Preparation method of palladium monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia

Abstract

The application discloses a preparation method of a Pd monatomic catalyst for efficiently electrocatalytically reducing ammonia synthesis, which comprises the following steps: co-treating Pd(PPh3)4 and CNT, wherein Pd is coordinated with P atoms and is stably arranged on the surface of the CNT with a conjugated structure through a P-C bond to obtain the Pd monatomic catalyst for efficiently electrocatalytically reducing ammonia synthesis; and the catalyst prepared by the method can effectively improve the activity of electrocatalytic NO3 ‑ reduction for preparing ammonia.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of energy catalysis, and relates to a preparation method of a Pd monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia. BACKGROUND

[0002] In nature, nitrogen cycle plays a key role in maintaining life. Artificial synthesis of ammonia is one of the largest industrial synthetic chemicals in the world. At present, artificial synthesis of ammonia is widely used in the fields of agriculture, chemical industry, medicine and energy storage due to its high energy density, easy liquefaction and convenient transportation. At present, almost all ammonia in industry is synthesized by the Haber-Bosch process, which requires high-temperature and high-pressure reaction conditions and has problems of high energy consumption and large greenhouse gas emission. The N=N bond energy (941 kJ / mol) is very high and is difficult to break. Plasma-assisted activation of nitrogen to produce nitrate is a good way. In this case, direct reduction of nitrate to ammonia can supplement ammonia production without depleting fossil fuels. In fact, the lower bond dissociation energy n=O (204 kJ / mol) makes NO3 - an ideal nitrogen source for ammonia synthesis.

[0003] The electrochemical method is simple in operation and high in efficiency, and can directly reduce aqueous NO3 - to NH3. These processes require less energy than the Haber-Bosch process, and can solve environmental problems by building a new nitrogen cycle between NO3 - and NH3. However, many by-products such as NO2 - , N2, N2O, etc. are usually produced in the reduction reaction of NO3 - , which makes it an important problem to improve the selectivity of NO3 - reduction to produce ammonia, and the most fundamental reason is that the activity of electrocatalytic reduction of NO3 - to prepare ammonia is low. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned shortcomings of the prior art, and to provide a preparation method of a Pd monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia, which can effectively improve the activity of electrocatalytic reduction of NO3 - to prepare ammonia.

[0005] To achieve the above-mentioned purpose, the preparation method of the Pd monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia comprises: co-treating Pd(PPh3)4 and CNT, wherein Pd is coordinated with P atoms and stabilized on the surface of CNT with a conjugated structure through a P-C bond to obtain the Pd monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia.

[0006] Specifically comprising the following steps:

[0007] The carbon nanotubes CNT are dispersed in CH2Cl2, Pd(PPh3)4 is added, the loading amount of Pd metal is controlled to be 0.5-5 wt%, ultrasonic treatment is conducted to fully mix them, then stirring is conducted to completely volatilize CH2Cl2, and after grinding, heat treatment is conducted to obtain a Pd monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia.

[0008] The ratio of the carbon nanotubes CNT and Pd(PPh3)4 is (0.1-0.5) g:(0.01-0.05) g.

[0009] The ratio of the carbon nanotubes CNT and CH2Cl2 is (0.1-0.5) g:(20-100) ml.

[0010] The ultrasonic treatment time is 10-60 min.

[0011] The specific process of the stirring to completely volatilize CH2Cl2 is as follows:

[0012] Under magnetic stirring, the stirring time is 5-12 h, the rotating speed is controlled to be 300-500 rpm, and the stirring is conducted until CH2Cl2 is completely volatilized.

[0013] The grinding time is 10-30 min.

[0014] The specific process of the heat treatment is as follows: the sample is placed into a tube furnace, the heating rate is 2-10 ℃ / min, and the heat treatment is conducted for 3-6 h under the protection of argon.

[0015] The temperature in the heat treatment process is 300-600 ℃.

[0016] The present application has the following beneficial effects:

[0017] The preparation method of the Pd monatomic catalyst for efficient electrocatalytic reduction synthesis of ammonia has the advantages that the conjugated structure on the surface of the multi-walled carbon nanotubes CNT and the defects caused by P atom doping provide more sites for anchoring Pd monatomic, the NO3 - adsorption and activation are facilitated to improve the electrocatalytic activity of NO3 - reduction for preparing ammonia, the reaction conditions are simple, the activity is high, and the method is suitable for further scale production. It should be noted that the present application introduces a weak electronegative heteroatom P to improve the coordination environment around the metal atom Pd, reduce the adsorption energy of the intermediate in the reaction process, and has higher ammonia production activity and selectivity.

