Cucurbit [6] uril carbon-loaded iron-doped nickel phosphide nanosheet catalyst as well as preparation method and application thereof

Abstract

The invention discloses a Cucurbit [6] uril carbon-loaded iron-doped nickel phosphide nanosheet catalyst as well as a preparation method and application thereof. The catalyst comprises a carrier and an active component, the carrier is cucurbit [6] uril carbon; the active component is an iron-doped nickel phosphide nanosheet. The cucurbit [6] uril carbon-loaded iron-doped nickel phosphide nanosheet catalyst has excellent seawater electrolysis catalytic activity, and in alkaline simulated seawater (1M KOH + 0.5 M NaCl), when the current densities are respectively 100 mA / cm < 2 > and 500 mA / cm < 2 >, the required overpotentials are respectively 266 mV and 333 mV; the excellent selectivity of 98% and the stability of 1800 h can be achieved; and the stability can reach 600h in real seawater.

Description

Technical Field

[0001] This application relates to a six-membered cucurbitacinium carbon-supported iron-doped nickel phosphide nanosheet catalyst, its preparation method, and its application, belonging to the field of electrocatalysis technology. Background Technology

[0002] The scarcity of water resources is the main bottleneck limiting the application of pure water electrolysis. Therefore, seawater electrolysis has become a more promising method for hydrogen production. However, impurity ions in seawater can severely corrode the catalyst during electrolysis, and the high concentration of chloride ions in seawater leads to chlorine evolution side reactions that compete with the oxygen evolution reaction, affecting its efficiency. Therefore, it is essential to develop seawater oxygen evolution reaction catalysts with high activity, high stability, and high selectivity. Among them, transition metal phosphides have many advantages as oxygen evolution reaction catalysts, such as good conductivity and controllable structure. Therefore, how to effectively utilize transition metal phosphides or improve their catalytic activity in seawater electrolysis is a research hotspot. However, existing nickel phosphide catalysts are susceptible to chloride ions in seawater. - It is susceptible to corrosion, has poor stability and low selectivity; nickel phosphide nanosheets are prone to agglomeration, resulting in insufficient exposure of active sites and limited catalytic activity; single metal doping or support loading makes it difficult to simultaneously optimize electronic structure and corrosion resistance. Summary of the Invention

[0003] To address the problems existing in the prior art, the purpose of this application is to provide an iron-doped nickel phosphide nanosheet catalyst supported on a six-membered cucurbitacinium (CBC) substrate, its preparation method, and its application. In this catalyst, Fe doping regulates the electron density of Ni, and the structure of the six-membered cucurbitacinium (CBC) substrate inhibits nanosheet aggregation and forms interfacial coupling, thus giving it good catalytic activity, selectivity, and stability.

[0004] According to a first aspect of this application, an iron-doped nickel phosphide nanosheet catalyst supported on a six-membered cucurbitacinium ring is provided.

[0005] A six-membered cucurbitacin-carbon supported iron-doped nickel phosphide nanosheet catalyst, the catalyst comprising a support and an active component; The carrier is a six-membered cucurbitacin; The active component is iron-doped nickel phosphide nanosheets.

[0006] The catalytic mechanism of the iron-doped nickel phosphide nanosheet catalyst supported by hexacyclic cucurbitacinium (CBC) is as follows: Fe doping induces a decrease in the electron density of Ni sites and an upward shift of the d-band center, optimizing the adsorption energy of oxygen intermediates; simultaneously, the CBC support not only inhibits nanosheet aggregation, but its interfacial coupling further modulates the electronic environment of Fe, jointly promoting the in-situ formation of the active phase Ni(Fe)OOH and inhibiting Cl-. - Adsorption.

[0007] Iron-doped nickel phosphide nanosheet catalysts supported on hexa-membered cucurbitacinium (CBC) nanosheets not only exhibit excellent activity, but also benefit from Fe doping to regulate the electron density of Ni. The CBC structure inhibits nanosheet aggregation and interfacial coupling, resulting in catalysts with good catalytic activity, selectivity, and stability. Specifically, adjusting the electron density of nickel through heterojunction structures or metal doping effectively enhances catalytic activity; using supporting materials such as commercially available carbocarbons (CCFs) and MOFs effectively prevents nanosheet aggregation while exposing surface active sites; and adjusting the morphology of nickel phosphide nanoparticles increases their specific surface area, thereby improving catalyst activity.

