A nickel-nickel silicate catalyst, its preparation method and application

Abstract

The application provides a nickel-nickel silicate catalyst and a preparation method and application thereof, and relates to the technical field of catalyst preparation.In the application, an active solution containing a first surfactant and a second surfactant is provided first, then a nickel source alcohol solution is added to the active solution which is subjected to ultrasonic treatment to obtain a nickel-containing mixed solution, then a pH regulator, an alcohol solvent and a silicon source are sequentially added to the nickel-containing mixed solution, a suspension is obtained after reaction, then the suspension is sequentially subjected to centrifugal, washing and drying treatment to obtain a precursor powder, the precursor powder is subjected to calcination treatment in an air atmosphere, a nickel silicate nanosphere intermediate is obtained, and reduction treatment is performed on the nickel silicate nanosphere intermediate in a reducing atmosphere, so that a three-dimensional supported nickel-nickel silicate catalyst is obtained.The nickel-nickel silicate catalyst has efficient photoelectrocatalytic performance, and exhibits excellent selectivity in a chlorine evolution reaction, and low-cost nickel is used to replace noble metal, so that the cost is significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to a nickel-nickel silicate catalyst, its preparation method, and its application. Background Technology

[0002] Chlorine, as the cornerstone of modern chemical industry, plays an irreplaceable role in commodity disinfection, wastewater treatment, pharmaceuticals, and polyvinyl chloride (PVC) synthesis. Global annual demand exceeds 75 million tons, and its production primarily relies on the energy-intensive chlor-alkali process. Currently, industrial-grade chlorine evolution catalysts mainly depend on precious metal oxides, with ruthenium-based and iridium-based materials as the core. However, the scarcity and high cost of ruthenium and iridium resources severely restrict their large-scale application. Furthermore, in the competition between the oxygen evolution reaction (OER) and the chlorine evolution reaction (CER), where thermodynamic potentials highly overlap, these catalysts often struggle to achieve efficient and selective control of chlorine evolution products. This not only leads to reduced Faraday efficiency but also poses safety hazards due to the generation of oxygen byproducts.

[0003] The nickel-coated nickel catalysts disclosed in the prior art are designed for water-gas shift reactions under gas phase conditions. However, the loading of metallic nickel on the nickel silicate substrate is low, resulting in a lack of a mechanism to regulate the separation efficiency of photogenerated carriers. Consequently, the catalysts cannot meet the requirements of the photocatalytic seawater co-evolution of chlorine and hydrogen in terms of photoresponse. Summary of the Invention

[0004] One objective of the first aspect of this invention is to provide a method for preparing a nickel-nickel silicate catalyst, thereby solving the technical problems of high cost, poor chlorine evolution selectivity, and low photocatalytic efficiency of precious metal catalysts in the prior art.

[0005] Another objective of the first aspect of this invention is to improve the stability of the catalyst for the reduction preparation of nickel-nickel silicate.

[0006] The second aspect of this invention aims to provide a nickel-nickel silicate catalyst prepared by a method for preparing a nickel-nickel silicate catalyst.

[0007] The third aspect of this invention aims to realize the application of nickel-nickel silicate catalysts in photocatalysis and / or electrocatalysis.

[0008] According to the first aspect of the present invention, the present invention provides a method for preparing a nickel-nickel silicate catalyst, comprising the following steps: An active solution comprising a first surfactant and a second surfactant is provided, wherein the first surfactant is polyvinylpyrrolidone and the second surfactant is selected from any one of sodium citrate, potassium citrate, tannic acid and ascorbic acid; Add a nickel-source alcohol solution to the ultrasonically treated active solution to obtain a nickel-containing mixed solution; A pH adjuster, an alcohol solvent, and a silicon source are added sequentially to the nickel-containing mixed solution, and a suspension is obtained after the reaction; wherein the molar ratio of the nickel source to the silicon source in the nickel source alcohol solution is any value in the range of 1:(0.8-1.2); The suspension was subjected to centrifugation, washing and drying in sequence to obtain precursor powder; The precursor powder was calcined in air to obtain nickel silicate nanosphere intermediates. The nickel silicate nanosphere intermediate is reduced in a reducing atmosphere to partially reduce nickel silicate to metallic nickel in situ. The reduction temperature is any value between 500℃ and 600℃, thereby obtaining a three-dimensional supported nickel-nickel silicate catalyst. The loading of metallic nickel in the nickel-nickel silicate catalyst is any value between 40wt% and 50wt%.

[0009] Optionally, the nickel source is selected from any one of nickel nitrate, nickel acetate, and nickel chloride; The molar concentration of nickel ions in the nickel source alcohol solution is any value between 0.1 mol / L and 0.3 mol / L.

