Supported dual-atom catalyst, preparation method therefor and use thereof

Abstract

The present application relates to the technical field of catalyst preparation, and discloses a supported dual-atom catalyst, a preparation method therefor and a use thereof. The supported dual-atom catalyst has a well-defined dual-atom configuration, and in the preparation process of the supported dual-atom catalyst, a diamine compound having two amine functional groups is used as a dual-atom structure-directing agent and a stabilizer; by regulating the chain length of the diamine compound, the distance between two atoms having a strong interaction can be precisely regulated and controlled. The preparation method is simple, and can realize large-scale preparation of a distance-controllable supported heteronuclear dual-atom catalyst, without relying on a metal precursor and an instrument, wherein the prepared supported Pt-Au heteronuclear dual-atom catalyst has excellent ammonia synthesis performance and exhibits good electrochemical recyclability.

Description

A supported diatomic catalyst, its preparation method and application Technical Field

[0001] This application relates to a supported diatomic catalyst, its preparation method, and its application, belonging to the field of catalyst preparation technology. Background Technology

[0002] Diatom catalysts (DACs) have attracted widespread attention in the field of catalysis due to their high atom utilization and synergistic catalytic effect between two atomic sites. The distance between atoms plays a crucial role in diatomic synergistic catalysis, and its catalytic performance varies significantly with changes in the distance between adjacent atoms. Therefore, precisely controlling the distance between diatoms is key to optimizing catalytic performance. Current research on diatomic catalysts focuses on developing novel preparation methods, accurately identifying metal positions and atom pairs, and revealing the structure-activity relationship between diatomic configuration and reaction performance. The control of the distance between the two atoms in diatomic catalysts is still in its early stages, with few published reports.

[0003] Professor Lu's team precisely prepared Pt1Ni1 diatomic and Pt1+Ni1 bis-monoatomic catalysts on g-C3N4 support using atomic layer deposition (ALD) technology, taking advantage of the steric hindrance effect between metal-organic precursors during the ALD process [Angew. Chem. Int. Ed. 2022, 61, e202211919]. The interatomic spacing of the Pt1+Ni1 bis-monoatomic catalysts is shown in the figure. Much larger than Pt1Ni1 diatomic Adjustable interatomic spacing was achieved. The Pt1Ni1 diatomic catalyst exhibited optimal performance, approximately 13 times and 2 times that of the Pt1 single-atom and Pt1+Ni1 dual-single-atom catalysts, respectively. Mechanistic studies revealed significant electron transfer in the Pt1Ni1 diatomic structure, which was absent in the Pt1+Ni1 dual-single-atom structure. However, the aforementioned method contained unpaired dual-single atoms, failing to achieve precise control over the interatomic spacing. Researcher Wang's team used three different impregnation schemes to prepare NiFe-isote diatomic catalysts, NiFe-N bridge diatomic catalysts, and NiFe-bonding diatomic catalysts, respectively, achieving controllable adjustment of the interatomic spacing [Angew. Chem. Int. Ed. 2022, 61, e202211919]. (The text then abruptly shifts to a discussion of NiFe-isote diatomic catalysts and their interatomic spacing, which seems unrelated to the previous paragraphs.) ) or NiFe-bonding diatomic catalyst (atomic spacing) Compared to NiFe-N bridge diatomic catalysts (atomic spacing) With suitable interatomic distances and electronic properties, the NiFe-N bridge diatomic catalyst can nearly double the electroreduction performance of CO2. A series of characterization and theoretical calculations show that Ni transfers more electrons to Fe in the NiFe-N bridge diatomic catalyst, optimizing the electron distribution at the Fe center, resulting in suitable adsorption strength for the *COOH intermediate, and promoting *CO desorption, thereby improving the catalyst's activity and selectivity. However, this method utilizes the porosity of ZIF-8 to prepare diatomic catalysts through co-impregnation, which presents the challenge of accurately distinguishing between target diatomic pairs and densely packed atoms. Precise quantification and statistical analysis of the interatomic distance at the atomic scale requires a combination of more precise characterization techniques. Currently, there is a lack of simple and universal methods in the field of diatomic catalyst synthesis to precisely controllably adjust the interatomic distance between paired diatoms in diatomic catalysts.