[0008] According to a second aspect of this application, a method for preparing the above-described six-membered cucurbitacinol carbon-supported iron-doped nickel phosphide nanosheet catalyst is provided.

[0009] A method for preparing the above-described six-membered cucurbitacinol carbon-supported iron-doped nickel phosphide nanosheet catalyst, the method comprising the following steps: S1. Calcining the six-membered cucurbit ring yields six-membered cucurbit ring carbon; S2. Dissolve the nickel source, iron source, morphology modifier, precipitant and the six-membered cucurbitacin ring carbon in a solvent to obtain a homogeneous solution, and then perform hydrothermal reaction, washing and drying in sequence to obtain NiFe LDH / CBC. S3. The phosphorus source and the NiFe LDH / CBC are placed upstream and downstream, respectively, and phosphating is performed under an inactive gas atmosphere to obtain the iron-doped nickel phosphide nanosheet catalyst supported by the six-membered cucurbit ring carbon.

[0010] Optionally, in S1, the calcination temperature is 300~1000°C and the time is 90~180 min.

[0011] Optionally, in S1, the heating rate of the calcination is 2~10°C / min.

[0012] Optionally, in S2, the nickel source is at least one of nickel nitrate and nickel chloride.

[0013] Optionally, in S2, the iron source is at least one of ferrous sulfate and ferric nitrate.

[0014] Optionally, in S2, the morphology modifier is ammonium fluoride.

[0015] Optionally, in S2, the precipitant is urea.

[0016] Optionally, in S2, the ratio of the amount of nickel source, the amount of iron source, the morphology modifier, the precipitant and the six-membered cucurbitacinium carbon is (1~3) mmol: (0.25~0.75) mmol: (5~15) mmol: (12.5~37.5) mmol: (50~150) mg.

[0017] Optionally, in step S2, the solvent is water.

[0018] Optionally, in S2, the temperature of the hydrothermal reaction is 90~150°C and the time is 180~540 min.

[0019] Optionally, in S2, the heating rate of the hydrothermal reaction is 1~5°C / min.

[0020] Optionally, in step S2, the washing solvent is water or ethanol, and the water and ethanol are used alternately for washing.

[0021] Optionally, in S3, the mass ratio of the phosphorus source to the NiFe LDH / CBC is (100~1000):(10~100).

[0022] Optionally, in step S3, the inactive gas is N2.

[0023] Optionally, in S3, the phosphating temperature is 300~400°C and the time is 120~180 min.

[0024] Optionally, in S3, the heating rate of the phosphating is 1~5°C / min.

[0025] According to a third aspect of this application, an application is provided for the six-membered cucurbitacinol carbon-supported iron-doped nickel phosphide nanosheet catalyst described above, or the six-membered cucurbitacinol carbon-supported iron-doped nickel phosphide nanosheet catalyst prepared by the above preparation method, in seawater electrolysis.

[0026] In this application, CBC refers to six-membered cucurbitacinium; NiFeP refers to iron-doped nickel phosphide nanosheets; and NiFeP / CBC catalyst refers to an iron-doped nickel phosphide nanosheet catalyst supported on six-membered cucurbitacinium.

[0027] The beneficial effects that this application can produce include: 1) This application provides a six-membered cucurbitacinium-based carbon-supported iron-doped nickel phosphide nanosheet catalyst, NiFeP / CBC catalyst, which exhibits excellent seawater electrolysis catalytic activity. In alkaline simulated seawater (1M KOH + 0.5M NaCl), when the current density is 100 and 500 mA / cm², respectively... 2The required overpotentials are 266 and 333 mV, respectively; it achieves excellent selectivity of 98% and stability of 1800 h; and it achieves stability of 600 h in real seawater.

