A NiO-MO x / NF sandwich structure monolithic catalyst and its preparation method and application

Abstract

The present invention discloses a NiO-MO x / NF sandwich structure integral catalyst and its preparation method and application belong to the field of catalyst technology. The present invention first uses a hydrothermal method to induce the in-situ release of nickel ions from the nickel substrate, and self-assembles with oxalic acid to form a three-dimensional interwoven NiC2O4 nanorod array. This process can construct a high specific surface area and hierarchical mesoporous structure without the need for an external nickel source, laying the foundation for subsequent functional modification; then, by utilizing the non-conductive properties of NiC2O4, the M ions are promoted to penetrate along the gaps between the nanorods to the interface of the nickel substrate and deposit during the electrodeposition process; finally, the NiC2O4 is converted into a porous NiO framework by calcination, thereby forming a "NiO shell-MO x The catalyst prepared by the layered sandwich structure of "intermediate layer-Ni substrate" has high activity, moisture resistance and long-term stability.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst technology, and particularly relates to a NiO-MO x / NF sandwich structure monolithic catalyst, preparation method and application thereof. Background Art

[0002] As a typical secondary pollutant, ground-level ozone is composed of volatile organic compounds (VOCs), carbon monoxide (CO) and nitrogen oxides (NO x ) is produced through photochemical reactions driven by solar radiation. Although ozone is widely used as a strong oxidant in air and water purification, its excessive release in industrial processes (such as pulp bleaching and wastewater treatment) and indoor environments (such as laser printers and ultraviolet disinfection equipment) has led to increasingly serious regional ozone pollution problems. Therefore, the development of efficient ozone removal technologies is of great significance for mitigating environmental risks and protecting human health.

[0003] Room temperature catalytic ozone decomposition technology has become a key development direction of ozone removal technology due to its green characteristics such as no secondary pollution and low energy consumption. Compared with precious metal catalysts, transition metal-based materials (such as Mn, Ni, Cu, Fe and their oxides) have become the core research object of ozone catalytic decomposition due to their abundant reserves, low cost and adjustable electronic structure. Among them, manganese oxide (MnO x ) has significant advantages in ozone catalysis due to its tunable crystal structure, abundant oxygen vacancies and multiple oxidation state characteristics. However, the environmental humidity has a great influence on the MnO x The inhibitory effect on catalytic performance remains a technical bottleneck. The competitive adsorption of water molecules on active sites will lead to hydroxylation of the catalyst surface, hindering the adsorption-activation process of ozone molecules on oxygen vacancies.

[0004] It is worth noting that nickel oxide (NiO)-based materials also exhibit excellent ozone decomposition activity and moisture stability. Gong et al. constructed a highly active and water-resistant Ni / NiO heterogeneous nanostructured catalyst by a citric acid sol-gel method, pointing out that its performance is due to the synergistic effect between metal Ni and NiO, which not only promotes electron transfer in the catalytic process, but also accelerates the desorption of water molecules under high humidity conditions (Gong, S., Wang, A., Wang, Y., Liu, H., Han, N., & Chen, Y. (2020). Heterostructured Ni / NiO Nanocatalysts for OzoneDecomposition); Wang et al. prepared powder catalysts with different Mn / Ni molar ratios by a hydrothermal method and verified their efficient ozone degradation ability in a fully humid environment (Wang, A., Wu, Y., Shen, X., Zhang, Q., Jian,H., & Han, C. (2024). Efficient ozone decomposition by amorphous Mn–Nibimetallic catalysts under an entire humidity environment). Further studies found that Ni doped into MnO x The lattice can form an amorphous Mn-Ni solid solution, which not only enhances the hydrophobicity of the catalyst to inhibit the enrichment of water molecules, but also promotes the conversion of adsorbed water into surface hydroxyl groups to participate in ozone decomposition, while accelerating the desorption of intermediate peroxides to promote the decomposition cycle.