[0004] Ammonia is an essential chemical for human survival and ecosystems, and is considered a key alternative fuel for green hydrogen and a crucial carrier for energy transition. Currently, ammonia synthesis mainly relies on the energy-intensive and carbon-intensive Haber-Bosch (HB) process, which uses nitrogen obtained from air separation and hydrogen obtained from fossil fuel reforming as feedstocks under high temperature and pressure conditions, resulting in significant carbon emissions and energy consumption. Electrocatalytic nitrate reduction reaction (e-NO3RR) enables large-scale ammonia production under environmentally friendly conditions while mitigating nitrate pollution, providing a dual benefit of "turning waste into treasure." However, the synthesis of ammonia via electrocatalytic nitrate reduction involves complex electron transfer processes and is subject to competition from the hydrogen evolution reaction. Therefore, designing highly selective electrocatalytic nitrate reduction catalysts has become a key challenge.

[0005] Diatom catalysts (DACs) have attracted widespread attention in the field of catalysis due to their high atom utilization and synergistic catalytic effect between two atomic sites. Compared with single-atom catalysts, DACs have higher metal loading, flexible combinations of multiple metal atoms, and unique microenvironments, exhibiting superior catalytic performance in many reactions. The advantages of increased metal atom number, the regulation of adsorption configuration of reactants and intermediates by the interaction between the two atoms, the synergistic effect between metal atoms and / or supports, and the reduction of reaction barriers have made them a hot research topic in the field of electrocatalytic nitrate reduction to ammonia.

[0006] In the synthesis of most DACs in the past, the lack of correlation between the two metal sites and the high randomness of their pairing led to a random and uncontrollable distribution of the two metal sites, resulting in a relatively low proportion of diatomic sites in the obtained catalysts. Single atoms, clusters, and nanoparticles also coexisted. This is especially true in the precise synthesis of heteronuclear diatomic catalysts, where the formation of homonuclear diatomic clusters makes the synthesis process difficult to control. Currently, wet chemical impregnation and atomic layer deposition (ALD) methods can accurately prepare diatomic sites in the preparation of heteronuclear DACs, but the limited "atom manufacturing" capabilities result in structural inhomogeneity, making it difficult to accurately distinguish between target diatomic pairs and dense atoms. Furthermore, most of these methods rely on expensive equipment and rare dinuclear metal complexes. Currently, there is a lack of simple and universal methods in the field of heteronuclear DAC synthesis for the precise and large-scale synthesis of stable heteronuclear diatomic catalysts with a high proportion of diatomic distributions. Summary of the Invention

[0007] To address the problem of precisely controlling the interatomic distance in existing diatomic catalyst technologies, this application proposes a preparation technique for a supported diatomic catalyst with adjustable spacing. This technique utilizes a diamine compound with two amino functional groups as a diatomic structure directing agent and stabilizer. By controlling the chain length of the diamine compound, the spacing between the two strongly interacting atoms can be precisely controlled. The preparation method is simple, independent of metal precursors and instruments, and enables large-scale preparation of supported diatomic catalysts with adjustable spacing.

[0008] The technical solution adopted in this application is as follows:

[0009] According to a first aspect of this application, a supported diatomic catalyst with adjustable spacing is provided, comprising a g-C3N4 support and platinum atoms;

[0010] The platinum atoms are distributed in pairs on the g-C3N4 support.

[0011] According to a second aspect of this application, a method for preparing the above-mentioned adjustable-spacing supported diatomic catalyst is provided, comprising the following steps:

[0012] S1. Obtain g-C3N4 powder;

[0013] S2. The mixture containing platinum ions, diamine compounds, and the g-C3N4 powder is continuously stirred to obtain a raw material liquid;

[0014] S3. Remove the solvent from the raw material liquid and dry it to obtain an intermediate product. Calcine the intermediate product to obtain the supported diatomic catalyst with adjustable spacing.

[0015] The diamine compound used in step S2 of this application acts as a diatomic structure directing agent and stabilizer. By utilizing two amino functional groups, platinum atoms are arranged in regular pairs, and the distance between the two atoms can be precisely controlled.

[0016] Optionally, in step S2, the hybrid configuration process includes:

[0017] An aqueous solution containing platinum ions is added to water, stirred until homogeneous, and then an aqueous solution of a diamine compound and g-C3N4 powder are added sequentially to obtain the mixture.

[0018] Optionally, the concentration of platinum ions in the aqueous solution containing platinum ions is 0.05M to 0.25M.

[0019] Optionally, the volume ratio of the aqueous solution containing platinum ions to the water is 100 μL to 200 μL: 50 mL.

[0020] Optionally, the aqueous solution containing platinum ions is selected from an aqueous solution of chloroplatinic acid.

[0021] Optionally, the concentration of the diamine compound in the aqueous solution is 0.05M to 0.25M.

[0022] Optionally, the volume ratio of the diamine compound aqueous solution to the water is 50 μL to 100 μL: 50 mL.

