Preparation of a supported Cu / nitrogen-doped carbon-based catalyst and application thereof to electrocatalytic preparation of phosphane

Abstract

The application discloses a kind of supported Cu / nitrogen-doped carbon-based catalyst preparation and its application of electrocatalytic preparation phosphine, the preparation process of catalyst of the application is: nitrogen-containing organic ligand is dispersed in solvent with carbon source, heating stirring, then copper salt solution is added to carry out coordination chelation, form solid-liquid mixed precursor with space confinement effect, then carry out two-stage pyrolysis, construct composite active site by metal copper nanocluster and nanocrystal in nitrogen-doped carbon skeleton, obtain catalyst.The catalyst of the application, preparation process is simple, and noble metal is used as active component, with low cost, with good electrocatalytic preparation phosphine performance and stability, with important research value and application potential.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to the preparation of a supported Cu / nitrogen-doped carbon-based catalyst and its application in the electrocatalytic preparation of phosphine. Background Technology

[0002] Phosphine (PH3) is an indispensable key electronic gas in the modern microelectronics and photovoltaic industries. As the primary N-type dopant source in the semiconductor industry, it is used to precisely introduce phosphorus atoms into the silicon lattice through chemical vapor deposition or ion implantation processes to control conductivity. It is a core raw material for manufacturing high-performance integrated circuits, memory chips, and PN junctions for solar cells. Simultaneously, it plays a decisive role in the preparation of III-V compound semiconductors such as indium phosphide (InP), directly supporting the development of cutting-edge optoelectronic technologies such as 5G communication, lidar, and high-brightness LEDs. It can be said that the purity and supply stability of phosphine have become key indicators for measuring the self-sufficiency capabilities of high-end manufacturing and are an important underlying material foundation driving the modern digital economy and green energy transformation.

[0003] Currently, the industrial production of phosphine mainly relies on the hydrolysis of active metal phosphides (such as aluminum phosphide and calcium phosphide). However, this method has the following significant drawbacks: extremely low safety, the hydrolysis reaction is violent and highly exothermic, making it prone to spontaneous combustion or explosion, and the byproduct treatment is complex; uncontrollable purity: traditional chemical methods make it difficult to adjust product purity through simple process parameters, especially for high-purity electronic-grade phosphine (6N and above) required for integrated circuit manufacturing; and high environmental impact: it generates a large amount of phosphorus-containing alkaline waste residue, which does not meet the requirements of green chemistry. In contrast, electrocatalytic reduction has advantages such as mild reaction conditions, easily controllable product purity (through current density adjustment), and cleanliness without pollution. However, existing metal-based catalysts suffer from serious hydrogen evolution side reactions, low current efficiency, and high environmental toxicity. Therefore, developing a highly active, highly selective, and environmentally friendly heteroatom-doped carbon-based catalyst is of great practical significance for promoting the industrial green upgrading of electronic specialty phosphine. Summary of the Invention

[0004] To address the problems existing in the above-mentioned technologies, this invention provides a method for preparing a supported Cu / nitrogen-doped carbon-based catalyst and its application in the electrocatalytic production of phosphine. The catalyst of this invention has the advantages of simple preparation, low cost, and good performance. As a phosphine production catalyst, it exhibits good stability, and its electrochemical approach can effectively improve the safety and process controllability of phosphine production, demonstrating significant application potential.

[0005] The technical solution adopted in this invention is as follows: A method for preparing a supported Cu / nitrogen-doped carbon-based composite catalyst includes the following steps: S1 precursor spatial confinement assembly: Nitrogen-containing organic ligands and carbon sources are dispersed in a solvent, heated to 40-60℃ and stirred for 2-5 h, then copper salt solution is added under heat preservation for coordination chelation, and stirring is continued for 2-5 h to form a solid-liquid mixed precursor with spatial confinement effect. S2 Multi-stage programmed temperature pyrolysis: The precursor obtained in step S1 is subjected to two-stage pyrolysis. The first stage is to heat to 200~400 ℃ under an inert atmosphere and perform isothermal treatment to induce preliminary carbonization of the ligands. The resulting nitrogen-rich groups are used to capture and lock copper species in situ. The second stage is to heat to 700~1000 ℃ under a reducing atmosphere and perform isothermal treatment. Through in-situ reduction and aggregate-restricted self-assembly, composite active sites composed of metallic copper nanoclusters and nanocrystals are constructed in the nitrogen-doped carbon framework, thus completing the preparation.

