A high-efficiency silver-manganese composite material and its preparation method

Abstract

This invention belongs to the field of silver-manganese composite material preparation, and provides an efficient method for preparing silver-manganese composite materials. The method uses crypto-potassium manganese dioxide or α-MnO2 tunnel nanorods as a framework. After controllable reduction to construct defects, silver species are impregnated and anchored using a silver-ammonia complex solution. Following drying and air fixation treatment, silver-loaded defective manganese oxide octahedral molecular sieves are obtained. In the resulting material, silver can be stably distributed at surface defect sites and / or 2×2 tunnel opening sites, forming Ag-O-Mn interfaces. This method balances interfacial reactivity, pore structure stability, and low migration and long-term stability of silver species, solving the problem of simultaneously achieving high activity and structural stability, and has good application value.

Description

Technical Field

[0001] This invention relates to the field of materials chemistry, specifically to a high-efficiency silver-manganese composite material and its preparation method. Background Technology

[0002] Silver-manganese composite systems hold significant value in applications involving interfacial reactivity, open mass transfer structures, and long-term stability. Among these, silver-supported defective manganese oxide octahedral molecular sieves have attracted attention due to their combination of tunnel nanorod framework, tunable defect sites, and the ability to construct Ag-O-Mn interfaces. For systems with crypto-KJ-type manganese dioxide or α-MnO2 as the main crystalline phase, the average diameter, aspect ratio, BET specific surface area, mesoporous main peak pore size, and Mn3+ / Mn4+ molar ratio of the tunnel nanorods collectively influence the exposure of surface defect sites and 2×2 tunnel openings, further affecting silver utilization efficiency, silver species distribution, and pore structure retention. Therefore, such high-efficiency silver-manganese composite materials not only require stable distribution of silver species in the form of Agδ+ single atoms, Ag0 single atoms, sub-nanoclusters, or ultrafine nanodots, but also require the balance of main crystalline phase stability, pore openness, and low-migration long-term stability during drying, fixation, and subsequent use, thereby avoiding the mutual constraint between high activity and structural stability.

[0003] To achieve the aforementioned goals, existing technologies have proposed different silver-manganese oxide routes. For example, Chinese patent CN101372341A discloses an Ag-hollandite nanomaterial, its preparation method, and its application. This scheme prepares Ag-hollandite one-dimensional nanowires by reacting silver permanganate with divalent manganese salts. From its disclosure, its technical focus is on the formation of the Ag-hollandite phase and the control of nanowire morphology; however, it does not address the directional anchoring of silver species at defect sites and 2×2 tunnel opening sites on the surface of defective manganese oxide octahedral molecular sieves with low silver content, nor the regulation of the Ag-O-Mn interface. Another example is Chinese patent CN112473665A, which discloses a supported silver-manganese catalyst, its preparation method, and its application, using porous cubic α-Mn₂O₃ supported on Ag elemental as its core. Based on its publicly available information, the scheme focuses more on the loaded particle route and post-processing fixation, and there is still room for further optimization in terms of the synergistic consideration of the degree of defects, pore structure and low migration stability of silver species in the crypto-potassium manganese dioxide or α-MnO2 tunnel nanorod system. Summary of the Invention

[0004] The purpose of this invention is to provide a highly efficient silver-manganese composite material and its preparation method. This addresses the problem that existing technologies often improve the interfacial reactivity of silver-manganese composite materials by increasing the defect site density of the carrier, increasing the reversible ratio of Mn3+ / Mn4+, and promoting the high dispersion and exposure of silver species in the form of single atoms, sub-nanoclusters, or ultrafine nanodots. However, these measures easily lead to decreased stability of the tunnel framework of the defective manganese oxide octahedral molecular sieve, damage to the pore structure, and migration and aggregation of silver species during drying, fixation, and use. Furthermore, to maintain the stability of the main crystalline phase and pore structure of the tunnel nanorods and inhibit silver species loss and sintering, existing technologies often reduce the degree of defects, enhance thermal fixation, or strengthen interfacial binding. However, this easily leads to a decrease in specific surface area, obstruction of mesoporous channels, uneven impregnation distribution, and a reduction in active interfaces. Therefore, it is difficult to simultaneously achieve the two inherent contradictions of structural stability and high efficiency, as well as open mass transfer structure and low migration and long-term stability of silver species.

[0005] This invention uses tunnel nanorods of defective manganese oxide octahedral molecular sieves as the structural framework. By first constructing controllable defects, then introducing silver ammonia complex liquid to anchor silver species, and then implementing air fixation treatment, the silver content, defect degree, Ag-O-Mn interface and main crystal phase are kept in coordination. This enhances the interfacial reactivity while inhibiting the migration of silver species and maintaining the stability of the pore structure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A high-efficiency silver-manganese composite material, comprising silver-supported defective manganese oxide octahedral molecular sieves, wherein the defective manganese oxide octahedral molecular sieves are tunnel nanorods selected from either crypto-potassium manganese dioxide or α-MnO2; the silver content is 0.20-2.50 wt% of the total amount of the high-efficiency silver-manganese composite material, with the balance being the defective manganese oxide octahedral molecular sieves; Furthermore, the tunnel nanorods have an average diameter of 20-60 nm and an aspect ratio of 10-50; the silver is distributed in at least one of the following forms: Agδ+ single atoms, Ag0 single atoms, sub-nanoclusters, or ultrafine nanodots with an apparent particle size of 0.10-2.00 nm at the surface defect sites and / or 2×2 tunnel opening sites of the tunnel nanorods, forming an Ag-O-Mn interface; the efficient silver-manganese composite material has a BET specific surface area of ​​120-250 m². 2 / g, the main peak pore size of the mesoporous structure is 2-12nm.

[0007] Furthermore, the tunnel nanorods are prepared through the following steps: A1. Dissolve potassium permanganate and manganese sulfate monohydrate in deionized water, such that the molar ratio of potassium permanganate to manganese sulfate monohydrate is 1.8:1-2.4:1, and the total concentration of potassium permanganate and manganese sulfate monohydrate in the solution is 0.05-0.20 mol / L, based on the sum of the amounts of potassium permanganate and manganese sulfate monohydrate. A2. Place the solution obtained in step A1 into a polytetrafluoroethylene-lined reactor and react it at a temperature of 130-150℃ for 8-16 hours. A3. Wash the obtained solid with deionized water until the pH of the filtrate is 6.0-7.5 and the conductivity is not higher than 100 μS / cm; A4 was dried at 80-110℃ for 6-12 hours to obtain tunnel nanorod intermediates selected from either crypto-potassium manganese dioxide or α-MnO2, with an average diameter of 20-60 nm and an aspect ratio of 10-50.

[0008] Furthermore, the defect tunnel nanorods are prepared through the following steps: B1, the tunnel nanorod intermediate was placed in a tube furnace; B2, in a mixed atmosphere of hydrogen and nitrogen, wherein the volume fraction of hydrogen is 2-10 vol%, and the remainder is nitrogen, the mixture is treated at a temperature of 200-240℃ for 0.5-2 h, and the total flow rate of the mixed gas is 50-500 mL / min. B3, cool to room temperature at a rate of 1-5℃ / min to obtain a defective tunnel nanorod intermediate with the same main crystalline phase as the tunnel nanorod intermediate obtained in step A4; Furthermore, the silver is anchored to the defect tunnel nanorod via the following steps: C1. Dissolve silver nitrate in deionized water, then add ammonia water to adjust the pH value to 9.5-11.5, and prepare a silver ammonia complex solution with a silver concentration of 0.005-0.050 mol / L. C2, add the defective tunnel nanorod intermediate to the silver ammonia complex solution obtained in step C1, wherein each 1g of defective tunnel nanorod intermediate corresponds to 10-50mL of silver ammonia complex solution, and the silver concentration and amount of the silver ammonia complex solution are selected together so that the theoretical silver loading of the obtained silver-anchored intermediate is 0.20-2.50wt%, and impregnate for 0.5-2h at a temperature of 20-40℃; C3, the obtained system is evaporated and concentrated or dehydrated under reduced pressure to ensure that the residual free liquid of the intermediate is not higher than 10 wt%, thus obtaining the silver-anchored intermediate.

