A single atom site catalyst and a method of making the same

Abstract

The present application relates to the field of catalysts, more particularly, it relates to a kind of single-atom site catalyst and its preparation method.The preparation method of a kind of single-atom site catalyst includes: S1, preparation precursor;S2, preparation intermediate;S3, preparation single-atom site catalyst.The present application generates cation vacancy by doping heteroatom into transition metal compound loaded on MXenes using ionic liquid, so that the single-atom site catalyst prepared not only has more active sites, but also can effectively stabilize dense single atom, thereby improving catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically, to a single-atom-site catalyst and its preparation method. Background Technology

[0002] In response to the global energy and environmental crisis, the development of environmentally friendly, renewable, and sustainable energy sources is urgently needed. Electrocatalysis and energy storage technologies, such as water electrolysis for hydrogen evolution, have become some of the most popular research areas in both academic and industrial applications. However, in the HER process, the high activation energy of the material itself requires a high potential to overcome the problem of slow reaction, thus it is essential to develop an active material that can accelerate the reaction rate and reduce the overpotential. Currently, the main commercially available bifunctional electrocatalysts are noble metals (Pt, Ru, and IrO2), but their high cost and poor stability have hindered their development. Single-atom catalysts have attracted great attention in the field of electrocatalysis due to their maximum atom utilization and tunable electronic properties. However, the accumulation of single atoms and their undesirable stability at high concentrations greatly limit further development. Summary of the Invention

[0003] This invention provides a single-atom site catalyst and its preparation method. By using ionic liquids to dope heteroatoms into transition metal compounds supported on MXenes to generate cation vacancies, the prepared single-atom site catalyst not only has more active sites, but also can effectively stabilize dense single atoms (Ru), thereby improving catalytic performance.

[0004] A method for preparing a single-atom-site catalyst includes the following steps:

[0005] S1: Preparation of precursor

[0006] Metal nitrate, urea, citric acid, ionic liquid and MXene are added to deionized water and heated at 100-200℃ for 10-15h. Then the mixture is cooled to room temperature, and the resulting product is repeatedly washed with ethanol and deionized water and dried at 50-90℃ for 20-30h to obtain the precursor.

[0007] S2: Preparation of intermediates

[0008] The precursor and chalcogenide powder were heated in an Ar atmosphere for 1-3 hours to obtain an intermediate.

[0009] S3: Preparation of single-atom-site catalysts

[0010] RuCl4 and the intermediate were placed in ethanol and stirred for 1-3 hours. The mixture was then dried at 60-80°C for 5-8 hours to obtain powder A. A portion of powder A was placed in an Ar / H2 atmosphere and heated to 280-350°C. The mixture was then cooled to room temperature. The resulting material was washed with ethanol and dried at 60-90°C to obtain a single-atom site catalyst.

[0011] As a preferred embodiment of the present invention, in step S1, the metal nitrate is one of Ni(NO3)2·6H2O and Co(NO3)2·6H2O.

[0012] As a preferred embodiment of the present invention, in step S1, the ionic liquid is one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1,3-dimethylimidazolium tetrafluoroborate, and 1,3-diisopropylimidazolium tetrafluoroborate.

[0013] As a preferred embodiment of the present invention, in step S1, MXene uses Mo2CT. x and Ti2CT x Any one of them.

[0014] As a preferred embodiment of the present invention, the chalcogenide powder in step S2 is one of Se powder and S powder.

[0015] As a preferred embodiment of the present invention, in step S2, heating is carried out in a quartz tube furnace, the precursor is placed in a ceramic boat at the downstream position of the quartz tube furnace, the chalcogen element powder is placed at the upstream position, the heating temperature is 300-400℃, and the heating rate is maintained at 10℃ / min.

[0016] The present invention also provides a single-atom site catalyst, which is prepared by the above-described method for preparing a single-atom site catalyst.

[0017] The present invention has the following advantages:

[0018] 1. This invention generates cation vacancies by doping transition metal compounds supported on MXenes with heteroatoms using ionic liquids. This results in a catalyst with more active sites and can effectively stabilize dense single atoms, thereby improving catalytic performance.

