A Pt CSA / Cu2O / NF composite material and its application in electrocatalytic reduction of nitrate to ammonia

Abstract

The application discloses a kind of Pt CSA / Cu2O / NF composite material and its application in electrocatalytic reduction of nitrate to ammonia, the Pt CSA Preparation method of the Pt / Cu2O / NF composite material is: Cu (OH) 2 / NF electrode sheet is obtained by depositing Cu (OH) 2 on nickel foam NF first, calcination under high temperature in nitrogen atmosphere, the obtained CuO / NF electrode sheet is cathode, electrolyte solution is used as electrolyte solution, and anode electrode is used to carry out electroreduction under preset constant voltage, so that CuO on the cathode is converted into Cu2O, Cu2O / NF electrode sheet is obtained, finally, Pt is loaded on the electrode sheet by electrodeposition, and the preparation is completed.The application precisely controls atomic dispersion of platinum by in-situ electrochemical deposition method, constructs single atom-nanocluster gradient distribution structure (Pt CSA / Cu2O / NF), realizes ultra-low loading of noble metal platinum, and has good application effect in electrocatalytic reduction of nitrate to ammonia.

Description

TECHNICAL FIELD

[0001] The application relates to a Pt CSA / Cu2O / NF composite material and application thereof in electrocatalytic reduction of nitrate to ammonia. BACKGROUND

[0002] Nitrogen cycle is a basic biogeochemical process for maintaining life on earth, and nitrate is an important intermediate in the nitrogen cycle. The concentration of nitrate in nature is usually at a relatively low level, while human activities, especially agricultural activities and industrial emissions, greatly increase the emission of nitrate. About 26.22 million tons of nitrate are discharged into water bodies in various ways every year, resulting in a sharp rise in the concentration of nitrate in water bodies, which in turn leads to a series of environmental and health problems.

[0003] Commonly used nitrate reduction catalysts mainly include noble metals (such as palladium and platinum) and transition metal oxides, which are widely studied due to their excellent catalytic performance. However, due to the high cost, the application thereof in large-scale application is limited. SUMMARY

[0004] In view of the above technical problems existing in the prior art, the purpose of the present application is to provide a Pt CSA / Cu2O / NF composite material and application thereof in electrocatalytic reduction of nitrate to ammonia.

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

[0006] A Pt CSA / Cu2O / NF composite material is prepared by the following steps:

[0007] 1) Preparation of CuO / NF: After pretreatment by cleaning, the pretreated foam nickel NF is used as a cathode, a Cu(NO3)2 aqueous solution is used as an electrolyte, and a platinum sheet is used as an anode counter electrode to perform electrochemical deposition under a preset constant voltage, so that Cu(OH)2 is deposited on the foam nickel NF to obtain a Cu(OH)2 / NF electrode sheet. The Cu(OH)2 / NF electrode sheet is calcined at high temperature in a nitrogen atmosphere to obtain a CuO / NF electrode sheet;

[0008] 2) Electro-reduction treatment: the CuO / NF electrode sheet in step 1) is used as a cathode, an electrolyte solution is used as an electrolyte, and a platinum sheet is used as an anode counter electrode to perform electro-reduction under a preset constant voltage, so that the CuO on the cathode is converted into Cu2O to obtain a Cu2O / NF electrode sheet;

[0009] 3) Pt loading on Cu2O / NF: dissolve the platinum source in the electrolyte solution, take the Cu2O / NF electrode sheet obtained in step 2) as the cathode, take a platinum sheet as the anode counter electrode, carry out electrodeposition at a preset constant voltage, so that the platinum source is reduced into Pt single atoms and clusters coexisting form, denoted as Pt CSA , Pt CSA loaded on the Cu2O / NF electrode sheet, and after natural air drying, a Pt CSA / Cu2O / NF composite material is obtained.

[0010] Further, in step 1), the concentration of the Cu(NO3)2 aqueous solution is 0.04-0.06 M, the constant voltage is 0.2-0.4 V, and the electrochemical deposition time is 0.5-2 h.

