NiSA / NiNP-NC catalyst as well as preparation method and application thereof

Abstract

The invention discloses a NiSA / NiNP-NC catalyst as well as a preparation method and application thereof, the preparation method of the catalyst comprises the following steps: mixing melamine and nickel salt in ethanol, drying by distillation in a water bath drying manner, and carrying out high-temperature pyrolysis on the obtained solid in a nitrogen atmosphere to form a porous carbon material; finally, the obtained carbon material is added into a nitric acid solution, heating, stirring, etching, suction filtration, washing and drying are conducted, then the catalyst (NiSA / NiNP-NC) is obtained, and the catalyst comprises a nitrogen-doped carbon matrix, nickel monatomic NiSA loaded on the carbon matrix and metallic nickel NiNP limited in the carbon matrix. The NiSA / NiNP-NC catalyst provided by the invention is a catalyst with many active sites and excellent oxygen reduction performance, can realize high selectivity of synthesis of hydrogen peroxide by two-electron oxygen reduction reaction at room temperature, and is applied to degradation of pollutants in wastewater as an electro-Fenton catalyst material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials and environment, and particularly relates to a kind of Ni SA / Ni NP -NC catalyst and its preparation method and application. BACKGROUND

[0002] Hydrogen peroxide has become an irreplaceable strategic chemical raw material in modern industry, medical health, environmental protection and emerging technology fields due to its environmental friendliness, strong oxidizing property, relative safety and multifunctionality. It plays a crucial role in promoting the progress of green chemistry, ensuring public health and safety, and promoting the development of cutting-edge technologies. The continuous optimization of production technology, especially the development of green and low-energy electrochemical synthesis method, will further enhance its competitiveness and consolidate its important position. To achieve efficient and practical electric hydrogen peroxide, a safe, environmentally friendly and low-energy method is needed to synthesize hydrogen peroxide.

[0003] Single-atom catalysts have high selectivity and activity. Single-atom catalysts have isolated atomic dispersion of metal active sites, usually transition metals such as iron, cobalt, nickel, manganese, platinum, etc. anchored in carbon-based carriers to form metal-nitrogen-carbon structures. This structure inhibits the four-electron oxygen reduction pathway. The lack of adjacent metal atoms prevents oxygen from dissociating and adsorbing and completely breaking the oxygen-oxygen bond, avoiding complete reduction of oxygen to water, promoting the two-electron oxygen reduction pathway. Isolated metal sites allow oxygen to adsorb in end-on or side-on form, accepting two electrons and combining with two protons to selectively generate hydrogen peroxide. Carrier doping of nitrogen, oxygen, sulfur, boron and other heteroatoms can regulate metal electronic structure, optimize key intermediate peroxide adsorption energy, achieve high activity and high selectivity, and surpass traditional catalysts in alkaline, neutral and acidic media. SUMMARY

[0004] In view of the above technical problems existing in the prior art, the purpose of the present application is to provide a kind of Ni SA / Ni NP -NC and its preparation method and application. The Ni SA / Ni NP -NC catalyst of the present application is a catalyst with multiple active sites and excellent oxygen reduction performance, which can achieve high selectivity of two-electron oxygen reduction reaction to synthesize hydrogen peroxide at room temperature. At the same time, as an electro-Fenton catalyst material, it is applied to degrade pollutants in wastewater.

[0005] The technical solution adopted by the present application is as follows:

[0006] A preparation method of a kind of Ni SA / Ni NP -NC catalyst, comprising the following steps:

[0007] S1: melamine and nickel salt are added into ethanol at the same time, mixed well to obtain a mixed solution A;

[0008] S2: the mixed solution A is placed in a water bath heating environment, and the mixed solution A is evaporated by water bath evaporation to obtain a solid B;

[0009] S3: pyrolysis of the solid B under a nitrogen atmosphere, carbonization of melamine in the solid B during pyrolysis and release of gas to form a porous carbon material;

[0010] S4: the carbon material obtained in step S3 is added into a nitric acid solution, heated and stirred for etching, suction filtration, washing and drying, and the obtained catalyst is marked as Ni SA / Ni NP -NC, the catalyst comprising a nitrogen-doped carbon matrix, nickel monatomic Ni SA supported on the carbon matrix and metallic nickel Ni NP limited in the carbon matrix.

