A black phosphorus-ferric tetraphosphide composite nanocatalyst and its preparation method
By preparing a pebble-shaped binary nanocomposite structure of black phosphorus-iron tetraphosphide composite nanoparticles, the problems of easy poisoning of noble metal catalysts and insufficient performance of non-noble metal catalysts were solved, and the high-efficiency and low-cost electrocatalytic ammonia synthesis effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN INSTITUTES OF ADVANCED TECHNOLOGY CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2022-06-28
- Publication Date
- 2026-05-26
AI Technical Summary
Existing precious metal catalysts are prone to poisoning and have short lifespans in the electrochemical synthesis of ammonia, while non-precious metal catalysts have low catalytic performance and insufficient stability, making it difficult to meet the requirements of low-energy consumption and environmentally friendly ammonia synthesis.
A highly active catalyst was prepared by using a pebble-shaped binary nanocomposite structure of black phosphorus-iron tetraphosphide composite nanoparticles, synthesized in one step by ball milling, and then exposed by ultrasonic cleaning with organic solvent.
It exhibits excellent electrocatalytic ammonia synthesis activity at low temperature and ambient pressure, with an ammonia synthesis rate of 80 μg/h/mgcat, which significantly improves catalytic performance and reduces costs.
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Figure CN116536699B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of energy catalysis technology, specifically relating to a black phosphorus-iron tetraphosphide composite nanocatalyst, its preparation method, and its application. Background Technology
[0002] Ammonia is an important chemical and energy material. Nitrogen atoms are essential components of biomolecules, making them necessary for pharmaceuticals and fertilizers. They also have wide applications in non-biological fields such as dyes, explosives, and resins, all requiring ammonia as a raw material. Ammonia can be cracked to produce hydrogen, thus ammonia is also widely used as a hydrogen storage material in the energy sector. The synthesis of ammonia from atmospheric nitrogen is hailed as one of the greatest scientific advances of the 20th century, with over 1% of the Earth's total energy used annually for ammonia synthesis. Currently, the most common method for ammonia synthesis is the Haber-Bosch cycle: nitrogen and hydrogen are used as reactants, and the reaction is carried out under high temperature and high pressure conditions using thermocatalysis based on Fe-based or Ru-based catalysts. However, thermocatalysis (300-550 degrees Celsius, 15-25 MPa) consumes large amounts of fossil fuels, and the combustion of fossil fuels leads to the emission of the greenhouse gas carbon dioxide. Faced with increasingly prominent global energy and environmental issues, energy conservation and emission reduction remain major challenges for the ammonia synthesis industry.
[0003] Electrochemical ammonia synthesis overcomes the thermodynamic limitations of the traditional Haber process, allowing the reaction to proceed at low temperatures and atmospheric pressures. This not only reduces the energy consumption required for the high temperature and pressure of the Haber process but also lowers the equipment requirements, making it a low-energy, environmentally friendly, and efficient synthesis method. Highly efficient electrocatalysts play a crucial role in electrochemical ammonia synthesis; currently, ammonia synthesis catalysts mainly include noble metal catalysts and non-noble metal catalysts.
[0004] Noble metal catalysts are typically catalysts containing elements such as Ru, Pd, and Pt. Using nitrogen and water as feedstock, they synthesize ammonia at a rate of 2.78 × 10⁻⁸ mol·s⁻¹·cm⁻² at 20°C. Commonly used non-noble metal catalysts are mainly transition metal oxide catalysts. For example: 1) Using Ni-SDC and SSC as cathode and anode catalysts, and sulfonated polysulfone polymer (SPSF) as the proton exchange material, moist hydrogen is introduced at the anode and dry nitrogen at the cathode for electrocatalytic ammonia synthesis; the ammonia synthesis rate reaches 6.5 × 10⁻⁹ mol·s⁻¹·cm⁻² at 2V and 80°C. 2) Using a La₀.₈Cs₀.₂Fe₀.₈Ni₀.₂O₃ + δ perovskite compound as the cathode for electrocatalytic ammonia synthesis, the ammonia synthesis rate reaches 9.21 × 10⁻⁷ mol·s⁻¹·cm⁻² at 400°C and 1.4V.