[0006] Further, in step S1, the nitrogen-containing organic ligand is selected from one or more of the following: o-phenylenediamine, dicyandiamide, 1,10-o-phenanthroline, 2-methylimidazole, melamine, phthalocyanine, porphyrin, preferably 1,10-o-phenanthroline or 2-methylimidazole.

[0007] Further, in step S1, the carbon source is selected from one or more of the following: glucose, sucrose, polyacrylonitrile (PAN), graphene oxide, carbon nanotubes, preferably graphene oxide or polyacrylonitrile.

[0008] Furthermore, in step S1, the mass ratio of the nitrogen-containing organic ligand to the carbon source is 1:10 to 1:20, preferably 1:12-15.

[0009] Further, in step S1, the solvent is selected from one or more of deionized water, ethanol, isopropanol, dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), preferably a deionized water-ethanol mixed solvent with a volume ratio of 0.5-2:1; the ratio of the total mass of the nitrogen-containing organic ligand and the carbon source to the volume of the solvent is 1g:20~100mL, preferably 1g:50mL.

[0010] Further, in step S1, the copper salt is selected from one or more of the following: copper chloride, copper nitrate, copper sulfate, copper acetate, copper acetylacetonate, preferably copper acetate or copper chloride.

[0011] Further, in step S1, the molar ratio of the copper salt to the mass of the nitrogen-containing organic ligand is 4-10 mmol:1g, preferably 5-6 mmol:1g.

[0012] Furthermore, in step S2, the calcination atmosphere in the first stage is Ar, the isothermal treatment temperature is 300℃±20℃, the isothermal holding time is 3-7h, preferably 4-5h, and the heating rate is 5~10 ℃ / min.

[0013] Furthermore, in step S2, during the second-stage pyrolysis process, the reducing atmosphere is an Ar-H2 mixture containing 10-30% H2 by volume, preferably an Ar-H2 mixture containing 20% ​​H2 by volume; the isothermal treatment temperature is 800-850℃, the isothermal holding time is 2-6 h, preferably 3-4 h, and the heating rate is 5-10 ℃ / min.

[0014] This invention also discloses the application of the aforementioned supported Cu / nitrogen-doped carbon-based composite catalyst in the electrolytic preparation of phosphine. The electrolytic preparation of phosphine is carried out in an electrolytic cell, which is divided into a cathode chamber and an anode chamber by an N117 membrane. An electrode coated with the aforementioned supported Cu / nitrogen-doped carbon-based composite catalyst is used as the cathode, and a separate anode electrode is provided. A hypophosphorous acid solution containing red phosphorus is used as the electrolyte in the cathode chamber, and a dilute sulfuric acid aqueous solution is used as the electrolyte in the anode chamber to perform electrocatalytic preparation of phosphine.

[0015] Furthermore, the anode electrode is an IrO2-Ta2O5 / Ti electrode, with a molar ratio of Ir to Ta of 1:2-4, and the loading of IrO2-Ta2O5 on the Ti electrode is 5-15%; in the electrolyte of the cathode chamber, the concentration of hypophosphite solution is 1-10M, the concentration of red phosphorus is 5-50g / L, and the concentration of dilute sulfuric acid aqueous solution is 0.5-3M.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) The preparation of a supported Cu / nitrogen-doped carbon-based catalyst of the present invention utilizes the prior chelation of nitrogen-containing organic ligands with copper salts and the spatial confinement effect of carbon source during pyrolysis to effectively suppress excessive aggregation of metallic copper at high temperature. The pyridine nitrogen and pyrrole nitrogen sites in the nitrogen-doped carbon skeleton generate strong electronic interactions with the supported Cu, inducing local charge non-uniform distribution in the metal center, thereby reducing the energy barrier for PP bond activation and significantly improving the selectivity of electrocatalytic phosphine preparation.

[0017] 2) At a current density of 300 mA / cm 2 Under high current density conditions, 223.41 mL of phosphine was produced within 3 hours, while exhibiting good stability and showing great application potential. Attached Figure Description

[0018] Figure 1 SEM image of the catalyst prepared in Example 1; Figure 2 SEM image of the catalyst prepared in Example 2; Figure 3 The image shows a SEM image of the catalyst prepared in Comparative Example 1. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific examples, but the scope of protection of the present invention is not limited thereto: Example 1: Preparation and application of supported Cu / nitrogen-doped carbon-based composite catalysts S1: 0.5 g of 1,10-phenanthroline and 6.0 g of graphene oxide were dispersed in 325 mL of a co-solvent of deionized water and ethanol (volume ratio 1:1) and stirred continuously at 50 °C for 4 h. Then, 10 mL of 0.25 mol / L copper acetate solution was added dropwise to the system, and stirring was continued for 3.5 h to form a solid-liquid mixed precursor.