[0011] Further, in step S1, the nickel source is one of nickel nitrate, nickel acetate, nickel chloride and nickel sulfate, preferably nickel acetate.

[0012] Further, in step S1, the feeding ratio of melamine and nickel salt is 1g: 0.85-1.85mmol, preferably 1g: 1.125-1.25mmol.

[0013] Further, in step S2, the temperature of the water bath is 60-80℃.

[0014] Further, in step S3, the pyrolysis temperature is 700-900℃, and the time is 2-4h.

[0015] Further, in step S4, the concentration of the nitric acid is 8-10mol / L, the etching temperature is 70-90℃, and the etching time is 2-4h.

[0016] The application also discloses the application of the Ni SA / Ni NP -NC catalyst, and the application of the Ni SA / Ni NP -NC catalyst in electrocatalytic production of hydrogen peroxide or treatment of pollutant wastewater by electrocatalytic Fenton reaction.

[0017] Further, the application provides the application of the Ni SA / Ni NP -NC catalyst in electrocatalytic production of hydrogen peroxide, which comprises the following steps:

[0018] Step 1: the Ni SA / Ni NP -NC catalyst is used in electrocatalytic production of hydrogen peroxide.-NC catalyst is supported on carbon paper and used as cathode material;

[0019] Step 2: Using the electrochemical working device as the electrochemical generator, a three-electrode measurement system is employed. The cathode material from Step 1 is used as the working electrode, a platinum sheet as the anode, and saturated calomel as the reference electrode. The anode and cathode are placed parallel to each other in the electrolytic cell. The working cathode electrode and the counter anode electrode are connected to a DC power supply via wires. Oxygen is continuously introduced into the solution, and the mixture is continuously stirred.

[0020] Furthermore, in the application of electrocatalytic hydrogen peroxide production, a constant potential mode test is used, conducted at a potential of -0.7 vs. SCE, with sodium sulfate as the electrolyte and an electrolyte concentration of 0.05 mol / L.

[0021] In this invention, the principle of the electro-Fenton degradation method for pollutants in water is as follows: Under constant potential output conditions, the introduced oxygen undergoes a two-electron oxygen reduction reaction at the cathode to produce hydrogen peroxide. Then, the hydrogen peroxide reacts with Fe... 2+ The reaction generates hydroxyl radicals, which effectively promote the degradation and mineralization of pollutants.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) Ni obtained by the present invention SA / Ni NP -NC catalysts, used for the electrocatalytic synthesis of hydrogen peroxide, possess a large number of Ni active sites existing in the form of single atoms, and a large number of oxygen-containing functional groups exist around the Ni single atoms. By utilizing the synergistic effect of these two, the adsorption of oxygen on the catalyst surface is improved, which helps to regulate the adsorption energy of oxygen intermediates and further improves the selectivity of hydrogen peroxide.

[0024] (2) Using different nickel salts as the nickel source and melamine as the nitrogen and carbon source, the final material is obtained through high-temperature calcination and acid leaching. During the pyrolysis process, melamine is converted into g-C3N4, which further carbonizes and releases CN. x Gases such as NH3 are used. These gases can activate carbon materials to form porous structures and also introduce oxygen functional groups. Most of the generated nickel particles are removed by high-temperature (900℃) evaporation and acid leaching to obtain N-loaded materials. iSA / Ni NP The porous carbon material is described. The catalyst prepared by this invention exhibits excellent selectivity for hydrogen peroxide, significantly increases the yield of hydrogen peroxide, and can be used in electro-Fenton systems for the efficient degradation of various pollutants in wastewater.

[0025] (3) In Ni SA / Ni NP The NC catalyst exhibits extremely high degradation rates for pollutants, demonstrating promising application prospects and versatility. Attached Figure Description

[0026] Figure 1 Ni in this invention SA / Ni NP -NC-1, Ni SA / Ni NP -NC-2, Ni SA / Ni NP XRD pattern of NC-3;

[0027] Figure 2 Ni in Embodiments 1-4 of the present invention SA / Ni NP -NC-1, Ni SA / Ni NP -NC-2, Ni SA / Ni NP -NC-3, Ni SA / Ni NP SEM image of NC-4;

[0028] Figure 3 Ni in this invention SA / Ni NP -TEM image and EDX mapping image of NC-1;

[0029] Figure 4 Ni in this invention SA / Ni NP -TEM and EDX mapping images of NC-2;

[0030] Figure 5 Ni in this invention SA / Ni NP -TEM and EDX mapping images of NC-3;

[0031] Figure 6 Comparison of hydrogen peroxide yield curves with electrolysis time when the catalysts obtained in Examples 1-4 are used respectively for electrocatalytic hydrogen peroxide production reaction.