[0005] Precious metal catalysts exhibit superior catalytic performance, but they are susceptible to poisoning, have short lifespans, and are particularly expensive, making them unsuitable for practical applications. Non-precious metal catalysts, while offering significant cost advantages, suffer from lower catalytic performance and insufficient stability. Therefore, further research is needed to develop inexpensive and high-performance electrocatalysts to improve ammonia synthesis rates and meet production requirements. Summary of the Invention
[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a black phosphorus-iron tetraphosphide composite nanoparticle that exhibits excellent activity in the electrocatalytic synthesis of ammonia, and whose preparation process is simple and inexpensive.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0008] Firstly, this invention provides a black phosphorus-iron tetraphosphide composite nanocatalyst, which is a nano-binary composite structure formed by encapsulating pebble-shaped iron tetraphosphide nanocrystals with black phosphorus crystals.
[0009] Secondly, this invention provides a method for preparing a black phosphorus-iron tetraphosphide composite nanocatalyst, comprising the following steps:
[0010] 1) Add red phosphorus powder and iron powder to a high-energy ball mill jar and add steel balls. After ball milling, black powder is obtained.
[0011] 2) Place the black powder in an organic solvent, centrifuge using ultrasound, and remove the lower precipitate to obtain a solution of the black phosphorus-iron tetraphosphide composite nanocatalyst. During the reaction, excess black phosphorus will adhere to the surface of the nanocatalyst, reducing its activity. Therefore, it is necessary to use an organic solvent combined with ultrasonic cleaning to expose as many active catalytic sites as possible.
[0012] Specifically, the organic solvent in step 2) is NMP, DMF, or ethanol.
[0013] Furthermore, in the above-mentioned preparation method for black phosphorus-iron tetraphosphide composite nanocatalyst, the mass ratio of red phosphorus powder to iron powder is 6:2 to 3:2.
[0014] Furthermore, in step 1), the ball milling process is performed at 1000–1500 rpm for 6–9 hours.
[0015] Furthermore, in step 2), the ratio of organic solvent to black powder is (3-4) mL: 1 g.
[0016] Furthermore, in step 2), the ultrasound time is 25–40 min.
[0017] Furthermore, the centrifugation conditions in step 2) are 4500–600 rpm for 10–20 min.
[0018] The present invention also provides the application of the above-mentioned black phosphorus-iron tetraphosphide composite nanocatalyst or the black phosphorus-iron tetraphosphide composite nanocatalyst prepared by the above-mentioned method in the electrocatalytic synthesis of ammonia.
[0019] Compared with the prior art, the present invention has the following outstanding effects:
[0020] 1) This invention uses a one-step ball milling synthesis process, under appropriate process conditions, to directly convert red phosphorus powder and iron powder into nanoparticles with black phosphorus-iron tetraphosphide composite components. After simple cleaning and dispersion, the active sites distributed on the surface are further exposed.
[0021] Characterization analysis revealed the presence of numerous nanoscale black phosphorus-iron tetraphosphide two-phase structures in the catalyst. Electrocatalytic experiments verified the exceptional activity of this novel material in the electrocatalytic synthesis of ammonia. Attached Figure Description
[0022] Figure 1 The XRD pattern of the black phosphorus-ferric tetraphosphide composite nanocatalyst is shown.
[0023] Figure 2 This is a scanning electron microscope image of the black phosphorus-iron tetraphosphide composite nanocatalyst in Example 2;
[0024] Figure 3 This is an atomic force microscope image of the black phosphorus-iron tetraphosphide composite nanocatalyst in Example 2;
[0025] Figure 4 This is a transmission electron microscope image of the black phosphorus-iron tetraphosphide composite nanocatalyst in Example 2;
[0026] Figure 5 The images are X-ray electron microscope and high-resolution transmission electron microscope images of the black phosphorus-iron tetraphosphide composite nanocatalyst spheres in Example 2.