[0023] Optionally, the diamine compound has the molecular formula NH2-(CH3). n -NH2, n=2-10.

[0024] Optionally, the diamine compound is selected from at least one of 1,6-hexanediamine (HA) and ethylenediamine (EA).

[0025] Optionally, the solid-liquid ratio of the g-C3N4 powder to the aqueous solution containing platinum ions is 400 mg: 100 μL to 200 μL.

[0026] Optionally, in step S2, the conditions for continuous stirring include a stirring time of 18 to 36 hours.

[0027] Optionally, in step S3, the drying temperature is from 60°C to 80°C.

[0028] Optionally, the solvent removal is performed by heating, and the heating temperature is 60°C to 80°C.

[0029] Optionally, the calcination conditions include: calcination in an inactive atmosphere, a heating rate of 4–6 °C / min, a calcination temperature of 200 °C–400 °C, and a calcination time of 2–3 h.

[0030] Optionally, in step S1, the g-C3N4 powder is obtained by calcining urea.

[0031] Optionally, the conditions for calcining urea include: a heating rate of 4-6°C / min, a calcination temperature of 400°C-600°C, and a calcination time of 3-5 hours.

[0032] According to a third aspect of this application, a preparation method for a supported Pt-Au heteronuclear diatomic catalyst is provided. 1,6-hexanediamine (HA) is used as a diatomic structure directing and stabilizing agent, exhibiting a well-defined diatomic configuration. The preparation method is simple, independent of metal precursors and specialized equipment, and enables large-scale preparation of diatomic catalysts. The prepared supported Pt-Au heteronuclear diatomic catalyst exhibits superior electrocatalytic nitrate reduction performance and demonstrates good electrochemical stability.

[0033] A method for preparing a supported Pt-Au heteronuclear diatomic catalyst includes the following steps:

[0034] S1. Calcining urea yields g-C3N4 powder;

[0035] S2. Add water and the g-C3N4 powder to the aqueous solution of H2PtCl6 to obtain a mixture I. Stir the mixture I, remove the solvent, dry the product and then calcine it II to obtain Pt1 / g-C3N4.

[0036] S3. Add 1,6-hexanediamine aqueous solution to the aqueous dispersion containing Pt1 / g-C3N4, stir II, then add HAuCl4 aqueous solution to obtain mixture II, stir mixture II, remove solvent, dry the product and calcine III to obtain the supported Pt-Au heteronuclear diatomic catalyst.

[0037] The addition of 1,6-hexanediamine serves as a diatomic structure directing agent and stabilizer.

[0038] Optionally, in step S1, the conditions for calcination I include: a heating rate of 4℃ / min to 6℃ / min, a calcination temperature of 400℃ to 600℃, and a calcination time of 3h to 5h.

[0039] Optionally, in step S2, the concentration of the aqueous solution of H2PtCl6 is 0.05M to 0.25M.

[0040] Optionally, in step S2, the ratio of the amount of g-C3N4 powder to the aqueous solution of H2PtCl6 and water is 0.5g: 100μL~200μL: 100mL~150mL.

[0041] Optionally, in step S2, the conditions for calcination II include: a heating rate of 4℃ / min to 6℃ / min, a calcination temperature of 200℃ to 400℃, and a calcination time of 1h to 3h.

[0042] Optionally, in step S2, the stirring time is 12h to 36h.

[0043] Optionally, in step S3, the concentration of the 1,6-hexanediamine aqueous solution is 0.05M to 0.25M.

[0044] In this application, 1,6-hexanediamine acts as a diatomic structure directing agent and stabilizer.

[0045] Optionally, in step S3, the volume ratio of the aqueous dispersion of Pt1 / g-C3N4 to the aqueous solution of 1,6-hexanediamine is 25 mL: 50 μL to 100 μL.

[0046] Optionally, in step S3, the concentration of the HAuCl4 aqueous solution is 0.05M to 0.25M.

[0047] Optionally, in step S3, the volume ratio of the aqueous dispersion of Pt1 / g-C3N4 to the aqueous solution of HAuCl4 is 25 mL: 10 μL to 50 μL.

[0048] Optionally, in steps S2 and S3, the conditions for removing the solvent independently include: heating at 60°C to 80°C until the solvent is completely evaporated.

[0049] Optionally, in steps S2 and S3, the drying conditions independently include: a drying temperature of 60°C to 80°C and a drying time of 6h to 18h.

[0050] Optionally, in step S3, the conditions for calcination III include: under an inactive atmosphere, a heating rate of 4℃ / min to 6℃ / min, a calcination temperature of 100℃ to 300℃, and a calcination time of 0.5h to 2h.