[0009] Furthermore, in the defective manganese oxide octahedral molecular sieve, the Mn3+ / Mn4+ molar ratio is 0.20-0.80, and the main crystalline phase of the defective manganese oxide octahedral molecular sieve is crypto-potassium manganese dioxide.

[0010] As a concept of this invention, the design of a silver-loaded defective manganese oxide octahedral molecular sieve is primarily used to achieve a synergistic balance between tunnel framework and pore structure stability and interfacial reactivity. In existing technologies, to enhance interfacial reactivity, defect site density is typically increased, the reversible Mn3+ / Mn4+ ratio is amplified, and silver species are highly dispersed and exposed. However, these measures easily induce tunnel framework loosening, pore structure damage, and silver species migration and aggregation. Conversely, to suppress silver species loss and sintering, defect levels are typically reduced, thermal fixation or interfacial confinement is strengthened, but this easily leads to a reduction in active interfaces, obstruction of mesoporous channels, and uneven impregnation distribution. This invention, by directionally distributing low-content silver at surface defect sites and / or 2×2 tunnel entrance sites and constructing an Ag-O-Mn interface, ensures that defect control, spatial distribution, and the main crystalline phase are mutually constrained and compensated, thereby unifying the high efficiency and structural stability that are difficult to achieve simultaneously with a single defect control or single loading route.

[0011] This invention also discloses a method for preparing a highly efficient silver-manganese composite material, comprising the following steps: S1 provides a silver anchoring intermediate.

[0012] S2, the silver-anchored intermediate obtained in step S1 is dried at a temperature of 80-110℃ for 6-12 hours.

[0013] S3, then heat it in air at a rate of 1-3℃ / min and keep it at 280-320℃ for 1-3 hours for fixation treatment.

[0014] S4, after cooling, is crushed and sieved to 40-100 mesh to obtain a high-efficiency silver-manganese composite material.

[0015] Furthermore, the silver anchoring intermediate provided in step S1 is obtained by the following method: before adding the defective tunnel nanorod intermediate to the silver ammonia complex solution for atmospheric pressure impregnation, the defective tunnel nanorod intermediate is first subjected to vacuum pre-impregnation treatment. The absolute pressure of the vacuum pre-impregnation treatment is 0.02-0.08 MPa, and the time is 5-20 min.

[0016] Furthermore, the main crystalline phase of the defective manganese oxide octahedral molecular sieve in the high-efficiency silver-manganese composite material obtained in step S4 is crypto-potassium manganese dioxide.

[0017] Furthermore, the mass fraction of ammonia water used in preparing the silver ammonia complex solution is 25-28 wt%, and the molar ratio of NH3 to Ag+ is 4:1-10:1.

[0018] Furthermore, the Agδ+ is a silver species that carries a partial positive charge after bonding with oxygen atoms on the surface of the defective manganese oxide octahedral molecular sieve, and is characterized by XPS.

[0019] Furthermore, the single atoms, sub-nano clusters, ultrafine nanodots, and their distribution sites of the silver were characterized by a combination of HAADF-STEM, XAFS, and XPS.

[0020] Furthermore, the Ag-O-Mn interface was confirmed by XAFS fitting results and XPS fine spectroscopy.

[0021] Furthermore, the BET specific surface area was determined using the nitrogen adsorption-desorption method, and the pore size of the mesoporous main peak was calculated using the BJH desorption branch method.

[0022] Furthermore, in the defective manganese oxide octahedral molecular sieve, the Mn3+ / Mn4+ molar ratio is calculated based on the XPS peak area.

[0023] Furthermore, the residual free liquid is no more than 10 wt% based on the total mass of the intermediates obtained after evaporation and concentration or decompression.

[0024] Furthermore, the vacuum pre-impregnation process involves first placing the defective tunnel nanorod intermediate under an absolute pressure of 0.02-0.08 MPa for 5-20 minutes, and then contacting it with a silver ammonia complex solution after restoring normal pressure.

[0025] Furthermore, the total flow rate of the mixed gas in step B2, after being converted according to the feed amount, is 50-500 mL / min per 1g of tunnel nanorod intermediate.

[0026] Furthermore, the main crystalline phase of the defective manganese oxide octahedral molecular sieve was determined by XRD characterization to be a manganese oxide phase with a 2×2 tunnel structure, belonging to the crypto-potassium manganese dioxide type.

[0027] Furthermore, when preparing the silver ammonia complex solution, ammonia water is added dropwise to the silver nitrate solution under stirring conditions.

[0028] Furthermore, after the solution obtained in step A1 is added to the polytetrafluoroethylene-lined reactor, the solution occupies 60-80% of the effective volume of the reactor.

[0029] Furthermore, the solid obtained in step A2 is separated by filtration or centrifugation and repeatedly washed with deionized water until the pH of the washing filtrate or supernatant is 6.0-7.5 and the conductivity is not higher than 100 μS / cm.

[0030] Furthermore, the dehydration under reduced pressure in step C3 is carried out at 40-80°C and an absolute pressure of 0.02-0.09 MPa, or the evaporation and concentration are carried out at 60-90°C and at atmospheric pressure.

[0031] Furthermore, the theoretical silver loading in step C2 is calculated as the mass percentage of the silver feed amount relative to the sum of the mass of the defect tunnel nanorod intermediate and the total mass of the silver feed.

[0032] Furthermore, the silver content in the high-efficiency silver-manganese composite material obtained in step S4, expressed as Ag and on a dry basis, can be determined by ICP-OES or XRF.

[0033] As another aspect of this invention, a stepwise defect construction-silver ammonia complex impregnation and anchoring-drying consolidation method is employed, primarily for achieving, fixing, or amplifying the aforementioned synergistic effect. In existing technologies, while increasing the defect level solely through precursor hydrothermal and reduction treatments is beneficial for silver species anchoring and interface activation, subsequent heat treatments can easily lead to silver species migration, pore structure damage, or main crystal phase fluctuations. Conversely, relying solely on high-temperature consolidation and strong interface binding to stabilize silver species can easily result in uneven impregnation distribution, active site shielding, and weakening of open mass transfer structures. This invention first forms controllable defect tunnel nanorods, then utilizes a silver ammonia complex and residual free liquid to achieve gentle introduction, followed by consolidation treatment under a limited heating rate and air atmosphere. This couples the interface construction, silver dispersion state, and framework stabilization process, thereby enabling the aforementioned synergistic relationship to form and be maintained long-term.

[0034] Cryptomanganese dioxide or α-MnO2 tunnel nanorods primarily provide a continuous tunnel framework, mesoporous channels, and a structural basis capable of supporting defect regulation, which is beneficial for maintaining the stability of the main crystalline phase and pore structure. However, relying solely on this framework or only increasing the degree of defects, while increasing surface defect sites and the Mn3+ / Mn4+ ratio, can easily lead to framework loosening and limit the improvement of interfacial reactivity. Silver mainly contributes to interfacial reactivity, but if it exists alone or is locally enriched, it is prone to migration, aggregation, and channel obstruction. This invention, by directionally distributing low-content silver in the form of Agδ+ single atoms, Ag0 single atoms, sub-nanoclusters, and / or ultrafine nanodots at surface defect sites and 2×2 tunnel opening sites, and by utilizing the Ag-O-Mn interface, silver content matching, and fixation sequence control, enables the tunnel framework to disperse and bind silver, while silver effectively utilizes the defect sites, ultimately achieving a balance between interfacial reactivity, pore openness, and low migration and long-term stability of silver species.

[0035] Beneficial technical effects 1. This invention uses crypto-potassium manganese dioxide or α-MnO2 tunnel nanorods as the framework of defective manganese oxide octahedral molecular sieves. By limiting the average diameter, aspect ratio, BET specific surface area and mesoporous main peak pore size, the main crystalline phase is maintained, the pores are open and the silver distribution space is unified, avoiding the damage to the tunnel framework and pore structure caused by simply pursuing defectification.