[0005] However, these traditional powder catalysts suffer from issues such as easy agglomeration, difficulty in recycling, and weak interfacial bonding. The development of monolithic catalysts that combine structural stability with high activity remains a key research direction. Furthermore, research on non-precious metal-Ni bimetallic monolithic catalysts for ozone decomposition is still relatively scarce. Therefore, optimizing the preparation strategy to manipulate the material structure and increase oxygen vacancy density to further enhance catalytic activity and water resistance remains an urgent issue. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention proposes a NiO-MO x / NF sandwich structure monolithic catalyst and its preparation method and application. The catalyst provided by the present invention uses NiO as the main active component and loads a small amount of MO by electrodeposition. x , using MO x The composite effect of NiO and NiO enhances the hydrophobicity of the catalyst to inhibit the enrichment of water molecules. At the same time, through the unique "NiO shell-MO xThe layered structure design of "intermediate layer-Ni substrate" significantly improves the ozone decomposition activity and long-term catalytic stability of the catalyst.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] The present invention provides a NiO-MO x The preparation method of a sandwich structure monolithic catalyst of NiC2O4 / NF comprises the following steps: in situ growing NiC2O4 on a nickel substrate by a hydrothermal method to obtain NiC2O4 / NF; then doping MO by electrodeposition x , and calcined to obtain the NiO-MO x / NF sandwich structure monolithic catalyst; wherein M is manganese or cobalt; and x is 1-3.

[0009] Technical principle: The present invention constructs a high-performance non-precious metal ozone decomposition composite catalyst through a three-step process of hydrothermal-electrodeposition-calcination. Specifically, the hydrothermal method is first used to induce the in-situ release of nickel ions from the nickel substrate, which self-assembles with oxalic acid to form a three-dimensional interwoven NiC2O4 nanorod array. This process can construct a high specific surface area and hierarchical mesoporous structure without the need for an external nickel source, laying the foundation for subsequent functional modification. Then, the non-conductive property of NiC2O4 is utilized to promote the penetration of M ions along the gaps between the nanorods to the interface of the nickel substrate for deposition (rather than simple surface loading) during the electrodeposition process. Finally, NiC2O4 is converted into a porous NiO framework by calcination, thereby forming a "NiO shell-MO" structure. x The catalyst has a layered sandwich structure of "intermediate layer-Ni substrate" and has high activity, moisture resistance and long-term stability.

[0010] Furthermore, the process of in-situ growing NiC2O4 on the nickel substrate using a hydrothermal method includes: dissolving oxalic acid and ammonium chloride in water to obtain a mixed solution; immersing the nickel substrate in the mixed solution, and obtaining NiC2O4 / NF through a hydrothermal reaction.

[0011] Furthermore, the nickel substrate is selected from nickel foam, nickel mesh, nickel honeycomb or nickel sheet.

[0012] Furthermore, the molar ratio of oxalic acid to ammonium chloride is (0.5-2):1; and / or,

[0013] The temperature of the hydrothermal reaction is 80-120° C., and the time of the hydrothermal reaction is 12-36 hours.

[0014] Furthermore, the voltage of the electrodeposition is -1.2~1.8V, and the deposition time of the electrodeposition is 1800~3000s.

[0015] Furthermore, the MO is doped by electro-deposition xThe process includes: using soluble M salt solution as electrolyte, NiC2O4 / NF as working electrode, and adopting three-electrode system for electrodeposition to obtain NiC2O4-MO x / NF.

[0016] Furthermore, the soluble M salt in the soluble M salt solution is selected from one of manganese acetate, manganese nitrate, manganese sulfate, cobalt nitrate and cobalt sulfate; and the concentration of the soluble M salt solution is 0.2-0.25 mol / L.

[0017] Furthermore, the calcination temperature is 350-450° C., the calcination time is 1-2 hours, and the rate of heating to the calcination temperature is 5-10° C. / min.

[0018] The present invention provides a NiO-MO x / NF sandwich structure monolithic catalyst is prepared according to the preparation method described in the above technical solution.

[0019] The present invention also provides a NiO-MO described in the above technical solution x Application of sandwich structure monolithic catalyst of 100 nm / NF in catalytic decomposition of ozone.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] (1) The nickel substrate is in situ induced to release nickel ions through a hydrothermal method, and the nickel ions are coordinated with oxalic acid to form a three-dimensional interwoven NiC2O4 nanorod array. This method can form a high specific surface area and hierarchical mesoporous characteristics without adding additional nickel sources, laying the foundation for subsequent functional modification.