[0051] Optionally, in step S3, the stirring time for stirring II is 0.5h to 2h.

[0052] Optionally, in step S3, the stirring time for stirring II is 12h to 36h.

[0053] According to a fourth aspect of this application, a supported Pt-Au heteronuclear diatomic catalyst prepared by the above-described preparation method is provided, wherein platinum atoms and gold atoms are arranged in pairs on the supported Pt-Au heteronuclear diatomic catalyst.

[0054] According to the fifth aspect of this application, a supported Pt-Au heteronuclear diatomic catalyst prepared by the above preparation method or the above supported Pt-Au heteronuclear diatomic catalyst is provided for use in the reduction of nitrate to produce ammonia.

[0055] The beneficial effects of this application include:

[0056] (1) This application is the first to propose the use of diamine compounds with two amino functional groups for precise control of the interatomic distance in a diatomic catalyst.

[0057] (2) The interatomic spacing between paired atoms in the diamine catalyst provided in this application can be precisely and controllably adjusted. The amino groups at both ends of the diamine compound pair the two diatoms through complexation, and during the thermal decomposition process, the movement of the two atoms is spatially restricted, guiding them to form a diatomic configuration on the g-C3N4 substrate. By controlling the chain length of the diamine compound, the interatomic spacing can be precisely controlled.

[0058] (3) The positions of metal atoms and atom pairs in the diatomic catalyst provided in this application can be easily and accurately identified. The interatomic spacing in the diatomic catalyst is statistically analyzed according to the EMARS methodology [J.Am.Chem.Soc.2021,143(37),15243-15249] to achieve accurate quantification of the interatomic spacing.

[0059] (4) The preparation method provided in this application is simple, does not depend on metal precursors and special instruments, has mild reaction conditions, and can realize the large-scale preparation of diatomic catalysts.

[0060] (5) The preparation method of the supported Pt-Au heteronuclear diatomic catalyst provided in this application uses 1,6-hexanediamine for the precise synthesis of heteronuclear diatoms. The amino groups at both ends of the hexanediamine molecule pair the two heteronuclear diatoms through complexation and restrict the movement of the two atoms in space during the thermal decomposition process, guiding them to form a diatomic configuration on the g-C3N4 substrate, thereby achieving the purpose of precise synthesis of the supported Pt-Au heteronuclear diatomic catalyst.

[0061] (6) The preparation method provided in this application employs a two-step method to introduce two atoms: firstly, the first atom Pt is loaded into the defect of g-C3N4, and then the second metal atom Au is introduced under the guidance of 1,6-hexanediamine. This method can achieve precise control and dispersion of platinum single atoms through independent optimization of reaction conditions, avoiding uncertain reactions or undesirable pairings caused by the simultaneous introduction of two metal atoms.

[0062] (7) The Pt-Au heteronuclear diatomic particles prepared by the method provided in this application can be used as catalysts for the electrocatalytic reduction of nitrate to ammonia, with an ammonia yield as high as 3347.6 μg / h. -1 mg-1 It has a Faraday efficiency of 96%, which is better than most single-atom / diatomic catalysts reported to date. Attached Figure Description

[0063] Figure 1 shows the aberration-corrected high-angle annular dark-field scanning transmission microscope image of the Pt2 / C3N4-HA diatomic catalyst in Example 1.

[0064] Figure 2 shows the aberration-corrected high-angle annular dark-field scanning transmission microscope image of the Pt2 / C3N4-EA diatomic catalyst in Example 2;

[0065] Figure 3 shows the aberration-corrected high-angle annular dark-field scanning transmission microscope image of the Pt2 / C3N4-none atomic catalyst in the comparative example.

[0066] Figure 4 is a schematic diagram of the interatomic spacing distribution of the atomic catalysts described in Examples 1-2 and Comparative Example 1.

[0067] Figure 5 is a spherical aberration-corrected high-angle annular dark-field scanning transmission microscope image of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application.

[0068] Figure 6 shows the X-ray diffraction pattern of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application;

[0069] Figure 7 shows the near-edge X-ray absorption fine structure spectrum of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application, wherein a is the normalized Pt L3 edge X-ray absorption near-edge structure spectrum of the supported Pt-Au heteronuclear diatomic catalyst in Example 1 of this application, and b is the normalized Au L3 edge X-ray absorption near-edge structure spectrum of the supported Pt-Au heteronuclear diatomic catalyst in Example 1 of this application;

[0070] Figure 8 is a schematic diagram of the ammonia yield and Faraday efficiency at different potentials in the electrocatalytic nitrate reduction to ammonia production performance test of the Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application.