[0028] 2) This application provides a method for preparing an iron-doped nickel phosphide nanosheet catalyst supported on a six-membered cucurbit ring carbon. The preparation method uses abundant and readily available raw materials, has scientifically reasonable reaction conditions, is simple and easy to implement, and is easy to scale up for production. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the NiFeP / CBC catalyst in Example 1 of this application; Figure 2 Synchrotron radiation X-ray near-edge fine structure spectra of the catalysts in Example 1 and Comparative Examples 1-2 of this application; Figure 3 Synchrotron radiation extended edge X-ray structure spectra of the catalysts in Example 1 and Comparative Examples 1-2 of this application; Figure 4 These are test graphs showing the alkaline simulated seawater electrolysis activity of the catalysts in Example 1 and Comparative Examples 1-2 of this application; Figure 5 This is a graph showing the electrolytic stability of the NiFeP / CBC catalyst in Example 1 of this application under alkaline simulated seawater (1 M KOH + 0.5 M NaCl). Figure 6 This is a graph showing the electrolytic stability of the Ni2P catalyst in Comparative Example 1 of this application in alkaline simulated seawater (1 M KOH + 0.5 M NaCl). Figure 7 This is a graph showing the electrolytic stability of the NiFeP catalyst in Comparative Example 2 of this application in alkaline simulated seawater (1 M KOH + 0.5 M NaCl). Figure 8 This is a graph showing the electrolytic stability of the NiFeP / CBC catalyst in alkaline seawater (1 M KOH + seawater) in Example 1 of this application. Figure 9 This is an oxygen Faraday efficiency diagram, i.e., a selectivity diagram, for the catalysts in Example 1 and Comparative Examples 1-2 of this application. Detailed Implementation

[0030] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0031] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0032] The six-membered cucurbit[6]urea was synthesized according to the method described in the literature (Highly symmetric columnar channels in metal-free cucurbit[n]uril hydrate crystals (n=6, 8). D. Bardelang, KA Udachin, DM Leek, JA Ripmeester, CrystEngComm 2007, 9,973.). Ni(NO3)2·6H2O and FeSO4·7H2O were both purchased from Sinopharm. NH4F, CO(NH2)2 and NaH2PO2·H2O were all purchased from Aladdin.

[0033] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0034] Electrocatalytic oxygen evolution performance test (the scan range was selected with reference to the standard hydrogen electrode): (1) Electrode preparation: Electrochemical tests were performed in a three-electrode glass electrolytic cell. The working electrode was prepared by dispersing a certain amount of catalyst (the product obtained in the examples and comparative examples) in 950 μl of isopropanol, followed by adding 50 μl of perfluorinated resin (Nafion) and sonicating. Then, 25 μL of the above mixture was dropped onto nickel foam (0.25 cm² area). 2 The catalyst was prepared by drying, with a platinum mesh as the counter electrode and Hg / HgO as the reference electrode. The catalyst content supported on the nickel foam was 1 mg / cm³. 2 .

[0035] (2) Electrochemical performance test: First, a cyclic voltammetric scan was performed in an alkaline simulated seawater (1M KOH + 0.5M NaCl) solution under N2 atmosphere. The scan rate was 100 mV / s, the scan range was 0-1V, and the number of scans was 20. This step was to clean the catalyst surface and activate it.

[0036] (3) Seawater hydrolysis performance test: The test was conducted in an alkaline simulated seawater solution (1M KOH + 0.5M NaCl). Polarization curves were used to characterize the electrocatalytic oxygen evolution performance of the catalyst, with a scan rate of 5 mV / s and a scan range of 0-1.6V.

[0037] (4) Seawater stability test: In an alkaline simulated seawater (1M KOH + 0.5M NaCl) solution, the scanning current was kept constant at 500mA and the scanning time was 1800h to detect the change in the required overpotential; in an alkaline seawater (1M KOH + seawater) solution, the scanning current was kept constant at 500mA and the scanning time was 600h to detect the change in the required overpotential.

[0038] (5) Seawater Selectivity Test: The Faraday efficiency of oxygen production in NiFeP / CBC was tested using a dual-chamber H-type cell with a Nafion membrane separating the anode and cathode. Oxygen generated was collected after 15 min of constant current testing at different current densities and analyzed by gas chromatography. A thermal conductivity detector (TCD) was used to detect and quantify the generated oxygen. During the constant current test, the oxygen was measured at 30 cm⁻¹. 3 Ar is continuously introduced into the anode chamber at a flow rate of / min.

[0039] The X-ray powder diffractometer used is Rigaku's Min Flex 600; The scanning electron microscopy analysis was performed using a Hitachi SU-8010 scanning electron microscope. The high-resolution transmission electron microscope used was the ESCALAB 250Xi from FEI Corporation, USA. The electrochemical performance was tested using a Zana IM6 electrochemical workstation.