[0022] (2) During the electrodeposition process, M ions preferentially penetrate the surface of the nickel substrate through the mesoporous channels between the NiC2O4 nanorods, rather than being directly deposited on the outer layer of NiC2O4. After calcination, NiC2O4 is converted into a porous NiO framework, and finally a "NiO shell-MO x The "intermediate layer-Ni substrate" layered structure promotes electron transfer and exposes more active sites, giving it excellent ozone decomposition activity and stability under high humidity conditions.

[0023] (3) The present invention constructs NiO-MO with high activity, moisture resistance and long-term stability through a three-step process of hydrothermal-electrodeposition-calcination. x / NF sandwich structure integral catalyst, and the method of the present invention can be expanded by adapting different nickel substrates (such as nickel foam, nickel mesh) or replacing electrolyte metal salts (such as manganese acetate, cobalt nitrate), providing a universal technical path for the development of non-precious metal ozone decomposition catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 NiO-MnO prepared in Example 1 x SEM image of the sandwich structure monolithic catalyst of NF / NF (200 μm);

[0026] Figure 2 NiO-MnO prepared in Example 1 x SEM image of the sandwich structure monolithic catalyst of NF (10 μm);

[0027] Figure 3 The NF in step (1) of Example 1, the NiC2O4 / NF in step (2), and the NiC2O4-MnO in step (3) are x / NF and NiO-MnO in step (4) x XRD pattern of / NF;

[0028] Figure 4 NiO-MnO prepared in Example 1 x Raman spectrum of the sandwich structure monolithic catalyst of 100 nm / NF;

[0029] Figure 5 NiO-MnO prepared in Example 1 x Long-term ozone catalytic decomposition results of the sandwich structure monolithic catalyst of / NF. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The embodiment of the present invention provides a NiO-MO x The preparation method of a sandwich structure monolithic catalyst of NiC2O4 / NF comprises the following steps: in situ growing NiC2O4 on a nickel substrate by a hydrothermal method to obtain NiC2O4 / NF; then doping MO by electrodeposition x, and calcined to obtain the NiO-MO x / NF sandwich structure monolithic catalyst; wherein M is manganese or cobalt; and x is 1-3.

[0033] In a preferred embodiment, when M is manganese, MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence of manganese is +2, +3, +4; when M is cobalt, MO x It is Co3O4.

[0034] In a preferred embodiment, the process of in-situ growth of NiC2O4 on a nickel substrate using a hydrothermal method includes: dissolving oxalic acid and ammonium chloride in water to obtain a mixed solution; immersing the nickel substrate in the mixed solution, and obtaining NiC2O4 / NF through a hydrothermal reaction.

[0035] In a preferred embodiment, the nickel substrate is selected from nickel foam, nickel mesh, nickel honeycomb or nickel sheet, more preferably nickel foam; the size of the nickel substrate is 2 cm×3 cm.

[0036] In a preferred embodiment, a pretreatment step is further included before immersing the nickel substrate in the mixed solution; the pretreatment includes: placing the nickel substrate in a 1 mol / L HCl solution and ultrasonicating for 1 minute to remove the oxide layer, then ultrasonicating in deionized water and anhydrous ethanol solution for 10 minutes respectively, and then placing it in an 80°C oven to dry.

[0037] In a preferred embodiment, the nickel substrate has a porosity of 95 PPI and a thickness of 2.1 mm.

[0038] In a preferred embodiment, the molar ratio of oxalic acid to ammonium chloride is (0.5-2):1, more preferably 1:1.

[0039] In a preferred embodiment, based on the usage of 6 mmol of ammonium chloride, the usage of water is 30 mL.

[0040] In a preferred embodiment, the temperature of the hydrothermal reaction is 80-120° C., and the time of the hydrothermal reaction is 12-36 hours. During the hydrothermal reaction, oxalic acid, ammonium chloride, and the nickel substrate undergo a chemical reaction to generate NiC 2 O 4 .

[0041] In a preferred embodiment, the voltage of the electrodeposition is -1.2~1.8V, and the deposition time of the electrodeposition is 1800~3000s, more preferably 1800~2700s. The present invention controls the MO by controlling the electrodeposition time. x The loading amount, the electrodeposition time is too short, and the MO content in the catalyst is too high. x The loading amount is too low, the active components are few, and the catalyst performance is poor; the electrodeposition time is too long, and a large amount of MO xWhen grown on a nickel substrate, the active components overlap with each other, resulting in a reduction in active sites and a decrease in catalyst performance.

