CoS2 / PVIPS / PPyNTS nano material, preparation method and application in electro-catalytic nitrogen oxidation

Abstract

The invention belongs to the field of new energy and electrochemical catalysis, and particularly relates to a CoS2 / PVIPS / PPyNTs nano material, a preparation method thereof and application of the CoS2 / PVIPS / PPyNTs nano material in electro-catalytic nitrogen oxidation. Comprising the following steps: loading cobalt disulfide on a poly (1-vinyl-3-propane sulfonic acid group imidazolium salt) / polypyrrole nanotube, and preparing CoS2 / PVIPS / PPyNTs. The CoS2 / PVIPS / PPyNTs modified electrode is prepared by loading the CoS2 / PVIPS / PPyNTs on carbon cloth. Under an alkaline condition, CoS2 is taken as an active center, the polypyrrole nanotube is taken as a carrier, and the ionic liquid is taken as a linking agent and a structure inducer, so that the OER process can be inhibited, and the NOR reaction activity can be enhanced, and therefore, the yield of nitrate radicals is improved, higher Faraday efficiency is shown, and meanwhile, good stability is achieved; and a new thought and a new method are provided for research and design of the NOR electrocatalyst at normal temperature and normal pressure.

Description

Technical Field

[0001] The present invention belongs to the field of new energy and electrochemical catalysis, and specifically relates to CoS2 / PVIPS / PPyNTs nanomaterials and a preparation method and application in electrocatalytic nitrogen oxidation. Background Art

[0002] Nitrogen fixation, defined as the conversion of inert nitrogen (N2) into reactive nitrogen (nitrogen-containing compounds), is one of the most important chemical processes in nature. With the rapid growth of the global population, natural nitrogen fixation is far from meeting the needs of human activities. As a result, artificial nitrogen fixation has emerged. One important nitrogen-containing compound is nitrate, which is mainly produced by a two-step process consisting of the Haber-Bosch (HB) process and the Ostwald oxidation process. Despite its great contribution, huge energy consumption and carbon emissions are inevitably generated in this process. Therefore, it is necessary to develop new methods for nitrate preparation, especially driven by renewable energy. In this regard, the electrochemical nitrogen oxidation reaction (NOR) for nitrate synthesis under mild conditions has been developed and considered as a potential alternative. Compared with the current centralized two-step process, electrochemical NOR can achieve small-scale, distributed production and is also compatible with intermittent renewable energy.

[0003] Unlike artificial NRR inspired by natural nitrogenase, no living organisms use N2 and O2 to directly produce aqueous nitrate solutions. It can be seen that the advantages of electrocatalytic nitrogen oxidation (NOR) are obvious. It not only reduces energy consumption and carbon emissions, but also can achieve small-scale on-demand production. Therefore, the development of an efficient NOR catalyst is of great significance for achieving energy conservation, atom economy and carbon-free goals. Transition metal sulfides have variable crystal structures and adjustable phase components, high electrocatalytic activity, low oxygen evolution side reaction activity, abundant reserves and low prices. They are very potential NOR catalysts and have attracted widespread attention. CoS2 has entered our field of vision due to its high catalytic activity, low cost, variable crystal structure and adjustable phase components. It can be used as a very potential NOR catalyst, but because of its inherent shortcomings of poor stability and easy aggregation of metal-based catalysts, we chose PVIPS / PPyNT S The nanotubes serve as a matrix for stabilization. Summary of the invention

[0004] One of the purposes of the present invention is to provide a CoS2 / PVIPS / PPyNT with low price and high catalytic performance. S Nanomaterials.