[0027] Figure 6 The catalytic reaction efficiency of the black phosphorus-iron tetraphosphide composite nanocatalyst in Example 2 under different voltages;
[0028] Figure 7 The results show the catalytic activity test results under different phosphorus-to-iron ratios, where Ti is a pure titanium mesh used as a blank control, and Fe... [1] P [4] Fe [1] P [6] Fe [1] P
[14] Fe [1] P
[32] Mix represents the nanocatalysts prepared in Comparative Example 2, Example 1, Example 2, Example 3 and Example 4, respectively. Detailed Implementation
[0029] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.
[0030] In Example 1, red phosphorus powder (5g) and iron powder (4g) were added to a high-energy ball mill jar along with 30g of steel balls. After ball milling at 1200rpm for 7 hours, a black powder was obtained. The powder was placed in 20mL of organic solvent (NMP, DMF, or ethanol) and sonicated for 30 minutes, followed by centrifugation (5000rpm, 15 minutes) to remove the lower precipitate, thus obtaining a solution of the nanocatalyst.
[0031] In Example 2, red phosphorus powder (5g) and iron powder (2g) were added to a high-energy ball mill jar along with 30g of steel balls. After ball milling at 1200rpm for 7 hours, a black powder was obtained. The powder was placed in 20mL of organic solvent (NMP, DMF, or ethanol) and sonicated for 30 minutes, followed by centrifugation (5000rpm, 15 minutes) to remove the lower precipitate, thus obtaining a solution of the nanocatalyst.
[0032] In Example 3, red phosphorus powder (5g) and iron powder (1g) were added to a high-energy ball mill jar along with 30g of steel balls. After ball milling at 1200rpm for 7 hours, a black powder was obtained. The powder was placed in 20mL of organic solvent (NMP, DMF, or ethanol) and sonicated for 30 minutes, followed by centrifugation (5000rpm, 15 minutes) to remove the lower precipitate, thus obtaining a solution of the nanocatalyst.
[0033] In Example 4, 5g of black phosphorus nanoparticles and 5g of ferric tetraphosphide nanoparticles were added to a conventional planetary ball mill jar along with 30g of steel balls. After ball milling at 300 rpm for 1 hour, a black powder was obtained. The powder was placed in 20mL of organic solvent (NMP, DMF, or ethanol) and sonicated for 30 minutes, followed by centrifugation (5000 rpm, 15 minutes) to remove the lower precipitate, thus obtaining a solution of the nanocatalyst.
[0034] Characterization of catalyst structure
[0035] The morphology and composition of the obtained catalysts were studied using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Taking the nanocatalyst prepared in Example 2 as an example, the XRD pattern of the catalyst showed that it possessed characteristic peaks of both iron tetraphosphide and black phosphorus crystals. Figure 1 This indicates that it possesses two different crystal compositions. Under scanning electron microscopy, the catalyst appears as a material with a size mostly around 100-300 nm. Figure 2 After careful analysis using an atomic force microscope, it can be seen that the thickness and diameter are close in value, which is a typical characteristic of granular materials. Figure 3 The catalyst, as observed in transmission electron microscopy (TEM) of (eBP NFs), exhibits a non-uniform distribution of color intensity. Figure 4 This may be due to the presence of two different crystals, iron tetraphosphide and black phosphorus.
[0036] Dark-field electron microscopy images clearly show that the catalyst particles are composed of smaller pebble-shaped microparticles with a diameter of 10-20 nm. Figure 5 a) Elemental analysis revealed a uniform distribution of iron and phosphorus elements within the catalyst particles. Figure 5 b, Figure 5 c). In high-resolution transmission electron microscopy images, regions with different lattice distributions in the catalyst structure can be clearly distinguished. Figure 5 d), after magnification, the crystal structures of iron tetraphosphide and black phosphorus can be distinguished. Figure 5 e, Figure 5 f, Figure 5 g, Figure 5 h).