[0071] Figure 9 is a cyclic schematic diagram of the electrocatalytic nitrate reduction to ammonia production performance of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application. Detailed Implementation

[0072] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0073] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0074] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0075] Example 1

[0076] Step 1: Place urea in an alumina crucible and calcine it in a muffle furnace at 550°C for 4 hours with a heating rate of 5°C / min to obtain a light yellow powder g-C3N4.

[0077] Step 2: Add 160 μL of 0.1 M H₂PtCl₆·6H₂O aqueous solution to 50 mL of water and stir continuously to obtain a homogeneous solution. Then add 85 μL of 0.15 M 1,6-hexanediamine aqueous solution to the above solution, mix well, and then add 400 mg g-C₃N₄ to the above solution and stir continuously for 24 h.

[0078] Step 3: Heat at 80℃ to remove the aqueous solvent, dry at 60℃ overnight, and calcine the obtained product in N2 at 350℃ for 2 hours to obtain a supported diatomic catalyst with adjustable spacing. The final product is denoted as Pt2 / C3N4-HA diatomic catalyst.

[0079] Example 2

[0080] Step 1: Place urea in an alumina crucible and calcine it in a muffle furnace at 550°C for 4 hours with a heating rate of 5°C / min to obtain a light yellow powder g-C3N4.

[0081] Step 2: Add 160 μL of 0.1 M H₂PtCl₆·6H₂O aqueous solution to 50 mL of water and stir continuously to obtain a homogeneous solution. Then add 85 μL of 0.15 M ethylenediamine aqueous solution to the above solution, mix well, and then add 400 mg of C₃N₄ to the above solution and stir continuously for 24 h.

[0082] Step 3: Heat at 80℃ to remove the aqueous solvent, dry at 60℃ overnight, and calcine the obtained product in N2 at 350℃ for 2 hours to obtain a supported diatomic catalyst with adjustable spacing. The final product is denoted as Pt2 / C3N4-EA diatomic catalyst.

[0083] Comparative Example 1

[0084] Step 1: Place urea in an alumina crucible and calcine it in a muffle furnace at 550°C for 4 hours with a heating rate of 5°C / min to obtain a light yellow powder g-C3N4.

[0085] Step 2: Add 160 μL of 0.1 M H₂PtCl₆·6H₂O aqueous solution to 50 mL of water and stir continuously to obtain a homogeneous solution. Then add 400 mg g-C₃N₄ to the above solution and stir continuously for 24 h.

[0086] Step 3: Heat at 80℃ to remove the aqueous solvent, dry at 60℃ overnight, and calcine the obtained product in N2 at 300℃ for 2 hours to obtain a supported diatomic catalyst with adjustable spacing. The final product is denoted as Pt2 / C3N4-none atomic catalyst.

[0087] Test Example 1

[0088] The microstructure of the diatomic catalysts prepared in Examples 1-2 and Comparative Example 1 of this application was observed, and the following experimental results were obtained:

[0089] (1) The Pt2 / C3N4-HA diatomic catalyst prepared in Example 1 of this application was observed and photographed using a spherical aberration-corrected high-angle annular dark-field scanning transmission microscope, resulting in the electron microscope image shown in Figure 1. As can be clearly seen from Figure 1, atoms are arranged in regular pairs throughout the entire region of the Pt2 / C3N4-HA diatomic catalyst, with only a very small number of atoms randomly dispersed as single atoms, and no particulate matter present.

[0090] (2) The Pt2 / C3N4-EA diatomic catalyst prepared in Example 2 of this application was observed and photographed using a spherical aberration-corrected high-angle annular dark-field scanning transmission microscope, resulting in the electron microscope image shown in Figure 1. As can be clearly seen from Figure 1, in the entire region of the Pt2 / C3N4-EA diatomic catalyst, atoms are arranged in regular pairs, with only a very small number of atoms randomly dispersed as single atoms, and no particulate matter exists.

[0091] (3) The Pt2 / C3N4-none atomic catalyst prepared in Comparative Example 1 of this application was observed and photographed using a spherical aberration-corrected high-angle annular dark-field scanning transmission microscope, resulting in the electron microscope image shown in Figure 1. As can be clearly seen from Figure 1, a large number of atoms are concentrated and randomly dispersed as single atoms in the entire region of the Pt2 / C3N4-none atomic catalyst, with no obvious and easily distinguishable atom pairs and no particulate matter present.