[0019] 2. The NiSe2 used in this invention has a layered structure, which not only possesses good HER performance but also has a large specific surface area, enabling it to adsorb more Ru single atoms as active sites; Mo2CT x It is a high-performance support material with excellent chemical stability, metallic conductivity and hydrophilic properties.

[0020] 3. This invention injects N, B, and F into the composite material via IL, simultaneously exposing more active sites and increasing electronegativity, thus enhancing the Ru / NBF-NiSe2 / Mo2CT composition. x It can collect more protons. Attached Figure Description

[0021] Figure 1 This is a schematic flowchart of the preparation method of the single-atom site catalyst used in the embodiments of the present invention.

[0022] Figure 2 Mo2CT in the embodiments of the present invention x NBF-Ni-DLH / Mo2CT x NBF-NiSe2 / Mo2CT x and Ru / NBF-NiSe2 / Mo2CT x Corresponding morphological diagram.

[0023] Figure 3 The Ru / NBF-NiSe2 / Mo2CT prepared in the embodiments of the present invention x TEM image.

[0024] Figure 4 The Ru / NBF-NiSe2 / Mo2CT prepared in the embodiments of the present invention x XRD pattern.

[0025] Figure 5 The Ru / NBF-NiSe2 / Mo2CT prepared in the embodiments of the present invention x NBF-NiSe2 / Mo2CT x and NiSe2 / Mo2CT x EPR diagram.

[0026] Figure 6 The Ru / NiSe2 / Mo2CT prepared in the embodiments of the present invention x and Ru / NBF-NiSe2 / Mo2CT x Aberration electron micrograph.

[0027] Figure 7 The Ru / NiSe2 / Mo2CT prepared in the embodiments of the present invention x and Ru / NBF-NiSe2 / Mo2CT x A schematic diagram of the contact angle.

[0028] Figure 8 The images shown are SEM, XRD, and EPR images of the NBF-MoS2 prepared in the embodiments of the present invention.

[0029] Figure 9 The images shown are SEM, XRD, and EPR images of the NBF-NiS prepared in the embodiments of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0031] Example 1

[0032] A method for preparing a single-atom-site catalyst, such as Figure 1 As shown, it includes the following steps:

[0033] S1: Preparation of precursor

[0034] The mixture consists of Ni(NO3)2·6H2O, urea, 0.05 parts citric acid, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 0.1 parts Mo2CT. x The product was added to 60 parts of deionized water and heated at 150°C for 12 hours. It was then cooled to room temperature, and the resulting product was repeatedly washed with ethanol and deionized water, followed by drying at 70°C for 24 hours to obtain the precursor, NBF-Ni-LDH / Mo2CT. x During this process, B, N and F can be injected into the composite material through the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate. This not only exposes more active sites and enhances electronegativity in the composite material, but also improves the ability of the generated single-atom site catalyst to collect more protons.

[0035] Mo2CT x The synthesis includes the following steps: Two parts of Mo2Ga2C powder were ground for 1 hour and then slowly added to 20 parts of HF solution. The mixture was reacted for 7 days in a magnetically stirred heating sleeve at 55°C. The resulting product was then centrifuged at 10,000 rpm for 10 minutes and repeatedly washed with deionized water until the pH reached 6. Finally, the material was completely dried in a freeze dryer to obtain Mo2CT. x .

[0036] S2: Preparation of intermediates

[0037] 100 samples of the precursor NBF-Ni-LDH / Mo2CT were used. x A ceramic boat containing 400 parts of Se powder was placed downstream of a quartz tube furnace, while another sample was placed upstream. The calcination chamber was maintained at 350°C in an Ar atmosphere at a heating rate of 10°C / min for 1 hour to obtain the intermediate NBF-NiSe2 / Mo2CT. xDuring this process, the precursor undergoes a redox reaction with Se powder to generate NiSe2, which is then uniformly loaded onto Mo2CT. x Furthermore, due to the influence of heteroatoms B, N, and F, cation vacancies (Ni vacancies) appear on the NiSe2 surface.