[0010] Optionally, the silicon source is selected from any one of tetraethoxysilane, methyl orthosilicate, and propyl orthosilicate.

[0011] Optionally, the gas in the reducing atmosphere is hydrogen or a mixture of hydrogen and argon.

[0012] Optionally, the heating rate of the reduction treatment is any value between 5℃ / min and 10℃ / min, and the reduction time is any value between 2h and 3h.

[0013] Optionally, the calcination temperature is any value between 300℃ and 500℃, the heating rate is any value between 5℃ / min and 10℃ / min, and the treatment time is any value between 1h and 4h.

[0014] Optionally, the step of sequentially adding a pH adjuster, an alcohol solvent, and a silicon source to the nickel-containing mixed solution to react and form a suspension further includes the following steps: A pH adjuster is added to the nickel-containing mixed solution to adjust the pH value to 10-14, and the solution is ultrasonically treated to obtain an alkaline nickel-containing mixed solution. The pH adjuster is ammonia or urea. An alkaline nickel-containing alcohol-water system is prepared by adding an alcohol solvent to the alkaline nickel-containing mixed solution and then treating it with ultrasound. The alcohol solvent is at least one of methanol, ethanol, n-propanol, isopropanol, or n-butanol. The silicon source was added to the alkaline nickel-containing alcohol-water system, and the suspension was prepared after stirring for 20-60 minutes.

[0015] According to a second aspect of the present invention, the present invention also provides a nickel-nickel silicate catalyst prepared by the above preparation method, the nickel-nickel silicate catalyst comprising a nickel silicate substrate and metallic nickel, the nickel silicate substrate having a spherical three-dimensional network framework structure, the metallic nickel being loaded on the surface and inside the nickel silicate substrate, and the loading amount of metallic nickel in the nickel-nickel silicate catalyst being any value between 40wt% and 50wt%.

[0016] Optionally, the diameter of the nickel silicate substrate is any value between 150nm and 250nm, and the particle size of the metallic nickel is any value between 4nm and 5nm.

[0017] According to a third aspect of the present invention, the present invention also provides the application of the above-described nickel-nickel silicate catalyst in photocatalysis and / or electrocatalysis.

[0018] This invention utilizes the synergistic dispersion and morphology-directing effects of a first and a second surfactant in an active solution, combined with ultrasonic treatment and precise control of the molar ratio of nickel and silicon sources, to obtain nickel silicate nanosphere intermediates. Subsequently, in-situ reduction treatment at 500℃-600℃ in a reducing atmosphere causes some nickel in the nickel silicate lattice to precipitate and anchor in situ, thereby preparing a three-dimensional supported nickel-nickel silicate catalyst with a nickel loading of 40wt%-50wt%. This nickel-nickel silicate catalyst not only reduces costs by replacing expensive ruthenium and iridium catalysts with low-cost nickel-based materials, but also leverages the unique three-dimensional structure and plasmon resonance effect formed by the high nickel loading to enable photocatalysis and electrocatalysis, allowing for efficient chlorine evolution reaction (CHE) and hydrogen evolution reaction (HER), and improving the selectivity of the CHE reaction relative to the oxygen evolution reaction (OER).

[0019] Furthermore, the heating rate of the reduction treatment in this invention is any value between 5℃ / min and 10℃ / min, and the reduction time is any value between 2h and 3h.

[0020] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1This is a schematic flowchart of a method for preparing a nickel-nickel silicate catalyst according to an embodiment of the present invention; Figure 2 yes Figure 1 The diagram shown illustrates the process of forming a suspension. Figure 3 This is a schematic diagram of the synthesis of the nickel-nickel silicate catalyst according to Example 1 of the present invention; Figure 4 This is a transmission electron microscope image of the nickel-nickel silicate catalyst according to Example 1 of the present invention; Figure 5 This is an energy dispersive X-ray spectral elemental surface scan of the nickel-nickel silicate catalyst according to Example 1 of the present invention; Figure 6 This is the surface-enhanced Raman spectrum of the nickel-nickel silicate catalyst according to Example 1 of the present invention; Figure 7 This is a performance diagram of the nickel-nickel silicate catalyst according to Example 1 of the present invention for the chlorine evolution reaction; Figure 8 This is a performance diagram of the nickel-nickel silicate catalyst according to Example 1 of the present invention for the hydrogen evolution reaction; Figure 9 This is a comparison image of the nickel-nickel silicate catalyst under light and dark conditions according to Example 1 of the present invention; Figure 10 This is a comparison diagram of the on / off light of the nickel-nickel silicate catalyst according to Example 1 of the present invention; Figure 11 This is a diagram illustrating the chlorine evolution reaction performance of a nickel-nickel silicate catalyst in seawater according to Example 1 of the present invention. Figure 12 This is a statistical chart of the yield of pure photocatalysis using the nickel-nickel silicate catalyst according to Example 1 of the present invention; Figure 13 The graph shows the performance of the nickel-silica catalyst in the chlorine evolution reaction according to Comparative Example 1. Figure 14 The graph shows the performance of the hydrogen evolution reaction based on the nickel-silica catalyst in Comparative Example 1. Figure 15 The images are based on transmission electron microscopy images of the nickel-nickel silicate catalyst in Comparative Example 2. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0023] Figure 1 This is a schematic flowchart illustrating a method for preparing a nickel-nickel silicate catalyst according to an embodiment of the present invention.

