Preparation method and application of single-atom Fe / CeO2 catalyst

Abstract

The present invention provides a preparation method and application of a single-atom Fe / CeO2 catalyst. Specifically, cerium nitrate (Ce(NO3)3·6H2O) is used as a carrier, a metal salt is used as a precursor, and uniform two-dimensional nanosheets are formed by a sol-gel method and air annealing. The single-atom Fe / CeO2 catalyst prepared in the embodiment of the present invention can catalyze ethanol steam reforming to produce hydrogen with high selectivity and high efficiency at low reaction temperature, demonstrating the superior performance of the single-atom catalyst. The synthesis method of the single-atom two-dimensional catalyst provided by the present invention has the advantages of low preparation temperature, universal applicability, simplicity, simple equipment, and environmental friendliness, providing a new approach and new ideas for the application of single-atom materials in catalysis, energy conversion and other fields.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials and catalysis technology, in particular to a preparation method and application of a single-atom Fe / CeO2 catalyst. Background Art

[0002] Single-atom catalysts (SACs) are specialized supported metal catalysts characterized by the presence of single atoms on a support, devoid of homoatomic metal-metal bonds. Their unique structure allows them to exhibit significantly superior activity, selectivity, and stability compared to conventional nanocatalysts. Their exceptional performance has sparked a worldwide research boom. With the development of advanced characterization techniques (such as synchrotron X-ray absorption and spherical aberration electron microscopy), SACs have made it possible to elucidate the structure-activity relationship of catalysts at the sub-angstrom atomic scale, providing a practical platform for studying catalytic mechanisms. Existing SAC preparation methods can be broadly divided into two categories: one requiring cutting-edge instrumentation, such as mass-selective mass spectrometry and ALD; the other relying on traditional wet chemical methods, including coprecipitation, impregnation, deposition-precipitation, and photo / electrochemical deposition. However, the former suffers from demanding preparation conditions, high costs, and limitations on large-scale production; the latter suffers from poor atomic dispersion, demanding preparation steps, and significant pollution in large-scale production.

[0003] Ethanol steam reforming (ESR) using renewable ethanol as a feedstock is considered a promising hydrogen production pathway due to its high hydrogen production efficiency, sustainable ethanol production (biofermentation), and low toxicity. However, the ESR reaction is a highly endothermic reaction and can generally only be carried out under high temperature conditions. Ethanol reforming is accompanied by numerous side reactions, such as ethanol decomposition, hydrogenolysis, dehydration, and aldol condensation, which produce a variety of byproducts. Therefore, ethanol reforming is a very complex process. Furthermore, high temperatures can lead to catalyst sintering and deactivation, and also cause large amounts of carbon deposits, which seriously affect catalytic activity. Consequently, efforts have been focused on developing efficient and stable catalysts for ESR. Currently, precious metal catalysts offer the best catalytic performance, but their high cost has led to the development of numerous non-precious metal catalysts, all of which inevitably face problems such as sintering and carbon deposition. Single-atom catalysts, however, offer a promising approach for ESR catalysis because their active components are well-dispersed, possess numerous active sites, and are less susceptible to carbon deposition on individual atoms. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a single-atom Fe / CeO2 catalyst to solve the problems of high cost and inability to large-scale production in the existing single-atom catalyst preparation process, as well as the high temperature and easy deactivation of ethanol steam reforming hydrogen production catalysts.

[0005] The present invention is achieved in that:

[0006] The present invention addresses the current problems of harsh single-atom catalyst preparation processes, high costs, limited large-scale production, and the potential for pollution. Furthermore, ethanol steam reforming hydrogen production catalysts have the disadvantages of requiring high temperatures and being easily deactivated. Therefore, a novel single-atom Fe / CeO2 catalyst preparation method and a single-atom Fe / CeO2 catalyst for catalyzing ethanol reforming hydrogen production at low reaction temperatures are proposed. The single-atom Fe / CeO2 catalyst preparation method specifically utilizes citric acid as a complexing agent and ethylenediamine and nitric acid as bulking agents. A two-dimensional single-atom Fe / CeO2 catalyst with a large specific surface area is obtained through drying, calcining in argon, and air annealing. This catalyst can catalyze ESR at low temperatures with high catalytic efficiency.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] like Figure 1 As shown, the preparation method of the single-atom Fe / CeO2 catalyst includes the following steps:

[0009] 1) Dissolve a certain amount of citric acid, ferric nitrate, and cerium nitrate in deionized water and stir evenly to form a mixed solution; the atomic ratio of Fe:Ce is 5 to 20:100.