[0042] In a preferred embodiment, the MO is doped by electrodeposition. x The process includes: using soluble M salt solution as electrolyte, NiC2O4 / NF as working electrode, and adopting three-electrode system for electrodeposition to obtain NiC2O4-MO x / NF.

[0043] In a preferred embodiment, the soluble M salt in the soluble M salt solution is selected from one of manganese acetate, manganese nitrate, manganese sulfate, cobalt nitrate and cobalt sulfate; in a typical but non-limiting example, the soluble M salt is manganese acetate or cobalt nitrate; the concentration of the soluble M salt solution is 0.2~0.25 mol / L.

[0044] In a preferred embodiment, the calcination temperature is 350-450°C, the calcination time is 1-2 hours, and the rate of heating to the calcination temperature is 5-10°C / min. By controlling the calcination temperature, the present invention ensures that NiC2O4 is completely decomposed into NiO, thereby ensuring the catalytic performance of the catalyst. If the calcination temperature is too low, NiC2O4 will not be completely decomposed into NiO, resulting in a decrease in catalyst performance. If the calcination temperature is too high, the active components will sinter, resulting in a decrease in active sites and a decrease in catalyst performance.

[0045] The present invention provides a NiO-MO x / NF sandwich structure monolithic catalyst, prepared according to the preparation method described in the above technical solution; wherein M is manganese or cobalt; and x is 1-3.

[0046] In a preferred embodiment, when M is manganese, MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence of manganese is +2, +3, +4; when M is cobalt, MO x It is Co3O4.

[0047] The present invention also provides a NiO-MO described in the above technical solution x Application of sandwich structure monolithic catalyst of 100 nm / NF in catalytic decomposition of ozone.

[0048] The room temperature and normal temperature in the embodiments of the present invention refer to "25±2°C".

[0049] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0050] Example 1

[0051] A NiO-MnOx The preparation method of the sandwich structure monolithic catalyst of / NF is as follows:

[0052] (1) Nickel foam (NF) with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0053] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0054] (3) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, NiC2O4 / NF in step (2) as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 2700 s. After the deposition was completed, the sample was fully rinsed with deionized water and dried in an oven at 80 °C to obtain NiC2O4-MnO x / NF composite materials.

[0055] (4) NiC2O4-MnO in step (3) x The / NF composite material was placed in a muffle furnace and heated to 450℃ at 5℃ / min in air atmosphere for 2h to obtain NiO-MnO x / NF sandwich structure monolithic catalyst, in which MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence states of manganese are +2, +3 and +4.

[0056] Figure 1 NiO-MnO prepared in Example 1 x Scanning electron micrograph of the sandwich-structured monolithic catalyst of α-Si / α-NF (200 μm). Figure 2 NiO-MnO prepared in Example 1 x SEM image of the sandwich structure monolithic catalyst of 10μm / NF. Figure 1 and Figure 2Scanning electron microscopy results show that the outermost layer of the catalyst prepared in Example 1 is composed of densely arranged rod-shaped nickel oxide nanostructures, the middle layer is wrapped with manganese oxide nanowires, and the innermost layer is a nickel substrate. The three together construct a sandwich structure with clear hierarchical characteristics. The characteristic of NiO preferentially adsorbing ozone molecules reduces the interaction between water molecules and MnO. x contact probability, inhibiting the water molecule-induced MnO x Inactivation.

[0057] Figure 3 The NF in step (1) of Example 1, the NiC2O4 / NF in step (2), and the NiC2O4-MnO in step (3) are x / NF and NiO-MnO in step (4) x / NF XRD pattern. Figure 3 It can be seen that NiO-MnO x In addition to the characteristic peaks of nickel foam from (111), (200) and (220) crystal planes, / NF also has NiO characteristic peaks from (111), (200), (220), (311) and (222). No obvious MnO x The reason for the characteristic peak is that the characteristic peak of NF is too strong, which leads to the formation of MnO by electrodeposition. x The characteristic peaks are not obvious.