[0038] S3: Preparation of single-atom-site catalysts

[0039] 50 parts RuCl4 and 50 parts intermediate NBF-NiSe2 / Mo2CT x The mixture was added to 30 parts of ethanol, stirred for 1 hour, and dried at 70°C for 6 hours to obtain powder A. 50 parts of powder A were placed in an Ar / H2 atmosphere and heated to 300°C at a rate of 2°C / min, then cooled to room temperature. The resulting material was washed with ethanol and dried overnight at 80°C to obtain a single-atom-site catalyst, namely Ru / NBF-NiSe2 / Mo2CT. x Ru is anchored and induced by Ni vacancies, exhibiting a single-atom distribution at high concentrations, which improves the catalytic performance of the material.

[0040] In this embodiment, NiSe2 is used as a layered structure, which not only possesses good bifunctional catalytic activity but also has a large specific surface area that allows for the adsorption of more Ru single atoms as active sites; Mo2CT x It is a high-performance support material with excellent chemical stability, metallic conductivity and hydrophilic properties.

[0041] See Figure 2 Mo2CT x NBF-Ni-DLH / Mo2CT x NBF-NiSe2 / Mo2CT x and Ru / NBF-NiSe2 / Mo2CT x For the corresponding morphology, see Figure 3 Ru / NBF-NiSe2 / Mo2CT x The corresponding transmission electron microscope (TEM) images can be found in Ru / NBF-NiSe2 / Mo2CT. x The edge of the material shows exposed NiSe2 crystal planes (220) with a spacing of 0.210 μm. See [reference needed]. Figure 4 From NBF-NiSe2 / Mo2CT x NiSe2 and Mo2CT can be distinguished from the characteristic peaks of the XRD. x After doping with a single atom of Ru, Ru / NBF-NiSe2 / Mo2CT x With NBF-NiSe2 / Mo2CT xThe characteristic peaks remained consistent, indicating that the Ru atoms did not change NBF-NiSe2 / Mo2CT x lattice.

[0042] Example 2

[0043] S1: Preparation of precursor

[0044] Mix Ni(NO3)2·6H2O, urea, 0.05 parts citric acid, and 0.1 parts Mo2CT. x The product was added to 60 parts of deionized water and heated at 150°C for 12 hours. It was then cooled to room temperature, and the resulting product was repeatedly washed with ethanol and deionized water, followed by drying at 70°C for 24 hours to obtain the precursor, which was Ni-LDH / Mo2CT. x .

[0045] S2: Preparation of intermediates

[0046] 100 samples of the precursor Ni-LDH / Mo2CT were used. x A ceramic boat containing 400 parts of Se powder was placed downstream of a quartz tube furnace, while another sample was placed upstream. The calcination chamber was maintained at 350°C in an Ar atmosphere at a heating rate of 10°C / min for 1 hour to obtain the intermediate NiSe2 / Mo2CT. x .

[0047] S3: Preparation of single-atom-site catalysts

[0048] 50 parts RuCl4 and 50 parts intermediate NiSe2 / Mo2CT x The mixture was placed in 30 parts of ethanol, stirred for 1 hour, and dried at 70°C for 6 hours to obtain powder A. 50 parts of powder A were placed in an Ar / H2 atmosphere and heated to 300°C at a rate of 2°C / min, then cooled to room temperature. The resulting material was washed with ethanol and dried overnight at 80°C to obtain a single-atom site catalyst, namely Ru / NiSe2 / Mo2CT. x .

[0049] See Figure 5 NBF-NiSe2 / Mo2CT x The trapped electrons from Ni vacancies produce a strong EPR signal at g = 2.003, while NiSe2 / Mo2CT x The absence of a signal indicates that the introduction of ionic liquids generates a large number of Ni vacancies in the material, while the presence of Ru leads to Ru / NBF-NiSe2 / Mo2CT. x The decrease in vacancies indicates that vacancies can attract single-atom Ru to fill them, resulting in a reduction in the EPR signal.

[0050] See Figure 6 The small bright spots in the image represent Ru atoms. It can be seen that, for the same Ru content, NiSe2 (NBF-NiSe2 / Mo2CT) containing cation vacancies... x In NiSe2, Ru occupies its cation vacancies to form a more uniform single-atom structure; while in NiSe2 without cation vacancies, Ru accumulates.