[0011] Further, in step 2), the electrolyte is a 0.05-0.2 M aqueous sodium sulfate solution, the voltage for electro-reduction is -0.2 V to -0.4 V, and the electro-reduction time is 15-30 minutes.

[0012] Further, in step 3), the specific process is as follows: taking the CuO / NF electrode sheet as the working electrode, a platinum sheet as the counter electrode, and a 0.05-0.2 M aqueous sodium sulfate solution as the electrolyte, the platinum source is chloroplatinic acid hexahydrate, and the amount of Pt in the platinum source is 0.19-0.4 mg / cm 2 , calculated based on the electrode area of the foam nickel (NF) substrate; the constant voltage for electrodeposition is -0.1 V to -0.3 V, and the electrodeposition time is 10-30 minutes.

[0013] Further, in step 1), the high-temperature calcination temperature is 500-600℃, and the calcination time is 1-3 h.

[0014] The application also provides the use of the Pt CSA / Cu2O / NF composite material in electrocatalytic reduction of nitrate to ammonia. CSA The application also provides the use of the Pt CSA / Cu2O / NF composite material in electrocatalytic reduction of nitrate to ammonia.

[0015] Further, in the reaction process of electrocatalytic reduction of nitrate to ammonia, the constant voltage potential is -0.3 V to -0.4 V, preferably -0.35 V to -0.39 V.

[0016] Further, the electrolyte is a 0.05-0.3 M aqueous sodium sulfate solution.

[0017] Compared with the prior art, the present application has the beneficial effects that:

[0018] 1) The present application utilizes Pt CSA / Cu2O / NF composite electrode, through an electrochemical reduction method, can convert the difficult-to-degrade nitrate pollutants in water into ammonia at a low potential (-0.39 V vs. RHE), thereby effectively removing the nitrate pollutants in water, simple operation, convenient management, and wide social and economic benefits.

[0019] 2) The present application precisely controls the atomic dispersion of platinum by an in-situ electrochemical deposition method, constructs a single atom-nanocluster gradient distribution structure (Pt CSA / Cu2O / NF), realizes ultra-low loading of noble metal platinum (only 1 / 75 of traditional platinum-based catalysts), greatly improves the atomic utilization rate, and significantly alleviates the industrialization bottleneck problem of high-cost noble metal catalysts.

[0020] 3) The Pt CSA / Cu2O / NF composite electrode applied in the present application is synthesized by a green and environmentally friendly method, has the characteristics of many catalytic active sites and long service life, has ultra-high catalytic removal and degradation performance for nitrate pollutants, and has the characteristics of long catalytic life, and has very broad application prospects in the application of electrocatalytic treatment of nitrate in wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structural schematic diagram of the device for electrocatalytic reduction of nitrate to ammonia used in the present application;

[0022] Figure 2 is a scanning electron microscope image of the Pt CSA / Cu2O / NF composite material prepared in Example 1;

[0023] Figure 3 is a graph showing the change of the concentration of each substance in the catholyte over time in the electrocatalytic reaction of the Pt CSA / Cu2O / NF prepared in Example 1 for reducing nitrate in 4 hours;

[0024] Figure 4 is a comparison chart of the effect of reducing nitrate to ammonia in Examples 1-5;

[0025] Figure 5 is a comparison chart of the effect of reducing nitrate to ammonia in the electrocatalytic reaction when the cathode uses the composite material of Examples 1, 8-9 and the nickel foam substrate, respectively; Figure 5 The histogram is the selectivity result, and the dotted line chart is the conversion rate result.

[0026] Figure 6In Example 10, Pt was used 10 times. CSA Figure showing the results of the electrocatalytic reduction reaction of the Cu2O / NF composite material. Detailed Implementation

[0027] 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.

[0028] The following schematic diagrams show the structure of the electrocatalytic reduction device for nitrate to ammonia used in Examples 1-7. Figure 1 As shown.