[0032] Figure 7 Comparison of hydrogen peroxide production curves with electrolysis time when catalysts obtained in Comparative Examples 1-6 are used respectively for electrocatalytic hydrogen peroxide production reaction.

[0033] Figure 8 Comparison of hydrogen peroxide production curves with electrolysis time when the catalysts obtained in Example 1 and Comparative Example 7 are used respectively for electrocatalytic hydrogen peroxide production reaction.

[0034] Figure 9aThe results show the comparison of the electrolysis performance of atrazine with electrolysis time when the catalysts obtained in Examples 1-4 are used respectively.

[0035] Figure 9b The results show the comparison of the electrolysis performance of atrazine with electrolysis time when the catalysts obtained in Comparative Examples 1-6 are used respectively. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0037] Example 1, Catalyst Ni SA / Ni NP The preparation of -NC-1 includes the following steps:

[0038] 1) Add 4g of melamine and 5mmol of Ni(CH3COO)2·6H2O to 20mL of ethanol respectively. Evaporate the solution at 70℃ by water bath evaporation. Grind the obtained solid and collect the powder in a ceramic boat. Place the boat in the center of a tube furnace and heat it to 900℃ at 5℃ / min under N2 atmosphere. Keep it at 900℃ for 3 hours to obtain porous carbon material.

[0039] 2) The carbon material obtained in step 1) was immersed in a 10 mol / L HNO3 aqueous solution and etched by stirring at 80°C for 3 hours. After filtration, washing, and drying, Ni was obtained. SA / Ni NP -NC-1 catalyst.

[0040] Example 2

[0041] The catalyst preparation steps in Example 2 were the same as in Example 1, except that Ni(CH3COO)2·6H2O was replaced with an equal molar amount of Ni(NO3)2·6H2O. All other conditions remained unchanged, and Ni was finally obtained. SA / Ni NP -NC-2 catalyst.

[0042] Example 3

[0043] The catalyst preparation steps in Example 3 were repeated in Example 1, except that Ni(CH3COO)2·6H2O was replaced with an equimolar amount of NiCl2·6H2O. All other conditions remained unchanged, ultimately yielding Ni... SA / Ni NP -NC-3 catalyst.

[0044] Example 4

[0045] The catalyst preparation steps in Example 3 were the same as in Example 1, except that "Ni(CH3COO)2·6H2O was replaced with an equimolar amount of Ni(SO4)2·6H2O", while all other conditions remained unchanged, ultimately yielding Ni SA / Ni NP -NC-4 catalyst.

[0046] Comparative Examples 1-6

[0047] The preparation steps of the catalysts in Comparative Examples 1-6 were repeated in Example 1, except that the amount of Ni(CH3COO)2·6H2O was replaced with 0.5 mmol, 1.5 mmol, 2.5 mmol, 3.5 mmol, 4.5 mmol and 6.5 mmol respectively, while the other conditions remained unchanged.

[0048] Comparative Example 7

[0049] The catalyst preparation steps in Comparative Example 7 were repeated in Example 1, except that step 2 was omitted, while the other conditions remained unchanged.

[0050] The catalysts prepared in Comparative Examples 1-7 were labeled as Ni SA / Ni NP -NC-5 catalyst, Ni SA / Ni NP -NC-6 catalyst, Ni SA / Ni NP -NC-7 catalyst, Ni SA / Ni NP -NC-8 catalyst, Ni SA / Ni NP -NC-9 catalyst, Ni SA / Ni NP -NC-10 catalyst and Ni SA / Ni NP -NC-11 catalyst.

[0051] Figure 1 For Ni SA / Ni NP -NC-1, Ni SA / Ni NP -NC-2, Ni SA / Ni NP The XRD patterns of -NC-3 all showed diffraction peaks of carbon. In addition, a small amount of nickel particles were detected and no characteristic peaks of nickel oxide were detected, indicating that the residual nickel may exist in the form of single atoms.

