Method for preparing a metal single-atom catalyst with ultrahigh loading by vacuum pyrolysis

Abstract

The application discloses a method for preparing a metal single-atom catalyst with super-high metal loading capacity through vacuum pyrolysis and relates to the technical field of metal single-atom catalyst preparation. The technical scheme is specifically as follows: S1: loading a metal salt on a nitrogen-containing carbon carrier and then drying; S2: pyrolyzing the product of S1 at 300 DEG C-750 DEG C under a negative pressure of -0.1 to -0.03 Mpa for 0.01-5 h, so that a single-atom catalyst is obtained. The method can be used for preparing the single-atom catalyst with the metal loading capacity of more than 40 wt%, and the single-atom catalyst has super-high metal loading capacity.

Description

Technical Field

[0001] This invention relates to the field of metal single-atom catalyst preparation technology, and more specifically, to a method for preparing ultra-high loading metal single-atom catalysts by vacuum pyrolysis. Background Technology

[0002] Catalysts play a crucial role in chemical reactions, accelerating reaction rates, improving selectivity, and reducing energy consumption. Single-atom catalysts (SACs) are an emerging type of catalytic material in which an active metal is covalently linked to the support surface, existing as a single atom. Due to their unique charge and energy structure, single-atom catalysts typically exhibit catalytic properties significantly different from traditional nanocatalysts and bulk catalysts. They also possess a series of advantages such as high atom utilization and high stability, demonstrating immense application value in energy conversion devices (e.g., fuel cells, metal-air batteries, water electrolysis for hydrogen production, lithium batteries), environmental remediation (e.g., pollutant treatment, plastic recycling), organic synthesis (e.g., benzene oxidation, methane oxidation, olefin epoxidation), pharmaceutical analysis, and food testing, thus attracting widespread attention in recent years.

[0003] However, the catalytic activity of a catalyst depends not only on the properties of the active sites themselves but also on the number of catalytic sites. It is well known that due to excess surface free energy, microscopic particles exhibit a thermodynamic aggregation tendency during heat treatment. High-load catalysts, due to the close proximity of metal particles, struggle to maintain atomic-level dispersion of metal species during heat treatment, easily forming metal clusters or metal nanoparticles. Therefore, the metal loading of single-atom catalysts is typically limited to below 5 wt%, far lower than that of traditional nanocatalysts. This results in low mass activity of single-atom catalysts, hindering their industrial application. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing ultra-high metal single-atom catalysts by vacuum pyrolysis, which can prepare single-atom catalysts with a metal loading of more than 40 wt% and ultra-high metal loading.

[0005] The above-mentioned technical objective of this invention is achieved through the following technical solution: a method for preparing ultra-high loading metal single-atom catalysts by vacuum pyrolysis, specifically comprising the following steps:

[0006] S1: Load the metal salt onto a nitrogen-containing carbon support and then dry it;

[0007] S2: The product of S1 is pyrolyzed at 300℃-750℃ under a vacuum of -0.1 to -0.03 MPa for 0.01-5 hours to obtain a single-atom catalyst.

[0008] Furthermore, the nitrogen-containing carbon support is either carbon nitride or nitrogen-doped graphene.

[0009] Furthermore, the metal salt component is a transition metal or a noble metal element.

[0010] Furthermore, the transition metal and noble metal elements are platinum, palladium, ruthenium, iridium, manganese, iron, cobalt, nickel, copper, zinc, vanadium, chromium, niobium, molybdenum, gold, and mixtures thereof.

[0011] In summary, the present invention has the following beneficial effects:

[0012] 1. The prepared single-atom catalyst can achieve a metal loading of over 30 wt%;

[0013] 2. The method has strong applicability and is suitable for a variety of metallic elements and composite metallic components;

[0014] 3. The synthesis method is simple and easy to scale up industrially. Attached Figure Description

[0015] Figure 1 These are XRD patterns of Embodiments 1 and 2 of the present invention;

[0016] Figure 2 These are the XPS, STEM, and EXAFS results from Embodiment 1 of this invention;

[0017] Figure 3 This is a TEM image of Embodiment 2 of the present invention. Detailed Implementation

[0018] The following is in conjunction with the appendix Figure 1-3 The present invention will be described in further detail below.

[0019] A method for preparing ultra-high loading metal single-atom catalysts by vacuum pyrolysis specifically includes the following steps:

[0020] S1: Load the metal salt onto a nitrogen-containing carbon support and then dry it;

[0021] S2: The product of S1 is pyrolyzed at 300℃-750℃ under a vacuum of -0.1 to -0.03 MPa for 0.01-5 hours to obtain a single-atom catalyst.