[0018] Further, the content of the noble metal Pd used in the present application is 0.5-3wt%, the content is low, the atomic utilization rate is high, the cost can be controlled within a certain range, and the single-atom catalyst structure is simple, which is helpful for in-depth understanding of the mechanism of electrocatalytic reduction of nitrate. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The spherical aberration electron microscope graph of Pd-P SAC in Example 1;

[0020] Figure 2 The LSV curve graph of Pd-P SAC in Example 1 in 0.1M KNO3 and 1M KOH electrolyte;

[0021] Figure 3a The electrocatalytic ammonia synthesis activity graph of the catalyst with different proportions of Pd loaded on CNT at each potential in Example 1, Example 2 and Example 3;

[0022] Figure 3b The faradic efficiency graph of the catalyst with different proportions of Pd loaded on CNT at each potential in Example 1, Example 2 and Example 3;

[0023] Figure 4a The electrocatalytic ammonia synthesis activity graph of the catalyst with different calcination temperatures at each potential in Example 1, Example 4 and Example 5;

[0024] Figure 4b The faradic efficiency graph of the catalyst with different calcination temperatures at each potential in Example 1, Example 4 and Example 5;

[0025] Figure 5 The ammonia yield and faradic efficiency (bias =-0.3V vs.RHE ) graph of the catalyst in Example 1 at different concentrations;

[0026] Figure 6a The electrocatalytic ammonia synthesis activity graph of the catalyst with different supports at each potential in Example 4;

[0027] Figure 6b The faradic efficiency graph of the catalyst with different supports at each potential in Example 4;

[0028] Figure 7a The electrocatalytic ammonia synthesis activity graph of the catalyst with different coordination environments at each potential in Example 5;

[0029] Figure 7b The faradic efficiency graph of the catalyst with different coordination environments at each potential in Example 5. DETAILED DESCRIPTION

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0031] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0032] The preparation method of the highly efficient electrocatalytic reduction Pd single-atom catalyst (Pd-PSAC catalyst) for ammonia synthesis according to the present invention includes the following steps:

[0033] Weigh 0.1-0.5 g of carbon nanotubes (CNTs) and disperse them in 20-100 ml of CH2Cl2. Add 0.01-0.05 g of Pd(PPh3)4, controlling the Pd metal loading at 0.5-5 wt%. Then, sonicate for 10-60 min to ensure thorough mixing. Stir magnetically for 5-12 h at a speed of 300-500 rpm until CH2Cl2 is completely volatilized. Grind in a mortar for 10-30 min. Then, place in a tube furnace and heat at 300-600 °C under argon protection for 3-6 h at a heating rate of 2-10 °C to obtain Pd-P SAC catalysts with different Pd loadings.

[0034] Electrocatalytic NO3 production at ambient temperature and pressure was conducted in a commercially available H-type reactor. - The ammonia production activity was tested using the indophenol blue spectrophotometric method according to GB / T18204.25-2000.

[0035] Example 1

[0036] The preparation process of 0.5% Pd / CNT is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.025g of Pd(PPh3)4 is added, controlling the Pd metal loading at 0.5wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing, and then stirred magnetically for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 0.5wt% (ICP result: 0.442wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia-producing activity was characterized using the indophenol blue spectrophotometric method (GB / T 18204.25-2000).

[0037] The preparation process of 3% Pd / CNT was as follows: 0.1 g of carbon nanotubes (CNTs) were dispersed in 40 ml of CH2Cl2, and 0.03 g of Pd(PPh3)4 was added, controlling the Pd metal loading at 1 wt%. The mixture was ultrasonically treated for 20 min to ensure thorough mixing. Then, under magnetic stirring, the mixture was stirred for 5 h at a speed of 500 rpm until the CH2Cl2 was completely volatilized. The dried sample was then ground in a mortar for 10 min, and then placed in a tube furnace. The temperature was increased at a rate of 5 °C / min, and the mixture was heat-treated at 500 °C under argon protection for 4 h to obtain a catalyst with a Pd loading of approximately 3 wt% (ICP result: 3.34 wt%). Electrocatalytic NO3-reduction was then performed at room temperature and pressure in a commercially available H-type reactor. - The ammonia-producing activity was characterized using the indophenol blue spectrophotometric method (GB / T 18204.25-2000).

