Preparation method of platinum group metal catalyst and platinum group metal catalyst
By using graphite phase nitrided carbon powder as a support and chloride ions in the preparation of platinum group metal catalysts, the problem of difficult preparation of high load and high dispersion platinum group metal catalysts is solved, and the high loading of atomic-scale dispersed catalysts is achieved Quantity and high stability simplify the preparation process and reduce costs.
Patent Information
- Application Number
- CN202411646612.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-02-25
Smart Images
Figure CN119500221A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present disclosure relate to catalyst technology and hydrogen energy application fields, and specifically, to a preparation method of a platinum group metal catalyst and a platinum group metal catalyst. Background Art
[0002] Atomically dispersed metal catalysts have the dual advantages of heterogeneous and homogeneous catalysts. They not only show the maximum utilization of metal atoms and ultra-high intrinsic activity, but also are easy to separate from products. They are widely used in the field of energy and chemical industry. Hydrogen energy is considered to be an important carrier for achieving green and low-carbon development at the energy-consuming end. It is of great significance to reduce greenhouse gas emissions such as carbon dioxide and achieve carbon peak and carbon neutrality goals. However, the flammable and explosive physical properties of hydrogen (H2) and its extremely low volumetric energy density limit its large-scale application. The storage and transportation of hydrogen through organic liquid hydrogen storage carriers (LOHC) is a necessary means to develop green hydrogen energy. In this context, the development of highly dispersed platinum group metal catalysts at the atomic level and the realization of efficient formate hydrogen storage are effective ways to solve the above problems.
[0003] Although atomically dispersed platinum group metal catalysts have high metal utilization, the metal dispersion is closely related to the loading. It is difficult to form atomic-level dispersion at high loading, and the atomic-level dispersed catalysts have poor stability in the reaction, which limits their large-scale promotion and application. At present, the main ways to improve the dispersion of supported platinum group metal catalysts are to obtain highly dispersed and highly stable platinum group metal catalysts through the confinement effect of carriers such as molecular sieves or by adjusting the metal-carrier interaction.
[0004] However, the above method is highly dependent on the choice of carrier, and has relatively high requirements for carrier properties and preparation process, which further limits the preparation and application of highly dispersed platinum group metal catalysts at the atomic level. In addition, since the dispersion of metals is increased by controlling the low loading of metals, it is often necessary to add excess catalyst to achieve the required number of catalytic active sites, which is costly. Summary of the invention
[0005] The purpose of the present disclosure is to provide a method for preparing a platinum group metal catalyst and a platinum group metal catalyst, thereby overcoming, at least to a certain extent, the problem of difficulty in obtaining high-loaded and highly dispersed platinum group metal catalysts on a large scale due to the limitations and defects of the relevant technologies.
[0006] According to one aspect of the present disclosure, there is provided a method for preparing a platinum group metal catalyst, comprising: dissolving a platinum group metal chloride in deionized water to dilute the solution to a target concentration, adding a planar two-dimensional lamellar graphite phase carbon nitride powder to the solution and stirring the solution to obtain a catalyst precursor; and sintering the catalyst precursor at a high temperature to obtain an atomically dispersed supported platinum group metal catalyst.
[0007] In an exemplary embodiment of the present disclosure, the basic structural units of the graphite-phase carbon nitride powder are triazine ring and 3-s-triazine ring.
[0008] In an exemplary embodiment of the present disclosure, the graphite-phase carbon nitride powder is prepared by calcining urea at a high temperature.
[0009] In an exemplary embodiment of the present disclosure, the heating rate of the calcination is 0.1 to 2° C. / min, the calcination temperature is 450 to 750° C., and the calcination time is 2 to 10 h.
[0010] In an exemplary embodiment of the present disclosure, the stirring speed is 500-800 rpm, and the stirring time is 8-12 hours.
