Preparation method of black phosphorus / metal-organic framework composite water splitting electrocatalyst
By combining electrochemical and ultrasonic exfoliation methods to prepare ultrathin black phosphorus nanosheets and metal-organic framework composites, the problems of high cost of noble metal-based catalysts and easy degradation of black phosphorus were solved, and efficient and stable water splitting electrocatalysts were prepared, which are suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN INST OF TECH
- Filing Date
- 2023-05-30
- Publication Date
- 2026-06-05
AI Technical Summary
The high cost and scarcity of noble metal-based catalysts in existing technologies limit their application in renewable energy technologies. Furthermore, the active lone pair electrons on the surface of black phosphorus nanosheets make them prone to degradation, affecting the stability of electrocatalytic water splitting. Existing preparation methods for BP/MOF composite materials are complex and unsuitable for large-scale production.
Ultrathin black phosphorus nanosheets were prepared by combining electrochemical exfoliation and ultrasonic exfoliation, and then composited with a metal-organic framework. After treatment with cobalt acetate and 2-methylimidazole solution, the nanosheets were heat-treated under an inert atmosphere to prepare a black phosphorus/metal-organic framework composite water splitting electrocatalyst.
The prepared electrocatalyst exhibits excellent performance, mild and safe reaction conditions, high product yield, and low production cost. Moreover, the overpotential only increases by 9 mV after 2000 cycles, demonstrating good stability and economic benefits.
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Figure CN116641097B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for preparing a water splitting electrocatalyst. Background Technology
[0002] The energy crisis and environmental problems have made the development of clean and renewable energy sources imperative to replace non-renewable energy sources such as fossil fuels. Electrochemical water splitting provides an effective pathway for the development of renewable energy. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are crucial half-reactions in the water splitting process. Currently, noble metal-based electrocatalysts exhibit the most efficient water splitting activity, particularly Pt-based HER catalysts and Ir / Ru-based OER catalysts. However, the high cost and scarcity of these noble metal-based catalysts limit their practical application in renewable energy technologies.
[0003] Black phosphorus (BP), as an emerging two-dimensional material, has become a potential metal-free electrocatalyst for HER and OER due to its attractive properties, such as tunable band gap, high carrier mobility, and unique anisotropic structure. However, the presence of active lone pairs of electrons on the surface of BP nanosheets makes them highly susceptible to degradation, thus affecting the long-term stability of BP electrocatalytic water splitting. Theoretical studies have shown that metal-organic frameworks (MOFs) possess good conductivity and excellent electrocatalytic performance. Therefore, combining BP and MOF allows for a stable and efficient electron flow that continuously migrates from BP to MOF. This not only effectively suppresses the activity of lone pairs of electrons in BP, but also the strong synergistic effect of BP and MOF contributes to the electrocatalytic activity of BP / MOF. Research on many similar materials has been conducted. Patent CN110078034A discloses a method for preparing a metal-organic framework-coated two-dimensional black phosphorus composite for gas detection or gas storage using terephthalic acid, aminated terephthalic acid, dimethylimidazole, and terephthalic acid as ligands via a solvothermal process. Patent CN114381315A discloses a bidirectional composite black phosphorus quantum dot / copper-based metal-organic framework (MOF) lubricant additive prepared using 1,3,5-benzenetricarboxylic acid as a ligand via a combination of solvothermal and ball milling. Patent CN108745404A discloses a composite material for waste gas treatment, consisting of carbon nitride prepared from urea, a layer-by-layer self-assembly method to modify the porous carbon nitride surface with a metal-organic framework, and a mixture of this metal-organic framework and two-dimensional black phosphorus material, filtered to form a black phosphorus / MOF-modified carbon nitride membrane. Patent CN109602919A discloses a composite material for tumor therapy, consisting of a core-shell MOF coated with sodium polystyrene benzenesulfonate modified with dimethylimidazole as a ligand. Patent CN112421038A discloses a composite material of black phosphorus nanosheets coated with a metal-organic framework, its preparation method, and its applications.
[0004] The aforementioned patents are applied to gas detection and storage, lubricant additives, waste gas treatment, and tumor treatment, respectively, but there is no research on electrocatalysis, especially electrocatalytic water splitting. Furthermore, the preparation methods are complex and the reaction conditions are harsh, making large-scale production difficult.
[0005] Current research on BP / MOF electrocatalysts is limited, especially on BP / MOF water splitting electrocatalysts. As my country is a major energy consumer, developing a stable and efficient electrocatalyst for simultaneous water splitting and oxygen / hydrogen production is of great significance. Obtaining a stable and efficient experimental method for preparing clean energy (H2 and O2) electrocatalysts will be beneficial in addressing the energy crisis and environmental pollution problems. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing a highly efficient water splitting electrocatalyst. The electrocatalyst obtained by this method has excellent performance and good reproducibility, mild and safe reaction conditions, high product yield, and low production cost, and has good economic benefits and application prospects.