[0051] See Figure 7 After adding ionic liquid, Ru / NBF-NiSe2 / Mo2CT x The water contact angle is lower, which shows that the addition of ionic liquid can increase the hydrophilicity of the material.

[0052] Example 3

[0053] Under stirring, 20 parts of ammonium thiomolybdate were dispersed in 20 parts of N,N-dimethylformamide (DMF) and 0.1 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate for 15 minutes. The resulting mixture was then transferred to an autoclave and reacted at 210 °C for 15 hours. The product was collected by centrifugation and washed several times with water and ethanol. The product was then annealed in N2 at 450 °C for 1 hour to obtain NBF-MoS2 nanosheets.

[0054] See Figure 8 The SEM image (left), XRD image (middle), and EPR image (right) of NBF-MoS2 show that NBF-MoS2 contains Mo vacancies.

[0055] Example 4

[0056] Ni(NO3)2·6H2O, urea, 0.05 parts of C6H8O7·H2O and 0.1 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate were added to 60 parts of deionized water. The solution was heated at 150°C for 12 hours. After cooling to room temperature, the material was repeatedly washed with ethanol and deionized water and then dried at 70°C for 24 hours to obtain Ni-LDH.

[0057] The sulfidation step was carried out in a horizontal tube furnace made of quartz, with 100 parts of Ni-LDH stored in a ceramic boat located downstream of the quartz tube furnace. Another sample containing 400 parts of S powder was placed upstream. The calcination chamber was heated at 350°C in an Ar / H2 atmosphere at a heating rate of 10°C / min for 1 hour, after which the target product NBF-NiS was successfully obtained.

[0058] See Figure 9 The SEM image (left), XRD image (middle), and EPR image (right) of NBF-NiS show that NBF-NiS contains Ni vacancies.

[0059] In Examples 3 and 4, the addition of ionic liquids during the synthesis of MoS2 and NiS resulted in the generation of corresponding cation vacancies, further demonstrating the universality of the method for generating cation vacancies using ionic liquids in this invention. Any obvious variations or modifications derived therefrom are still within the protection scope of the preparation method of this invention.

[0060] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing a single-atom-site catalyst, characterized in that, Includes the following steps: S1: Preparation of precursor Ni(NO3)2∙6H2O, urea, citric acid, ionic liquid and MXene were added to deionized water and heated at 100-200℃ for 10-15h. Then the mixture was cooled to room temperature, and the resulting product was repeatedly washed with ethanol and deionized water and dried at 50-90℃ for 20-30h to obtain the precursor. S2: Preparation of intermediates The precursor and Se powder were heated in an Ar atmosphere for 1-3 hours to obtain the intermediate. S3: Preparation of single-atom-site catalysts RuCl4 and the intermediate were placed in ethanol and stirred for 1-3 hours. The mixture was then dried at 60-80°C for 5-8 hours to obtain powder A. A portion of powder A was placed in an Ar / H2 atmosphere and heated to 280-350°C. The mixture was then cooled to room temperature. The resulting material was washed with ethanol and dried at 60-90°C to obtain a single-atom site catalyst.

2. The method for preparing a single-atom-site catalyst according to claim 1, characterized in that, In step S1, the ionic liquid is one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1,3-dimethylimidazolium tetrafluoroborate, and 1,3-diisopropylimidazolium tetrafluoroborate.

3. The method for preparing a single-atom-site catalyst according to claim 1, characterized in that, In step S1, MXene uses Mo2CT. x and Ti2CT x Any one of them.

4. The method for preparing a single-atom-site catalyst according to claim 1, characterized in that, In step S2, heating is carried out in a quartz tube furnace. The precursor is placed in a ceramic boat downstream of the quartz tube furnace, and the chalcogen element powder is placed upstream. The heating temperature is 300-400℃, and the heating rate is maintained at 10℃ / min.

5. A single-atom-site catalyst, characterized in that, It is prepared by the method for preparing a single-atom site catalyst according to any one of claims 1-4.

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