[0092] (4) The interatomic spacing in the diatomic catalysts prepared in Examples 1-2 and Comparative Example 1 was statistically analyzed using the EMARS methodology [J.Am.Chem.Soc.2021,143(37),15243-15249], resulting in the interatomic spacing distribution diagram shown in Figure 4. Analysis of more than 2400 atoms in the Pt2 / C3N4-HA diatomic catalyst showed that the interatomic spacing with the highest probability distribution was 0.49 nm. Analysis of more than 2300 atoms in the Pt2 / C3N4-EA diatomic catalyst showed that the interatomic spacing with the highest probability distribution was 0.22 nm. Analysis of more than 1950 atoms in the Pt2 / C3N4-none diatomic catalyst showed that the interatomic spacing with the highest probability distribution was 0.29 nm. As can be seen from Figure 4, the addition of diamine compounds with two amine functional groups can effectively regulate the interatomic spacing.

[0093] Example 3: Preparation of Supported Pt-Au Heteronuclear Diatomic Catalyst

[0094] Step 1: Place urea in an alumina crucible and calcine it in a muffle furnace at 550°C for 4 hours with a heating rate of 5°C / min to obtain a light yellow powder g-C3N4.

[0095] Step 2: Add 150 μL of 0.1 M H₂PtCl₆·6H₂O aqueous solution to 120 mL of water and stir continuously to obtain a homogeneous solution. Then, add 500 mg g-C₃N₄ to the above solution, stir continuously for 24 h, heat at 80 °C to remove the aqueous solvent, and dry at 60 °C overnight. The resulting product is calcined in N₂ at 200 °C for 2 h at a heating rate of 5 °C / min to obtain Pt₁ / g-C₃N₄.

[0096] Step 3: Disperse 300 mg Pt1 / g-C3N4 SACs in 25 mL of water, then add 85 μL of 0.1 M 1,6-hexanediamine aqueous solution. After stirring for 1 h, add 25 μL of 0.1 M HAuCl4·4H2O aqueous solution to the mixture, and stir for another 23 h. After the water has completely evaporated at 80 °C and dried overnight at 60 °C, calcine the collected product at 200 °C for 1 h under N2 at a heating rate of 5 °C / min. The final product is designated as Pt-Au heteronuclear diatomic catalyst.

[0097] Test Example 2

[0098] The supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application was subjected to microstructural observation, compositional analysis, and performance testing. All electrochemical measurements in the performance testing were performed in an H-type electrolytic cell, using the Pt-Au heteronuclear diatomic catalyst (1.5 × 1.5 cm⁻¹) prepared in Example 1. 2Using a CHI 760E electrochemical workstation as the working electrode, commercial carbon rods and Hg / HgO were used as the counter and reference electrodes, respectively. A Nafion 211 membrane separated the two chambers of the H-type cell, and the ammonia concentration of the product was determined by UV-Vis spectrophotometry. Utilizing the above H-type electrolytic cell, the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 was used to test the electrocatalytic reduction of nitrate to ammonia. The specific steps were as follows: In the cathode electrolyte (containing 7.14 mM NO3...)... - Add 0.1M 60mL KNO3 to the solution, and add 10mL of high-purity argon gas (min) -1 ) The electrolyte was continuously injected into the cathode cell and stirred at 200 rpm. During the reaction, NO3 was subjected to different potentials. - RR conducted a 3-hour experiment, using linear sweep voltammetry (LSV) at 5 mV s. -1 The reaction was carried out at a rate of [missing information] to evaluate the ammonia yield and Faraday efficiency of the catalyst. For stability testing, NO3 [missing information] - The RR experiment was conducted at -0.2V / RHE with a stirring speed of 200 rpm. The electrolyte solution was changed every 3 hours, and the experiment was repeated 5 times under the same working electrode.

[0099] Results analysis:

[0100] (1) The supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application was observed and photographed using a spherical aberration-corrected high-angle annular dark-field scanning transmission microscope, resulting in the electron microscope image shown in Figure 5. As can be clearly seen from Figure 5, in the entire region of the Pt1-Au1 / g-C3N4 diatomic catalyst, a large number of atoms are arranged in regular pairs, with only a very small number of atoms randomly dispersed as single atoms, and no particulate matter exists.

[0101] (2) The g-C3N4 and the prepared supported Pt-Au heteronuclear diatomic catalyst in Example 1 of this application were subjected to compositional analysis using an X-ray diffractometer, resulting in the X-ray diffraction patterns shown in Figure 6. As can be seen from Figure 6, the XRD pattern of the Pt-Au heteronuclear diatomic catalyst is very similar to that of g-C3N4. The absorption peaks at 12.9° and 27.6° correspond to the (002) and (100) crystal planes of g-C3N4, respectively. There are no characteristic peaks of Pt and Au particles, which confirms that Pt and Au species are supported on the g-C3N4 substrate in atomic form.