[0040] Example 1 (1) Preparation of CBC: 100 mg of hexacyclic cucurbitacin was placed in a small porcelain boat and calcined in a tube furnace for 2 h. Heating rate: 5 °C / min; calcination temperature: 900 °C, 2 h; then the product was collected by natural cooling.

[0041] (2) Preparation of NiFe LDH / CBC: 2 mmol nickel nitrate hexahydrate, 0.5 mmol ferrous sulfate, 10 mmol ammonium fluoride, 25 mmol urea and 100 mg CBC were dissolved in 30 ml of deionized water and stirred at room temperature for 1 h to form a homogeneous solution. Then, a hydrothermal reaction was carried out at 120 °C for 6 h with a heating rate of 2 °C / min. The solution was then cooled naturally and washed three times with deionized water and anhydrous ethanol, and then dried in an oven.

[0042] (3) Preparation of NiFeP / CBC: 400 mg of sodium hypophosphite monohydrate and 40 mg of NiFe LDH / CBC were placed in the upstream and downstream of a tube furnace, respectively. Then N2 was introduced, the phosphating temperature was 300℃, the heating time was 2h, the heating rate was 2℃ / min, and then the product was collected after natural cooling.

[0043] Comparative Example 1 (1) Preparation of Ni(OH)2: Dissolve 2 mmol nickel nitrate hexahydrate, 10 mmol ammonium fluoride and 25 mmol urea in 30 ml of deionized water, and then stir at room temperature for 1 h to form a homogeneous solution; then carry out hydrothermal reaction at 120℃ for 6 h, with a heating rate of 2℃ / min, and cool naturally. Finally, wash with deionized water and anhydrous ethanol three times alternately, and put it in an oven to dry.

[0044] (2) Preparation of Ni2P: 400 mg of sodium hypophosphite monohydrate and 40 mg of Ni(OH)2 were placed at the upstream and downstream sides of a tube furnace, respectively. Then N2 was introduced, the phosphating temperature was 300℃, the heating time was 2 h, the heating rate was 2℃ / min, and then the product was collected after natural cooling.

[0045] Comparative Example 2 (1) Preparation of NiFe LDH: Dissolve 2 mmol nickel nitrate hexahydrate, 0.5 mmol ferrous sulfate, 10 mmol ammonium fluoride and 25 mmol urea in 30 ml of deionized water, and then stir at room temperature for 1 h to form a homogeneous solution; then carry out hydrothermal reaction at 120℃ for 6 h, with a heating rate of 2℃ / min, and cool naturally. Finally, wash with deionized water and anhydrous ethanol three times alternately, and put it in an oven to dry.

[0046] (2) Preparation of NiFeP: 400 mg of sodium hypophosphite monohydrate and 40 mg of NiFe LDH were placed at the upstream and downstream sides of a tube furnace, respectively. Then N2 was introduced, the phosphating temperature was 300℃, the heating time was 2 h, the heating rate was 2℃ / min, and then the product was collected after natural cooling.

[0047] Characterization test Taking the NiFeP / CBC catalyst in Example 1 as a typical example: Figure 1 The image shows a scanning electron microscope (SEM) image of the NiFeP / CBC catalyst in Example 1 of this application. The results show that NiFeP nanosheets are uniformly distributed on CBC.

[0048] Figure 2 The synchrotron X-ray near-edge fine structure spectra of the catalysts in Example 1 and Comparative Examples 1-2 of this application show that the Ni K-edge absorption edge position of NiFeP / CBC is shifted to a higher energy direction compared to Ni2P, and the valence state of Ni is between 0 and 3, further confirming the electron-deficient state of Ni.

[0049] Figure 3 The synchrotron radiation extended edge X-ray structure spectra of the catalysts in Example 1 and Comparative Examples 1-2 of this application show that 1.85 Å and 2.60 Å correspond to the Ni-P and Ni-M bonds of NiFeP / CBC, respectively.

[0050] Figure 4 The figures show the alkaline simulated seawater electrolysis activity test results of the catalysts in Example 1 and Comparative Examples 1-2 of this application. The results show that the NiFeP / CBC catalyst in Example 1 has excellent seawater catalytic activity.