[0005] The second object of the present invention is to provide a method of using CoS2 / PVIPS / PPyNT S NOR electrocatalytic modified electrodes prepared by nanomaterials are used for electrocatalytic nitrogen oxidation.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows: CoS2 / PVIPS / PPyNT S The nanomaterial preparation method comprises the following steps:

[0007] 1) Add methyl orange to deionized water, disperse by ultrasonic, then add FeCl3 6H2O, continue to disperse by ultrasonic, then add pyrrole (Py), transfer to an ice water bath, stir and react for 6 hours, centrifuge, wash, and dry to obtain PPyNTs nanotubes;

[0008] 2) Add PPyNT to N,N-dimethylformamide S Nanotubes, ultrasonic dispersion, then add allyl chloride and KOH, after ultrasonic dispersion, transfer to a 60℃ oil bath, stir and react for 24h, centrifuge, wash, and vacuum dry to obtain PPyNT S -CH2-CH=CH2 nanotubes;

[0009] 3) Add PPyNT to anhydrous ethanol S -CH2-CH=CH2 nanotubes, ultrasonically dispersed, then added 1-vinyl-3-propanesulfonic acid imidazolate (VIPS) and initiator azobisisobutyronitrile (AIBN), transferred to 80 ° C oil bath, under nitrogen protection, reflux reaction for 5 hours, after the reaction, centrifuged, washed, vacuum dried, poly 1-vinyl-3-propanesulfonic acid imidazolate / polypyrrole nanotubes (PVIPS / PPyNT S nanotubes);

[0010] 4) PVIPS / PPyNT S The nanotubes were dispersed in water, and then CoCl2·6H2O and thioacetamide (TAA) were added in sequence and stirred evenly. The resulting reaction system was subjected to hydrothermal reaction. The resulting product was washed with distilled water and anhydrous ethanol in sequence, centrifuged, and vacuum dried to obtain CoS2 / PVIPS / PPyNT. S Nanomaterials.

[0011] Furthermore, the above-mentioned CoS2 / PVIPS / PPyNT S Nanomaterial, in step 3), the initiator is azobisisobutyronitrile (AIBN).

[0012] Furthermore, the above-mentioned CoS2 / PVIPS / PPyNT S Nanomaterials, step 4), by mass ratio, CoCl2·6H2O:PVIPS / PPyNT S Nanotubes = 1.5:1.

[0013] Furthermore, the above-mentioned CoS2 / PVIPS / PPyNTS Nanomaterial, in step 4), the hydrothermal reaction is: placing the obtained reaction system in a Teflon reactor with a polytetrafluoroethylene liner and performing a hydrothermal reaction at 200° C. for 24 hours.

[0014] A CoS2 / PVIPS / PPyNT-based S The NOR electrocatalytic modified electrode of nanomaterials is based on carbon cloth and the above-mentioned CoS2 / PVIPS / PPyNT S CoS2 / PVIPS / PPyNT made of nanomaterials attached to carbon cloth S Modified electrode.

[0015] A CoS2 / PVIPS / PPyNT-based S A method for preparing a NOR electrocatalytic modified electrode of a nanomaterial, the preparation method comprising the following steps:

[0016] 1) CoS2 / PVIPS / PPyNT S The nanomaterial is ultrasonically dispersed in a mixed solution of anhydrous ethanol and Nafion to obtain a uniformly dispersed composite modifier;

[0017] 2) Apply the evenly dispersed composite modifier to the clean carbon cloth surface and dry it at room temperature to obtain CoS2 / PVIPS / PPyNT S Modified electrode.

[0018] Furthermore, in the above preparation method, the volume ratio of anhydrous ethanol:Nafion solution is 92:8.

[0019] The present invention provides a CoS2 / PVIPS / PPyNT-based S Application of NOR electrocatalytic modified electrodes of nanomaterials in electrocatalytic nitrogen oxidation to synthesize nitrate.

[0020] Further, the method is as follows: based on CoS2 / PVIPS / PPyNT S The NOR electrocatalytic modified electrode of nanomaterials was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode to form a three-electrode system to achieve electrocatalytic oxidation of nitrogen in 0.1 M potassium hydroxide solution.