[0010] 2) Adding a certain amount of ethylenediamine and nitric acid to the mixed solution obtained in step 1) successively, stirring for a period of time, adding ammonia water until the pH value of the solution reaches about 6, stirring and drying the solution until it becomes molten, and then placing it in a forced air drying oven and drying it for 24 hours to obtain a catalyst precursor.

[0011] 3) The catalyst precursor obtained in step 2) was placed in a quartz tube of a tube furnace. Argon was passed through the quartz tube for one hour to expel the air. At the same time, the tube furnace was heated to 400°C at a heating rate of 10°C / min. The quartz tube was then placed in the tube furnace and kept warm for 3 hours.

[0012] 4) The sample calcined in step 3) was placed in a muffle furnace, and the temperature was increased to 400° C. at a heating rate of 10° C. / min in an air environment, and maintained for 3 h.

[0013] Furthermore, in step 1), in addition to ferric nitrate and cerium nitrate, nickel nitrate may be added to modify the catalyst.

[0014] The present invention discloses a method for preparing a single-atom Fe / CeO2 catalyst. The prepared single-atom Fe / CeO2 catalyst has a single-phase structure in crystal form and a porous nanosheet structure with a thickness of 1 to 50 nm. The specific surface area of ​​the single-atom Fe / CeO2 catalyst is 30 to 400 m 2 g -1 The single-atom Fe / CeO2 catalyst has the characteristics of adjustable composition and uniform element distribution. By further adjusting the active ingredients, a single-atom 5Ni15Fe / CeO2 catalyst was obtained.

[0015] The present invention further discloses the preparation of a single-atom Fe / CeO2 catalyst using a sol-gel method and its application in ethanol steam reforming to produce hydrogen. Specifically, an ethanol-water solution was injected into a reaction apparatus via a microinjection pump using argon as a carrier gas, and the hydrogen production performance was tested by heating. The results showed that the single-atom Fe / CeO2 catalyst exhibited good hydrogen selectivity and performance during ESR, and required a lower reaction temperature than other catalysts. Furthermore, attempts to modify the single-atom Fe / CeO2 catalyst revealed that the addition of nickel to the active ingredient increased hydrogen yield.

[0016] The present invention has the following advantages:

[0017] 1) The maximum temperature of the method for preparing single-atom Fe / CeO2 catalyst of the present invention is only 400°C, and the preparation temperature is low.

[0018] 2) The equipment for preparing the single-atom Fe / CeO2 catalyst of the present invention only requires a blast drying oven, a tubular furnace, and a muffle furnace. Compared with other methods for preparing single-atom catalysts, it has the advantages of simple equipment and low cost.

[0019] 3) The single-atom Fe / CeO2 catalyst of the present invention has a simple preparation process, easily controllable variables, can be produced on a large scale, and will not cause pollution.

[0020] 4) The present invention can further improve the hydrogen yield by adjusting the active components of the single-atom Fe / CeO2 catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the preparation method of the single-atom Fe / CeO2 catalyst provided by the present invention.

[0022] Figure 2 This is the structural characterization and morphological characterization of the single-atom Fe / CeO2 catalyst obtained in Example 1 of the present invention.

[0023] Figure 3 This is the morphology and element distribution diagram of the single-atom Fe / CeO2 catalyst obtained in Example 1 of the present invention.

[0024] Figure 4 This is a performance diagram of the thermal catalytic ethanol steam reforming hydrogen production of the single-atom Fe / CeO2 catalyst obtained in Example 1 of the present invention.

[0025] Figure 5 This is a performance diagram of the thermal catalytic ethanol steam reforming hydrogen production of the single-atom 5Ni15Fe / CeO2 catalyst obtained in Example 2 of the present invention.

[0026] Figure 6 The single-atom Fe / Ce obtained in Example 3 of the present invention 0.5 La 0.5 O x Performance diagram of the catalyst for thermal catalytic ethanol steam reforming to produce hydrogen. DETAILED DESCRIPTION

[0027] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0028] Example 1, preparation of single-atom Fe / CeO2 catalyst.