[0051] Figure 5 This is a graph showing the electrolytic stability of the NiFeP / CBC catalyst in Example 1 of this application under alkaline simulated seawater (1 M KOH + 0.5 M NaCl). Figure 6 This is a graph showing the electrolytic stability of the Ni2P catalyst in Comparative Example 1 of this application in alkaline simulated seawater (1 M KOH + 0.5 M NaCl). Figure 7 This is a graph showing the electrolytic stability of the NiFeP catalyst in Comparative Example 2 of this application under alkaline simulated seawater (1 M KOH + 0.5 M NaCl). The results indicate that the NiFeP / CBC catalyst in Example 1 (such as...) Figure 5 The catalyst shown exhibits excellent catalytic stability, maintaining its stability for over 1800 hours, significantly superior to the Ni2P catalyst in Comparative Example 1 (as shown). Figure 6 (as shown) and the NiFeP catalyst in ratio 2 (as shown) Figure 7 (As shown).

[0052] Figure 8 The figure shows the electrolytic stability of the NiFeP / CBC catalyst in Example 1 of this application in alkaline seawater (1 M KOH + seawater). The results show that the NiFeP / CBC catalyst in Example 1 has excellent catalytic stability.

[0053] Figure 9 The diagram shows the oxygen Faraday efficiency, or selectivity, of the catalysts in Example 1 and Comparative Examples 1-2 of this application. The results show that the NiFeP / CBC catalyst in Example 1 has high catalytic selectivity at different current densities.

[0054] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A six-membered cucurbitacinium-based carbon-supported iron-doped nickel phosphide nanosheet catalyst, characterized in that, The catalyst includes a support and an active component; The carrier is a six-membered cucurbitacin; The active component is iron-doped nickel phosphide nanosheets.

2. A method for preparing the iron-doped nickel phosphide nanosheet catalyst supported on a six-membered cucurbitacinium ring supported as described in claim 1, characterized in that, The preparation method includes the following steps: S1. Calcining the six-membered cucurbit ring yields six-membered cucurbit ring carbon; S2. Dissolve the nickel source, iron source, morphology modifier, precipitant and the six-membered cucurbitacin ring carbon in a solvent to obtain a homogeneous solution, and then perform hydrothermal reaction, washing and drying in sequence to obtain NiFe LDH / CBC. S3. The phosphorus source and the NiFe LDH / CBC are placed upstream and downstream, respectively, and phosphating is performed under an inactive gas atmosphere to obtain the iron-doped nickel phosphide nanosheet catalyst supported by the six-membered cucurbit ring carbon.

3. The preparation method according to claim 2, characterized in that, In S1, the calcination temperature is 300~1000°C and the time is 90~180 min; Preferably, in S1, the heating rate of the calcination is 2~10°C / min.

4. The preparation method according to claim 2, characterized in that, In step S2, the nickel source is at least one of nickel nitrate and nickel chloride; Preferably, in step S2, the iron source is at least one of ferrous sulfate and ferric nitrate; Preferably, in step S2, the morphology modifier is ammonium fluoride; Preferably, in step S2, the precipitant is urea; Preferably, in S2, the ratio of the amount of nickel source, the amount of iron source, the morphology modifier, the precipitant and the six-membered cucurbitacinium carbon is (1~3) mmol: (0.25~0.75) mmol: (5~15) mmol: (12.5~37.5) mmol: (50~150) mg.

5. The preparation method according to claim 2, characterized in that, In step S2, the solvent is water.

6. The preparation method according to claim 2, characterized in that, In S2, the temperature of the hydrothermal reaction is 90~150°C and the time is 180~540 min; Preferably, in S2, the heating rate of the hydrothermal reaction is 1~5°C / min.

7. The preparation method according to claim 2, characterized in that, In S3, the mass ratio of the phosphorus source to the NiFeLDH / CBC is (100~1000):(10~100).

8. The preparation method according to claim 2, characterized in that, In step S3, the inactive gas is N2.

9. The preparation method according to claim 2, characterized in that, In S3, the phosphating temperature is 300~400°C and the time is 120~180 min; Preferably, in S3, the heating rate of the phosphating is 1~5°C / min.

10. The application of the six-membered cucurbitacinol carbon-supported iron-doped nickel phosphide nanosheet catalyst of claim 1 or the six-membered cucurbitacinol carbon-supported iron-doped nickel phosphide nanosheet catalyst prepared by any one of claims 2 to 9 in seawater electrolysis.

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