[0038] The preparation process of Pd-P SAC (1% Pd / CNT) is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing, and then stirred magnetically for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. -The ammonia synthesis activity was tested using the indophenol blue spectrophotometric method (GB / T 18204.25-2000). Pd-P SAC showed the best performance, with ammonia synthesis activities of 1.34, 2.49, 4.38, 5.18, and 6.97 mg / h / cm² in 0.1 M KNO₃ + 1 M KOH at bias voltages of -0.2, -0.3, -0.4, -0.5, and -0.6 V, respectively. 2 The ammonia-Faraday efficiencies were 86.72%, 92.83%, 81.63%, 77.73%, and 71.33%, respectively.

[0039] Example 2

[0040] The preparation process of Pd-P SAC(1% Pd / CNT)-400 is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, it is stirred for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 400℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia-producing activity was characterized using the indophenol blue spectrophotometric method (GB / T 18204.25-2000).

[0041] The preparation process of Pd-P SAC(1% Pd / CNT)-500 is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, it is stirred for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia-producing activity was characterized using the indophenol blue spectrophotometric method (GB / T 18204.25-2000).

[0042] The preparation process of Pd-P SAC(1% Pd / CNT)-600 is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added. The Pd metal loading is controlled at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, the mixture is stirred for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 600℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia reduction activity was tested and characterized using the indophenol blue spectrophotometric method (GB / T 18204.25-2000). The experimental results showed that the Pd-P SAC catalyst calcined at 500 degrees Celsius had the best nitrate reduction activity.

[0043] Example 3

[0044] The preparation process of Pd-P SAC(1% Pd / CNT)-500 is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added. The Pd metal loading is controlled at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, the mixture is stirred for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia production activity of the catalyst was tested using the indophenol blue spectrophotometric method (GB / T 18204.25-2000). The Faradaic efficiencies of the catalyst for ammonia production under 1M KOH + 0.01 / 0.05 / 0.1 / 0.5 and 1M KNO3 conditions were 67.45, 89.32, 92.83, 87.57 and 79.56%, respectively.

[0045] Example 4

[0046] The preparation process of Pd / CNT is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added. The Pd metal loading is controlled at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, it is stirred for 5h at a speed of 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia production activity was tested using the indophenol blue spectrophotometric method (GB / T 18204.25-2000).

[0047] The preparation process of Pd / GO is as follows: 0.5g of graphene oxide is dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, it is stirred for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt%. This catalyst is then subjected to electrocatalytic NO3-reduction at room temperature and pressure in a commercially available H-type reactor. - The ammonia production activity was tested using the indophenol blue spectrophotometric method according to GB / T18204.25-2000.

[0048] The preparation process of Pd / CB is as follows: 0.5g of carbon black CB is dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, it is stirred for 5h at 500rpm until CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt%. This catalyst is then subjected to electrocatalytic NO3-reduction at room temperature and pressure in a commercially available H-type reactor. - The ammonia reduction activity was tested and characterized using the indophenol blue spectrophotometric method according to GB / T18204.25-2000. The experimental results showed that the Pd / CNT catalyst supported on carbon nanotubes (CNTs) had the best activity for nitrate reduction and the best Faradaic efficiency for ammonia.

[0049] Example 5

[0050] The preparation process of Pd-P SAC (1% Pd / CNT) is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of CH2Cl2, and 0.05g of Pd(PPh3)4 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing, and then stirred magnetically for 5h at 500rpm until the CH2Cl2 is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt% (ICP result: 0.803wt%). Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia production activity was tested using the indophenol blue spectrophotometric method (GB / T 18204.25-2000).

[0051] The preparation process of Pd-C SAC is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of dilute hydrochloric acid, and 0.04g of PdCl2 is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing, then stirred magnetically for 5h at 500rpm. The mixture is then freeze-dried overnight. The dried sample is ground in a mortar for 10min, and then placed in a tube furnace. The temperature is increased at 5℃ / min, and the sample is heat-treated at 500℃ under argon protection for 4h to obtain a catalyst with a Pd loading of approximately 1wt%. Electrocatalysis of NO3- under ambient temperature and pressure is then performed in a commercially available H-type reactor. - The ammonia production activity was tested using the indophenol blue spectrophotometric method according to GB / T18204.25-2000.