[0029] like Figure 1 As shown, the electrocatalytic reduction device for nitrate to ammonia includes an electrolytic cell and an electrochemical workstation. The electrolytic cell includes an anolyte and a counter electrode for storing the anolyte, a cathode for storing the catholyte, a working electrode, and a reference electrode (the cathode and reference electrodes are connected), and a cation exchange membrane.

[0030] A sampling port is provided at the top of the cathode cell; a connecting pipe is provided at the bottom of the anode cell and the cathode cell; a cation exchange membrane separating the anode cell and the cathode cell is provided in the connecting pipe. A platinum electrode is used as the counter electrode; an Ag / AgCl electrode is used as the reference electrode; and the Pt electrode provided in Example 1 is used as the working electrode. CSA The electrode is a Cu₂O / NF composite material; the anolyte is an aqueous solution of sodium sulfate (0.1 mol / L); the catholyte is a mixed aqueous solution of sodium sulfate and sodium nitrate (0.1 mol / L sodium sulfate and 50 mg / L sodium nitrate). The counter electrode, working electrode, and reference electrode are all connected to the electrochemical workstation.

[0031] The electrode area of ​​both the counter electrode and the working electrode is 4 cm². 2 (2cm × 2cm); an Ag / AgCl electrode is used as a reference electrode, with an electrode spacing of 8cm. The reaction volume of the electrolyte in the cathode cell is 150ml. The reaction volume of the electrolyte in the anolyte cell is 150ml.

[0032] Example 1

[0033] A method using Pt CSA A method for the electrocatalytic reduction of nitrate to ammonia using Cu2O / NF composite materials; this method utilizes the electrocatalytic reduction of nitrate to achieve nitrate degradation; and it uses Pt. CSA The preparation method of Cu2O / NF composite material includes the following steps:

[0034] 1) Preparation of Cu(OH)2 / NF electrode sheet: First, the cut foam nickel was placed in a 3 mol / L hydrochloric acid solution and ultrasonically cleaned for half an hour. After cleaning, it was washed with deionized water until it was neutral, then washed with ethanol three times and dried. Then, with the foam nickel as the cathode, the platinum sheet as the anode, and the silver / silver chloride (Ag / AgCl) electrode as the reference electrode, 0.475 g of copper nitrate trihydrate solid was dissolved in deionized water to prepare a 0.05 mol / L copper nitrate electrolyte. The electrodeposition was carried out at a constant voltage of 0.31 V vs. RHE, and the electrodeposition time was 1 hour, to obtain the Cu(OH)2 / NF electrode sheet.

[0035] 2) Preparation of Cu2O / NF electrode sheet: The Cu(OH)2 / NF electrode sheet was calcined at 550°C for 2h under a nitrogen atmosphere to obtain a CuO / NF electrode sheet. Then, with the CuO / NF electrode sheet as the cathode, the platinum sheet as the anode, and the silver / silver chloride (Ag / AgCl) electrode as the reference electrode, the electro-reduction was carried out in a 0.1 mol / L sodium sulfate solution at a constant voltage of -0.39 V vs. RHE, and the electrolysis time was 15 minutes, to obtain the Cu2O / NF electrode sheet.

[0036] 3) Preparation of Pt CSA / Cu2O / NF composite material: 4.1 mg of chloroplatinic acid hexahydrate was dissolved in 50 mL of 0.1 mol / L Na2SO4 solution at room temperature to obtain the solution as the electrolyte. Then, with the Cu2O / NF electrode sheet as the cathode, the platinum sheet as the anode, and the silver / silver chloride (Ag / AgCl) electrode as the reference electrode, the electrodeposition was carried out in the prepared electrolyte at a constant voltage of -0.19 V vs. RHE for 15 minutes, to finally obtain the Pt CSA / Cu2O / NF composite material.