[0020] S2: The precursor obtained in step S1 was subjected to two-stage pyrolysis under an argon atmosphere: in the first stage, the temperature was increased to 300 °C at 7 °C / min and held at a constant temperature for 5 h; in the second stage, the temperature was increased to 850 °C at 5 °C / min under an H2-Ar atmosphere with a volume fraction of 20% H2 and held at a constant temperature for 3 h, and then naturally cooled to room temperature to obtain the target catalyst.

[0021] Preparation of the cathode catalytic electrode: 9 mg of the catalyst obtained in Example 1 was mixed with 800 μL of ethanol and 200 μL of 5% Nafion solution, and sonicated at 500 W for 40 min to obtain catalyst ink. The catalyst ink was then coated onto a 9 cm... 2 One side of the carbon paper electrode serves as a cathode for the electrolytic preparation of phosphine.

[0022] Experiment on the electrocatalytic preparation of phosphine: The reaction was carried out in an electrolytic cell divided into a cathode chamber and an anode chamber by an N117 membrane. The cathode was the cathode catalytic electrode prepared above, and the anode was a commercial IrO2-Ta2O5 / Ti electrode with a molar ratio of Ir to Ta of 1:3 and an IrO2-Ta2O5 loading of 10% on the Ti electrode. 3 g of red phosphorus was added to 300 mL of 5 M hypophosphoric acid solution to form the cathode electrolyte required for the reaction, and the anode electrolyte was 300 mL of 1 M H2SO4 solution. The cathode and anode chambers were each equipped with a storage tank. The electrolyte in the cathode chamber was pumped out by a peristaltic pump, entered the cathode storage tank, and then returned to the cathode chamber, forming a circulating flow of the cathode electrolyte. Similarly, the anode electrolyte circulated between the anode chamber and the anode storage tank. Following the above experimental procedure, the yield of phosphine was tested at different current densities, and the results are shown in Table 1. Table 1. Phosphine production at different times .

[0023] Table 1 shows that the Cu-based catalyst prepared can achieve efficient preparation of phosphine. As the current density increases, the yield of arsine also increases. The supported Cu / nitrogen-doped carbon catalyst without precious metals has good application potential.

[0024] Example 2: Test on the effect of calcination temperature (Phase 1 / Phase 2) The experimental process of Example 2 was repeated in Example 1, except that the two-stage pyrolysis process in step S2 was changed. Specifically, in the first stage, the temperature was raised to 200 °C at 7 °C / min and held at a constant temperature for 5 h; in the second stage, the temperature was raised to 700 °C at 5 °C / min in an H2-Ar atmosphere with a volume fraction of 20% H2 and held at a constant temperature for 3 h, and then naturally cooled to room temperature. All other conditions remained unchanged, and the target catalyst was finally obtained.

[0025] The catalyst obtained in Example 2 was used to prepare a cathode catalytic electrode according to the method in Example 1, and was used for the electrolytic preparation of phosphine. The yield of phosphine was tested at different current densities, and the results are shown in Table 2. Table 2. Phosphine production at different times .

[0026] Example 2 shows the performance of phosphine under different calcination conditions. Compared with Example 1, the difference in performance is small. Therefore, the catalyst preparation within the specified optimized calcination temperature range has little impact on the electrocatalytic preparation of phosphine.

[0027] Example 3: The effect of hydrogen content in the second stage The experimental process of Example 3 was repeated in Example 1, except that "in the two-stage pyrolysis process in step S2, the calcination atmosphere of the second stage was changed to an H2-Ar atmosphere with a volume fraction of 30% H2", and the other conditions remained unchanged, and the target catalyst was finally obtained.

[0028] The catalyst obtained in Example 3 was used to prepare a cathode catalytic electrode according to the method in Example 1, and was used for the electrolytic preparation of phosphine. The yield of phosphine was tested at different current densities, and the results are shown in Table 3. Table 3. Phosphine production at different times .

[0029] Table 3 shows that when the hydrogen content was changed to 30% in the second stage, the catalyst calcination also showed good electrocatalytic phosphine production performance, with little difference from Examples 1 and 2, and also showed good application prospects.