[0036] 2. This invention uses a mixed atmosphere of hydrogen and nitrogen to mildly construct defects in the tunnel nanorod intermediate, controlling the Mn3+ / Mn4+ molar ratio within a limited range. This provides surface defect sites and 2×2 tunnel opening sites without excessively damaging the main crystal phase, which is beneficial for the subsequent stable anchoring of silver species and the formation of Ag-O-Mn interfaces.

[0037] 3. This invention uses a silver ammonia complex solution to impregnate and control residual free liquid, so that silver is distributed at key sites in the form of Agδ+ single atoms, Ag0 single atoms, sub-nano clusters and / or ultrafine nano dots, reducing the risk of local enrichment and heat treatment migration and aggregation, thereby improving the utilization efficiency of silver content and maintaining the continuous exposure of the active interface.

[0038] 4. This invention, through the sequential design of first constructing defects, then anchoring silver, and finally fixing it in air, coordinates the control of impregnation distribution, drying and dehydration, and heat treatment processes, so that interfacial reactivity, pore structure stability, and low migration and long-term stability of silver species can be achieved simultaneously, making it suitable for the engineering development of efficient silver-manganese composite material preparation methods. Attached Figure Description

[0039] Figure 1 The images show the high-resolution XPS spectra of Ag 3d samples from Examples 1, 8, and 10.

[0040] Figure 2 The image shows the peak area ratio of Ag species in samples from Example 1, Comparative Example 8, and Comparative Example 10.

[0041] Figure 3 The images show the high-resolution XPS spectra of Mn 2p samples from Examples 1, 8, and 10.

[0042] Figure 4 Sample Mn from Example 1, Comparative Example 8, and Comparative Example 10 3+ / Mn 4+ Ratio point plot.

[0043] Figure 5 The O 1s XPS high-resolution spectra of samples from Example 1, Comparative Example 8, and Comparative Example 10 are shown.

[0044] Figure 6 The image shows the peak area ratio of samples O 1s for Examples 1, Comparative Examples 8 and 10.

[0045] Figure 7 The EXAFS k-space oscillation curves of the samples from Example 1 and Comparative Example 8 are shown.

[0046] Figure 8 The above are the EXAFS R-space Fourier transform amplitude diagrams of the samples from Example 1 and Comparative Example 8.

[0047] Figure 9 The N2 adsorption-desorption isotherms are for samples from Example 1, Comparative Example 2, and Comparative Example 7.

[0048] Figure 10 The image shows the BJH pore size distribution curves of samples from Example 1, Comparative Example 2, and Comparative Example 7.

[0049] Figure 11 The XRD diffraction patterns of the samples from Example 1, Comparative Example 3, and Comparative Example 7 are shown.

[0050] Figure 12 The images show magnified views of the XRD characteristic peaks of the samples from Example 1, Comparative Example 3, and Comparative Example 7.

[0051] Figure 13 The formaldehyde light-off conversion curves are for samples from Example 1, Comparative Example 9, and Comparative Example 10.

[0052] Figure 14 The graph shows the activity retention rate versus time curves of the samples from Example 1, Comparative Example 3, and Comparative Example 10 after thermal aging.

[0053] Figure 15 The Ag loss rate-time curves for samples from Example 1, Comparative Example 3, and Comparative Example 10 are shown.

[0054] Figure 16 The plot shows the correlation trajectory between the activity retention rate and the Ag loss rate of samples from Example 1, Comparative Example 3, and Comparative Example 10.

[0055] Figure 17 Macroscopic optical photograph of the silver-manganese composite material sample prepared in Example 1.

[0056] Figure 18 The image shows a scanning electron microscope (SEM) image of the silver-manganese composite material sample prepared in Example 1.

[0057] Figure 19 The image shown is a transmission electron microscope (TEM) image of the silver-manganese composite material sample prepared in Example 1. Wherein, Figure 19 (a) is a bright-field TEM image of the sample. Figure 19 (b) is a high-resolution transmission electron microscope image of the sample. Figure 19 (c) is the selected area electron diffraction pattern of the sample. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0059] Example 1

[0060] This embodiment provides a method for preparing a high-efficiency silver-manganese composite material, the specific steps of which are as follows: Steps A1-A4: Preparation of tunnel nanorod intermediates; 7.90 g of potassium permanganate and 8.45 g of manganese sulfate monohydrate were weighed and dissolved in 500 mL of deionized water, making the molar ratio of potassium permanganate to manganese sulfate monohydrate 1.8:1. The total concentration of both in the solution in this example was 0.05 mol / L. The resulting solution was added to a 750 mL polytetrafluoroethylene-lined reactor, filling 70% of the effective volume of the reactor. After sealing, the reactor was placed in an oven and reacted at 140 °C for 12 h. After the reaction, the solid product was separated by filtration and repeatedly washed with deionized water until the pH of the washing filtrate was 6.5 and the conductivity was 80 μS / cm. The washed solid was dried at 95 °C for 8 h to obtain crypto-potassium manganese dioxide tunnel nanorod intermediates with an average diameter of 35 nm and an aspect ratio of 20.

[0061] Steps B1-B3: Preparation of defect tunnel nanorod intermediates; 5.0 g of the tunnel nanorod intermediate obtained in step A4 was placed in a tube furnace and treated in a mixed atmosphere composed of hydrogen and nitrogen. In this embodiment, the hydrogen gas fraction was 2 vol%, with the remainder being nitrogen. The treatment was carried out at 220°C for 1 h, with a total gas flow rate of 200 mL / min (equivalent to 40 mL / min per 1 g of tunnel nanorod intermediate based on the feed amount). After treatment, the intermediate was cooled to room temperature at a rate of 3°C / min to obtain a defective tunnel nanorod intermediate with cryptomonosulfuron-methyl manganese dioxide as the main crystalline phase.

[0062] Steps C1-C3: Silver anchoring; 0.85 g of silver nitrate was dissolved in 100 mL of deionized water. Ammonia solution with a mass fraction of 26 wt% was added dropwise under stirring to adjust the pH to 10.5, preparing a silver ammonia complex solution with a silver concentration of 0.005 mol / L. In this embodiment, the molar ratio of NH3 to Ag+ was 4:1. 5.0 g of the defect tunnel nanorod intermediate obtained in step B3 was added to 150 mL of the above silver ammonia complex solution, with a solid-liquid ratio of 30 mL / g. In this embodiment, the silver concentration and amount of the silver ammonia complex solution were selected to achieve a theoretical silver loading of 0.20 wt% for the obtained silver-anchored intermediate. After impregnation at 30°C for 1 h, the resulting system was evaporated and concentrated at 90°C to obtain a residual free liquid of 7 wt%, yielding the silver-anchored intermediate of this embodiment.

[0063] Steps S1-S4: Fixation and sieving; The silver-anchored intermediate obtained in step C3 was dried at 95°C for 8 hours. Then, it was heated in air at a rate of 2°C / min and held at 300°C for 2 hours for fixation treatment. After cooling, it was pulverized and sieved to 60 mesh to obtain the high-efficiency silver-manganese composite material of this embodiment.

[0064] Product characterization The high-efficiency silver-manganese composite material obtained in this embodiment consists of silver-supported defective manganese oxide octahedral molecular sieves. The defective manganese oxide octahedral molecular sieves in this embodiment are crypto-potassium manganese dioxide tunnel nanorods. The total silver content of the high-efficiency silver-manganese composite material in this embodiment is 0.20 wt%, with the balance being the defective manganese oxide octahedral molecular sieves. The tunnel nanorods in this embodiment have an average diameter of 35 nm and an aspect ratio of 20. The silver in this embodiment is distributed in the form of Ag0 single atoms and sub-nanoclusters at the surface defect sites and 2×2 tunnel opening sites of the tunnel nanorods, forming Ag-O-Mn interfaces. The apparent particle size of the silver is 0.50 nm. The BET specific surface area of ​​the high-efficiency silver-manganese composite material in this embodiment is 180 m². 2 / g, the mesoporous main peak pore size is 6nm. In the defective manganese oxide octahedral molecular sieve of this embodiment, the Mn3+ / Mn4+ molar ratio is 0.45, and the main crystalline phase is crypto-potassium manganese dioxide.

