working electrode at the optimized potential. Each cycle replaced the fresh electrolyte, and other parameters remained unchanged;

[0059] (3) NH 4 +Concentration detection: The detection of ammonia nitrogen adopts the Nessler's reagent method. A certain amount of electrolyte is taken out from the reactor and diluted to 5 mL. Then, 100 μL of sodium tartrate solution and 150 μL of Nessler's reagent are added to the diluted solution. After standing for 10 - 15 min, the absorbance at 420 nm is detected using ultraviolet-visible spectrophotometry. Standard curve plotting: Using ammonium chloride as the ammonia source, a series of standard solutions with different concentrations are configured to plot the standard curve.

[0060] NO 3 - Concentration detection: A certain amount of electrolyte is taken out from the reactor and diluted to 5 mL. Then, 100 μL of 1M HCl and 10 μL of 0.8 wt% sulfamic acid solution are added to the diluted solution. The absorption spectrum is measured using an ultraviolet-visible spectrophotometer, and the absorption intensities at wavelengths of 200 and 275 nm are recorded. Finally, the absorbance value is calculated according to the formula: A = A 220nm - 2A 275nm . Standard curve plotting: Using potassium nitrate as the nitrogen source, a series of standard solutions with different concentrations are configured to plot the standard curve.

[0061] NO 2 - Concentration detection: Preparation method of nitrite color reagent (a mixture of N-(1-naphthyl)ethylenediamine dihydrochloride (0.2 g), sulfanilamide (4 g), phosphoric acid (10 mL, ρ = 1.70 g / mL) and ultrapure water (50 mL). Make up to 100 mL.). Detection method: A certain amount of electrolyte is taken out from the reactor and diluted to 5 mL. Then, 100 μL of the color reagent is added to the diluted solution, and after mixing evenly, it is left standing for 10 min. The absorption spectrum is detected using an ultraviolet-visible spectrophotometer, and the absorption intensity at a wavelength of 540 nm is recorded. Standard curve plotting: Using sodium nitrite as the nitrogen source, a series of standard solutions with different concentrations are configured to plot the standard curve.

[0062] Figure 6 LSV comparison chart of unselenized stainless steel, selenium-modified stainless steel prepared in Comparative Example 1, and selenium-nitrogen-modified stainless steel prepared in Example 1 as electrocatalytic materials, Figure 7 is the nitrate reduction performance comparison chart of unselenized stainless steel, selenium-modified stainless steel prepared in Comparative Example 1, and selenium-nitrogen-modified stainless steel prepared in Example 1 as electrocatalytic materials. It can be seen from Figure 6 that when using selenium-nitrogen-modified stainless steel as the electrocatalytic material, the current density in the electrolysis reaction is significantly higher than that of unselenized stainless steel and also higher than that of selenium-modified stainless steel prepared in Comparative Example 1. It can be seen from Figure 7It can be seen that when selenium-nitrogen modified stainless steel is used as the electrocatalytic material, indicators such as the ammonia Faraday efficiency, nitrate conversion rate, ammonia selectivity, and ammonia yield in the electrocatalytic reduction of nitrate are significantly higher than those of unselenized stainless steel, and are also significantly improved compared to the selenium-modified stainless steel prepared in Comparative Example 1. This shows that the selenium-nitrogen modified stainless steel material in the present invention has better performance in electrocatalytic nitrate reduction than unmodified stainless steel and selenium-modified stainless steel.

[0063] Figure 8 Figure is a comparison chart of LSV of the selenium-nitrogen modified stainless steel prepared in Example 1 as the electrocatalytic material in the presence and absence of nitrate ions. It can be seen from the figure that when nitrate ions are present, the current density increases significantly, indicating that the selenium-nitrogen modified stainless steel material has strong activity for nitrate reduction.

[0064] Figure 9-10 Figures - Figure 9-10 are the Faraday efficiency, nitrate conversion rate, ammonia selectivity, and ammonia yield diagrams of the selenium-nitrogen modified stainless steel material prepared in Example 1 at 5 different voltages respectively. Figure 9 It can be seen that when the selenium-nitrogen modified stainless steel prepared in Example 1 is used as the electrocatalytic material, the Faraday efficiency is the highest at -1.35V, reaching 83.48%; as the voltage increases, the Faraday efficiency decreases. The nitrate conversion rate increases with the increase of voltage and reaches the highest at -1.45V. The ammonia selectivity and ammonia yield of electrocatalytic nitrate reduction to synthesize ammonia both increase with the increase of voltage, and the ammonia selectivity and ammonia yield both reach the highest at -1.55V.