[0011] In an exemplary embodiment of the present disclosure, the target concentration is 0.0005 to 1 g / 10 mL, and the weight of the graphite-phase carbon nitride powder is 1 to 10 g.
[0012] In an exemplary embodiment of the present disclosure, the high temperature sintering temperature is 300-400° C., the heating rate is 1-5° C. / min, and the holding time is 1-10 h.
[0013] In an exemplary embodiment of the present disclosure, the metal loading in the supported platinum group metal catalyst is 0.05 to 10 wt.%.
[0014] In an exemplary embodiment of the present disclosure, the method further includes: using the supported platinum group metal catalyst for a structure-insensitive carbon dioxide hydrogenation reduction reaction to produce formate, testing the intrinsic activity of the supported platinum group metal catalyst, and determining the dispersion state of the metal.
[0015] According to one aspect of the present disclosure, a platinum group metal catalyst is provided. The platinum group metal catalyst is prepared according to any one of the above-mentioned methods for preparing the platinum group metal catalyst.
[0016] In the technical solution provided in the embodiment of the present disclosure, on the one hand, a highly dispersed platinum group metal catalyst at the atomic level can be obtained by simple over-volume impregnation and high-temperature calcination. Mainly through the metal-carrier interaction between the platinum group metal and the graphite phase carbon nitride powder carrier and the synergistic effect of the chloride ions contained in the platinum group metal chloride, the dispersion of the platinum group metal on the carrier is jointly promoted, so that the dispersion and hydrogenation performance of the prepared platinum group metal catalyst are controllable, and it is easy to form a high-loaded supported platinum group metal catalyst dispersed at the atomic level, and improve its catalytic stability. On the other hand, compared with traditional supported precious metal catalysts, the embodiment of the present disclosure does not rely on the choice of load, maximizes the load requirement of the atomic-level dispersed catalyst, and regulates the dispersion of the supported platinum group metal catalyst by the synergistic effect of chloride ions and metal-carrier interactions, improves the load range of the atomic-level highly dispersed platinum group metal catalyst, and due to the use of a two-dimensional planar carrier of graphite phase carbon nitride, more active sites can be provided for the adsorption and desorption of reactants and products, breaking the dilemma of low atomic-level highly dispersed catalyst load and cumbersome carrier preparation, increasing the load and simplifying the preparation process. On the other hand, the raw materials used to prepare the catalyst are widely available and inexpensive, the preparation process has low cost and short preparation cycle, which reduces energy consumption, increases the scope of application, is easy to implement, and is suitable for industrial mass production.
[0017] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.
[0019] Figure 1 The flowchart schematically shows a method for preparing a platinum group metal catalyst in an embodiment of the present disclosure.
[0020] Figure 2 The HAADF-STEM image of the 10 wt.% Pt / C3N4 catalyst prepared according to Example 1 after CO2 hydrogenation reaction is schematically shown.
[0021] Figure 3 A schematic diagram showing the intrinsic activity of catalysts with different loadings prepared according to Example 1 in the CO2 hydrogenation to formate reaction is shown.
[0022] Figure 4The HAADF-STEM image of the 10 wt.% Ir / C3N4 catalyst prepared according to Example 2 after CO2 hydrogenation reaction is schematically shown.
[0023] Figure 5 A schematic diagram showing the intrinsic activity of catalysts with different loadings prepared according to Example 2 in the CO2 hydrogenation to formate reaction.
[0024] Figure 6 The HAADF-STEM image of the 10 wt.% Pd / C3N4 catalyst prepared according to Example 3 after CO2 hydrogenation reaction is schematically shown.
[0025] Figure 7 A schematic diagram showing the intrinsic activity of catalysts with different loadings prepared according to Example 3 in the production of formate by CO2 hydrogenation reaction.
[0026] Figure 8 TEM and EDS spectra of the 2 wt.% Ir / CeO2 catalyst prepared according to Comparative Example 1.