[0007] To achieve the above objectives, the following technical solution is adopted:
[0008] A method for preparing a black phosphorus / metal-organic framework composite water splitting electrocatalyst includes the following steps:
[0009] (1) Ultrathin BP (FL-BP) was prepared by combining electrochemical exfoliation and ultrasonic exfoliation.
[0010] (2) Add the ultrathin BP layer to the methanol solution of cobalt acetate, and add the methanol solution of 2-methylimidazole while stirring. Let stand, centrifuge, wash with alcohol, and dry.
[0011] (3) The product was heat-treated under an inert atmosphere to obtain a black phosphorus / metal-organic framework composite water splitting electrocatalyst.
[0012] According to the above scheme, in step 1, the electrochemical stripping method uses a block of BP wrapped with carbon cloth as the cathode and a Pt electrode as the anode. The solute used in the electrolyte is tetrabutylammonium bromide, hexadecyltrimethylammonium chloride or hexadecyloxyammonium chloride; the solvent used is N,N-dimethylformamide, N-methylpyrrolidone or dimethyl sulfoxide.
[0013] According to the above scheme, the solution concentration for electrochemical stripping of black phosphorus in step 1 is 1-3 mmol; the stripping time is 1-5 h.
[0014] According to the above scheme, the ultrasonic processing power of the ultrasonic stripping method in step 1 is 800-1500W, the start / stop time ratio is 6:1, and the processing time is 2-4h.
[0015] According to the above scheme, the settling time in step 2 is 12-48 hours.
[0016] According to the above scheme, the heat treatment atmosphere in step 3 is N2 and Ar, the temperature is 250-350℃, and the time is 1-2h.
[0017] According to the above scheme, the mass ratio of black phosphorus to metal-organic framework in the black phosphorus / metal-organic framework composite water splitting electrocatalyst obtained in step 3 is (1-3):6.
[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0019] The preparation method of the black phosphorus / metal-organic framework composite water splitting electrocatalyst disclosed in this invention has excellent performance and good reproducibility. The reaction conditions are mild and safe, and the product yield is high with low production cost, which has good economic benefits and application prospects.
[0020] The black phosphorus / metal-organic framework composite water splitting electrocatalyst obtained in this invention operates at 10 mA cm⁻¹ -2 The water splitting potential at the current density is as low as 1.64V, which is better than previously reported BP-based bifunctional catalysts.
[0021] The black phosphorus / metal-organic framework composite water splitting electrocatalyst obtained by this invention has excellent stability. After 2000 cycles of water splitting electrocatalysis testing, the overpotential only increased by 9mV, overcoming the defect of poor stability of black phosphorus nanosheets. Attached Figure Description
[0022] Figure 1 XRD patterns of BP and MOF obtained in Examples 1 and 2 and BP / MOF (2:6) obtained in Example 4.
[0023] Figure 2 Comparison of the long-term stability of the water splitting reaction of BP / MOF (2:6) obtained in Example 4 in 1M potassium hydroxide electrolyte. Detailed Implementation
[0024] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.
[0025] Example 1:
[0026] Preparation of black phosphorus nanosheets.
[0027] 0.05 g of carbon cloth-wrapped block BP was used as the cathode, and a Pt electrode as the anode. 0.0645 g of tetrabutylammonium bromide (TBAB) was dissolved in 100 mL of N,N-dimethylformamide (DMF) as the electrolyte. The layering process was carried out under an inert N2 gas atmosphere with a constant voltage of -10 V for 3 h. After layering, the peeled BP sheets were sonicated for 3 h. Then, the BP sheets were rapidly transferred to conical centrifuge tubes and centrifuged at 3000 rpm for 5 min to remove any unpeeled thick layers of BP sheets. Subsequently, the sheets were centrifuged at 12000 rpm for 0.5 h and washed three times with methanol to remove impurities, yielding black phosphorus nanosheets (FL-BP).
[0028] Example 2:
[0029] Preparation of MOFs.
[0030] Weigh 1.99 g of C4H6CoO4.4(H2O) (0.04 mol) and 2.63 g of 2-methylimidazole (0.16 mol), and add them separately to 20 mL of methanol to obtain two solutions (A and B). Add the latter (B) rapidly to the former (A), and stir the mixture magnetically for 1 h. Let it stand for 24 h, wash the precipitate three times with methanol, and then dry it under vacuum at 60 °C for 2 h. Finally, heat-treat the obtained product at 300 °C for 2 h under a N2 atmosphere to obtain a purple product, which was named MOF.
[0031] Example 3:
[0032] Preparation of BP / MOF (1:6).
[0033] 0.199 g of C4H6CoO4.4(H2O) (0.04 mol) and 3 mg of FL-BP were added to 20 mL of methanol, and 0.263 g of 2-methylimidazole (0.16 mol) was added to 20 mL of methanol, yielding two solutions (A and B). The latter (B) was rapidly added to the former (A), and the mixture was magnetically stirred for 1 h, allowed to stand for 24 h, and the precipitate was washed three times with methanol and then dried under vacuum at 60 °C for 2 h. Finally, the product was heat-treated at 300 °C for 2 h under a N2 atmosphere to obtain a black product, named BP / MOF(1:6).