[0058] Figure 4 NiO-MnO prepared in Example 1 x Raman spectrum of the sandwich structure monolithic catalyst of 100 nm / 100 nm. Figure 4 It can be seen that the Raman spectrum at 499 cm -1 The characteristic peak of NiO appeared at 645 cm -1 MnO appeared x characteristic peaks, proving that NiO and MnO x Successful loading on nickel foam.

[0059] Example 2

[0060] A NiO-MnO x The preparation method of the sandwich structure monolithic catalyst of / NF is as follows:

[0061] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0062] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0063] (3) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, NiC2O4 / NF in step (2) as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 2400 s. After the deposition was completed, the sample was fully rinsed with deionized water and dried in an oven at 80 °C to obtain NiC2O4-MnO x / NF composite materials.

[0064] (4) NiC2O4-MnO in step (3) x The / NF composite material was placed in a muffle furnace and heated to 450℃ at 5℃ / min in air atmosphere for 2h to obtain NiO-MnO x / NF sandwich structure monolithic catalyst, in which MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence states of manganese are +2, +3 and +4.

[0065] Example 3

[0066] A NiO-MnO x The preparation method of the sandwich structure monolithic catalyst of / NF is as follows:

[0067] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0068] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0069] (3) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, NiC2O4 / NF in step (2) as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 3000 s. After the deposition was completed, the sample was fully rinsed with deionized water and dried in an oven at 80 °C to obtain NiC2O4-MnO x / NF composite materials.

[0070] (4) NiC2O4-MnO in step (3) x The / NF composite material was placed in a muffle furnace and heated to 450℃ at 5℃ / min in air atmosphere for 2h to obtain NiO-MnO x / NF sandwich structure monolithic catalyst, in which MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence states of manganese are +2, +3 and +4.

[0071] Example 4

[0072] A NiO-MnO x The preparation method of the sandwich structure monolithic catalyst of / NF is as follows:

[0073] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0074] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0075] (3) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, NiC2O4 / NF in step (2) as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 2700 s. After the deposition was completed, the sample was fully rinsed with deionized water and dried in an oven at 80 °C to obtain NiC2O4-MnO x / NF composite materials.

[0076] (4) NiC2O4-MnO in step (3) x The / NF composite material was placed in a muffle furnace and heated to 350℃ at 5℃ / min in air atmosphere for 2h to obtain NiO-MnO x / NF sandwich structure monolithic catalyst, in which MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence states of manganese are +2, +3 and +4.

[0077] Example 5

[0078] A NiO-MnO x The preparation method of the sandwich structure monolithic catalyst of / NF is as follows:

[0079] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0080] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0081] (3) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, NiC2O4 / NF in step (2) as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 2700 s. After the deposition was completed, the sample was fully rinsed with deionized water and dried in an oven at 80 °C to obtain NiC2O4-MnO x / NF composite materials.

[0082] (4) NiC2O4-MnO in step (3) x The / NF composite material was placed in a muffle furnace and heated to 400 °C at 5 °C / min in air atmosphere and calcined for 2 h to obtain NiO-MnO x / NF sandwich structure monolithic catalyst, in which MO x It is a mixture of MnO, MnO2 and Mn2O3, that is, the valence state of manganese is +2, +3, and +4.

[0083] Example 6

[0084] A method for preparing a NiO-Co3O4 / NF sandwich structure monolithic catalyst comprises the following steps:

[0085] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0086] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0087] (3) Using 0.2 mol / L cobalt nitrate (Co(NO3)2·6H2O) solution as the electrolyte, the NiC2O4 / NF in step (2) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of -1.2 V and a deposition time of 1800 s. After deposition, the sample was thoroughly rinsed with deionized water and dried in an oven at 80°C to obtain a NiC2O4-Co(OH)2 / NF composite material.

[0088] (4) The NiC2O4-Co(OH)2 / NF composite material prepared in step (3) was placed in a muffle furnace, heated to 450°C at a rate of 5°C / min in an air atmosphere, and calcined for 2 h to obtain a NiO-Co3O4 / NF sandwich structured monolithic catalyst.

[0089] Comparative Example 1

[0090] A method for preparing a NiO / NF monolithic catalyst comprises the following steps:

[0091] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0092] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0093] (3) The NiC2O4 / NF prepared in step (2) was placed in a muffle furnace, heated to 450°C at a rate of 5°C / min under air atmosphere, and calcined for 2 h to obtain a NiO / NF monolithic catalyst.