[0102] (3) Synchrotron radiation was used to analyze the composition of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 of this application, as well as PtO2, Pt foil, Au2O3, and Au foil, resulting in the near-edge X-ray absorption fine structure spectrum shown in Figure 7. Figure 7a shows the normalized Pt L3 edge X-ray absorption near-edge structure spectrum of the supported Pt-Au heteronuclear diatomic catalyst in Example 1 of this application. It can be seen that the white line intensity of Pt1-Au1 / g-C3N4 is higher than that of the platinum foil but lower than that of PtO2, indicating that Pt carries a partial positive charge (Pt...). δ+ ,0<δ<4). Figure 7b is the normalized Au L3 edge X-ray absorption near-edge structure spectrum of the supported Pt-Au heteronuclear diatomic catalyst in Example 1 of this application. It can be seen that the white line intensity of the supported Pt-Au heteronuclear diatomic catalyst is between that of Au foil and Au2O3 standard, indicating the presence of cation Au(Au) δ+ (0 < δ < 3). As can be seen from Figure 7, the 1,6-hexanediamine molecule successfully fixes the Pt and Au atoms on the g-C3N4 substrate through Pt-N and Au-N bonds.

[0103] (4) Figure 8 is a schematic diagram of the ammonia yield and Faraday efficiency at different potentials in the electrocatalytic reduction of nitrate to ammonia performance test of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1.

[0104] (5) Figure 9 is a schematic diagram of the cyclic performance of the supported Pt-Au heteronuclear diatomic catalyst prepared in Example 1 for the electrocatalytic reduction of nitrate to ammonia. As can be seen from Figure 9, the supported Pt-Au heteronuclear diatomic catalyst still has good ammonia yield and Faraday efficiency after 6 cycles.

[0105] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A supported diatom catalyst with adjustable spacing, characterized in that, Includes g-C3N4 support and platinum atoms; The platinum atoms are distributed in pairs on the g-C3N4 support.

2. The method for preparing the adjustable-spacing supported diatom catalyst according to claim 1, characterized in that, Includes the following steps: S1. Obtain g-C3N4 powder; S2. The mixture containing platinum ions, diamine compounds, and the g-C3N4 powder is continuously stirred to obtain a raw material liquid; S3. Remove the solvent from the raw material liquid and dry it to obtain an intermediate product. Calcine the intermediate product to obtain the supported diatomic catalyst with adjustable spacing.

3. The preparation method according to claim 2, characterized in that, In step S2, the hybrid configuration process includes: An aqueous solution containing platinum ions is added to water, stirred until homogeneous, and then an aqueous solution of a diamine compound and g-C3N4 powder are added sequentially to obtain the mixture.

4. The preparation method according to any one of claims 2-3, characterized in that, The concentration of platinum ions in the aqueous solution containing platinum ions is 0.05M to 0.25M.

5. The preparation method according to any one of claims 2-4, characterized in that, The volume ratio of the aqueous solution containing platinum ions to the water is 100 μL to 200 μL: 50 mL.

6. The preparation method according to any one of claims 2-5, characterized in that, The aqueous solution containing platinum ions is selected from chloroplatinic acid aqueous solution.

7. The preparation method according to any one of claims 2-6, characterized in that, The concentration of the diamine compound in the aqueous solution is 0.05M to 0.25M.

8. The preparation method according to any one of claims 2-7, characterized in that, The volume ratio of the aqueous solution of the diamine compound to the water is 50 μL to 100 μL: 50 mL.

9. The preparation method according to any one of claims 2-8, characterized in that, The molecular formula of the diamine compound is NH2-(CH3). n -NH2, n=2-10.

10. The preparation method according to any one of claims 2-9, characterized in that, The diamine compound is selected from at least one of 1,6-hexanediamine (HA) and ethylenediamine (EA).

11. The preparation method according to any one of claims 2-10, characterized in that, The solid-liquid ratio of the g-C3N4 powder to the aqueous solution containing platinum ions is 400 mg: 100 μL to 200 μL.

12. The preparation method according to any one of claims 2-11, characterized in that, In step S2, the conditions for continuous stirring include a stirring time of 18 to 36 hours.

13. The preparation method according to any one of claims 2-12, characterized in that, In step S3, the drying temperature is from 60°C to 80°C.

14. The preparation method according to any one of claims 2-13, characterized in that, The solvent removal is performed by heating, and the heating temperature is 60℃~80℃.