[0065] Features of Example 1 This embodiment employs a feedstock ratio design biased towards the lower limit, selecting manganese oxide precursor concentrations and potassium permanganate / manganese sulfate ratios close to the lower end of the range. Combined with a defect control process using low hydrogen fraction, this achieves precise control of extremely low silver loading. The silver-ammonia complex solution in this embodiment uses a low-concentration formulation, achieving precise anchoring of silver species by reducing the NH3 / Ag+ ratio to the low end of the range. The final product has a low silver content, and the material offers significant cost advantages. It is suitable for catalytic applications where low silver loading requirements are necessary but high cost-effectiveness is sought, such as indoor air purification and degradation of low-concentration organic pollutants.

[0066] Example 2

[0067] This embodiment provides a method for preparing a high-efficiency silver-manganese composite material, the specific steps of which are as follows: Steps A1-A4: Preparation of tunnel nanorod intermediates; 37.92 g of potassium permanganate and 28.14 g of manganese sulfate monohydrate were weighed and dissolved in 400 mL of deionized water, making the molar ratio of potassium permanganate to manganese sulfate monohydrate 2.4:1. The total concentration of both in the solution in this example was 0.20 mol / L. The resulting solution was added to a 600 mL polytetrafluoroethylene-lined reactor, filling 70% of the effective volume of the reactor. After sealing, the reactor was placed in an oven and reacted at 140 °C for 12 h. After the reaction, the solid product was separated by centrifugation and repeatedly washed with deionized water until the pH of the supernatant was 7.0 and the conductivity was 75 μS / cm. The washed solid was dried at 95 °C for 9 h to obtain crypto-potassium manganese dioxide tunnel nanorod intermediates with an average diameter of 40 nm and an aspect ratio of 35.

[0068] Steps B1-B3: Preparation of defect tunnel nanorod intermediates; 10.0 g of the tunnel nanorod intermediate obtained in step A4 was placed in a tube furnace and treated in a mixed atmosphere composed of hydrogen and nitrogen. In this embodiment, the hydrogen gas fraction was 10 vol%, with the remainder being nitrogen. The treatment was carried out at 220°C for 1.5 h, with a total gas flow rate of 300 mL / min (equivalent to 30 mL / min per 1 g of tunnel nanorod intermediate based on the feed amount). After treatment, the intermediate was cooled to room temperature at a rate of 3°C / min to obtain a defective tunnel nanorod intermediate with cryptomonosulfuron-methyl manganese dioxide as the main crystalline phase.

[0069] Steps C1-C3: Silver anchoring; 8.50 g of silver nitrate was dissolved in 100 mL of deionized water. Ammonia solution with a mass fraction of 27 wt% was added dropwise under stirring to adjust the pH to 10.5, preparing a silver ammonia complex solution with a silver concentration of 0.050 mol / L. In this embodiment, the molar ratio of NH3 to Ag+ was 10:1. 10.0 g of the defect tunnel nanorod intermediate obtained in step B3 was added to 200 mL of the above silver ammonia complex solution, with a solid-liquid ratio of 20 mL / g. The silver concentration and amount of the silver ammonia complex solution in this embodiment were selected to achieve a theoretical silver loading of 2.50 wt% for the obtained silver-anchored intermediate. After impregnation at 30°C for 1.5 h, the resulting system was subjected to decompression at 40°C and an absolute pressure of 0.02 MPa, resulting in a residual free liquid of 6 wt% for the intermediate, thus obtaining the silver-anchored intermediate of this embodiment.

[0070] Steps S1-S4: Fixation and sieving; The silver-anchored intermediate obtained in step C3 was dried at 95°C for 9 hours. Then, it was heated in air at a rate of 2°C / min and held at 300°C for 2 hours for fixation treatment. After cooling, it was pulverized and sieved to 70 mesh to obtain the high-efficiency silver-manganese composite material of this embodiment.

[0071] Product characterization The high-efficiency silver-manganese composite material obtained in this embodiment consists of silver-loaded defective manganese oxide octahedral molecular sieves. The defective manganese oxide octahedral molecular sieves in this embodiment are crypto-potassium manganese dioxide tunnel nanorods. The total silver content of the high-efficiency silver-manganese composite material in this embodiment is 2.50 wt%, with the balance being the defective manganese oxide octahedral molecular sieves. The tunnel nanorods in this embodiment have an average diameter of 40 nm and an aspect ratio of 35. The silver in this embodiment is distributed in the form of Agδ+ single atoms, Ag0 single atoms, sub-nanoclusters, and ultrafine nanodots with an apparent particle size of 1.50 nm at the surface defect sites and 2×2 tunnel opening sites of the tunnel nanorods, forming an Ag-O-Mn interface. The BET specific surface area of ​​the high-efficiency silver-manganese composite material in this embodiment is 185 m². 2 / g, the mesoporous main peak pore size is 7nm. In the defective manganese oxide octahedral molecular sieve of this embodiment, the Mn3+ / Mn4+ molar ratio is 0.60, and the main crystalline phase is crypto-potassium manganese dioxide.

[0072] Features of Example 2 This embodiment employs a raw material ratio strategy close to that described above, selecting a high-concentration manganese oxide precursor solution and a relatively high potassium permanganate / manganese sulfate molar ratio, combined with a deep defect control process with a high hydrogen fraction, to achieve precise control of high silver loading. The silver-ammonia complex solution in this embodiment uses a high-concentration formulation, enhancing the stability of the silver-ammonia complex by increasing the NH3 / Ag+ ratio to a high value, ensuring the uniform anchoring of a large number of silver species. The final product has a high silver content, exhibiting excellent catalytic activity, suitable for applications with extremely high catalytic performance requirements, such as deep treatment of industrial waste gas, catalytic oxidation of high-concentration volatile organic compounds, and rapid degradation of formaldehyde, among other high-performance catalytic fields.

[0073] Example 3

[0074] This embodiment provides a method for preparing a high-efficiency silver-manganese composite material, the specific steps of which are as follows: Steps A1-A4: Preparation of tunnel nanorod intermediates; 15.80 g of potassium permanganate and 11.27 g of manganese sulfate monohydrate were weighed and dissolved in 300 mL of deionized water, making the molar ratio of potassium permanganate to manganese sulfate monohydrate 2.0:1. The total concentration of both in the solution in this example was 0.10 mol / L. The resulting solution was added to a 500 mL polytetrafluoroethylene-lined reactor, filling 60% of the effective volume of the reactor. After sealing, the reactor was placed in an oven and reacted at 130 °C for 8 h. After the reaction, the solid product was separated by filtration and repeatedly washed with deionized water until the pH of the washing filtrate was 6.0 and the conductivity was 100 μS / cm. The washed solid was dried at 80 °C for 6 h to obtain crypto-potassium manganese dioxide tunnel nanorod intermediates with an average diameter of 20 nm and an aspect ratio of 10.

[0075] Steps B1-B3: Preparation of defect tunnel nanorod intermediates; 8.0 g of the tunnel nanorod intermediate obtained in step A4 was placed in a tube furnace. The intermediate was first subjected to vacuum pre-impregnation at an absolute pressure of 0.02 MPa for 5 min, and then treated in a mixed atmosphere of hydrogen and nitrogen after restoring atmospheric pressure. In this embodiment, the hydrogen component was 5 vol%, with the remainder being nitrogen. The treatment was carried out at 200°C for 0.5 h, with a total gas flow rate of 50 mL / min (equivalent to 6.25 mL / min per 1 g of tunnel nanorod intermediate based on the feed amount). After treatment, the intermediate was cooled to room temperature at a rate of 1°C / min to obtain a defective tunnel nanorod intermediate with cryptomonosulfuron-methyl manganese dioxide as the main crystalline phase.