[0094] Comparative Example 2

[0095] A MnO x The preparation method of the / NF monolithic catalyst comprises the following steps:

[0096] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0097] (2) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, the pretreated nickel foam in step (1) as the working electrode, the platinum sheet as the counter electrode, and the saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 2700 s. After the deposition was completed, the sample was fully rinsed with deionized water and dried in an oven at 80 °C to obtain MnO x / NF.

[0098] (3) MnO in step (2) x The MnO / NF was placed in a muffle furnace and heated to 450°C at a rate of 5°C / min under air atmosphere and calcined for 2 h to obtain MnO x / NF monolithic catalyst.

[0099] Comparative Example 3

[0100] A MnO x -The preparation method of NiO / NF monolithic catalyst comprises the following steps:

[0101] (1) Nickel foam with a porosity of 95 PPI and a thickness of 2.1 mm was cut into rectangular pieces with a length of 3 cm and a width of 2 cm. The pieces were then placed in a 1 mol / L HCl solution and ultrasonicated for 1 min to remove the oxide layer. The pieces were then ultrasonicated in deionized water and anhydrous ethanol solutions for 10 min respectively. The pieces were then dried in an oven at 80 °C to obtain pretreated nickel foam.

[0102] (2) Dissolve 6 mmol H2C2O4·2H2O and 6 mmol NH4Cl powder in 30 mL deionized water and stir magnetically for 30 min until completely dissolved to obtain a mixed solution. Immerse the nickel foam pretreated in step (1) in the above mixed solution and transfer it to a 50 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 100°C for 24 h. After the hydrothermal reaction, cool it to room temperature, remove the sample, rinse it with deionized water three times, and dry it to obtain NiC2O4 / NF.

[0103] (3) The NiC2O4 / NF prepared in step (2) was placed in a muffle furnace, heated to 450°C at a rate of 5°C / min in an air atmosphere, and calcined for 2 h to obtain NiO / NF.

[0104] (4) Using 0.25 mol / L manganese acetate (Mn(CH3COO)2·4H2O) solution as the electrolyte, NiO / NF in step (3) as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition was performed with a deposition voltage of 1.5 V and a deposition time of 2700 s. After the deposition was completed, the sample was rinsed thoroughly with deionized water and dried in an oven at 80 °C to obtain MnO x -NiO / NF monolithic catalyst.

[0105] Comparative Example 4

[0106] A NiO-MnO x The preparation method of the sandwich structure integral catalyst of / NF is different from that of Example 1 in that, in step (3), the deposition time is 900s, and the rest is the same as Example 1.

[0107] Comparative Example 5

[0108] A NiO-MnO x The preparation method of the sandwich structure integral catalyst of / NF is different from that of Example 1 in that, in step (3), the deposition time is 3600s, and the rest is the same as Example 1.

[0109] Comparative Example 6

[0110] A NiO-MnO x The preparation method of the sandwich structure integral catalyst of / NF is different from that of Example 1 in that, in step (4), the temperature is raised to 250°C at 5°C / min and calcined for 2h in an air atmosphere. Other steps are the same as those of Example 1.

[0111] Comparative Example 7

[0112] A NiO-MnO x The preparation method of the sandwich structure integral catalyst of / NF is different from that of Example 1 in that, in step (4), the temperature is raised to 500°C at 5°C / min and calcined for 2h in an air atmosphere, and the rest is the same as that of Example 1.

[0113] The catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 7 were cut into 0.225 cm 3 The size of the ozone was wrapped with quartz wool and placed in the center of the quartz tube reactor for ozone catalytic decomposition reaction. The test results are shown in Table 1. The reaction was carried out at room temperature and pressure, with an ozone inlet concentration of 20 ppm, a relative humidity of 90%, and a space velocity of 60,000 h -1 The test time is 2 hours. Use an ozone detector to detect the outlet concentration and calculate the ozone conversion rate. The calculation formula for ozone conversion rate is as follows:

[0114] .