[0022] The nitrogen-containing carbon materials used as carriers include, but are not limited to, carbon nitride or nitrogen-doped graphene formed by the pyrolysis of one or more of the following: resins, polymers, porphyrins, phthalocyanines, melamine, dicyandiamide, and guanine. The metal species are one or more of the following: platinum, palladium, ruthenium, iridium, manganese, iron, cobalt, nickel, copper, zinc, vanadium, chromium, niobium, molybdenum, and gold. The metal elements can be added during the carrier preparation process, or the carrier can be prepared first, and then the active metal elements can be loaded through methods such as impregnation, precipitation, or ion exchange.

[0023] Example 1: Melamine was pyrolyzed at 600°C under an argon atmosphere to obtain a carbon nitride support. A 1.6M copper nitrate solution was impregnated onto the carbon nitride support at a ratio of 3 ml / g, and dried overnight. The resulting sample was pyrolyzed in a vacuum furnace at 600°C under vacuum (-0.1 MPa) for 2 h to obtain a single-atom copper catalyst with a loading of 43 wt%. Figure 2 As can be seen, the sample in this embodiment is rich in copper, but the copper atoms do not aggregate and are dispersed at the atomic level.

[0024] Example 2: The difference from Example 1 is that vacuum pyrolysis is replaced with atmospheric pressure pyrolysis under argon gas to obtain nano-copper particle catalyst.

[0025] Example 3: The difference from Example 1 is that the vacuum pyrolysis pressure is changed to -0.06 MPa, resulting in a single-atom copper catalyst with a loading of 38 wt%.

[0026] Example 4: The difference from Example 1 is that the concentration of the copper nitrate solution was changed to 0.1M, resulting in a single-atom catalyst with a loading of 3.4wt%.

[0027] Example 5: The difference from Example 1 is that the concentration of the copper nitrate solution was changed to 0.8M, resulting in a single-atom catalyst with a loading of 23.4wt%.

[0028] Example 6: The difference from Example 1 is that melamine is replaced with carbon black to obtain a nano-copper particle catalyst.

[0029] Example 7: The difference from Example 1 is that the vacuum pyrolysis temperature is changed to 300°C, resulting in a single-atom catalyst with a loading of 37.3 wt%.

[0030] Example 8: The difference from Example 1 is that the vacuum pyrolysis temperature is changed to 500°C, resulting in a single-atom catalyst with a loading of 40.8 wt%.

[0031] Example 9: The difference from Example 1 is that the vacuum pyrolysis temperature is changed to 750°C, resulting in a single-atom catalyst with a loading of 41.8 wt%.

[0032] Example 10: The difference from Example 1 is that the vacuum pyrolysis time is changed to 0.01 h, resulting in a single-atom catalyst with a loading of 36.2 wt%.

[0033] Example 11: The difference from Example 1 is that the vacuum pyrolysis time is changed to 5 hours, resulting in a single-atom catalyst with a loading of 45.3 wt%.

[0034] Example 12: The difference from Example 1 is that the copper nitrate solution was replaced with an iron nitrate solution, resulting in a single-atom catalyst with a loading of 36.4 wt%.

[0035] Example 13: The difference from Example 1 is that the copper nitrate solution was replaced with a cobalt nitrate solution, resulting in a single-atom catalyst with a loading of 37.8 wt%.

[0036] Example 14: The difference from Example 1 is that the copper nitrate solution was replaced with a nickel nitrate solution, resulting in a single-atom catalyst with a loading of 34.2 wt%.

[0037] Example 15: The difference from Example 1 is that the copper nitrate solution was replaced with a zinc nitrate solution, resulting in a single-atom catalyst with a loading of 44.8 wt%.

[0038] Example 16: The difference from Example 1 is that the copper nitrate solution was replaced with a vanadium nitrate solution, resulting in a single-atom catalyst with a loading of 35.4 wt%.

[0039] Example 17: The difference from Example 1 is that the copper nitrate solution was replaced with a chromium nitrate solution, resulting in a single-atom catalyst with a loading of 36.4 wt%.

[0040] Example 18: The difference from Example 1 is that the copper nitrate solution was replaced with a manganese nitrate solution, resulting in a single-atom catalyst with a loading of 33.8 wt%.

[0041] Example 19: The difference from Example 1 is that the copper nitrate solution was replaced with niobium nitrate solution, resulting in a single-atom catalyst with a loading of 41.7 wt%.

[0042] Example 20: The difference from Example 1 is that the copper nitrate solution was replaced with a molybdenum nitrate solution, resulting in a single-atom catalyst with a loading of 39.8 wt%.