[0029] The synthesis steps of single-atom Fe / CeO2 catalyst are as follows:

[0030] (1) Dissolve 5 g of citric acid in 10 mL of water and stir for 15 minutes.

[0031] (2) Add 0.28 g of Fe(NO3)2·9H2O and 2 g of Ce(NO3)3·6H2O to the citric acid aqueous solution, with the Fe:Ce atomic ratio being 15:100, and stir to dissolve for 15 min.

[0032] (3) 2.4 mL of nitric acid and 1.0 mL of ethylenediamine were added to the above solution in sequence, and then aqueous ammonia was added until the pH value of the solution reached about 6. The solution was stirred and dried until it was molten and then placed in a forced air drying oven for 24 h to obtain a catalyst precursor.

[0033] (4) The catalyst precursor was placed in a quartz tube in a tube furnace. Argon gas was passed through the tube for one hour to expel the air. The tube furnace was heated to 400°C at a heating rate of 10°C / min. The quartz tube was then placed in the tube furnace and held at this temperature for 3 hours. The calcined sample was placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min in an air environment and held for 3 hours. The sample was allowed to cool naturally and then removed for characterization.

[0034] Figure 2 a is the X-ray diffraction pattern of Fe / CeO2, Figure 2 In a, there is only the diffraction peak of CeO2, and no diffraction peak of Fe, which indicates that the Fe element is sufficiently dispersed in the sample; Figure 2b is the N2 adsorption-desorption curve of Fe / CeO2. The specific surface area of ​​the sample is 305.91m 2 g -1 ; Figure 2 c is the microscopic morphology of Fe / CeO2. Figure 2 c It can be seen that the sample has a loose and porous sheet structure, which means that the sample has a larger specific surface area and can provide more active sites for the reaction; Figure 2 d is a high-resolution image of Fe / CeO2, which shows that the Fe element is distributed singly in the sample and there is no aggregation phenomenon.

[0035] Figure 3 This is the morphology and element distribution diagram of Fe / CeO2. Figure 3 It can be seen that Fe is evenly distributed in the sample. Figure 2 Mutual verification.

[0036] Example 2, preparation of single-atom 5Ni15Fe / CeO2 catalyst.

[0037] The synthesis steps of the single-atom 5Ni15Fe / CeO2 catalyst are as follows:

[0038] (1) Dissolve 2.5 g of citric acid in 10 mL of water and stir for 15 minutes.

[0039] (2) Add 0.034g Ni(NO3)2·6H2O, 0.143g Fe(NO3)2·9H2O and 1g Ce(NO3)3·6H2O to the citric acid aqueous solution, so that the atomic ratio of Ni:Fe:Ce is 5:15:100, and stir and dissolve for 15 minutes.

[0040] (3) 1.2 mL of nitric acid and 0.5 mL of ethylenediamine were added to the above solution in sequence, and then aqueous ammonia was added until the pH value of the solution reached about 6. The solution was stirred and dried until it was molten and then placed in a forced air drying oven for 24 h to obtain a catalyst precursor.

[0041] (4) The catalyst precursor was placed in a quartz tube in a tube furnace. Argon gas was passed through the tube for one hour to expel the air. The tube furnace was heated to 400°C at a heating rate of 10°C / min. The quartz tube was then placed in the tube furnace and held at this temperature for 3 hours. The calcined sample was placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min in an air environment. The temperature was maintained for 3 hours. The sample was allowed to cool naturally and then removed for experiment.

[0042] Example 3, single-atom Fe / Ce 0.5 La 0.5 O x Preparation of catalyst.

[0043] Single-atom Fe / Ce0.5 La 0.5 O x The synthesis steps of the catalyst are as follows:

[0044] Referring to the method described in Example 2, 0.143g Fe(NO3)2·9H2O, 0.5g Ce(NO3)3·6H2O and 0.499g La(NO3)3·6H2O were added in this example, and the atomic ratio of Fe:Ce:La was 15:50:50. Other conditions were the same as in Example 2, and the obtained single-atom Fe / Ce 0.5 La 0.5 O x catalyst.

[0045] Example 4, application of single-atom Fe / CeO2 catalyst.