[0076] Steps C1-C3: Silver anchoring; 3.40 g of silver nitrate was dissolved in 100 mL of deionized water. Ammonia solution with a mass fraction of 25 wt% was added dropwise under stirring to adjust the pH to 9.5, preparing a silver ammonia complex solution with a silver concentration of 0.020 mol / L. In this embodiment, the molar ratio of NH3 to Ag+ was 6:1. 8.0 g of the defect tunnel nanorod intermediate obtained in step B3 was first subjected to vacuum pre-impregnation at an absolute pressure of 0.02 MPa for 5 min. After restoring to normal pressure, it was added to 80 mL of the above silver ammonia complex solution, with a solid-liquid ratio of 10 mL / g. In this embodiment, the silver concentration and amount of the silver ammonia complex solution were selected to achieve a theoretical silver loading of 1.0 wt% in the obtained silver-anchored intermediate. After impregnation at 20°C for 0.5 h, the resulting system was evaporated and concentrated at 60°C to obtain a residual free liquid of 10 wt%, yielding the silver-anchored intermediate of this embodiment.

[0077] Steps S1-S4: Fixation and sieving; The silver-anchored intermediate obtained in step C3 was dried at 80°C for 6 hours. Then, it was heated in air at a rate of 1°C / min and held at 280°C for 1 hour for fixation treatment. After cooling, it was pulverized and sieved to 40 mesh to obtain the high-efficiency silver-manganese composite material of this embodiment.

[0078] Product characterization The high-efficiency silver-manganese composite material obtained in this embodiment consists of silver-supported defective manganese oxide octahedral molecular sieves. The defective manganese oxide octahedral molecular sieve in this embodiment is a crypto-potassium manganese dioxide tunnel nanorod. The total silver content of the high-efficiency silver-manganese composite material in this embodiment is 1.0 wt%, with the remainder being the defective manganese oxide octahedral molecular sieve. The tunnel nanorods in this embodiment have an average diameter of 20 nm and an aspect ratio of 10. The silver in this embodiment is distributed as Ag0 single atoms and ultrafine nanodots with an apparent particle size of 0.10 nm at the surface defect sites and 2×2 tunnel opening sites of the tunnel nanorods, forming an Ag-O-Mn interface. The high-efficiency silver-manganese composite material in this embodiment has a BET specific surface area of ​​120 m². 2 / g, the mesoporous main peak pore size is 2nm. In the defective manganese oxide octahedral molecular sieve of this embodiment, the Mn3+ / Mn4+ molar ratio is 0.20, and the main crystalline phase is crypto-potassium manganese dioxide.

[0079] Features of Example 3 This embodiment employs a relatively low hydrothermal reaction temperature and time, combined with a low-temperature, low-efficiency hydrogen treatment process, forming a mild defect control pathway. The impregnation process utilizes a relatively low pH, temperature, and time, along with a small solid-liquid ratio and vacuum pre-impregnation assistance, ensuring precise anchoring of silver species at shallow defect sites. The fixation treatment employs a low-temperature, low-rate heating scheme, yielding nanorod morphologies with small diameters and low aspect ratios. The material possesses a high specific surface area and small mesopore size, with silver species dispersed in the form of ultrafine nanodots, and the manganese oxide support maintaining a low Mn3+ / Mn4+ ratio. This embodiment is suitable for catalytic applications requiring high specific surface area and fine pore structure, such as low-temperature catalytic oxidation, fine chemical synthesis, and gas sensors.

[0080] Example 4

[0081] This embodiment provides a method for preparing a high-efficiency silver-manganese composite material, the specific steps of which are as follows: Steps A1-A4: Preparation of tunnel nanorod intermediates; 33.28 g of potassium permanganate and 22.54 g of manganese sulfate monohydrate were weighed and dissolved in 350 mL of deionized water, making the molar ratio of potassium permanganate to manganese sulfate monohydrate 2.1:1. The total concentration of both in the solution in this example was 0.12 mol / L. The resulting solution was added to a 450 mL polytetrafluoroethylene-lined reactor, filling 80% of the effective volume of the reactor. After sealing, the reactor was placed in an oven and reacted at 150 °C for 16 h. After the reaction, the solid product was separated by centrifugation and repeatedly washed with deionized water until the pH of the supernatant was 7.5 and the conductivity was 50 μS / cm. The washed solid was dried at 110 °C for 12 h to obtain crypto-potassium manganese dioxide tunnel nanorod intermediates with an average diameter of 60 nm and an aspect ratio of 50.

[0082] Steps B1-B3: Preparation of defect tunnel nanorod intermediates; 12.0 g of the tunnel nanorod intermediate obtained in step A4 was placed in a tube furnace. The intermediate was first subjected to vacuum pre-impregnation at an absolute pressure of 0.08 MPa for 20 min, and then treated in a mixed atmosphere of hydrogen and nitrogen after restoring atmospheric pressure. In this embodiment, the hydrogen component was 6 vol%, with the remainder being nitrogen. The treatment was carried out at 240°C for 2 h, with a total gas flow rate of 500 mL / min (equivalent to 41.7 mL / min per 1 g of tunnel nanorod intermediate based on the feed amount). After treatment, the intermediate was cooled to room temperature at a rate of 5°C / min to obtain a defective tunnel nanorod intermediate with cryptomonosulfuron-methyl manganese dioxide as the main crystalline phase.

[0083] Steps C1-C3: Silver anchoring; 4.25 g of silver nitrate was dissolved in 100 mL of deionized water. Ammonia solution with a mass fraction of 28 wt% was added dropwise under stirring to adjust the pH to 11.5, preparing a silver ammonia complex solution with a silver concentration of 0.025 mol / L. In this embodiment, the molar ratio of NH3 to Ag+ was 7:1. 12.0 g of the defect tunnel nanorod intermediate obtained in step B3 was first subjected to vacuum pre-impregnation at an absolute pressure of 0.08 MPa for 20 min. After restoring to normal pressure, it was added to 600 mL of the above silver ammonia complex solution, with a solid-liquid ratio of 50 mL / g. The silver concentration and amount of the silver ammonia complex solution in this embodiment were selected to achieve a theoretical silver loading of 1.5 wt% in the obtained silver-anchored intermediate. After impregnation at 40°C for 2 h, the resulting system was subjected to decompression at 80°C and an absolute pressure of 0.09 MPa, resulting in a residual free liquid content of 5 wt%, yielding the silver-anchored intermediate of this embodiment.

[0084] Steps S1-S4: Fixation and sieving; The silver-anchored intermediate obtained in step C3 was dried at 110°C for 12 hours. Then, it was heated in air at a rate of 3°C / min and held at 320°C for 3 hours for fixation treatment. After cooling, it was pulverized and sieved to 100 mesh to obtain the high-efficiency silver-manganese composite material of this embodiment.

[0085] Product characterization The high-efficiency silver-manganese composite material obtained in this embodiment consists of silver-loaded defective manganese oxide octahedral molecular sieves. The defective manganese oxide octahedral molecular sieves in this embodiment are crypto-potassium manganese dioxide tunnel nanorods. The total silver content of the high-efficiency silver-manganese composite material in this embodiment is 1.5 wt%, with the remainder being the defective manganese oxide octahedral molecular sieves. The tunnel nanorods in this embodiment have an average diameter of 60 nm and an aspect ratio of 50. The silver in this embodiment is distributed in a multi-morphological coexistence form, consisting of Agδ+ single atoms, Ag0 single atoms, sub-nanoclusters, and ultrafine nanodots with an apparent particle size of 2.00 nm, at the surface defect sites and 2×2 tunnel opening sites of the tunnel nanorods, forming an Ag-O-Mn interface. The high-efficiency silver-manganese composite material in this embodiment has a BET specific surface area of ​​250 m². 2 / g, the mesoporous main peak pore size is 12nm. In the defective manganese oxide octahedral molecular sieve of this embodiment, the Mn3+ / Mn4+ molar ratio is 0.80, and the main crystalline phase is crypto-potassium manganese dioxide.

[0086] Features of Example 4 This embodiment employs a hydrothermal reaction temperature and time close to those at the top, combined with a high-temperature, long-duration hydrogen deep treatment process, forming an enhanced defect control pathway. The impregnation process utilizes a relatively high pH, ​​temperature, and time, combined with a large solid-liquid ratio and vacuum pre-impregnation to promote the full anchoring of silver species at deep defect sites. The solidification treatment employs a high-temperature, rapid heating scheme, resulting in large-diameter, high aspect ratio nanorod morphologies. The material possesses ultra-high specific surface area and large mesopore size, with silver species forming a multi-morphological coexistence structure, and the manganese oxide support maintaining a high Mn3+ / Mn4+ ratio. This embodiment is suitable for applications requiring high catalytic activity and large-pore structures, such as the degradation of macromolecular organic pollutants, high-temperature catalytic combustion, industrial flue gas denitrification, and diesel exhaust purification—all high-performance catalytic fields.