[0052] The preparation process of Pd-N SAC is as follows: 0.5 g of carbon nanotubes (CNTs) are dispersed in 40 ml of ultrapure water, and 0.06 g of Pd(NH3)4(NO3)2 is added, controlling the Pd metal loading at 1 wt%. The mixture is ultrasonically treated for 20 min to ensure thorough mixing, then stirred magnetically for 5 h at 500 rpm. The mixture is then freeze-dried overnight. The dried sample is ground in a mortar for 10 min, and then placed in a tube furnace. The temperature is increased at 5 °C / min, and the sample is heat-treated at 500 °C under argon protection for 4 h to obtain a catalyst with a Pd loading of approximately 1 wt%. Electrocatalysis of NO3- is then performed at room temperature and pressure in a commercially available H-type reactor. - The ammonia production activity was tested using the indophenol blue spectrophotometric method according to GB / T18204.25-2000.

[0053] The preparation process of Pd-O SAC (1% Pd / CNT) is as follows: 0.5g of carbon nanotubes (CNTs) are dispersed in 40ml of acetonitrile, and 0.07g of Pd(OAC)₂ is added, controlling the Pd metal loading at 1wt%. The mixture is ultrasonically treated for 20min to ensure thorough mixing. Then, under magnetic stirring, it is stirred for 5h at 500rpm until the acetonitrile is completely volatilized. The dried sample is then ground in a mortar for 10min. The sample is then placed in a tube furnace and heat-treated at 500℃ under argon protection for 4h at a heating rate of 5℃ / min to obtain a catalyst with a Pd loading of approximately 1wt%. Electrocatalytic NO₃⁻ is then performed at room temperature and pressure in a commercially available H-type reactor. - The ammonia reduction activity was characterized using the indophenol blue spectrophotometric method (GB / T18204.25-2000). Experimental results showed that the P-coordinated catalyst exhibited the best activity and ammonia Faradaic efficiency for nitrate reduction.

[0054] Example 6

[0055] The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to the present invention includes the following steps:

[0056] 0.1 g of carbon nanotubes (CNTs) were dispersed in 20 ml of CH2Cl2, and 0.01 g of Pd(PPh3)4 was added. The mixture was then sonicated for 10 min to ensure thorough mixing. The mixture was then stirred magnetically for 5 h at a speed of 300 rpm until the CH2Cl2 was completely volatilized. The mixture was then ground in a mortar for 10 min and then placed in a tube furnace. The furnace was heated at a rate of 2 °C / min and then heat-treated at 300 °C under argon protection for 3 h to obtain Pd-P SAC catalysts with different Pd loadings.

[0057] Example 7

[0058] The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to the present invention includes the following steps:

[0059] 0.5 g of carbon nanotubes (CNTs) were dispersed in 100 ml of CH2Cl2, and 0.05 g of Pd(PPh3)4 was added. The mixture was then sonicated for 60 min to ensure thorough mixing. The mixture was then stirred magnetically for 12 h at a speed of 500 rpm until the CH2Cl2 was completely volatilized. The mixture was then ground in a mortar for 30 min and then placed in a tube furnace. The furnace was heated at a rate of 10 °C / min and then heat-treated at 600 °C under argon protection for 6 h to obtain Pd-P SAC catalysts with different Pd loadings.

[0060] Example 8

[0061] The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to the present invention includes the following steps:

[0062] 0.3 g of carbon nanotubes (CNTs) were dispersed in 50 ml of CH2Cl2, and 0.03 g of Pd(PPh3)4 was added. The mixture was then sonicated for 35 min to ensure thorough mixing. The mixture was then stirred magnetically for 8 h at a speed of 400 rpm until the CH2Cl2 was completely volatilized. The mixture was then ground in a mortar for 20 min and then placed in a tube furnace. The furnace was heated at a rate of 6 °C / min and then heat-treated at 450 °C under argon protection for 4.5 h to obtain Pd-P SAC catalysts with different Pd loadings.

[0063] Example 9

[0064] The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to the present invention includes the following steps:

[0065] 0.2 g of carbon nanotubes (CNTs) were dispersed in 30 ml of CH2Cl2, and 0.03 g of Pd(PPh3)4 was added. The mixture was then sonicated for 20 min to ensure thorough mixing. The mixture was then stirred magnetically for 6 h at a speed of 350 rpm until the CH2Cl2 was completely volatilized. The mixture was then ground in a mortar for 15 min and then placed in a tube furnace. The furnace was heated at a rate of 4 °C / min and then heat-treated at 350 °C under argon protection for 4 h to obtain Pd-P SAC catalysts with different Pd loadings.