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] 1. CoS2 / PVIPS / PPyNT prepared by the present invention SThe NOR electrocatalytic modified electrode of nanomaterials, due to the presence of CoS2, enables N2 to be oxidized to produce nitrate with the participation of cobalt disulfide on the surface of nanotubes, realizing nitrogen oxidation at room temperature and pressure, reducing energy consumption and environmental pollution.

[0023] 2. CoS2 / PVIPS / PPyNT prepared by the present invention S The NOR electrocatalytic modified electrode of nanomaterials showed the advantages of strong electrochemical performance, good stability, and good linearity.

[0024] 3. CoS2 / PVIPS / PPyNT prepared by the present invention S The NOR electrocatalytic modified electrode of nanomaterials makes it possible to produce nitrate ions through electrocatalytic nitrogen oxidation, providing new ideas and methods for the practical application of electrocatalytic nitrogen fixation.

[0025] 4. In the present invention, the price of cobalt is relatively low and the storage capacity is large. At the same time, poly 1-vinyl-3-propanesulfonic acid imidazole salt / polypyrrole nanotube (PVIPS / PPyNT S ) as the substrate to synthesize the cobalt sulfide-organic conductive composite, which promotes the dispersion of cobalt sulfide on the organic conductive polymer and the electron mobility in electrochemical catalysis, and further improves the catalytic performance of metal sulfide.

[0026] 5. The modified electrode prepared by the present invention is low in price, good in stability, simple in operation and fast in reaction speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 CoS2 / PVIPS / PPyNT S Electron microscope image of nanotubes;

[0028] Among them, (a) CoS2 / PVIPS / PPyNT S Scanning electron microscope (SEM) images of nanotubes;

[0029] (b) CoS2 / PVIPS / PPyNT S Transmission electron microscopy (TEM) image of nanotubes.

[0030] Figure 2 CoS2 / PVIPS / PPyNT S XRD patterns of nanomaterials.

[0031] Figure 3 CoS2 / PVIPS / PPyNT S LSV plots of the modified electrode in saturated N2 and Ar, respectively.

[0032] Figure 4CoS2 / PVIPS / PPyNT S Nitrate yield and Faraday efficiency of the modified electrode at different voltages.

[0033] Figure 5 CoS2 / PVIPS / PPyNT S Nitrate yield and Faradaic efficiency of the modified electrode after six consecutive catalytic reactions for two hours at the same voltage.

[0034] Figure 6 For carbon cloth (CC) and CoS2 / PVIPS / PPyNT S Nitrate production and Faradaic efficiency values ​​at 1.75 V (vs. RHE) under different conditions. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with preferred embodiments and drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0036] Example 1 The preparation method of CoS2 / PVIPS / PPyNTs nanomaterial (I) is as follows:

[0037] 1) Preparation of polypyrrole (PPyNTs) nanotubes: 0.05 g of methyl orange was added to 30 mL of deionized water, and after ultrasonic dispersion, 0.249 g of FeCl3·6H2O was added. After further ultrasonic dispersion, 0.115 mL of pyrrole (Py) was added, and the mixture was stirred in an ice-water bath for 6 h. The mixture was centrifuged, washed, and vacuum dried to obtain PPyNTs nanotubes.

[0038] 2) PPyNT S -CH2-CH=CH2 nanotubes: Add 0.03 g PPyNT to 50 mL N,N-dimethylformamide (DMF) S Nanotubes were ultrasonically dispersed, and then 0.3 mL of propylene chloride (Cl-CH2-CH=CH2) and 0.1 g of KOH were added. After ultrasonic dispersion for 5 min, the mixture was transferred to an oil bath, stirred at 60 °C for 24 h, centrifuged, washed, and dried in vacuo at 50 °C to obtain PPyNTs-CH2-CH=CH2 nanotubes.