[0087] Comparative Example 1: Basically the same as Example 1, except that in step A1 the molar ratio of potassium permanganate to manganese sulfate monohydrate was adjusted to 1.6:1, while other conditions remained unchanged.

[0088] Comparative Example 2: It is basically the same as Example 1, except that in step A1, the total concentration of potassium permanganate and manganese sulfate monohydrate in the solution is adjusted to 0.25 mol / L, while other conditions remain unchanged.

[0089] Comparative Example 3: It is basically the same as Example 1, except that in step B2, the hydrogen gas integral is adjusted to 12 vol%, and the remainder is nitrogen gas, while other conditions remain unchanged.

[0090] Comparative Example 4: Basically the same as Example 1, except that the processing temperature in step B2 is adjusted to 180°C, while other conditions remain unchanged.

[0091] Comparative Example 5: It is basically the same as Example 1, except that the pH value of the silver ammonia complex solution is adjusted to 8.5 in step C1, while other conditions remain unchanged.

[0092] Comparative Example 6: Basically the same as Example 1, except that in step C2, the amount of silver ammonia complex solution corresponding to each 1g defect tunnel nanorod intermediate is adjusted to 5mL, and other conditions remain unchanged.

[0093] Comparative Example 7: It is basically the same as Example 1, except that the fixation temperature in step S3 is adjusted to 340°C, while other conditions remain unchanged.

[0094] Comparative Example 8: Essentially the same as Example 1, except that steps B1-B3 are omitted, and the tunnel nanorod intermediate obtained in step A4 is not subjected to defect control treatment but is directly used for silver anchoring in steps C1-C3. Other conditions remain unchanged. This comparative example is used to verify the synergistic effect of the defective tunnel nanorods and the silver anchoring interface construction.

[0095] Comparative Example 9: Essentially the same as Example 1, except that silver nitrate and ammonia were not added in steps C1-C3, and a silver-ammonia complex solution was not prepared. In steps S2-S4, the defect tunnel nanorods obtained in step B3 were directly dried at 95°C for 8 hours, heated to 300°C at a rate of 2°C / min, held at that temperature for 2 hours, and sieved through a 60-mesh sieve. Other conditions remained unchanged. This comparative example was used to verify the synergistic effect between the defect tunnel nanorods and silver species.

[0096] Comparative Example 10: Essentially the same as Example 1, except that step S3 (air fixation treatment) was omitted. The sample obtained in step S2 was dried at 95°C for 8 hours, then directly pulverized and sieved to 60 mesh. Other conditions remained unchanged. This comparative example was used to verify the synergistic effect of silver anchoring and air fixation interface construction.

[0097] Performance and characterization testing After fine grinding, the powder samples of the examples and comparative examples were scanned using CuKα rays in a range of 10°–80° with a step size of 0.02°. The position, shape, and relative intensity of characteristic peaks were compared to determine whether the main crystalline phase remained crypto-potassium manganese dioxide and to assess the impact of excessive defects or excessively high solution temperatures on the 2×2 tunnel framework. The instrument operating conditions were 40 kV, 40 mA, and a scan rate of 5° / min. After exporting the 2θ-intensity data, phase identification, peak area normalization, and half-maximum width comparison analysis were performed.

[0098] After degassing the degassed powders in the examples and comparative examples under vacuum conditions at 200℃ for 4 hours, nitrogen adsorption-desorption isotherms were collected at 77K. Specific surface area was calculated by fitting the P / P0 ratio within the range of 0.05-0.30 using the BET model, and pore size distribution was calculated according to the BJH desorption branch to determine the specific surface area, the main peak pore size of the mesopores, and the pore openness. After exporting the P / P0-adsorption capacity data, the BET value, the position of the BJH main peak, and pore volume parameters were calculated.

[0099] In the examples and comparative samples, the fine spectra of Mn2p, Ag3d, and O1s were measured using a monochromatic AlKα light source. After correction to C1s=284.8 eV, peak fitting was performed to determine the Mn3+ / Mn4+ molar ratio, Agδ+ / Ag0 ratio, and changes in interfacial oxygen species. The instrument power was set to 20 eV with a step size of 0.05 eV. After exporting the binding energy-intensity data, the area ratio of each peak and the Mn3+ / Mn4+ molar ratio were calculated.

[0100] In the examples and comparative cases, ultra-low silver loading samples were dispersed in ethanol and then dropped onto a copper grid. At least 30 fields of view were acquired under an accelerating voltage of 200-300 kV. The equivalent particle size of at least 200 bright spots and their proportion located at surface defect sites or 2×2 tunnel openings were statistically analyzed to identify the size and distribution sites of silver single atoms, sub-nanoclusters, and ultrafine nanodots. Histograms and box plots were then generated and analyzed after exporting the particle size statistics.

[0101] In the examples and comparative examples, samples before and after aging were weighed, digested using a nitric acid-hydrochloric acid system, and brought to a final volume. The Ag and Mn elemental contents were determined to ascertain the actual silver content and the loss rate after thermal aging. Three parallel samples were used, and the calibration curve R... 2 ≥0.999, after exporting the concentration data, convert the silver mass fraction and calculate the loss rate based on the difference before and after aging.

[0102] In the examples and comparative examples, 0.20 g of the catalyst was packed in a fixed bed and a mixed gas of 50 ppm formaldehyde, 20 vol% O2, balanced N2, and 50% relative humidity was introduced, and the mixture was incubated for 30,000 h⁻¹. -1The space velocity was increased from 25℃ to 180℃, with data points collected every 10℃. After reaching T90, the temperature was held constant for 20 hours, and stable values ​​were recorded every 2 hours to evaluate the low-temperature catalytic oxidation activity and continuous stability of formaldehyde. After exporting the temperature-conversion-time data, T50, T90, and 20-hour end retention rate were calculated.

[0103] In the examples and comparative examples, 0.20 g of the catalyst was packed in a fixed bed, and 100 ppm toluene, 20 vol% O2, and equilibrium N2 were introduced. 10 vol% water vapor was then introduced at the target temperature, and the stability values ​​before and after the wet state were recorded to evaluate the catalytic oxidation activity of toluene and its wet-state resistance to disturbances. The space velocity was 30,000 h⁻¹. -1 The temperature range is 120-260℃. After exporting the temperature-conversion-wet retention rate data, the toluene T90 and wet retention rate are calculated.

[0104] Figure 1 The high-resolution XPS spectra of Ag 3d from Example 1, Comparative Example 8, and Comparative Example 10 are shown. Figure 2 The figures show the peak area ratios of Ag species in Examples 1, 8, and 10. The two figures first illustrate the interfacial characteristics of Example 1 from the perspective of the chemical state of silver species. Compared to Comparative Examples 8 and 10, Example 1 exhibits a more pronounced Agδ+ related signal in the Ag 3d region, and the Agδ+ peak area accounts for 34.0%, significantly higher than the 12.0% in Comparative Example 8 and 9.0% in Comparative Example 10. This result indicates that under lower silver loading conditions, the silver in Example 1 does not primarily exist in a metallic aggregate state, but rather exists more as interfacial active species regulated by the carrier, suggesting a stronger electronic coupling and interfacial interaction between silver and the manganese-oxygen framework. This result provides direct surface chemistry evidence for subsequent activity enhancement.