[0043] Example 21: The difference from Example 1 is that the copper nitrate solution was replaced with chloroplatinic acid solution, resulting in a single-atom catalyst with a loading of 44.3 wt%.

[0044] Example 22: The difference from Example 1 is that the copper nitrate solution was replaced with a palladium nitrate solution, resulting in a single-atom catalyst with a loading of 39.4 wt%.

[0045] Example 23: The difference from Example 1 is that the copper nitrate solution was replaced with chloroiridium acid solution, resulting in a single-atom catalyst with a loading of 42.4 wt%.

[0046] Example 24: The difference from Example 1 is that the copper nitrate solution was replaced with ruthenium chloride solution, resulting in a single-atom catalyst with a loading of 36.8 wt%.

[0047] Example 25: The difference from Example 1 is that the copper nitrate solution was replaced with chloroauric acid solution, resulting in a single-atom catalyst with a loading of 38.9 wt%.

[0048] Example 26: The difference from Example 1 is that the copper nitrate solution was replaced with a chloride salt solution, resulting in a single-atom catalyst with a loading of 43.4 wt%.

[0049] Example 27: The difference from Example 1 is that the copper nitrate solution was replaced with a carbonate solution, resulting in a single-atom catalyst with a loading of 44.8 wt%.

[0050] Example 28: The difference from Example 1 is that the copper nitrate solution was replaced with a phosphate solution, resulting in a single-atom catalyst with a loading of 42.8 wt%.

[0051] Example 29: The difference from Example 1 is that the copper nitrate solution was replaced with a sulfate solution, resulting in a single-atom catalyst with a loading of 43.1 wt%.

[0052] Example 30: The difference from Example 1 is that the copper nitrate solution was replaced with chloroplatinic acid and zinc nitrate solution to obtain a single-atom catalyst with a loading of 42 wt%.

[0053] Example 31: The difference from Example 1 is that the copper nitrate solution was replaced with a molybdenum chloride and zinc nitrate solution to obtain a single-atom catalyst with a loading of 40.5 wt%.

[0054] Example 32: The difference from Example 1 is that the copper nitrate solution was replaced with a solution of chloroplatinic acid, chloroiridium acid, copper nitrate, ferric nitrate and zinc nitrate, resulting in a single-atom catalyst with a loading of 43.7 wt%.

[0055] Example 33: The difference from Example 1 is that melamine is replaced with guanine, resulting in a single-atom catalyst with a loading of 29 wt%.

[0056] Example 34: The difference from Example 1 is that melamine was replaced with porphyrin, resulting in a single-atom catalyst with a loading of 27.3 wt%.

[0057] Example 35: The difference from Example 1 is that melamine was replaced with dicyandiamide, resulting in a single-atom catalyst with a loading of 42.4 wt%.

[0058] Example 36: The difference from Example 1 is that melamine was replaced with phthalocyanine to obtain a single-atom catalyst with a loading of 21.8 wt%.

[0059] from Figure 3 The presence of numerous metal particles demonstrates the remarkable effectiveness of this method.

[0060] The application properties of the catalyst involved in this invention are illustrated using the low-temperature oxidation of acetone and oxygen to produce acetone and isopropanol as an example. This is only to more clearly illustrate the outstanding effects of this invention and is not intended to limit the scope of its application. The catalytic performance evaluation method provided is as follows:

[0061] 100 mg of catalyst was added to 70 ml of acetonitrile. Propane and oxygen were introduced at 6 bar in a sealed reactor, and the mixture was stirred at 175 °C for 6 h. After cooling to room temperature, samples were taken. The samples were filtered, and the yields of acetone and isopropanol were determined by gas chromatography.

[0062] The results are shown in Table 1.

[0063] Table 1

[0064]

[0065]

[0066] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing ultra-high loading metal single-atom catalysts by vacuum pyrolysis, characterized in that, S1: a metal salt is loaded onto a nitrogen-containing carbon support and then dried; S2: The product of S1 is pyrolyzed at 300℃-750℃ under a vacuum of -0.1~-0.03Mpa for 0.01-5h to obtain a single-atom catalyst; The nitrogen-containing carbon support is either carbon nitride or nitrogen-doped graphene. The prepared single-atom catalyst achieved a metal loading of over 30 wt%. The metal is a transition metal.

2. The method for preparing ultra-high loading metal single-atom catalysts by vacuum pyrolysis according to claim 1, characterized in that: The transition metals are platinum, palladium, ruthenium, iridium, manganese, iron, cobalt, nickel, copper, zinc, vanadium, chromium, niobium, molybdenum, gold, and mixtures thereof.

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