[0039] 3) PVIPS / PPyNT S Nanotubes: Add 0.025 g PPyNT to 40 mL of anhydrous ethanol S-CH2-CH=CH2 nanotubes, ultrasonically dispersed, then added 0.2g 1-vinyl-3-propanesulfonic acid imidazole salt (VIPS) and 0.004g initiator azobisisobutyronitrile (AIBN), transferred to an oil bath, and refluxed at 80°C for 5h under nitrogen protection. After the reaction, centrifuged, washed, and vacuum dried at 50°C for 12h to obtain PVIPS / PPyNT S Nanotubes.

[0040] 4) CoS2 / PVIPS / PPyNT S Preparation of nanomaterials: Take a 100mL beaker, add 10mg PVIPS / PPyNTs and 60mL deionized water, ultrasonicate for 15 minutes to completely disperse them, then add 15.3mg cobalt chloride hexahydrate and 50.5mg thioacetamide, ultrasonicate for 5 minutes to completely disperse them. After the ultrasonicate is finished, transfer the mixed solution to a 100mL polytetrafluoroethylene stainless steel autoclave, and hydrothermally react at 200℃ for 24h. After the reaction is finished, wash the product with distilled water and ethanol, centrifuge, and vacuum dry to obtain CoS2 / PVIPS / PPyNTs. S Nanomaterials.

[0041] (II) Comparative Example:

[0042] Preparation of CoS / Co9O8 nanomaterials: Take a 100mL beaker, add 60mL deionized water, 240mg cobalt chloride hexahydrate and 270mg thioacetamide into it in sequence, ultrasonicate for 5min to make it completely mixed, then transfer the solution to a 100mL polytetrafluoroethylene stainless steel autoclave, and hydrothermally react at 200℃ for 24h. After the reaction, the product is washed with distilled water and ethanol in sequence, centrifuged and vacuum dried to obtain CoS / Co9O8 nanomaterials.

[0043] (III) Testing

[0044] 1. If Figure 1 As shown, Figure 1 a in the middle is CoS2 / PVIPS / PPyNT S Scanning electron microscope (SEM) images of nanomaterials; Figure 1 b in the figure is CoS2 / PVIPS / PPyNT S Transmission electron microscope (TEM) image of nanomaterials. Figure 1 It can be seen that the CoS2 / PVIPS / PPyNT prepared by the present invention S The surface of the nanomaterial exhibits a tubular texture.

[0045] 2. Figure 2This is the XRD diagram of CoS2 / PVIPS / PPyNTs nanomaterials. It can be seen from the figure that the present invention successfully synthesized tubular CoS2 / PVIPS / PPyNTs nanomaterials.

[0046] Example 2 Based on CoS2 / PVIPS / PPyNT S The preparation method of the NOR electrocatalytic modified electrode (I) of nanomaterials is as follows:

[0047] 1) Take 1.5 mg of the dried CoS2 / PVIPS / PPyNT prepared in Example 1 S The nanomaterial was added with 460 μL of anhydrous ethanol and 40 μL of Nafion solution, and ultrasonically dispersed for 30 min to obtain a black suspension with a concentration of 3 mg / mL, which was the composite modifier and was set aside.

[0048] 2) Electrode processing: Cut the carbon cloth into 1cm×1.5cm size for later use.

[0049] 3) Preparation of modified electrode: Use a rubber-tipped dropper to repeatedly pipette the composite modifier prepared in step 1) and apply it to the surface of a clean carbon cloth, and dry it naturally at room temperature to obtain CoS2 / PVIPS / PPyNT S Nanomaterial electrocatalytic modified electrodes.

[0050] (II) Electrochemical performance test

[0051] 1. CoS2 / PVIPS / PPyNT S Comparison of linear sweep voltammetric curves of NOR electrocatalytic modified electrodes of nanomaterials in saturated Ar and N2

[0052] Method: In an electrolytic cell containing 0.1 M KOH solution, CoS2 / PVIPS / PPyNT S The nanomaterial electrocatalytic modified electrode was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode. The experiment was carried out on a CHI1040c electrochemical workstation, and its attached computer software was used for the acquisition and processing of experimental data. The linear sweep voltammetry test was carried out in the potential range of 0.85V to 1.25V (vs. RHE), and the stable linear sweep voltammogram was recorded.