[0037] The Pt CSA / Cu2O / NF composite material of Example 1 was used in the method of electrocatalytic reduction of nitrate to ammonia, and the specific process was as follows:

[0038] An electrocatalytic reduction of nitrate to ammonia device with a H-shaped two-chamber structure as shown in Figure 1 was constructed, and the Pt CSA / Cu2O / NF electrode sheet composite material prepared in Example 1 was used as the cathode working electrode, and the platinum electrode was used as the anode counter electrode. The electrode area of the working electrode and the counter electrode was both 4 cm 2The cathode and anode are each 2cm x 2cm, with an Ag / AgCl electrode as the reference electrode. The electrode spacing between the cathode and anode is 8cm. The constant voltage is -0.39V vs. RHE. The electrolyte in the cathode cell is a mixed aqueous solution of sodium sulfate and sodium nitrate (sodium sulfate concentration is 0.1mol / L, and sodium nitrate content is 50mg / L). The counter electrode, working electrode, and reference electrode are all connected to the electrochemical workstation.

[0039] Simulating natural inorganic wastewater, the reaction volume of the electrolyte in the cathode cell was 150 ml. The electrolyte in the anode cell was a 0.1 mol / L sodium sulfate aqueous solution, with a reaction volume of 150 ml. Samples of the electrolyte in the cathode cell were taken and analyzed at different time points during the electrocatalytic reaction. The results of the electrocatalytic reaction at each time point are shown in Table 1. The results after 4 hours of electrocatalytic reaction are shown in... Figure 4 As shown in Table 2.

[0040] Pt prepared in Example 1 CSA The changes in the concentrations of various substances in the catholyte over time during the electrocatalytic reduction of nitrate by / Cu2O / NF within 4 hours are shown in the figure. Figure 3 .from Figure 3 It can be seen that nitrate is completely converted after 120 min of electrocatalytic reaction, and the selectivity of ammonium ions is close to 100%.

[0041] Examples 2-5:

[0042] The experimental procedures of Examples 2-5 are the same as those of Example 1, except that "Pt" CSA In the experiment of electrocatalytic reduction of nitrate to ammonia using the Cu2O / NF composite material, the constant voltage of the electrocatalytic reaction was replaced from -0.39V vs. RHE to -0.19V vs. RHE, -0.29V vs. RHE, -0.49V vs. RHE, and -0.59V vs. RHE", with other conditions remaining unchanged. The experimental results are shown in Table 1 for each time period, and the results after 4 hours of electrocatalytic reaction are shown in Table 2. Figure 4 As shown in Table 2.

[0043] Table 1. Pt CSA The conversion rate of nitrate to ammonia by the Cu2O / NF composite electrode at different potentials and time periods

[0044]

[0045] Table 2. Pt CSA The selectivity of ammonia ions in the electrocatalytic reduction of nitrate to ammonia by the Cu2O / NF composite electrode at different potentials for 4 hours was observed.

[0046]

[0047] From Table 1, Table 2 and Figure 3 It can be seen that the Pt CSA / Cu2O / NF composite material can exhibit excellent nitrate reduction performance at a low working potential of -0.39 V vs. RHE, removing all 50 mg / L of nitrate pollutants in wastewater in a short time of 1.5 h, and the ammonia ion selectivity is close to 100%.

[0048] Example 6

[0049] Example 6 Pt SA The preparation method of the Pt SA / Cu2O / NF composite material is repeated Example 1, the difference is only in step 3), when electrodeposition of Pt, the amount of chloroplatinic acid hexahydrate is replaced from 4.1 mg to 2.05 mg to control the formation of Pt single atoms, and the rest of the conditions remain unchanged, finally Pt SA / Cu2O / NF composite material is obtained.

[0050] Example 6 Pt C / Cu2O / NF composite material is applied in the reaction of electrocatalytic reduction of nitrate to ammonia, the specific experimental conditions repeat Example 1, and the electrocatalytic reaction results of each time period are shown in Table 3, and the results of electrocatalytic reaction for 4 h are shown in Table 4.

[0051] Example 7

[0052] Example 7 Pt C / Cu2O / NF composite material is obtained.