[0027] Fig. 9 Schematic diagram of the intrinsic activity of different carriers prepared according to Comparative Example 1 in the CO2 hydrogenation to formate reaction. DETAILED DESCRIPTION
[0028] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.
[0029] The terms "a", "an", "the" and "said" used in this specification are used to indicate the presence of one or more elements / components, etc.; the terms "including" and "having" are used to express an open-ended inclusion and mean that there may be additional elements / components, etc. in addition to the listed elements / components, etc.; the terms "first" and "second" etc. are used only as labels and are not intended to limit the quantity of their objects.
[0030] Atomically dispersed platinum group metal catalysts have high atomic utilization, but the metal dispersion is closely related to the loading. It is difficult to form atomic dispersion at high loading, and the atomically dispersed catalysts have poor stability in the reaction, which limits their large-scale promotion and application. At present, the main ways to improve the dispersion of supported platinum group metal catalysts are to obtain highly dispersed and highly stable platinum group metal catalysts through the confinement effect of carriers such as molecular sieves or by adjusting the metal-carrier interaction.
[0031] However, the above methods are highly dependent on the choice of carriers, and have relatively high requirements for the properties of the carriers and the preparation process, which further limits the large-scale preparation and application of highly dispersed platinum group metal catalysts at the atomic level. Transition metal oxides / carbides / nitrides are commonly used carriers, which are usually three-dimensional spherical / tubular materials, further limiting their spatial utilization of metals. Therefore, the development of platinum group metal catalysts supported by planar two-dimensional lamellar structures and the promotion of the formation of atomically dispersed precious metal catalysts through the addition of chloride ions and the regulation of metal-carrier interactions are of great significance for improving catalyst loading, cyclic stability, and increasing the adsorption activation sites of reactants.
[0032] In order to solve the above technical problems, the present disclosure provides a method for preparing a supported platinum group metal catalyst in an embodiment, which is used to prepare an atomically dispersed platinum group metal catalyst at a high load. Platinum group metal chloride is selected as a metal precursor, and a planar two-dimensional lamellar graphite phase carbon nitride is used as a carrier. The metal-carrier interaction is regulated by high-temperature sintering to form an atomically dispersed supported catalyst. Finally, the metal dispersion is adjusted by the synergistic effect of chloride ions and metal-carrier interaction to obtain a high-load atomically dispersed supported platinum group metal catalyst.
[0033] refer to Figure 1 As shown in, the preparation method of the platinum group metal catalyst mainly comprises the following steps:
[0034] In step S110, platinum group metal chloride is dissolved in deionized water to dilute the solution to a target concentration, and graphite phase carbon nitride powder with a planar two-dimensional sheet structure is added to the solution and stirred to obtain a catalyst precursor;
[0035] In step S120, the catalyst precursor is sintered at high temperature to obtain an atomically dispersed supported platinum group metal catalyst.
[0036] Next, the preparation method of the platinum group metal catalyst in the embodiment of the present disclosure is described in detail.
[0037] In step S110, platinum group metal chloride is dissolved in deionized water to dilute the solution to a target concentration, and graphite phase carbon nitride powder with a planar two-dimensional sheet structure is added to the solution and stirred to obtain a catalyst precursor.
[0038] In the disclosed embodiments, platinum group metal chloride can be used as a metal precursor, and graphite phase carbon nitride powder can be used as a carrier. The platinum group metal chloride can be any one of chloroplatinic acid, chloroiridic acid, and palladium chloride. The graphite phase carbon nitride powder is g-C3N4 powder. The graphite phase carbon nitride powder is a planar two-dimensional sheet structure, and the basic structural unit of the graphite phase carbon nitride powder is a triazine ring and a 3-s-triazine ring.