[0053] like Figure 3 As shown, CoS2 / PVIPS / PPyNT SThe linear sweep voltammetry (LSV) comparison diagram of the NOR electrocatalytic modified electrode of the nanomaterial in saturated N2 and saturated Ar, respectively. The upper curve is the linear sweep voltammetry comparison diagram under saturated N2 conditions, and the lower curve is the linear sweep voltammetry comparison diagram under saturated Ar conditions. In the potential range of 1.25V to 1.85V (vs. RHE), the current density under saturated N2 conditions is significantly higher than that under saturated Ar conditions, which indicates that the prepared CoS2 / PVIPS / PPyNT S The nanomaterial electrocatalytic modified electrode has NOR activity.

[0054] 2. CoS2 / PVIPS / PPyNT S Optimal catalytic voltage of nanomaterial-modified electrodes

[0055] CoS2 / PVIPS / PPyNT S The nanomaterial electrocatalytic modified electrode was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode. The experiment was carried out on a CHI1040c electrochemical workstation, including the collection and processing of experimental data. In a 0.1 M KOH solution, the voltage value was taken every 0.1 V in the potential range of 1.55 V to 2.05 V (vs. RHE), and a two-hour chronoamperometric test was performed.

[0056] like Figure 4 As shown, CoS2 / PVIPS / PPyNT S The nitrate yield and Faraday efficiency of the nanomaterial electrocatalytic modified electrode at different voltages. The most suitable voltage was finally determined to be 1.75V (vs. RHE), at which the catalyst modified electrode had the highest nitrate yield and higher Faraday efficiency.

[0057] 3. Catalyst stability measurement

[0058] CoS2 / PVIPS / PPyNT S The NOR electrocatalytic modified electrode of the nanomaterial was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode. The experiment was carried out on a CHI1040c electrochemical workstation, including the collection and processing of experimental data. Six two-hour chronoamperometric tests were performed continuously in a 0.1 M KOH solution at a potential of 1.75 V (vs. RHE).

[0059] Figure 5 CoS2 / PVIPS / PPyNT SThe nitrate yield and Faraday efficiency of the nanomaterial electrocatalytic modified electrode were catalyzed for six consecutive times for two hours at the same voltage. It can be seen that there was still 85% nitrate yield and Faraday efficiency value after the sixth catalysis, proving that the prepared CoS2 / PVIPS / PPyNT S Nanomaterials have good stability.

[0060] 4. CoS2 / PVIPS / PPyNT S Source of N in the products of electrocatalytic synthesis of nanomaterials

[0061] The NOR electrocatalytic modified electrode of CoS2 / PVIPS / PPyNTs nanomaterials was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode. The experiment was carried out on a CHI1040c electrochemical workstation, including the collection and processing of experimental data. Figure 6 For carbon cloth (CC) and CoS2 / PVIPS / PPyNT S Nitrate production and Faraday efficiency values ​​at 1.75 V (vs. RHE) under different conditions, in order to exclude the factors such as electrolyte, electrocatalyst, feed gas, etc. that affect the electrolysis of NO3 - No NO3 was detected in N2 saturated electrolyte (O / C) without external potential, Ar saturated electrolyte at 1.75 V (vs. RHE) and CC bottom conditions. - , thus confirming the detected NO3 - CoS2 / PVIPS / PPyNT S Produced by electrocatalytic oxidation of N2 using nanomaterials.

[0062] The above description is only a preferred embodiment of the present invention, which is only illustrative and not restrictive of the present invention. A person skilled in the art will understand that many changes, modifications and even equivalent changes may be made to the present invention within the spirit and scope defined by the claims of the present invention, but all of them will fall within the scope of protection of the present invention.