[0115] Table 1 Ozone conversion rate

[0116] It can be clearly seen from the data in Table 1 that the NiO-MO prepared by the present invention x The conversion rate of ozone of the / NF sandwich structure integral catalyst is much higher than that of the catalyst materials prepared in Comparative Examples 1 to 7, and has a significant ozone purification effect. Comparative Example 1-5 shows that when the electroplating time is 2700s and the calcination temperature is 450°C, the catalyst material (Example 1) obtained has the best effect in catalyzing ozone degradation, with an ozone conversion rate of 94.1%. Example 6 prepared a NiO-Co3O4 / NF integral catalyst by the same strategy, verifying that the method provided by the present invention can be expanded to the preparation of other metal oxide / nickel-based composite catalytic systems by replacing the metal salt in the electrolyte. Compared with Example 1, Comparative Example 3 differs in that the order of electroplating and calcination is different. In Comparative Example 3, NiC2O4 / NF is first calcined to generate NiO / NF, and then electrochemically deposited MnO x Compared with the catalyst material prepared in Example 1, its ozone conversion rate is reduced by 23.4%, indicating that after hydrothermal generation of NiC2O4, only after electrochemical deposition of MnO x The catalyst material obtained by calcining has a better ozone catalytic degradation effect. x The loading amount of MnO is too low, the active components are less, and the catalyst performance is poor. In Comparative Example 5, the electrodeposition time is too long, and a large amount of MnO x When grown on a nickel foam substrate, excessive deposition of manganese oxide can cause the NiO layer to fall off, resulting in decreased performance of the catalyst in Comparative Example 5. In Comparative Example 6, when the calcination temperature was too low, NiC2O4 was not completely decomposed into NiO, resulting in decreased performance of the catalyst in Comparative Example 6. In Comparative Example 7, when the calcination temperature was too high, the higher temperature caused the active components on the catalyst to sinter, resulting in a reduction in active sites and, consequently, decreased performance of the catalyst.

[0117] Figure 5 NiO-MnO prepared in Example 1 x The long-term ozone catalytic decomposition results of the sandwich structure monolithic catalyst of / NF, Figure 5 In the equation, C0 represents the inlet concentration of ozone, RH represents the relative humidity, and GHSV represents the air velocity. Figure 5 It can be seen that within 32 hours, the conversion rate of ozone by the catalyst prepared in Example 1 was always maintained at about 90%, and the catalytic performance did not decrease significantly, indicating that the catalyst prepared in Example 1 has long-term stability.

[0118] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A NiO-MO x A method for preparing a sandwich structure monolithic catalyst of / NF, characterized in that: The following steps are involved: Oxalic acid and ammonium chloride are dissolved in water to obtain a mixed solution; a nickel substrate is immersed in the mixed solution to obtain NiC2O4 / NF through a hydrothermal reaction; and then MO is doped by electrodeposition. x , and calcined to obtain the NiO-MO x / NF sandwich structure monolithic catalyst; wherein M is manganese or cobalt; x is 1 to 3; The voltage of the electrodeposition is -1.2~1.8V, and the deposition time of the electrodeposition is 1800~3000s; The calcination temperature is 350-450° C., the calcination time is 1-2 hours, and the rate of heating to the calcination temperature is 5-10° C. / min.

2. The preparation method according to claim 1, characterized in that The nickel substrate is selected from nickel foam, nickel mesh, nickel honeycomb or nickel sheet.

3. The preparation method according to claim 1, characterized in that The molar ratio of oxalic acid to ammonium chloride is (0.5-2):1; and / or the temperature of the hydrothermal reaction is 80-120° C., and the time of the hydrothermal reaction is 12-36 hours.

4. The preparation method according to claim 1, characterized in that The process of doping MOx by electrodeposition includes: using a soluble M salt solution as an electrolyte, using NiC2O4 / NF as a working electrode, and adopting a three-electrode system for electrodeposition to obtain NiC2O4-MO x / NF.

5. The preparation method according to claim 4, characterized in that The soluble M salt in the soluble M salt solution is selected from one of manganese acetate, manganese nitrate, manganese sulfate, cobalt nitrate and cobalt sulfate; the concentration of the soluble M salt solution is 0.2-0.25 mol / L.

6. A NiO-MO x / NF sandwich structure monolithic catalyst, prepared by the preparation method according to any one of claims 1 to 5.

7. A NiO-MO as claimed in claim 6 x Application of sandwich structure monolithic catalyst of 100 nm / NF in catalytic decomposition of ozone.

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