[0053] Example 7 Pt C / Cu2O / NF composite material is applied in the reaction of electrocatalytic reduction of nitrate to ammonia, the specific experimental conditions repeat Example 1, and the electrocatalytic reaction results of each time period are shown in Table 3, and the results of electrocatalytic reaction for 4 h are shown in Table 4.

[0054] Example 8

[0055] Example 8 Cu2O / NF composite material is prepared by repeating Example 1, the difference is only that step 3) of electrodeposition of Pt is omitted, i.e. no Pt is loaded, and the rest of the conditions remain unchanged, finally Cu2O / NF composite material is obtained.

[0056] Example 8: The Cu2O / NF composite material was applied in the electrocatalytic reduction of nitrate to ammonia. The specific experimental conditions were repeated in Example 1. The electrocatalytic reaction results at each time point are shown in Table 3. The results after 4 hours of electrocatalytic reaction are shown in Table 3. Figure 5 As shown in Table 4.

[0057] Example 9

[0058] Example 9Pt CSA The preparation method of / NF composite material includes the following steps:

[0059] 1) First, place the cut nickel foam in a 3 mol / L hydrochloric acid solution and ultrasonically clean for half an hour. After cleaning, rinse with deionized water until neutral, then rinse three times with ethanol and dry.

[0060] 2) At room temperature, 4.1 mg of chloroplatinic acid hexahydrate was dissolved in 50 mL of 0.1 mol / L Na₂SO₄ solution, and the resulting solution was used as the electrolyte. Then, using nickel foam as the cathode, platinum sheet as the anode, and a silver / silver chloride (Ag / AgCl) electrode as the reference electrode, electrodeposition was performed in the prepared electrolyte using a constant voltage method for 15 minutes, with a voltage of -0.39 V vs. RHE, ultimately yielding Pt. CSA / NF composite materials.

[0061] Example 9Pt CSA The / NF composite material was used in the electrocatalytic reduction of nitrate to ammonia. The specific experimental conditions were repeated in Example 1. The electrocatalytic reaction results at each time point are shown in Table 3. The results after 4 hours of electrocatalytic reaction are shown in... Figure 5 As shown in Table 4.

[0062] Table 3. Pt CSA The conversion rate of nitrate to ammonia by the Cu2O / NF composite electrode and the control sample for 4 hours was [not specified].

[0063]

[0064] Table 4. Pt CSA Selectivity of the Cu2O / NF composite electrode and control sample for the electrocatalytic reduction of nitrate to ammonia for 4 hours.

[0065]

[0066] From Table 3, Table 4 and Figure 5 As can be seen from this, adding a low load of Pt, Pt CSA The Cu₂O / NF composite material can completely convert nitrates to ammonia, removing all 50 mg / L of nitrate pollutants from wastewater. Controlling the Pt loading results in a coexistence of Pt single atoms and clusters. CSA / Cu2O / NF composites compared to Pt C / Cu2O / NF and Pt SA / Cu2O / NF exhibits excellent nitrate reduction performance, demonstrating that the single-atom-cluster coexistence Pt structure constructed by precisely controlling the Pt loading (0.02wt%) is a successful model. CSA The Cu2O / NF composite material exhibits significant advantages in the electrocatalytic reduction of nitrates.

[0067] Example 10

[0068] In Example 1, the electrocatalytic reduction of nitrate was carried out for 4 hours, after which electrolysis was stopped. The catholyte was drained and replaced with fresh catholyte for the next electrocatalytic reaction; this was repeated 10 times to verify the Pt content. CSA Recyclability of Cu2O / NF composite materials. Pt CSA The electrocatalytic reduction dechlorination results of the / Cu2O / NF composite material after 10 repeated applications are as follows: Figure 6 As shown.

[0069] from Figure 6 It can be seen that in Pt CSA The Cu2O / NF composite material exhibits good stability in electrocatalytic performance after being reused 10 times.