Claims

1. CoS2 / PVIPS / PPyNTs nanomaterial, characterized in that: The preparation method comprises the following steps: 1) Add methyl orange to deionized water, disperse by ultrasonic, then add FeCl3·6H2O, continue to disperse by ultrasonic, then add pyrrole, transfer to an ice water bath, stir and react for 6 h, centrifuge, wash, and dry to obtain PPyNTs nanotubes; 2) Add PPyNTs nanotubes to N,N-dimethylformamide, disperse by ultrasonication, then add propylene chloride and KOH, disperse by ultrasonication, transfer to a 60°C oil bath, stir and react for 24 hours, centrifuge, wash, and vacuum dry to obtain PPyNTs-CH2-CH=CH2 nanotubes; 3) Add PPyNTs-CH2-CH=CH2 nanotubes to anhydrous ethanol, disperse by ultrasonication, then add 1-vinyl-3-propanesulfonic acid imidazole salt and initiator to carry out reflux reaction, after the reaction is completed, centrifuge, wash, and vacuum dry to obtain PVIPS / PPyNTs nanotubes; 4) Disperse PVIPS / PPyNTs nanotubes in water, then add CoCl2·6H2O and thioacetamide in turn, stir evenly, and perform hydrothermal reaction on the obtained reaction system. The obtained product is washed with distilled water and anhydrous ethanol in turn, centrifuged, and vacuum dried to obtain CoS2 / PVIPS / PPyNTs. S Nanomaterials.

2. CoS2 / PVIPS / PPyNT according to claim 1 S Nanomaterials, characterized in that In step 3), the initiator is azobisisobutyronitrile (AIBN).

3. CoS2 / PVIPS / PPyNT according to claim 1 S Nanomaterials, characterized in that In step 3), the reflux reaction is carried out in an oil bath at 80° C. under nitrogen protection for 5 hours.

4. CoS2 / PVIPS / PPyNT according to claim 1 S Nanomaterials, characterized in that In step 4), according to the mass ratio, CoCl2·6H2O:PVIPS / PPyNT S Nanotubes = 1.5:

1.

5. CoS2 / PVIPS / PPyNT according to claim 1 S Nanomaterials, characterized in that In step 4), the hydrothermal reaction is as follows: placing the obtained reaction system in a Teflon reactor with a polytetrafluoroethylene liner and performing a hydrothermal reaction at 200° C. for 24 hours.

6. CoS2 / PVIPS / PPyNT according to any one of claims 1 to 5 S The NOR electrocatalytic modified electrode of nanomaterials is characterized by: The CoS2 / PVIPS / PPyNT according to any one of claims 1 to 5 is used as a carbon cloth substrate. S CoS2 / PVIPS / PPyNT made of nanotubes attached to carbon cloth S Modified electrode.

7. The CoS2 / PVIPS / PPyNT-based method according to claim 6 S The method for preparing a NOR electrocatalytic modified electrode of nanomaterials is characterized in that: The preparation method comprises the following steps: 1) CoS2 / PVIPS / PPyNT as described in any one of claims 1 to 5 S The nanomaterial is ultrasonically dispersed in a mixed solution of anhydrous ethanol and Nafion to obtain a uniformly dispersed composite modifier; 2) Apply the evenly dispersed composite modifier to the clean carbon cloth surface and dry it at room temperature to obtain CoS2 / PVIPS / PPyNT S Modified electrode.

8. The preparation method according to claim 7, characterized in that: By volume ratio, anhydrous ethanol:Nafion solution=92:

8.

9. The CoS2 / PVIPS / PPyNT-based method according to claim 6 S Application of NOR electrocatalytic modified electrodes of nanomaterials in electrocatalytic nitrogen oxidation.

10. The use according to claim 9, characterized in that: The method is as follows: the CoS2 / PVIPS / PPyNT-based S The NOR electrocatalytic modified electrode of nanomaterials was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode to form a three-electrode system to achieve electrocatalytic oxidation of nitrogen in 0.1 M potassium hydroxide solution.

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