[0037] Catalytic performance testing
[0038] The catalytic performance of the dispersions of black phosphorus-ferric tetraphosphide composite nanoparticles prepared in Examples 1-4 was tested using the following methods:
[0039] Electrochemical catalytic activity was measured using a CHI 760E electrochemical workstation (Shanghai, Chenhua) in a standard three-electrode configuration with an H-type gas-tight electrolytic cell. The H-type electrolytic cell (50 mL chamber volume) was separated using a Nafion 211 membrane, which was pre-treated in 3% H₂O₂ and 0.5 M H₂SO₄ solutions at 80 °C for 1 h, and then washed with ultrapure water. A platinum (Pt) plate and a saturated calomel electrode (SCE) were used as the counter and reference electrodes, respectively. 50 μL of an ethanol dispersion of black phosphorus-ferric tetraphosphide composite nanoparticles (1 mg·mL⁻¹) was used. -1 ) Lay on Ti mesh (1x1 cm) 2 The sample was dried at room temperature to obtain 0.05 mg·cm⁻¹.-2 The mass load. After the electrode is prepared, it is first subjected to 2mV·s. -1 Linear sweep voltammetry (LSV) was performed at a scan rate of [missing value], followed by ammonia synthesis assays and electrochemical it curves. Note that N2 was further purified by treatment with 0.1 M KOH and 0.05 M H2SO4 before being bubbled into the electrolyte cell. During electrochemical measurements, the gas was flowed at a rate of 50 mL / min. -1 The flow rate continuously permeates into the cathode chamber. According to the Nernst equation (ERHE=ESCE+0.059×pH+0.242), the potential is referenced to the reversible hydrogen electrode (RHE).
[0040] Comparative Example 1 consisted of black phosphorus nanoparticles dissolved in ethanol, and Comparative Example 2 consisted of ferric tetraphosphide nanoparticles dissolved in ethanol. Black phosphorus and ferric tetraphosphide were tested separately as catalysts, and the test procedures are as follows:
[0041] 1) Electrochemical catalytic activity was measured using a CHI 760E electrochemical workstation (Shanghai, Chenhua) in a standard three-electrode configuration with an H-type gas-tight electrolytic cell. The H-type electrolytic cell (50 mL chamber volume) was separated using a Nafion 211 membrane, which was pretreated in 3% H₂O₂ solution and 0.5 M H₂SO₄ solution at 80 °C for 1 h, and then washed with ultrapure water. A platinum (Pt) plate and a saturated calomel electrode (SCE) were used as the counter and reference electrodes, respectively. 50 μL of an ethanol dispersion of black phosphorus nanoparticles (1 mg·mL⁻¹) was... -1 ) Lay on Ti mesh (1x1 cm) 2 The sample was dried at room temperature to obtain 0.05 mg·cm⁻¹. -2 The mass load. After the electrode is prepared, it is first subjected to 2mV·s. -1 Linear sweep voltammetry (LSV) was performed at a scan rate of [missing value], followed by ammonia synthesis assays and electrochemical it curves. Note that N2 was further purified by treatment with 0.1 M KOH and 0.05 M H2SO4 before being bubbled into the electrolyte cell. During electrochemical measurements, the gas was [missing value] at a rate of 50 mL / min. -1 The flow rate continuously permeates into the cathode chamber. According to the Nernst equation (ERHE=ESCE+ 0.059×pH+0.242), the potential is referenced to the reversible hydrogen electrode (RHE).