[0052] Figure 2 For Ni SA / Ni NP -NC-1, NiSA / Ni NP -NC-2, Ni SA / Ni NP -NC-3, Ni SA / Ni NP SEM image of NC-4 Figure 2 Ni in (a) SA / Ni NP The -NC-1 sample exhibits a folded, banded structure, displaying a complex state of folded interweaving. Figure 2 (b)Ni in SA / Ni NP The NC-2 sample exhibits a distinct fibrous morphology and a relatively smooth surface. Figure 2 (c)Ni in SA / Ni NP The NC-3 sample exhibits a partially fibrous structure with more irregularly shaped fragments. Figure 2 (d) Ni in SA / Ni NP The -NC-4 sample exhibited poor structural regularity, with irregular distribution of blocky, flaky, and aggregated particles.

[0053] Figures 3-5 Ni SA / Ni NP -NC-1, Ni SA / Ni NP -NC-2, Ni SA / Ni NP TEM and EDX mapping images of NC-3. A small number of nickel particles were observed in the TEM image, and the mapping image confirms the presence of C, N, and Ni in the sample. SA / Ni NP -NC-1, Ni SA / Ni NP -NC2, Ni SA / Ni NP -NC-3 is evenly distributed. Ni SA / Ni NP -NC-1 shows a more uniform distribution of Ni element in the EDX mapping plot compared to Ni. SA / Ni NP -NC-2, Ni SA / Ni NP -NC-3 and Ni SA / Ni NP -NC-4, Ni SA / Ni NP The acetate ions in -NC-1 are beneficial for nickel dispersion and anchoring in the carbon mesh. The nickel content in the sample was determined by ICP-MS.SA / Ni NP The nickel loading of the -NC-1 catalyst is 1.21 wt%, Ni SA / Ni NP -NC-2 and Ni SA / Ni NP The nickel loadings in -NC-3 are 1.13 wt% and 0.77 wt%, respectively.

[0054] Application Example 1:

[0055] The electro-hydrogen peroxide production performance of the catalysts in Examples 1-4 and Comparative Examples 1-6 was verified respectively:

[0056] Take 20 mg of catalyst, 50 μL of 60 wt% polytetrafluoroethylene dispersion, 2 ml of isopropanol and 0.4 ml of water, and sonicate for 30 min to disperse evenly to obtain catalyst slurry. Finally, coat the slurry on carbon paper (2 cm × 2 cm), and dry to obtain cathode.

[0057] The electrochemical generator was used as the electrochemical working device, and a three-electrode measurement system was adopted in a 250 mL single-chamber electrolytic cell. The catalyst-coated carbon paper was used as the cathode, the platinum sheet as the anode, and the saturated calomel as the reference electrode. The anode and cathode were placed parallel to each other in the electrolytic cell, and the other end of the anode and cathode were connected to the corresponding electrodes of the DC power supply. The electrolyte was a 0.05 M sodium sulfate aqueous solution with pH adjusted to 3, and the electrolyte volume was 200 mL. Oxygen was continuously introduced into the solution at a flow rate of 1 L / h, and the mixture was continuously stirred. The oxygen reduction potential range was -0.7 V vs. SCE.

[0058] Following the experimental procedure of Application Example 1, the comparison results of the hydrogen peroxide yield versus electrolysis time when the catalysts obtained in Examples 1-4 were used respectively are shown in the figure. Figure 6 As shown, Ni SA / Ni NP The higher nickel content in NC-1 promotes the production of hydrogen peroxide.

[0059] Following the experimental procedure of Application Example 1, when the catalysts obtained in Comparative Examples 1-6 were used respectively, the comparison results of the hydrogen peroxide production change curves with electrolysis time are shown below. Figure 7 As shown, Figure 7 The effects of catalysts prepared with different contents of nickel acetate precursor on hydrogen peroxide production were compared.

[0060] Following the experimental procedure of Application Example 1, the comparison results of the hydrogen peroxide yield versus electrolysis time when the catalysts obtained in Example 1 and Comparative Example 7 were used respectively are shown in the figure. Figure 8 As shown. (Through) Figure 8 The conclusion that can be drawn from the comparison results is: NiSA / Ni NP -NC-11 contains a large number of Ni particles without undergoing nitric acid etching. The presence of these large Ni particles may inhibit the two-electron oxygen reduction activity of some materials, thus leading to a decrease in the performance of hydrogen peroxide.