[0039] Platinum group metal chloride is dissolved in deionized water, and the concentration of the solution can be 0.01-0.1 g / mL, for example, it can be expressed as 0.1 g Pt / 1 mL H2O. The target concentration can be 0.0005-1 g / 10 mL. Furthermore, graphite phase carbon nitride powder can be added to the diluted solution for stirring. Among them, the weight of the added graphite phase carbon nitride powder can be 1-10 g. After adding the graphite phase carbon nitride powder, stirring can be carried out overnight, and the speed of stirring the graphite phase carbon nitride powder can be 500-800 rpm, and the stirring time can be 8-12 hours. After the stirring of the graphite phase carbon nitride powder is completed, it can be dried in the shade to obtain a catalyst precursor. The catalyst precursor can be a light yellow powder.
[0040] Among them, the graphite phase carbon nitride powder can be obtained by calcining and decomposing urea at high temperature. Among them, the heating rate of calcination can be 0.1-2°C / min, which can be set according to the heating program. The calcination temperature can be 450-750°C. The calcination time can be 2-10h. Exemplarily, g-C3N4 powder can be obtained by high-temperature calcination by a programmed temperature rising method, and the preparation method is: 30g of urea is placed in a 100mL crucible, and the temperature is increased to 450-750°C at a rate of 0.1-2°C / min, and kept at 450-750°C for 2-10h to obtain g-C3N4 powder.
[0041] In step S120, the catalyst precursor is sintered at high temperature to obtain an atomically dispersed supported platinum group metal catalyst.
[0042] In the disclosed embodiment, the catalyst precursor can be subjected to high temperature sintering, the temperature of high temperature sintering can be 300-400°C, the heating rate can be 1-5°C / min, and the holding time can be 1-10h. A supported platinum group metal catalyst refers to a catalyst in which the metal is dispersed on a carrier, and the metal loading refers to the ratio of the metal mass to the carrier mass. The greater the metal loading, the more metal is added, that is, the more platinum group metal chloride is added. The metal loading in the supported platinum group metal catalyst can be 0.05-10wt.%. The product of the target concentration after dilution and the volume is equal to the product of the catalyst mass and the metal loading.
[0043] Chloride ions in platinum group metal chlorides can also help disperse the metal during the sintering process. When the metal loading is controlled at 0.05 to 10 wt.%, a highly dispersed platinum group metal catalyst at the atomic level can be formed.
[0044] After obtaining the supported platinum group metal catalyst, the supported platinum group metal catalyst can be tested to determine the dispersion state of the metal therein. For example, the metal can be verified to be atomically dispersed by characterization means such as HAADF-STEM, and its microstructure and hydrogenation intrinsic activity can also be characterized and tested by the carbon dioxide hydrogenation reduction reaction, thereby confirming the atomic dispersion state of the metal by directly characterizing and averaging the activity data of the metal. In some embodiments, the distribution of active sites of the metal is determined by averaging the reaction activity of the metal through a structure-insensitive reaction such as carbon dioxide reduction to formate, thereby determining the dispersion state of the metal. For example, the reaction time can be adjusted to control the reaction conversion rate within a kinetic range of 10 to 20%, thereby obtaining the average reaction activity of the metal to prove the atomic dispersion state of the platinum group metal during the reaction.
[0045] The technical solution in the disclosed embodiment provides a method for preparing an atomic-level highly dispersed platinum group metal catalyst based on a planar two-dimensional sheet structure. The method uses a platinum group metal chloride salt as a precursor and a planar two-dimensional sheet structure g-C3N4 as a carrier, and combines processes such as over-volume impregnation, high-temperature calcination, and in-situ reduction to achieve in-situ generation of an atomic-level highly dispersed platinum group metal catalyst, and obtains a supported platinum group metal catalyst with high loading, high dispersion, and high cyclic stability, solving the problems of low loading and poor stability of atomic-level dispersed catalysts.
[0046] Next, the preparation method of the platinum group metal catalyst disclosed in the present invention is specifically described in conjunction with examples.
