A universal preparation method for ultrathin palladium-based nanosheets
Ultrathin palladium-based nanosheets were prepared by solvent thermal method, which solved the problem of low nitrogen reduction activity in ammonia synthesis at room temperature and pressure, and achieved efficient and stable ammonia production and high selective catalysis.
Patent Information
- Application Number
- CN202211636610.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-12
- Publication Date
- 2025-04-18
- Estimated Expiration
- 2042-12-12
AI Technical Summary
The prior art has low nitrogen reduction activity in ammonia synthesis at room temperature and pressure, low ammonia yield and Faraday efficiency, and poor selectivity.
The metal precursor such as Pd(acac)2 was reduced in a mixed solvent of ethylene glycol and DMF by solvent heat method, and then reacted under closed conditions. Ultrathin palladium-based nanosheets with controllable morphology were prepared.
The prepared ultrathin palladium-based nanosheets exhibit excellent electrocatalytic activity and stability in nitrogen reduction reaction, improving ammonia yield and Faraday efficiency, and having high selectivity.
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Figure CN115740484B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalyst preparation, and specifically relates to a method for preparing an ultrathin palladium-based nanosheet. The ultrathin palladium-based nanosheet, as a catalyst, exhibits high catalytic activity and excellent stability in nitrogen reduction reaction. Background Art
[0002] Two-dimensional materials have become one of the most widely studied materials due to the rich and unusual physical phenomena that occur when charge and heat transport are confined to a plane. The structure / electronic state of noble metal nanocatalysts generally plays an important role in catalytic activity. At present, two-dimensional noble metal nanomaterials have ultra-high specific surface area, excellent electron mobility and conductivity, and because of their special surface unsaturated atoms and unique electronic states, they provide great convenience for nitrogen adsorption and subsequent catalytic processes.
[0003] However, it is worth noting that the extremely stable N≡N bond (941 kJ mol -1 ) is difficult to break, and the strong competition from the hydrogen evolution reaction leads to extremely low ammonia yield and Faraday efficiency (FE), as well as poor selectivity. Therefore, the rational design and development of highly active and highly selective electrocatalysts is crucial to improving ammonia synthesis at room temperature and pressure. Studies have shown that since the α-palladium hydride formed on the surface of palladium-based catalysts can reduce the free energy barrier of nitrogen hydrogenation to form *N2H (the rate-limiting step in the electrochemical synthesis of ammonia), palladium-based nanomaterials can show good nitrogen reduction activity at low overpotentials. Therefore, two-dimensional palladium-based catalysts can be used as a potential catalyst for electrochemical synthesis of ammonia. Summary of the invention
[0004] The problem to be solved by the present invention is to provide a method for preparing an ultra-thin palladium-based nanosheet with controllable morphology by reducing palladium ions and other metal ion precursors through a simple solvent thermal method.
[0005] The technical solution adopted to solve the above problems is: add Pd(acac)2, Co(acac)2, Cu / Ag / Fe / Mo metal precursors to a mixed solvent of ethylene glycol and DMF, add 200 mg of KOH to adjust the pH of the solution, mix them evenly, react at 160°C under closed conditions for 8 hours, collect black solids after the reaction, wash them by centrifugation with ethanol / water, and vacuum dry them to obtain ultrathin palladium-based nanosheets.
[0006] In the above preparation method, the metal precursors are Cu(acac)2 / AgNO3 / Fe(acac)3 / Na2MoO4 respectively.
[0007] In the above preparation method, the molar ratio of the metal precursors of Pd(acac)2, Co(acac)2, and Cu / Ag / Fe / Mo is 1:1:0.5 to 1:1:2, preferably 1:1:1.
[0008] The volume ratio of ethylene glycol to DMF in the above preparation method is 1:0.5 to 1:2, preferably 1:1.
[0009] In the above preparation method: the amount of KOH used is 100 mg to 300 mg, preferably 200 mg.
[0010] In the above preparation method: the reduction reaction is carried out under closed conditions at 140-180°C for 6-10 hours, preferably at 160°C for 8 hours.
[0011] The beneficial effects of the present invention are as follows:
[0012] 1. The present invention uses ethylene glycol and DMF as solvents and KOH as a pH regulator, and adopts a simple solvent thermal method to reduce palladium ions and other metal ions into ultra-thin palladium-based nanosheets with regular shapes in one step. The method is simple, economical, and suitable for large-scale production.
[0013] 2. The prepared ultrathin palladium-based nanosheet catalyst has a unique ultrathin structure, large specific surface area, excellent electron mobility and conductivity. At the same time, due to its special surface unsaturated atoms and unique electronic structure, it provides great convenience for nitrogen adsorption and subsequent catalytic processes.
[0014] 3. The prepared ultrathin palladium-based nanosheets exhibit excellent electrocatalytic activity and stability in nitrogen reduction reaction. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a scanning electron microscope image of the PdCoCu, PdCoAg, PdCoFe and PdCoMo ultrathin palladium-based nanosheets prepared in Example 1.