[0061] Application Example 2:

[0062] Ni SA / Ni NP - Application of NC catalysts in electro-Fenton systems:

[0063] Take 20 mg of catalyst, 50 μL of 60 wt% polytetrafluoroethylene dispersion, 2 ml of isopropanol and 0.4 ml of water, and sonicate for 30 min to disperse evenly to obtain catalyst slurry. Finally, coat the slurry on carbon paper (2 cm × 2 cm), and dry to obtain cathode.

[0064] The electrochemical generator was used as the electrochemical operating device, employing a three-electrode measurement system in a 250 ml single-chamber electrolytic cell. Catalyst-coated carbon paper served as the cathode, a platinum sheet as the anode, and saturated calomel as the reference electrode. The anode and cathode were placed parallel to each other in the electrolytic cell, with the other ends connected to the corresponding electrodes of a DC power supply. The electrolyte was a 0.05 M sodium sulfate aqueous solution adjusted to pH 3, with 1 mM Fe added to the electrolyte to a final concentration. 2+ With a final concentration of 10 mg / L atrazine and an electrolyte volume of 200 mL, oxygen was continuously introduced into the solution at a flow rate of 1 L / h, and the mixture was continuously stirred. The oxygen reduction potential range was -0.7 V vs. SCE.

[0065] Following the experimental procedure of Application Example 1, when the catalysts obtained in Examples 1-4 were selected respectively, the electrolysis of atrazine with electrolysis time is shown in the figure. Figure 9a .

[0066] Following the experimental procedure of Application Example 1, when the catalysts obtained in Comparative Examples 1-6 were selected respectively, the electrolysis behavior of atrazine with electrolysis time is shown in the figure. Figure 9a .

[0067] like Figure 9a-9b As shown, Ni SA / Ni NP -NC-1 exhibits good performance in degrading 10 mg / L atrazine; atrazine is completely removed after 60 min of reaction. This result indicates that Ni SA / Ni NP -NC-1 is a promising electro-Fenton cathode material.

[0068] In the catalyst prepared by the method of the present invention, the presence of oxygen-containing functional groups enhances the two-electron oxygen reduction activity and selectivity of the material, thereby generating more hydrogen peroxide at the electro-Fenton cathode and further promoting the electro-Fenton reaction.

[0069] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A Ni SA / Ni NP The method for preparing -NC catalyst is characterized by, Includes the following steps: S1: Add melamine and nickel salt to ethanol and mix thoroughly to obtain mixture A; S2: Place the mixture A in a water bath heating environment and evaporate the mixture A by water bath evaporation to obtain solid B; S3: Pyrolyze solid B under a nitrogen atmosphere, causing the melamine in solid B to carbonize and release gas during the pyrolysis process, forming a porous carbon material; S4: The carbon material obtained in step S3 is added to a nitric acid solution, heated and stirred for etching, filtered, washed, and dried. The resulting catalyst is labeled as Ni. SA / Ni NP -NC, the catalyst includes a nitrogen-doped carbon matrix and a single-atom nickel supported on the carbon matrix. SA and metallic nickel (Ni) confined in a carbon matrix NP .

2. A Ni as described in claim 1 SA / Ni NP The method for preparing -NC catalyst is characterized by, In step S1, the nickel source is one of nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate, preferably nickel acetate.

3. A Ni as described in claim 1 SA / Ni NP The method for preparing -NC catalyst is characterized by, In step S1, the ratio of melamine to nickel salt is 1g:0.85-1.85mmol, preferably 1g:1.125-1.25mmol.

4. A Ni as described in claim 1 SA / Ni NP The method for preparing -NC catalyst is characterized by, In step S2, the temperature of the water bath is 60-80℃.

5. A Ni as described in claim 1 SA / Ni NP The method for preparing -NC catalyst is characterized by, In step S3, the pyrolysis temperature is 700-900℃ and the duration is 2-4h.

6. A Ni as described in claim 1 SA / Ni NP The method for preparing -NC catalyst is characterized by, In step S4, the concentration of nitric acid is 8-10 mol / L, the etching temperature is 70-90℃, and the etching time is 2-4 h.

7. A Ni prepared by the method according to any one of claims 1-6 SA / Ni NP -NC catalyst.

8. The Ni as described in claim 7 SA / Ni NP The application of -NC catalysts is characterized by... The Ni SA / Ni NP -NC catalysts are used for the electrocatalytic production of hydrogen peroxide or for the treatment of pollutant wastewater via the electrocatalytic Fenton reaction.

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