[0047] Example 1
[0048] This embodiment includes the following steps:
[0049] Step 1, material selection: Chloroplatinic acid (H2PtCl6·xH2O) is selected as a metal precursor, and two-dimensional planar material graphite phase carbon nitride powder g-C3N4 is used as a carrier. Urea is calcined at high temperature by a programmed temperature method to obtain g-C3N4 powder. The method for preparing graphite phase carbon nitride powder by calcining urea at high temperature is as follows: 30g of urea is placed in a 100mL crucible, heated at a rate of 0.1-2℃ / min, and kept at 450-750℃ for 2-10h to obtain g-C3N4 powder.
[0050] Step 2, preparation of supported catalyst: dissolve the chloroplatinic acid selected in step 1 in deionized water (0.01-0.1g Pt / 1ml H2O), dilute the solution to the target concentration according to the metal loading, and when chloroplatinic acid (H2PtCl6·xH2O) is selected as the metal precursor, the target concentration can be expressed as 0.00005-0.1g Pt / mL. Further, 1-10g of g-C3N4 can be added to the solution and stirred overnight at room temperature, the stirring speed is 500-800rpm, the stirring time is 8-12h, and then dried in the shade to obtain a light yellow solid powder to obtain a catalyst precursor.
[0051] Step 3, calcination: the catalyst precursor obtained in step 2 is subjected to high temperature sintering to obtain supported platinum group metal catalysts with different loadings, and the supported platinum group metal catalysts can be supported Pt / C3N4 catalysts. The sintering temperature is 300-500°C, the heating rate is 1-5°C / min, and the holding time is 1-10h. The metal loading of the supported platinum group metal catalyst can be 0.05-10wt.%.
[0052] Step 4: Characterization and catalytic activity test: The supported platinum group metal catalyst obtained in step 3 is directly used in the CO2 hydrogenation to formate reaction to test its intrinsic activity and characterize the microstructure of the supported platinum group metal catalyst after the reaction.
[0053] Figure 2 The HAADF-STEM image of the 10wt.% Pt / C3N4 catalyst prepared according to Example 1 after CO2 hydrogenation reaction is shown in FIG. Figure 2 Figure (a) and Figure 2 From the STEM images of different scales shown in Figure (b), it can be seen that the Pt / C3N4 catalyst can maintain high atomic-level dispersion on the two-dimensional planar material g-C3N4 when the loading is as high as 10wt.%, and no obvious metal agglomeration is observed.
[0054] Figure 3 Schematic diagram of the intrinsic activity of Pt / C3N4 catalysts with different loadings (0.05-10 wt.%) prepared according to Example 1 in CO2 hydrogenation reaction. Figure 3 It can be seen that for structure-insensitive reactions such as CO2 hydrogenation to formate, single atoms, nanoclusters, and nanoparticles can catalyze the reaction, so the dispersion state of the metal can be verified by averaging the reaction activity of the metal. In this example, when the Pt / C3N4 catalysts with different loadings show similar reaction activities, it indicates that the Pt in the catalyst has similar metal dispersion, that is, they are all dispersed at the atomic level.
[0055] Example 2
[0056] This embodiment includes the following steps:
[0057] Step 1, material selection: Chloroiridic acid (H2IrCl6·6H2O) is selected as a metal precursor, and two-dimensional planar material graphite phase carbon nitride powder g-C3N4 is used as a carrier. Urea is calcined at high temperature by a programmed temperature method to obtain g-C3N4 powder. The method for calcining urea at high temperature is as follows: 30g of urea is placed in a 100mL crucible, heated at a rate of 0.1-2℃ / min, and kept at 450-750℃ for 2-10h to obtain g-C3N4 powder.
[0058] Step 2, preparation of supported catalyst: dissolve the chloroiridic acid selected in step 1 in deionized water (0.01-0.1g Ir / 1ml H2O), dilute the solution to the target concentration according to the metal loading, and when chloroiridic acid (H2IrCl6·6H2O) is selected as the metal precursor, the target concentration can be expressed as 0.00005-0.1g Ir / mL. Further, 1-10g of g-C3N4 can be added to the solution and stirred overnight at room temperature, the stirring speed is 500-800rpm, the stirring time is 8-12h, and then dried in the shade to obtain a light yellow solid powder to obtain a catalyst precursor.