[0034] Example 4
[0035] Preparation of BP / MOF(2:6).
[0036] 0.199 g of C4H6CoO4.4(H2O) (0.04 mol) and 6 mg of FL-BP were added to 20 mL of methanol, and 0.263 g of 2-methylimidazole (0.16 mol) was added to 20 mL of methanol, yielding two solutions (A and B). The latter (B) was rapidly added to the former (A), and the mixture was magnetically stirred for 1 h, allowed to stand for 24 h, and the precipitate was washed three times with methanol and then dried under vacuum at 60 °C for 2 h. Finally, the resulting product was heat-treated at 300 °C for 2 h under a N2 atmosphere to obtain a black product, named BP / MOF(2:6).
[0037] Figure 1 The images show the XRD patterns of the BP / MOF (2:6) catalyst sample prepared in this example, and the BP and MOF nanomaterials prepared in Examples 1 and 2. Figure 1 It can be seen that the sample has obvious characteristic diffraction peaks of BP, but no obvious characteristic diffraction peaks of MOF. This may be because the composite material changes the phase of MOF.
[0038] Example 5
[0039] Preparation of BP / MOF(3:6).
[0040] 0.199 g of C4H6CoO4.4(H2O) (0.04 mol) and 9 mg of FL-BP were added to 20 mL of methanol, and 0.263 g of 2-methylimidazole (0.16 mol) was added to 20 mL of methanol, yielding two solutions (A and B). The latter (B) was rapidly added to the former (A), and the mixture was magnetically stirred for 1 h, allowed to stand for 24 h, and the precipitate was washed three times with methanol and then dried under vacuum at 60 °C for 2 h. Finally, the resulting product was heat-treated at 300 °C for 2 h under a N2 atmosphere to obtain a black product named BP / MOF(3:6).
[0041] Example 6
[0042] The obtained BP / MOF composite electrocatalyst was subjected to water splitting tests.
[0043] Accurately weigh 5 mg of the BP / MOF (2:6) prepared in Example 4, add 0.98 mL of ethanol and 0.02 mL of Nafion (5 wt%) solution, and sonicate for 30 minutes to mix thoroughly. Measure 0.15 mL of the dispersion and drop it onto two 1 cm x 1 cm sheets of carbon paper. After drying at room temperature, use these sheets as the working electrodes. Using an electrochemical workstation (CHI760E), in a two-electrode electrolytic cell, clamp the two sheets of carbon paper with electrode clamps. The reference electrode and counter electrode are the same piece, and the other piece serves as the working electrode. Using 1 M potassium hydroxide solution as the electrolyte, perform water splitting polarization curve testing on the BP / MOF (2:6) at a scan rate of 5 mV / s.
[0044] Figure 2 This is a linear sweep voltammogram of the BP / MOF (2:6) catalyst sample prepared in Example 4 in 1M potassium hydroxide electrolyte. The catalyst was measured at 10 mA cm⁻¹. -2 The water splitting potential at the specified current density is as low as 1.64 V, indicating that BP / MOF has good potential as a water splitting catalyst, which is superior to previously reported bifunctional BP-based catalysts. After 2000 cycles of continuous water splitting electrocatalytic testing, the overpotential increased by only 9 mV, indicating that the BP / MOF (2:6) catalyst prepared in this invention also has excellent water splitting electrocatalytic stability.
Claims
1. A method for preparing a black phosphorus / metal-organic framework composite water splitting electrocatalyst, characterized in that... Includes the following steps: (1) An ultrathin BP layer was prepared by combining electrochemical exfoliation and ultrasonic exfoliation; wherein, in the electrochemical exfoliation method, a block BP wrapped with carbon cloth was used as the cathode and a Pt electrode was used as the anode, and the solute used in the electrolyte was tetrabutylammonium bromide, hexadecyltrimethylammonium chloride or hexadecyloxyammonium chloride; the solvent used was N,N Dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide; the solution concentration for electrochemical stripping of black phosphorus is 1-3 mmol; the stripping time is 1-5 h; the ultrasonic treatment power is 800-1500 W, the start / stop time ratio is 6:1, and the treatment time is 2-4 h; (2) Add the ultrathin BP layer to the methanol solution of cobalt acetate, and add the methanol solution of 2-methylimidazole while stirring. Let stand for 12-48 h, centrifuge, wash with alcohol, and dry. (3) The product was heat-treated at 250-350 °C for 1-2 h under an inert atmosphere of N2 or Ar to obtain a black phosphorus / metal-organic framework composite water splitting electrocatalyst, wherein the mass ratio of black phosphorus to metal-organic framework was (1-3):6.