[0046] 10 mg of the single-atom Fe / CeO2 catalyst obtained in Example 1 was placed in a quartz tube and then placed in a tube furnace. Argon was introduced into the reactor as a carrier gas at a flow rate of 50 mL / min. An ethanol aqueous solution was injected into the reaction system via a microinjection pump to initiate the reaction. Each temperature point was kept warm for 30 minutes and then the gas composition was detected by gas chromatography. Performance test Figure 4 As shown in a, the hydrogen yield of the single-atom Fe / CeO2 catalyst reached 512 mmol g at 350 °C. -1 h -1 , which is 1.6 times that of Pt / CeRu and more than ten times that of non-precious metal catalysts, and the presence of hydrogen was detected at 125°C. Figure 4 b is the selectivity of ESR reaction catalyzed by single-atom Fe / CeO2 catalyst for hydrogen, which has always remained above 95%.

[0047] Example 5, Application of Single Atom 5Ni15Fe / CeO2 Catalyst

[0048] The 10 mg single-atom Fe / CeO2 catalyst in the quartz tube of Example 4 was replaced with 10 mg single-atom 5Ni15Fe / CeO2 catalyst in Example 2, and the other test conditions remained unchanged. Figure 5 As shown in a, the hydrogen yield of the single-atom 5Ni15Fe / CeO2 catalyst reached 596.06 mmol g at 350 °C. -1 h -1 It can be seen that adding Ni element to modify the Fe / CeO2 catalyst can improve the hydrogen yield and also maintain high hydrogen selectivity, such as Figure 5 As shown in b.

[0049] Example 6, single atom Fe / Ce 0.5 La 0.5 Ox Application of catalysts

[0050] The 10 mg single-atom Fe / CeO2 catalyst in the quartz tube of Example 4 was replaced with 10 mg single-atom Fe / CeO2 catalyst in Example 3. 0.5 La 0.5 O x The catalyst and other test conditions remain unchanged. Figure 6 As shown in a, at 350℃, single-atom Fe / Ce 0.5 La 0.5 O x The hydrogen yield of the catalyst was only 43.62 mmol g -1 h -1 , which is much lower than that of Fe / CeO2 catalyst and 5Ni15Fe / CeO2 catalyst. Figure 6 The hydrogen selectivity of b is also lower than the other two, which shows that La and Ce are not suitable to be used as bimetallic supports for single-atom Fe catalysts at the same time.

[0051] In general, the present invention discloses a universal method for preparing single-atom Fe / CeO2 catalysts using a sol-gel method, and modifying the catalyst by changing the active components of the single-atom Fe / CeO2 catalyst, and using it to catalyze ethanol steam reforming to produce hydrogen.

[0052] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. Application of a single-atom 5Ni15Fe / CeO2 catalyst in photothermal catalytic ethanol steam reforming to produce hydrogen, characterized in that: The hydrogen yield of the single-atom 5Ni15Fe / CeO2 catalyst can reach 596.06 mmol g at 350 °C. -1 h -1 ; The preparation method of the single-atom 5Ni15Fe / CeO2 catalyst is as follows: a. Dissolve citric acid in water to form a citric acid aqueous solution, and add nitrates of Fe, Ce, and Ni to the citric acid aqueous solution; the atomic ratio of Ni:Fe:Ce is 5:15:100; b. Adding ethylenediamine, nitric acid, and aqueous ammonia to the solution obtained in step a to form a colloid, and then drying to obtain a catalyst precursor; c. calcining the catalyst precursor in a tube furnace under an argon atmosphere; d. Anneal the sample calcined in step c in an air environment to obtain a single-atom 5Ni15Fe / CeO2 catalyst.

2. The use according to claim 1, characterized in that: In step b, ethylenediamine and nitric acid are first added to the solution obtained in step a, and then aqueous ammonia is added dropwise to form a colloid in the solution.

3. The use according to claim 1, characterized in that: Step c is as follows: the catalyst precursor is placed in a quartz tube, argon is passed through the quartz tube for one hour to expel the air, and the tube furnace is heated to 400°C at a heating rate of 10°C / min, and then the quartz tube is placed in the tube furnace and kept warm for 3 hours.

4. The use according to claim 1, characterized in that: Step d is specifically as follows: placing the sample calcined in step c into a muffle furnace, heating it to 400°C at a heating rate of 10°C / min in an air environment, and maintaining it for 3 hours.

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