[0059] Step 3, calcination: the catalyst precursor obtained in step 2 is subjected to high temperature sintering to obtain supported platinum group metal catalysts with different loadings, and the supported platinum group metal catalysts can be supported Ir / C3N4 catalysts. The sintering temperature is 300-500°C, the heating rate is 1-5°C / min, and the holding time is 1-10h. The metal loading of the supported platinum group metal catalyst can be 0.05-10wt.%.
[0060] Step 4: Characterization and catalytic activity testing: The supported platinum group metal catalyst obtained in step 3 is directly used in the CO2 hydrogenation to produce formate reaction, its intrinsic activity is tested and the microstructure of the catalyst before and after the reaction is characterized.
[0061] Figure 4The HAADF-STEM image of the 10wt.% Ir / C3N4 catalyst prepared according to Example 2 after CO2 hydrogenation reaction is shown in FIG. Figure 4 Figure (a) and Figure 4 From the STEM images of different scales shown in Figure (b), it can be seen that the Ir / C3N4 catalyst can maintain high atomic-level dispersion on the two-dimensional planar material g-C3N4 when the loading is as high as 10wt.%, and no obvious metal agglomeration is observed.
[0062] Figure 5 Schematic diagram of the intrinsic activity of Ir / C3N4 catalysts with different loadings (0.05-10wt.%) prepared according to Example 2 in the CO2 hydrogenation to formate reaction. For a structure-insensitive reaction such as CO2 hydrogenation to formate, single atoms, nanoclusters, and nanoparticles can all catalyze the reaction, so the dispersion state of the metal can be verified by averaging the reaction activity of the metal. In this example, when the Ir / C3N4 catalysts with different loadings show similar reaction activities, it indicates that the Ir in the catalyst has similar metal dispersion, that is, they are all in an atomic-level dispersion state.
[0063] Example 3
[0064] This embodiment includes the following steps:
[0065] Step 1, material selection: palladium chloride (PdCl2·3H2O) is selected as a metal precursor, and two-dimensional planar material graphite phase carbon nitride powder g-C3N4 is used as a carrier. Urea is calcined at high temperature by a programmed temperature method to obtain g-C3N4 powder. The method for preparing graphite phase carbon nitride powder by calcining urea at high temperature is as follows: 30g of urea is placed in a 100mL crucible, heated at a rate of 0.1-2℃ / min, and kept at 450-750℃ for 2-10h to obtain g-C3N4 powder.
[0066] Step 2, preparation of supported catalyst: dissolve the palladium chloride selected in step 1 in deionized water (0.01-0.1g Pd / 1ml H2O), dilute the solution to the target concentration according to the metal loading, and when palladium chloride (PdCl2·3H2O) is selected as the metal precursor, the target concentration can be expressed as 0.00005-0.1g Pd / mL. Further, 1-10g of g-C3N4 can be added to the solution and stirred overnight at room temperature, the stirring speed is 500-800rpm, the stirring time is 8-12h, and then dried in the shade to obtain a light yellow solid powder to obtain a catalyst precursor.
[0067] Step 3, calcination: the catalyst precursor obtained in step 2 is subjected to high temperature sintering to obtain supported platinum group metal catalysts with different loadings, and the supported platinum group metal catalysts can be supported Pd / C3N4 catalysts. The sintering temperature is 300-500°C, the holding time is 1-10h, and the heating rate is 0.5-5°C / min. The metal loading of the supported platinum group metal catalyst can be 0.05-10wt.%.
[0068] Step 4: Characterization and catalytic activity testing: The supported platinum group metal catalyst obtained in step 3 is directly used in the CO2 hydrogenation to produce formate reaction, its intrinsic activity is tested and the microstructure of the catalyst before and after the reaction is characterized.