[0066] Example 10

[0067] The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to the present invention includes the following steps:

[0068] 0.4 g of carbon nanotubes (CNTs) were dispersed in 90 ml of CH2Cl2, and 0.04 g of Pd(PPh3)4 was added. The mixture was then sonicated for 50 min to ensure thorough mixing. The mixture was then stirred magnetically for 10 h at a speed of 450 rpm until the CH2Cl2 was completely volatilized. The mixture was then ground in a mortar for 25 min and then placed in a tube furnace. The furnace was heated at a rate of 8 °C / min and then heat-treated at 550 °C under argon protection for 5 h to obtain Pd-P SAC catalysts with different Pd loadings.

[0069] Targeting NO3 - To address the problems encountered in ammonia reduction, this invention utilizes the atomically dispersed metal sites on carbon nanotubes (CNTs) to enhance the reduction of NO3-. - The adsorption and activation of NO3- by the introduction of heteroatoms (P) reduces the adsorption energy of the metal active sites for the intermediate, thereby enabling the catalyst to achieve highly efficient electrocatalysis of NO3-.- The performance of ammonia synthesis by reduction was assessed. First, CNTs, Pd(PPh3)4, and CH2Cl were mixed and stirred to adsorb the metal precursor onto a support. Then, Pd single atoms were anchored onto CNTs through heat treatment. The prepared catalyst was then subjected to electrocatalytic NO3-reduction at room temperature and pressure in an H-type reactor. - Activity testing for ammonia synthesis via reduction. This catalyst not only fully utilizes the large specific surface area and good conductivity of carbon nanotubes, making them easy to support co-catalysts, but also leverages the Pd single atom to effectively enhance the overall electron transport capability of the catalyst. Furthermore, the introduction of P heteroatoms creates unsaturated metal coordination sites that further strengthen the control of NO3-. - The adsorption and activation of molecules, and the construction of a three-phase interface on the catalyst surface in the reactor, significantly enhance the electrocatalytic activity for ammonia synthesis, promoting the practical application of Pd single-atom catalysts in ammonia synthesis.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a single-atom catalyst for the efficient electrocatalytic reduction of Pd in ​​ammonia synthesis, characterized in that, include: Pd(PPh3)4 was co-treated with CNTs, in which Pd coordinated with P atoms and stabilized on the surface of the conjugated CNTs through PC bonds, resulting in a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis. Specifically, the following steps are included: Carbon nanotubes (CNTs) were dispersed in CH2Cl2, and Pd(PPh3)4 was added. The loading of Pd metal was controlled at 0.5-5 wt%. The mixture was then ultrasonically treated to ensure thorough mixing. After stirring, CH2Cl2 was completely volatilized. The mixture was then ground and heat-treated to obtain a single-atom Pd catalyst for the efficient electrocatalytic reduction of ammonia.

2. The method for preparing a single-atom Pd catalyst for the efficient electrocatalytic reduction of ammonia synthesis according to claim 1, characterized in that, The ratio of carbon nanotubes (CNTs) to Pd(PPh3)4 was (0.1-0.5)g:(0.01-0.05)g.

3. The method for preparing a single-atom Pd catalyst for the efficient electrocatalytic reduction of ammonia synthesis according to claim 1, characterized in that, The ratio of carbon nanotubes (CNTs) to CH2Cl2 is (0.1-0.5) g : (20-100) ml.

4. The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to claim 1, characterized in that, The ultrasonic treatment time is 10-60 minutes.

5. The method for preparing a single-atom catalyst for the efficient electrocatalytic reduction of Pd in ​​ammonia synthesis according to claim 1, characterized in that, The specific process by which the stirring completely volatilizes CH2Cl2 is as follows: Stir with magnetic stirring for 5-12 hours at a speed of 300-500 rpm until CH2Cl2 is completely volatilized.

6. The method for preparing a single-atom Pd catalyst for efficient electrocatalytic reduction of ammonia synthesis according to claim 1, characterized in that, The grinding time is 10-30 minutes.

7. The method for preparing a single-atom catalyst for the efficient electrocatalytic reduction of Pd in ​​ammonia synthesis according to claim 1, characterized in that, The specific process of heat treatment is as follows: place it in a tube furnace, heat at a rate of 2-10℃ / min, and heat treat for 3-6 hours under argon protection.

8. The method for preparing a single-atom catalyst for the efficient electrocatalytic reduction of Pd in ​​ammonia synthesis according to claim 1, characterized in that, The temperature during the heat treatment process is 300-600℃.

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