[0065] Figure 11 Figure Figure 9 is the ammonia yield and Faraday efficiency diagram of the selenium-nitrogen modified stainless steel material after 5 cycles of electrocatalytic nitrate reduction to synthesize ammonia. Figure 11 It can be seen that when the selenium-nitrogen modified stainless steel prepared in Example 1 is used as the electrocatalytic material, after 5 consecutive cycles, each cycle for 3 hours, the ammonia production efficiency and Faraday efficiency are still at a relatively high level.

[0066] Figure 12 Figure is the NH 4 + --N selectivity, NO 2 - --N selectivity and NO 3 - --N conversion rate diagram of the selenium-nitrogen modified stainless steel material after 5 cycles of electrocatalytic nitrate reduction to synthesize ammonia, with intermittent sampling every half hour. Figure 12 It can be seen that at different time periods, the NH 4 + --N, NO 2- --The generation rate of N is different. From 0 to 210 min, NH 4 + --N maintains a relatively high generation rate. After 210 min, the generation rate of NH 4 + --N drops significantly. For NO 2 - --N, its generation rate gradually decreases from 0 to 90 min; at 90 min, its generation rate approaches 0, and at this time, the concentration of NO 2 - --N accumulated in the electrolyte reaches the highest; after 90 min, NO 2 - --N is gradually converted into NH 4 + --N and consumed. By 300 min, NO 2 - --N is basically consumed. In addition, during the electrocatalytic reduction of nitrate to ammonia, the Faraday efficiency of ammonia production remains at a relatively high level. From 0 to 210 min, the FE remains above 80%; after 210 min, the FE decreases slightly but still remains above 75%.

[0067] The above-described embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention is subject to the claims.

Claims

1. A method for preparing a selenium-nitrogen modified stainless steel material, characterized in that: include: The stainless steel material, a selenium source and a nitrogen source are calcined in a sealed container to obtain the selenium-nitrogen modified stainless steel material; wherein the selenium source includes at least one of selenium powder, selenate and selenium oxide, and the nitrogen source includes at least one of melamine, ammonia water, ammonia gas, alanine and glycine; the calcination temperature is 550-600° C., and the calcination time is 1-2 hours.

2. The method for preparing a selenium-nitrogen modified stainless steel material according to claim 1, characterized in that: The stainless steel material includes at least one of 304 stainless steel, 316 stainless steel, and 316L stainless steel.

3. The method for preparing a selenium-nitrogen modified stainless steel material according to claim 1, characterized in that: The stainless steel material is in at least one of sheet, mesh and felt shapes.

4. The method for preparing a selenium-nitrogen modified stainless steel material according to claim 1, characterized in that: The method also includes the step of pre-treating the stainless steel material before calcining; the pre-treatment is: placing the stainless steel material in an alkali solution, soaking it at 70-100° C. for 2-6 hours; then taking it out, washing it with water and drying it.

5. The method for preparing a selenium-nitrogen modified stainless steel material according to claim 1, characterized in that: The ratio of the selenium source to the stainless steel material is 1 to 50 mg·cm -2 The ratio of the nitrogen source to the stainless steel material is 1 to 50 mg·cm -2 .

6. The method for preparing a selenium-nitrogen modified stainless steel material according to claim 5, characterized in that: The ratio of the selenium source to the stainless steel material is 17 mg·cm -2 The ratio of nitrogen source to stainless steel material is 2 mg cm -2 .

7. The method for preparing a selenium-nitrogen modified stainless steel material according to claim 1, characterized in that: The sealing is specifically: sealing with a graphite plate or sealing with a vacuum tube sealing machine under the protection of liquid nitrogen.

8. The selenium-nitrogen modified stainless steel material prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the selenium-nitrogen modified stainless steel material according to claim 8 as a nitrate reduction catalyst.

Images