[0016] Figure 2 It is an atomic force microscope image of the PdCoCu, PdCoAg, PdCoFe and PdCoMo ultrathin palladium-based nanosheets prepared in Example 1.
[0017] Figure 3 1 is the X-ray diffraction pattern of the PdCoCu, PdCoAg, PdCoFe and PdCoMo ultrathin palladium-based nanosheets prepared in Example 1.
[0018] Figure 4The ammonia yield and Faraday efficiency of the PdCoCu, PdCoAg, PdCoFe and PdCoMo ultrathin palladium-based nanosheets prepared in Example 1 in a nitrogen-saturated 0.1 mol / L KOH aqueous solution. DETAILED DESCRIPTION
[0019] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.
[0020] Example 1
[0021] 0.0125mmol of Pd(acac)2, 0.0125mmol of Co(acac)2 and 0.0125mmol of metal precursor Cu(acac)2 / AgNO3 / Fe(acac)3 / Na2MoO4 were added to a mixture of 5mL of ethylene glycol and 5mL of DMF, and ultrasonicated for 30min to obtain a uniformly mixed solution. 200mg of KOH was added to adjust the pH of the solution, and then the obtained solution was transferred to a reactor, and the reactor was placed in an oven at 160°C for 8 hours to obtain a black suspension, which was centrifuged, washed, and dried in a vacuum oven at 60°C to obtain ultrathin palladium-based nanosheets.
[0022] Example 2
[0023] 0.0125mmol of Pd(acac)2, 0.0125mmol of Co(acac)2 and 0.025mmol of Cu(acac)2 were added to a mixture of 5mL of ethylene glycol and 5mL of DMF, and ultrasonicated for 30min to obtain a uniformly mixed solution. 200mg of KOH was added to adjust the pH of the solution, and then the obtained solution was transferred to a reactor, which was placed in an oven at 160°C for 8 hours to obtain a black suspension, which was centrifuged, washed, and dried in a vacuum oven at 60°C to obtain ultrathin palladium-based nanosheets.
[0024] Example 3
[0025] 0.0125mmol of Pd(acac)2, 0.0125mmol of Co(acac)2 and 0.0125mmol of Cu(acac)2 were added to a mixture of 5mL of ethylene glycol and 5mL of DMF, and ultrasonicated for 30min to obtain a uniformly mixed solution. 400mg of KOH was added to adjust the pH of the solution, and then the obtained solution was transferred to a reactor, which was placed in an oven at 160°C for 8 hours to obtain a black suspension, which was centrifuged, washed, and dried in a vacuum oven at 60°C to obtain ultrathin palladium-based nanosheets.
[0026] Example 4
[0027] 0.0125mmol of Pd(acac)2, 0.0125mmol of Co(acac)2 and 0.0125mmol of Cu(acac)2 were added to a mixture of 10mL of ethylene glycol and 0mL of DMF, and ultrasonicated for 30min to obtain a uniformly mixed solution. 400mg of KOH was added to adjust the pH of the solution, and then the obtained solution was transferred to a reactor, which was placed in an oven at 160°C for 8 hours to obtain a black suspension, which was centrifuged, washed, and dried in a vacuum oven at 60°C to obtain ultrathin palladium-based nanosheets.
[0028] Example 5
[0029] 0.0125mmol of Pd(acac)2, 0.0125mmol of Co(acac)2 and 0.0125mmol of Cu(acac)2 were added to a mixture of 5mL of ethylene glycol and 5mL of DMF, and ultrasonicated for 30min to obtain a uniformly mixed solution. 400mg of KOH was added to adjust the pH of the solution, and then the obtained solution was transferred to a reactor, which was placed in an oven at 180°C for 6 hours to obtain a black suspension, which was centrifuged, washed, and dried in a vacuum oven at 60°C to obtain ultrathin palladium-based nanosheets.
Claims
1. A universal preparation method for ultrathin palladium-based nanosheets, characterized in that: Pd(acac)2, Co (acac)2 and Cu / Ag / Fe / Mo metal precursors are added to a mixed solvent of ethylene glycol and DMF, 200 mg of KOH is added to adjust the pH of the solution, and after uniform dispersion, the mixture is reacted at 160°C for 8 hours under closed conditions. After the reaction, the mixture is centrifugally washed with ethanol / water and vacuum dried to obtain ultrathin palladium-based nanosheets, wherein the molar ratio of the Pd(acac)2 to Co (acac)2 and Cu / Ag / Fe / Mo metal precursors is 1:1:(0.5-2), and the volume ratio of ethylene glycol to DMF is 1:(0.5-2).
2. The method for preparing an ultrathin palladium-based nanosheet according to claim 1, wherein: The metal precursor may be Cu(acac)2 / AgNO3 / Fe(acac)3 / Na2MoO4.