15. The preparation method according to any one of claims 2-14, characterized in that, The calcination conditions include: calcination in an inactive atmosphere, a heating rate of 4–6 °C / min, a calcination temperature of 200 °C–400 °C, and a calcination time of 2–3 h.

16. The preparation method according to any one of claims 2-15, characterized in that, In step S1, the g-C3N4 powder is obtained by calcining urea.

17. The preparation method according to any one of claims 2-16, characterized in that, The conditions for calcining urea include: a heating rate of 4-6℃ / min, a calcination temperature of 400℃-600℃, and a calcination time of 3-5h.

18. A method for preparing a supported Pt-Au heteronuclear diatomic catalyst, characterized in that, Includes the following steps: S1. Calcining urea yields g-C3N4 powder; S2. Add water and the g-C3N4 powder to the aqueous solution of H2PtCl6 to obtain mixture I. Stir the mixture I, remove the solvent, dry the product and then calcine it II to obtain Pt1 / g-C3N4. S3. Add 1,6-hexanediamine aqueous solution to the aqueous dispersion containing Pt1 / g-C3N4, stir II, then add HAuCl4 aqueous solution to obtain mixture II, stir mixture II III, remove solvent, dry the product and calcine III to obtain the supported Pt-Au heteronuclear diatomic catalyst; The addition of 1,6-hexanediamine serves as a diatomic structure directing agent and stabilizer.

19. The preparation method according to claim 18, characterized in that, In step S1, the conditions for calcination I include: a heating rate of 4℃ / min to 6℃ / min, a calcination temperature of 400℃ to 600℃, and a calcination time of 3h to 5h.

20. The preparation method according to any one of claims 18-19, characterized in that, In step S2, the concentration of the aqueous solution of H2PtCl6 is 0.05M to 0.25M.

21. The preparation method according to any one of claims 18-20, characterized in that, In step S2, the ratio of the amount of g-C3N4 powder to the aqueous solution of H2PtCl6 and water is 0.5g: 100μL~200μL: 100mL~150mL.

22. The preparation method according to any one of claims 18-21, characterized in that, In step S2, the conditions for calcination II include: a heating rate of 4℃ / min to 6℃ / min, a calcination temperature of 200℃ to 400℃, and a calcination time of 1h to 3h.

23. The preparation method according to any one of claims 18-22, characterized in that, In step S2, the stirring time is 12h to 36h.

24. The preparation method according to any one of claims 18-23, characterized in that, In step S3, the concentration of the 1,6-hexanediamine aqueous solution is 0.05M to 0.25M.

25. The preparation method according to any one of claims 18-24, characterized in that, In step S3, the volume ratio of the aqueous dispersion of Pt1 / g-C3N4 to the aqueous solution of 1,6-hexanediamine is 25 mL: 50 μL to 100 μL.

26. The preparation method according to any one of claims 18-25, characterized in that, In step S3, the concentration of the HAuCl4 aqueous solution is 0.05M to 0.25M.

27. The preparation method according to any one of claims 18-26, characterized in that, In step S3, the volume ratio of the aqueous dispersion of Pt1 / g-C3N4 to the aqueous solution of HAuCl4 is 25 mL: 10 μL to 50 μL.

28. The preparation method according to any one of claims 18-27, characterized in that, In steps S2 and S3, the conditions for removing the solvent independently include heating at 60°C to 80°C until the solvent is completely evaporated.

29. The preparation method according to any one of claims 18-28, characterized in that, In steps S2 and S3, the drying conditions independently include: a drying temperature of 60℃ to 80℃ and a drying time of 6h to 18h.

30. The preparation method according to any one of claims 18-29, characterized in that, In step S3, the conditions for calcination III include: under an inactive atmosphere, a heating rate of 4℃ / min to 6℃ / min, a calcination temperature of 100℃ to 300℃, and a calcination time of 0.5h to 2h.

31. The preparation method according to any one of claims 18-30, characterized in that, In step S3, the stirring time for step II is 0.5h to 2h.

32. The preparation method according to any one of claims 18-32, characterized in that, In step S3, the stirring time for step II is 12h to 36h.

33. The supported Pt-Au heteronuclear diatomic catalyst prepared by the preparation method according to any one of claims 18-33, characterized in that, Platinum and gold atoms are arranged in pairs on a supported Pt-Au heteronuclear diatomic catalyst.

34. The application of the supported Pt-Au heteronuclear diatomic catalyst prepared by the preparation method according to any one of claims 18-33 or the supported Pt-Au heteronuclear diatomic catalyst according to claim 32 in the reduction of nitrate to ammonia.

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