[0042] 2) Electrochemical catalytic activity was measured using a CHI 760E electrochemical workstation (Shanghai, Chenhua) in a standard three-electrode configuration with an H-type gas-tight electrolytic cell. The H-type electrolytic cell (50 mL chamber volume) was separated using a Nafion 211 membrane, which was pre-treated in 3% H₂O₂ solution and 0.5 M H₂SO₄ solution at 80 °C for 1 h, and then washed with ultrapure water. A platinum (Pt) plate and a saturated calomel electrode (SCE) were used as the counter and reference electrodes, respectively. 50 μL of an ethanol dispersion of iron tetraphosphide nanoparticles (1 mg·mL⁻¹) was... -1 ) Lay on Ti mesh (1x1 cm) 2 The sample was dried at room temperature to obtain 0.05 mg·cm⁻¹. -2 The mass load. After the electrode is prepared, it is first subjected to 2mV·s. -1 Linear sweep voltammetry (LSV) was performed at a scan rate of [missing value], followed by ammonia synthesis assays and electrochemical it curves. Note that N2 was further purified by treatment with 0.1 M KOH and 0.05 M H2SO4 before being bubbled into the electrolyte cell. During electrochemical measurements, the gas was flowed at a rate of 50 mL / min. -1 The flow rate continuously permeates into the cathode chamber. According to the Nernst equation (ERHE = ESCE + 0.059 × pH + 0.242), the potential is referenced to the reversible hydrogen electrode (RHE).
[0043] Table 1 Catalytic test results of black phosphorus-ferric tetraphosphide composite nanocatalysts with different phosphorus-iron ratios
[0044]
[0045]
[0046] The black phosphorus-iron tetraphosphide composite nanocatalyst in Example 2 was tested. By measuring the current density at different voltages, it was found that the optimal operating voltage was around -0.20V. Figure 6 a) Further testing of the catalytic reaction efficiency under different voltages revealed that the catalyst achieved its highest catalytic efficiency at -0.20V, with a peak ammonia synthesis efficiency approaching 80 μg / h / mgcat. Figure 6 b, Figure 6 c).
[0047] Catalytic activity at different phosphorus-iron ratios ( Figure 7 The catalyst was tested and showed good stability under general electrocatalytic ammonia synthesis conditions, while the optimal iron-phosphorus ratio was around 1:14.
Claims
1. A black phosphorus-ferric tetraphosphide composite nanocatalyst, characterized in that, The pebble-shaped iron tetraphosphide nanocrystals were Nano-binary composite structure formed by black phosphorus crystal encapsulation.
2. A method for preparing a black phosphorus-ferric tetraphosphide composite nanocatalyst, characterized in that, The catalyst prepared is a nano-binary composite structure formed by pebble-shaped iron tetraphosphide nanocrystals encapsulated by black phosphorus crystals. The method includes the following steps: 1) Red phosphorus powder and iron powder are added to a high-energy ball mill jar at a mass ratio of 6:2 to 3:2 and steel balls are added. After ball milling, black powder is obtained; 2) The black powder is placed in an organic solvent, ultrasonically centrifuged, and the lower precipitate is removed to obtain a solution of black phosphorus-iron tetraphosphide composite nanocatalyst. In step 1), the ball milling is performed at 1000-1500 rpm for 6-9 hours.
3. The preparation method of the black phosphorus-ferric tetraphosphide composite nanocatalyst according to claim 2, characterized in that, The organic solvent in step 2) is NMP, DMF or ethanol.
4. The preparation method of the black phosphorus-ferric tetraphosphide composite nanocatalyst according to claim 2, characterized in that, In step 2), the ratio of organic solvent to black powder is (3-4) mL: 1 g.
5. The preparation method of the black phosphorus-ferric tetraphosphide composite nanocatalyst according to claim 2, characterized in that, In step 2), the ultrasound time is 25 to 40 minutes.
6. The preparation method of the black phosphorus-ferric tetraphosphide composite nanocatalyst according to claim 2, characterized in that, The centrifugation conditions for step 2) are 4500-600 rpm for 10-20 min.
7. The application of the black phosphorus-iron tetraphosphide composite nanocatalyst according to claim 1 or the black phosphorus-iron tetraphosphide composite nanocatalyst prepared by any one of claims 2 to 6 in the electrocatalytic synthesis of ammonia.