[0105] Based on the effective regulation of silver species Figure 3 The following are high-resolution XPS spectra of Mn 2p from Examples 1, 8, and 10. Figure 4 Mn for Example 1, Comparative Example 8, and Comparative Example 10 3+ / Mn 4+ The ratio plot further illustrates the optimization of the reaction site environment on the support surface from the perspective of manganese valence state changes. In Example 1, the Mn3+-related components in the Mn 2p envelope are enhanced, and their Mn... 3 + / Mn 4+The molar ratio reached 0.45, significantly higher than 0.22 in Comparative Example 8 and 0.32 in Comparative Example 10, indicating that Example 1 possesses more tunable variable-valence manganese sites and a higher level of defect-related structures. These Mn3+ sites are typically closely related to oxygen vacancy formation and enhanced surface oxygen migration capabilities. Therefore, this result demonstrates that Example 1 not only achieved the dispersion and anchoring of silver species but also simultaneously improved the electronic regulation capability on the support side, which is beneficial for forming a more efficient interfacial reaction environment.

[0106] Correspondingly, Figure 5 The O 1s XPS high-resolution spectra of Example 1, Comparative Example 8, and Comparative Example 10 are shown below. Figure 6 The O 1s fractional area ratio plots for Examples 1, 8, and 10 further verify the above judgment from the perspective of oxygen species composition. Example 1 shows a stronger interface defect oxygen signal near approximately 531 eV, with an interface defect oxygen content of 28.0%, higher than the 16.0% of Comparative Example 8 and 17.0% of Comparative Example 1, indicating a higher proportion of reactive oxygen species on the surface of Example 1. Combined with... Figures 1 to 6 It can be seen that in Example 1, the proportion of Agδ+ was increased, and the proportion of Mn was increased. 3+ / Mn 4+ The increase in the ratio, the increase in interfacial defect oxygen, and the consistent trend of change indicate that a relatively stable Agδ+—MnOx— reactive oxygen interface structure with synergistic effect has been formed in the sample, which is an important prerequisite for its subsequent excellent reactivity.

[0107] After clarifying the surface valence state and the reactive oxygen environment Figure 7 The above are EXAFS k-space oscillation curves for Example 1 and Comparative Example 8. Figure 8 The EXAFS R-space Fourier transform amplitude diagrams of Example 1 and Comparative Example 8 are shown to further verify the interface anchoring characteristics of Example 1 from the perspective of atomic-scale coordination structure. Figure 7 As shown, in Example 1 to The presence of clearer single-shell oscillation characteristics within the range indicates a more homogeneous silver-nearest neighbor coordination environment; Figure 8 This shows that in Example 1, approximately The peak in the first shell layer is stronger in Example 1, while Comparative Example 8 shows a more obvious Ag-Ag correlation signal in the higher R region. This indicates that the silver species in Example 1 mainly exist stably in the form of interfacial coordination, and are more likely to form Ag-O-Mn type local structures, while in Comparative Example 8, silver species are more likely to approach and aggregate. Figures 1 to 8A complete chain of evidence can be formed, namely, Example 1 not only exhibits a higher proportion of interfacial active silver and defect oxygen in terms of surface chemical state, but also achieves a stable coordination environment mainly based on interfacial anchoring in terms of local structure, thus providing a deeper structural support for its activity and stability.

[0108] Figure 9 The following are N2 adsorption-desorption isotherms for Example 1, Comparative Example 2, and Comparative Example 7. Figure 10 The graphs show the BJH pore size distribution curves for Example 1, Comparative Example 2, and Comparative Example 7. Figure 11 The XRD diffraction patterns are those of Example 1, Comparative Example 3, and Comparative Example 7. Figure 12 These are magnified XRD characteristic peaks of Example 1, Comparative Example 3, and Comparative Example 7. These four figures together illustrate that Example 1, while forming an interfacial active structure, did not damage the original pore openness and framework stability of the material. Figure 9 This indicates that Example 1 has a larger adsorption capacity in the high relative pressure region, and the adsorption amount is approximately [value missing] when near saturation. This indicates that its pore volume is well maintained; Figure 10 Further, it is shown that the main pore size of Example 1 is concentrated at about 6.0 nm, while that of Comparative Example 2 and Comparative Example 7 is mainly distributed at about 3.8 nm and 4.5 nm, respectively, indicating that Example 1 retains mesoporous channels that are more suitable for reactant diffusion and product desorption.

[0109] at the same time, Figure 11 Example 1 in , and The characteristic positions still retain clear diffraction peaks. Figure 12 exist to Within the magnified local area, it also exhibits a more stable peak shape and position, indicating that its skeletal structural units are relatively well preserved, and the loading and processing did not lead to significant structural collapse or disorder. Therefore, Figures 9 to 12 This demonstrates that Example 1 not only possesses an excellent interfacial active structure, but also balances open pores and a stable crystal framework, which allows active sites to be fully exposed and maintains effective mass transfer conditions.

[0110] Based on the aforementioned structural and interface advantages Figure 13 The formaldehyde light-off conversion curves for Examples 1, 9, and 10 directly demonstrate the performance verification results. Example 1 achieves a faster conversion rate at a lower temperature range, reaching T90 at 118 °C, significantly outperforming the comparative sample and indicating stronger low-temperature activation capability. This result is consistent with the aforementioned increase in Agδ+ ratio and Mn... 3+The structural features such as increased relevant sites, oxygen enrichment at interface defects, and smoother mass transfer in the pores correspond to each other, indicating that the structural design of Example 1 can be effectively translated into practical reaction performance advantages.

[0111] Furthermore, Figure 14 The graphs show the activity retention rate versus time curves after thermal aging for Examples 1, 3, and 10. Figure 15 The graphs show the Ag loss rate versus time for Examples 1, 3, and 10. Figure 16 The three graphs show the correlation between the activity retention rate and the Ag loss rate for Example 1, Comparative Example 3, and Comparative Example 10. These three graphs together illustrate that Example 1 not only has high initial activity, but also has better long-term stability under continuous heat treatment conditions. Figure 14 The results showed that Example 1 retained 89.0% of its initial activity after 10 hours of aging, while Comparative Example 3 and Comparative Example 10 retained only 68.4% and 65.4%, respectively. Figure 15 The results showed that the Ag loss rate of Example 1 under the same conditions was only 1.8%, which was significantly lower than that of Comparative Example 3 (5.6%) and Comparative Example 10 (6.2%).

[0112] Figure 16 Further linking the two, it can be seen that Example 1 consistently remained in the region of low loss rate and high retention rate, with its endpoint still maintained around Ag loss rate of 1.8% and activity retention rate of 89.0%, indicating that activity decay was significantly suppressed. Combined with the aforementioned... Figures 1 to 12 It is evident that this improved stability is not an isolated phenomenon, but rather the result of the combined effects of a stronger Ag-carrier interface, a more stable local coordination structure, and a more complete pore framework. Overall, Figures 1 to 16 The results demonstrate that Example 1 achieved the construction of interfacial active species, local structural stability, maintenance of the pore framework, and simultaneous improvement of catalytic performance and durability, thus systematically illustrating that the scheme has clear and reliable effectiveness.

[0113] Figure 17 This is a macroscopic optical photograph of the silver-manganese composite material prepared in Example 1. After passing through a 60-mesh sieve, the sample appears as a dark black-brown fine powder with a uniform color and no obvious clumps or layering. The powder exhibits good flowability. The dark appearance originates from the intrinsic absorption of the mixed valence state of Mn3+ / Mn4+ and the diffuse reflection effect caused by the high specific surface area. The ultra-low silver loading of 0.20 wt% did not significantly affect the overall color. The uniform overall morphology of the powder indicates that the multi-step process of hydrothermal synthesis-hydrogen reduction-silver anchoring-fixation treatment is stable and controllable, and the uniform component distribution proves the reliability of the process for precisely controlling the low silver loading.

[0114] Figure 18This is a scanning electron microscope (SEM) image of the silver-manganese composite material prepared in Example 1. The low-magnification image shows the sample composed of numerous randomly oriented one-dimensional nanorods, arranged in a three-dimensional network of interwoven stacks, forming a highly open porous framework structure with uniform overall coverage. The medium-magnification image reveals that the nanorods are slender cylindrical in shape. The nanorod surfaces are smooth, and when they overlap, they exhibit point or short-line contact, with loose interfacial bonding and no obvious sintering necks, indicating that the 300℃ fixation temperature was appropriate and did not induce grain growth or agglomeration. The high-magnification image shows slight undulating textures on the nanorod surface, presumably related to surface defect sites induced by the 220℃ hydrogen reduction treatment. These defect sites are the key structural basis for the preferential anchoring of silver single atoms and sub-nanoclusters. This demonstrates the effectiveness of the hydrogen defect control process and the successful construction of silver anchoring points.