[0030] Comparative Example 1: No first-stage low-temperature roasting process The experimental process of Comparative Example 1 was repeated in Example 1, except that "the first stage of calcination was omitted in step S2, and the temperature was directly raised to 850 °C at 5 °C / min under an H2-Ar atmosphere with a volume fraction of 20% H2, and then kept at a constant temperature for 3 h, and then naturally cooled to room temperature". All other conditions remained unchanged, and the target catalyst was finally obtained.

[0031] The catalyst obtained in Comparative Example 1 was used to prepare a cathode catalytic electrode according to the method in Example 1, and was used for electrolytic preparation of phosphine. The yield of phosphine was tested at different current densities, and the results are shown in Table 4. Table 4. Phosphine production at different times .

[0032] The results in Table 4 show that, due to the lack of low-temperature carbonization and locking, copper species undergo severe agglomeration at high temperatures, which affects their loading stability, reduces catalyst utilization, and leads to a decline in phosphine production performance.

[0033] Comparative Example 2: No reducing atmosphere introduced The experimental process of Comparative Example 2 was repeated in Example 1, except that the calcination atmosphere in the second stage was changed to Ar in step S2, while the other conditions remained the same, and the target catalyst was finally obtained.

[0034] The catalyst obtained in Comparative Example 2 was used to prepare a cathode catalytic electrode according to the method in Example 1, and was used for electrolytic preparation of phosphine. The yield of phosphine was tested at different current densities, and the results are shown in Table 5. Table 5. Phosphine production at different times .

[0035] Comparative Example 2 results show that, due to the lack of reducing gas induction, the reduction of metallic copper species is incomplete and the aggregation-limited self-assembly cannot be achieved, resulting in a significant decrease in the performance of electrolytic preparation of phosphine.

[0036] Comparative Example 3: Changing the mass ratio of nitrogen-containing ligands to carbon sources The experimental process of Comparative Example 3 was repeated in Example 1, except that the amount of graphene oxide was changed to 2.5 g in step S1, while the other conditions remained the same, and the target catalyst was finally obtained.

[0037] The catalyst obtained in Comparative Example 3 was used to prepare a cathode catalytic electrode according to the method in Example 1, and was used for electrolytic preparation of phosphine. The yield of phosphine was tested at different current densities, and the results are shown in Table 6. Table 6. Phosphine production at different times .

[0038] Comparing the results of Example 1 and Comparative Example 3, it can be observed that the performance of phosphine is relatively similar at low current densities and in short time. However, as the current density and reaction time increase, the yield of phosphine drops sharply. Analysis of this result indicates that the excessive nitrogen-containing ligand content leads to the generation of excessive volatiles during pyrolysis, which damages the structural integrity of the carbon skeleton and results in poor mechanical stability of the catalyst at high current densities.

[0039] Comparative Example 4: Performance Testing of Changed Active Components (Fe, Ni / Pt) The experimental procedure of Comparative Example 4 was repeated in Example 1, except that "in step S1, 10 mL of 0.25 mol / L copper acetate solution was replaced with 10 mL of 0.25 mol / L aqueous solution of ferric nitrate, nickel nitrate, or potassium chloroplatinate", with all other conditions remaining unchanged, and the target catalyst was finally obtained.

[0040] The catalyst obtained in Comparative Example 4 was used to prepare a cathode catalytic electrode according to the method in Example 1, and was used for electrolytic preparation of phosphine. The yield of phosphine was tested at different current densities, and the results are shown in Table 7. Table 7. Phosphine production at different times .

[0041] Comparing the results of Example 1 and Comparative Example 4, it can be observed that the catalytic activity of phosphine preparation with Fe, Ni or Pt as active components is significantly reduced. This is because Ni or Pt is a HER catalyst, and in this experiment, HER is a competing reaction for phosphine preparation, thus resulting in a decrease in phosphine yield.

[0042] SEM images of the catalysts in Examples 1, 2, and 1 (Comparative Example 1) are shown below. Figure 1-3 As shown, it can be seen that the graphene-based catalyst still maintains the original sheet-like structure, but lacks the first-stage low-temperature calcination process of Comparative Example 1. The Cu content is reduced (Table 7), and the catalytic activity is reduced. Although Example 2 does not have a sheet-like structure, the Cu content is similar to that of Example 1. The slight difference in its activity comes from the difference in specific surface area.

[0043] Table 8. Cu content of examples and comparative examples .