[0070] 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 Pt CSA / Cu2O / NF composite material characterized in that The following steps are used to prepare: 1) Preparation of CuO / NF: After the pretreatment of the foam nickel NF, the pretreated foam nickel NF is used as the cathode, the electrolyte is Cu(NO3)2 aqueous solution, and the platinum sheet is used as the anode electrode to perform electrochemical deposition under a preset constant voltage, so that Cu(OH)2 is deposited on the foam nickel NF to obtain a Cu(OH)2 / NF electrode sheet, and the Cu(OH)2 / NF electrode sheet is calcined under a nitrogen atmosphere at high temperature to obtain a CuO / NF electrode sheet; 2) Electro-reduction treatment: the CuO / NF electrode sheet in step 1) is used as the cathode, the electrolyte is an electrolyte solution, and the platinum sheet is used as the anode electrode to perform electro-reduction under a preset constant voltage, so that the CuO on the cathode is converted into Cu2O to obtain a Cu2O / NF electrode sheet; 3) Pt loading on Cu2O / NF: Dissolve the platinum source in the electrolyte solution, take the Cu2O / NF electrode sheet obtained in step 2) as the cathode, and use a platinum sheet as the anode counter electrode, and carry out electrodeposition at a preset constant voltage to reduce the platinum source into Pt single atoms and clusters coexisting form, denoted as Pt CSA , Pt CSA loaded on the Cu2O / NF electrode sheet, and after natural air drying, a Pt CSA / Cu2O / NF composite material is obtained.

2. A Pt CSA / Cu2O / NF composite material, characterized in that The concentration of the Cu(NO3)2 aqueous solution in step 1) is 0.04-0.06M, the constant voltage is 0.2-0.4V, and the electrochemical deposition time is 0.5-2h.

3. A Pt as described in claim 1 CSA / Cu2O / NF composite material, characterized in that In step 2), the electrolyte is a 0.05-0.2M sodium sulfate aqueous solution, the voltage for electro-reduction is -0.2V to -0.4V, and the electro-reduction time is 15-30 minutes.

4. A Pt / Cu2O / NF composite according to claim 1, characterized in that CSA / Cu2O / NF composite, characterized in that The specific process of step 3) is: taking the CuO / NF electrode sheet as a working electrode, a platinum sheet as a counter electrode, an electrolyte as a 0.05-0.2M sodium sulfate aqueous solution, and a platinum source as chloroplatinic acid hexahydrate, and the amount of Pt in the platinum source is 0.19-0.4mg / cm2 based on the electrode area of the foam nickel NF substrate 2 ; the constant voltage of the electrodeposition is-0.1V to-0.3V, and the electrodeposition time is 10-30 minutes.

5. A Pt / Cu2O / NF composite according to claim 1, characterized in that CSA A Pt / Cu2O / NF composite according to claim 1, characterized in that In step 1), the temperature for high-temperature calcination is 500-600℃, and the calcination time is 1-3h.

6. A Pt / Cu2O / NF composite according to claim 1 CSA Use of the Pt / Cu2O / NF composite according to claim 1 in the electrocatalytic reduction of nitrates to ammonia.

7. Use according to claim 6, wherein The electro-catalytic reduction device for electro-catalytic reduction of nitrate to ammonia uses an H-shaped two-chamber electrolytic cell, the cathode chamber and the anode chamber are separated by a cation exchange membrane, and the Pt CSA / Cu2O / NF composite material is used as the cathode working electrode, a platinum electrode is used as the anode counter electrode, an Ag / AgCl electrode is used as the reference electrode, electrolyte is added into the cathode chamber and the anode chamber, and the electrolyte in the cathode chamber contains nitrate, and electro-catalytic reduction of nitrate to ammonia is carried out under constant voltage.

8. Use according to claim 7, wherein In the process of electrocatalytic reduction of nitrate to ammonia, the potential of the constant voltage is -0.3V to -0.4V.

9. Use according to claim 8, wherein In the process of electrocatalytic reduction of nitrate to ammonia, the potential of the constant voltage is -0.35V to -0.39V.

10. The use according to claim 7, wherein The electrolyte is a 0.05-0.3M sodium sulfate aqueous solution.

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