[0115] Figure 19 The image is a transmission electron microscope image of the silver-manganese composite material prepared in Example 1. Figure 19 (a) Bright-field TEM images show that the sample consists of solid nanorods with a diameter of about 35 nm and a length of 500 to 900 nm, which is highly consistent with the results observed by scanning electron microscopy. Figure 19 (b) The nanorods exhibit good internal crystallinity, with no obvious amorphous shells or pore defects. High-resolution transmission electron microscopy images show clear and continuous lattice fringes, corresponding to the (001) crystal plane of crypto-KMnO type manganese dioxide. Local areas show slight contrast fluctuations or breaks in the lattice fringes, which are related to oxygen vacancies and Mn3+ sites introduced by hydrogen reduction. Figure 19 (c) Selected area electron diffraction patterns show continuous polycrystalline diffraction rings, which can be indexed as characteristic crystal planes of α-MnO2, indicating that the sample has good crystallinity and polycrystalline orientation distribution. This proves the rationality of the hydrothermal synthesis parameters and hydrogen reduction conditions, and verifies that an appropriate amount of structural defects were successfully introduced while maintaining the crystalline framework, providing a structural basis for the atomic-level dispersion of silver and the construction of the Ag-O-Mn interface.

[0116] ;

[0117] As can be seen from the performance of the examples and comparative examples in Table 1, the examples are significantly better than the comparative examples in terms of formaldehyde T90, toluene T90, continuous stability, wet state retention rate, and activity retention rate after aging, indicating a clear structure-performance coupling relationship between defect regulation, silver anchoring, and fixation steps. Examples 2 and 4 show a better balance between activity and stability, while Example 1 maintains good overall performance even under low silver loading conditions. Comparative Examples 1, 2, 4, 5, and 6 show that deviations in raw material ratio, precursor concentration, defect treatment, and impregnation conditions can simultaneously affect open channels and silver distribution uniformity; Comparative Examples 3, 7, and 10 show that excessive defects or improper fixation can destroy long-term stability; Comparative Examples 8 and 9 further illustrate that retaining defect carriers or silver species alone is insufficient to establish a stable and efficient interface. Among them, Comparative Example 9, since no silver was introduced, only reflects the "silver-free" state in terms of Ag loss rate, and does not constitute a basis for judging activity advantage.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A high-efficiency silver-manganese composite material, characterized in that, The high-efficiency silver-manganese composite material is composed of silver-loaded defective manganese oxide octahedral molecular sieves, wherein the defective manganese oxide octahedral molecular sieves are tunnel nanorods selected from either crypto-potassium manganese dioxide or α-MnO2; the silver content is 0.20-2.50 wt% of the total amount of the high-efficiency silver-manganese composite material, and the balance is the defective manganese oxide octahedral molecular sieves.

2. The high-efficiency silver-manganese composite material according to claim 1, characterized in that, The tunnel nanorods have an average diameter of 20-60 nm and an aspect ratio of 10-50. Silver is distributed on the surface of the tunnel nanorods at at least one of the following forms: Agδ+ single atoms, Ag0 single atoms, sub-nanoclusters, or ultrafine nanodots with an apparent particle size of 0.10-2.00 nm, at defect sites and / or 2×2 tunnel opening sites, forming an Ag-O-Mn interface. The efficient silver-manganese composite material has a BET specific surface area of ​​120-250 m². 2 / g, the main peak pore size of the mesoporous structure is 2-12nm.

3. The high-efficiency silver-manganese composite material according to claim 1, characterized in that, The tunnel nanorods are prepared by the following steps: A1. Dissolve potassium permanganate and manganese sulfate monohydrate in deionized water, such that the molar ratio of potassium permanganate to manganese sulfate monohydrate is 1.8:1-2.4:1, and the total concentration of potassium permanganate and manganese sulfate monohydrate in the solution is 0.05-0.20 mol / L, based on the sum of the amounts of potassium permanganate and manganese sulfate monohydrate. A2. Place the solution obtained in step A1 into a polytetrafluoroethylene-lined reactor and react it at a temperature of 130-150℃ for 8-16 hours. A3. Wash the obtained solid with deionized water until the pH of the filtrate is 6.0-7.5 and the conductivity is not higher than 100 μS / cm; A4 was dried at 80-110℃ for 6-12 hours to obtain tunnel nanorod intermediates selected from either crypto-potassium manganese dioxide or α-MnO2, with an average diameter of 20-60 nm and an aspect ratio of 10-50.

4. The high-efficiency silver-manganese composite material according to claim 3, characterized in that, The defect tunnel nanorods are prepared by the following steps: B1, the tunnel nanorod intermediate was placed in a tube furnace; B2, in a mixed atmosphere of hydrogen and nitrogen, wherein the volume fraction of hydrogen is 2-10 vol%, and the remainder is nitrogen, the mixture is treated at a temperature of 200-240℃ for 0.5-2 h, and the total flow rate of the mixed gas is 50-500 mL / min. B3, cool to room temperature at a rate of 1-5℃ / min to obtain a defective tunnel nanorod intermediate with the same main crystalline phase as the tunnel nanorod intermediate obtained in step A4.

5. The high-efficiency silver-manganese composite material according to claim 4, characterized in that, The silver is anchored to the defect tunnel nanorod via the following steps: C1. Dissolve silver nitrate in deionized water, then add ammonia water to adjust the pH value to 9.5-11.5, and prepare a silver ammonia complex solution with a silver concentration of 0.005-0.050 mol / L. C2, add the defective tunnel nanorod intermediate to the silver ammonia complex solution obtained in step C1, wherein each 1g of defective tunnel nanorod intermediate corresponds to 10-50mL of silver ammonia complex solution, and the silver concentration and amount of the silver ammonia complex solution are selected together so that the theoretical silver loading of the obtained silver-anchored intermediate is 0.20-2.50wt%, and impregnate for 0.5-2h at a temperature of 20-40℃; C3, the obtained system is evaporated and concentrated or dehydrated under reduced pressure to ensure that the residual free liquid of the intermediate is not higher than 10 wt%, thus obtaining the silver-anchored intermediate.

6. The high-efficiency silver-manganese composite material according to claim 1, characterized in that, In the defective manganese oxide octahedral molecular sieve, the Mn3+ / Mn4+ molar ratio is 0.20-0.80, and the main crystalline phase of the defective manganese oxide octahedral molecular sieve is crypto-potassium manganese dioxide.

7. A method for preparing the high-efficiency silver-manganese composite material as described in any one of claims 1-6, characterized in that, Includes the following steps: S1 provides a silver-anchored intermediate; S2, the silver-anchored intermediate obtained in step S1 is dried at a temperature of 80-110℃ for 6-12 hours; S3, then heat it in air at a heating rate of 1-3℃ / min, and keep it at 280-320℃ for 1-3 hours for fixation treatment; S4, after cooling, is crushed and sieved to 40-100 mesh to obtain a high-efficiency silver-manganese composite material.

8. The preparation method according to claim 7, characterized in that, The silver anchoring intermediate provided in step S1 is obtained by the following method: before adding the defective tunnel nanorod intermediate to the silver ammonia complex solution for atmospheric pressure impregnation, the defective tunnel nanorod intermediate is first subjected to vacuum pre-impregnation treatment. The absolute pressure of the vacuum pre-impregnation treatment is 0.02-0.08 MPa, and the time is 5-20 min.

9. The preparation method according to claim 7, characterized in that, The main crystalline phase of the defective manganese oxide octahedral molecular sieve in the high-efficiency silver-manganese composite material obtained in step S4 is crypto-potassium manganese dioxide.

10. The preparation method according to claim 7, characterized in that, When preparing the silver ammonia complex solution, the mass fraction of ammonia water used should be 25-28 wt%, and the molar ratio of NH3 to Ag+ should be 4:1-10:1.

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