Claims

1. A method for preparing a supported Cu / nitrogen-doped carbon-based composite catalyst, characterized in that, Includes the following steps: S1 precursor spatial confinement assembly: Nitrogen-containing organic ligands and carbon sources are dispersed in a solvent, heated to 40-60℃ and stirred for 2-5 h, then copper salt solution is added under heat preservation for coordination chelation, and stirring is continued for 2-5 h to form a solid-liquid mixed precursor with spatial confinement effect. S2 Multi-stage programmed temperature pyrolysis: The precursor obtained in step S1 is subjected to two-stage pyrolysis. The first stage is to heat to 200~400 ℃ under an inert atmosphere for isothermal treatment to induce preliminary carbonization of ligands. The resulting nitrogen-rich groups are used to capture and lock copper species in situ. The second stage involves heating to 700-1000 ℃ in a reducing atmosphere and performing isothermal treatment. Through in-situ reduction and aggregated confined self-assembly, composite active sites composed of metallic copper nanoclusters and nanocrystals are constructed in the nitrogen-doped carbon framework, thus completing the preparation.

2. The preparation method according to claim 1, characterized in that, In step S1, the nitrogen-containing organic ligand is selected from one or more of the following: o-phenylenediamine, dicyandiamide, 1,10-o-phenanthroline, 2-methylimidazole, melamine, phthalocyanine, porphyrin, preferably 1,10-o-phenanthroline or 2-methylimidazole; In step S1, the carbon source is selected from one or more of the following: glucose, sucrose, polyacrylonitrile (PAN), graphene oxide, carbon nanotubes, preferably graphene oxide or polyacrylonitrile. In step S1, the mass ratio of nitrogen-containing organic ligand to carbon source is 1:10 to 1:20, preferably 1:12-15.

3. The preparation method according to claim 1, characterized in that, In step S1, the solvent is selected from one or more of deionized water, ethanol, isopropanol, dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), preferably a deionized water-ethanol mixed solvent with a volume ratio of 0.5-2:

1. The ratio of the total mass of the nitrogen-containing organic ligand and the carbon source to the volume of the solvent is 1 g: 20 ~ 100 mL, preferably 1 g: 50 mL.

4. The preparation method according to claim 1, characterized in that, In step S1, the copper salt is selected from one or more of the following: copper chloride, copper nitrate, copper sulfate, copper acetate, copper acetylacetonate, preferably copper acetate or copper chloride; In step S1, the molar ratio of the copper salt to the mass of the nitrogen-containing organic ligand is 4-10 mmol:1g, preferably 5-6 mmol:1g.

5. The preparation method according to claim 1, characterized in that, In step S2, the first stage calcination atmosphere is Ar, the constant temperature treatment temperature is 300℃±20℃, the constant temperature holding time is 3-7h, preferably 4-5h, and the heating rate is 5~10 ℃ / min.

6. The preparation method according to claim 1, characterized in that, In step S2, during the second-stage pyrolysis process, the reducing atmosphere is an Ar-H2 mixture containing 10-30% H2 by volume, preferably an Ar-H2 mixture containing 20% ​​H2 by volume; the isothermal treatment temperature is 800-850℃, the isothermal holding time is 2-6 h, preferably 3-4 h, and the heating rate is 5-10 ℃ / min.

7. A supported Cu / nitrogen-doped carbon-based composite catalyst prepared by the method according to any one of claims 1-6.

8. The application of the supported Cu / nitrogen-doped carbon-based composite catalyst according to claim 7 in the electrolytic preparation of phosphine.

9. The application as described in claim 8, characterized in that, The electrolytic preparation of phosphine is carried out in an electrolytic cell, which is divided into a cathode chamber and an anode chamber by an N117 membrane. The electrode coated with the supported Cu / nitrogen-doped carbon-based composite catalyst is used as the cathode, and a separate anode electrode is provided. The electrolyte in the cathode chamber is a hypophosphoric acid solution containing red phosphorus, and the electrolyte in the anode chamber is a dilute sulfuric acid aqueous solution, so as to carry out electrocatalytic preparation of phosphine.

10. The application as described in claim 9, characterized in that, The anode electrode is an IrO2-Ta2O5 / Ti electrode, with a molar ratio of Ir to Ta of 1:2-4, and the loading of IrO2-Ta2O5 on the Ti electrode is 5-15%; in the electrolyte of the cathode chamber, the concentration of hypophosphite solution is 1-10M, the concentration of red phosphorus is 5-50g / L, and the concentration of dilute sulfuric acid aqueous solution is 0.5-3M.

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