[0069] Figure 6 The HAADF-STEM image of the 10wt.% Pd / C3N4 catalyst prepared according to Example 3 after CO2 hydrogenation reaction. Figure 6 Figure (a) and Figure 6 From the STEM images of different scales shown in Figure (b), it can be seen that the Pd / C3N4 catalyst can maintain high atomic-level dispersion on the two-dimensional planar material g-C3N4 when the loading is as high as 10wt.%, and no obvious metal agglomeration is observed.
[0070] Figure 7 The figure is a schematic diagram of the intrinsic activity of Pd / C3N4 catalysts with different loadings (0.05-10wt.%) prepared according to Example 3 in the CO2 hydrogenation reaction. For a structure-insensitive reaction such as CO2 hydrogenation to formate, single atoms, nanoclusters, and nanoparticles can catalyze the reaction, so the dispersion state of the metal can be verified by averaging the reaction activity of the metal. In this example, when the Pd / C3N4 catalysts with different loadings show similar reaction activities, it indicates that the Pd in the catalyst has similar metal dispersion, that is, they are all in an atomic-level dispersion state.
[0071] Comparative Example 1
[0072] This embodiment includes the following steps:
[0073] Step 1: Material selection: Chloroiridic acid (H2IrCl6·6H2O) is selected as a metal precursor, and any one of commercial silicon oxide (SiO2), cerium oxide (CeO2), and titanium oxide (P25) is used as a carrier.
[0074] Step 2, preparation of supported catalyst: dissolve the chloroiridic acid selected in step 1 in deionized water (0.1gIr / 1ml H2O), dilute to the required concentration of 0.002g Ir / mL according to the metal loading, add 1g carrier and stir at room temperature overnight, the stirring speed is 500-800rpm, the stirring time is 8-12h, and then dry in the shade to obtain a light yellow solid powder to obtain a catalyst precursor.
[0075] Step 3: Calcination: The catalyst precursor obtained in step 2 is sintered at high temperature to obtain 2wt.% Ir / support catalysts loaded with different supports, wherein the sintering temperature is 300-500°C, the holding time is 1-10h, and the heating rate is 0.5-5°C / min.
[0076] Step 4: Characterization and catalytic activity testing: The catalyst obtained in step 3 is directly used in the CO2 hydrogenation reaction to produce formate, its intrinsic activity is tested and the microstructure of the catalyst before and after the reaction is characterized.
[0077] Figure 8 TEM and EDS spectra of the 2 wt.% Ir / CeO2 catalyst prepared according to Comparative Example 1. Figure 8 It can be seen that there is obvious metal agglomeration.
[0078] Fig. 9 Schematic diagram of the intrinsic activity of different catalysts in the CO2 hydrogenation to formate reaction. For a structure-insensitive reaction such as CO2 hydrogenation to formate, single atoms, nanoclusters, and nanoparticles can catalyze the reaction, so the dispersion state of the metal can be verified by averaging the reaction activity of the metal. In this embodiment, when the Ir / support catalysts with the same loading exhibit different reaction activities, it indicates that the dispersion of the Ir metal in the catalyst is quite different; and Ir / C3N4 has the highest activity, indicating that the dispersion of the metal Ir in the catalyst is the highest at this time.
[0079] The technical solution in the embodiment of the present disclosure can obtain an atomic-level highly dispersed platinum group metal catalyst by simple over-volume impregnation and high-temperature calcination. The preparation process is simple and easy to scale up for production. The dispersion of the metal on the carrier is mainly promoted by the metal-carrier interaction between the platinum group metal and the g-C3N4 carrier and the synergistic effect of the chloride ions contained in the platinum group metal chloride. The process is simple, the cost is low, the prepared atomic-level highly dispersed platinum group metal catalyst has a controllable loading and good structural stability in the hydrogen storage reaction. Compared with traditional supported precious metal catalysts, the prepared atomic-level highly dispersed platinum group metal catalyst has a loading range of up to 10wt.%, and due to the use of a two-dimensional planar carrier, more active sites can be provided for the adsorption and desorption of reactants and products, avoiding the problem of adding excessive catalysts in related technologies to achieve the required number of catalytic active sites, breaking the dilemma of low atomic-level highly dispersed catalyst loading, unstable structure, cumbersome preparation and large demand, and improving the effect. In addition, the raw materials involved in the embodiment of the present disclosure are widely available and inexpensive, the preparation process is low in cost, the application range is wide, and it is easy to implement. The entire preparation process is time-saving and energy-saving, and is suitable for industrial mass production.
[0080] In the disclosed embodiment, a platinum group metal catalyst prepared by the method of step S110 to step S120 is also provided. In the disclosed embodiment, the platinum group metal catalyst can be an atomically dispersed supported platinum group metal catalyst. Platinum group metal chloride is selected as a metal precursor, and a planar two-dimensional lamellar graphite phase carbon nitride is used as a carrier. The metal-carrier interaction is regulated by high-temperature sintering to form an atomically dispersed supported catalyst. Finally, the metal dispersion is adjusted by the synergistic effect of chloride ions and metal-carrier interaction to obtain a high-load atomically dispersed supported platinum group metal catalyst. It avoids the cumbersome carrier preparation process and the previous application problems of low atomically dispersed catalysts requiring a large amount of catalysts to be put into use, thereby reducing costs and increasing the scope of application.
[0081] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present disclosure, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.
[0082] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.
[0083] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.
Claims
1. A method for preparing a platinum group metal catalyst, characterized in that: include: Dissolving platinum group metal chloride in deionized water to dilute the solution to a target concentration, adding graphite phase carbon nitride powder having a planar two-dimensional sheet structure to the solution and stirring to obtain a catalyst precursor; The catalyst precursor is sintered at high temperature to obtain an atomic-level dispersed supported platinum group metal catalyst.
2. The method for preparing a platinum group metal catalyst according to claim 1, characterized in that: The basic structural units of the graphite phase carbon nitride powder are triazine ring and 3-s-triazine ring.
3. The method for preparing a platinum group metal catalyst according to claim 1 or 2, characterized in that: The graphite phase carbon nitride powder is obtained by calcining and decomposing urea at a high temperature.
4. The method for preparing a platinum group metal catalyst according to claim 3, characterized in that: The heating rate of the calcination is 0.1-2°C / min, the calcination temperature is 450-750°C, and the calcination time is 2-10h.
5. The method for preparing a platinum group metal catalyst according to claim 1, characterized in that: The stirring speed is 500-800 rpm, and the stirring time is 8-12 hours.
6. The method for preparing a platinum group metal catalyst according to claim 1, characterized in that: The target concentration is 0.0005-1 g / 10 mL, and the weight of the graphite phase carbon nitride powder is 1-10 g.
7. The method for preparing a platinum group metal catalyst according to claim 1, characterized in that: The high-temperature sintering temperature is 300-400° C., the heating rate is 1-5° C. / min, and the heat preservation time is 1-10 hours.
8. The method for preparing a platinum group metal catalyst according to claim 1, characterized in that: The metal loading in the supported platinum group metal catalyst is 0.05-10 wt.%.
9. The method for preparing a platinum group metal catalyst according to claim 1, characterized in that: The method further comprises: The supported platinum group metal catalyst is used for a structure-insensitive carbon dioxide hydrogenation reduction reaction to produce formate, and the intrinsic activity of the supported platinum group metal catalyst is tested to determine the dispersion state of the metal.
10. A platinum group metal catalyst, characterized in that The platinum group metal catalyst is prepared according to the method for preparing a platinum group metal catalyst according to any one of claims 1-9.