[0024] like Figure 1As shown in a specific embodiment, a method for preparing a nickel-nickel silicate catalyst includes the following steps: Step S100: Provide an active solution comprising a first surfactant and a second surfactant, wherein the first surfactant is polyvinylpyrrolidone and the second surfactant is selected from any one of sodium citrate, potassium citrate, tannic acid and ascorbic acid; Step S200: Add nickel source alcohol solution to the ultrasonically treated active solution to obtain a nickel-containing mixed solution; In step S300, a pH adjuster, an alcohol solvent, and a silicon source are added sequentially to a nickel-containing mixed solution, and a suspension is obtained after the reaction; wherein, the molar ratio of nickel source to silicon source in the nickel source alcohol solution is any value in the range of 1:(0.8-1.2); In step S400, the suspension is centrifuged, washed, and dried sequentially to obtain precursor powder. Step S500: The precursor powder is calcined in air to obtain nickel silicate nanosphere intermediate. In step S600, the nickel silicate nanosphere intermediate is reduced in a reducing atmosphere to reduce some of the nickel silicate to metallic nickel in situ. The reduction temperature is any value between 500℃ and 600℃, thereby obtaining a three-dimensional supported nickel-nickel silicate catalyst. The loading of metallic nickel in the nickel-nickel silicate catalyst is any value between 40wt% and 50wt%.

[0025] In this embodiment, the synergistic dispersion and morphology-directing effects of the first and second surfactants in the active solution, combined with ultrasonic treatment and precise control of the molar ratio of nickel and silicon sources, yielded nickel silicate nanosphere intermediates. Subsequently, in-situ reduction treatment at 500℃-600℃ in a reducing atmosphere caused some nickel in the nickel silicate lattice to precipitate and anchor in situ, thereby preparing a three-dimensional supported nickel-nickel silicate catalyst with a nickel loading of 40wt%-50wt%. This nickel-nickel silicate catalyst not only reduces costs by replacing expensive ruthenium and iridium catalysts with low-cost nickel-based materials, but also utilizes the unique three-dimensional structure and plasmon effect formed by the high nickel loading to enable photocatalysis and electrocatalysis, allowing for efficient chlorine evolution reaction (CHE) and hydrogen evolution reaction (HER), and improving the selectivity of the CHE reaction relative to the oxygen evolution reaction (OER).

[0026] In step S100, a first surfactant aqueous solution and a second surfactant aqueous solution are provided. The first surfactant aqueous solution and the second surfactant aqueous solution together form an active solution. The concentration of the first surfactant aqueous solution is any value between 8 mg / mL and 12 mg / mL, for example, 8 mg / mL, 10 mg / mL, 11 mg / mL or 12 mg / mL, or any other value between 8 mg / mL and 12 mg / mL. The average molecular weight of polyvinylpyrrolidone is any value between 8000 and 12000, for example, 8000, 10000, 11000 or 12000, or any other value between 8000 and 12000. The concentration of the second surfactant aqueous solution is any value between 0.15 mol / L and 0.3 mol / L, for example, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L, or any other value between 0.15 mol / L and 0.3 mol / L.

[0027] In step S200, a nickel source alcohol solution is added to the ultrasonically treated active solution. Utilizing the cavitation oscillation effect generated by ultrasound, the nickel source alcohol solution can instantly achieve uniform mixing with the active solution at the microscopic scale. During this process, the first surfactant in the active solution utilizes the steric hindrance effect of its polymer chain to construct a physical barrier, preventing the aggregation of high-concentration nickel ions due to mutual collisions. Meanwhile, the second surfactant mainly plays a role in complexation, slow release, and kinetic regulation. Utilizing the abundant carboxyl or hydroxyl functional groups in its molecular structure, the second surfactant can undergo strong coordination complexation with nickel ions. This complexation effectively reduces the concentration of free nickel ions in the nickel-containing mixed solution, avoiding the aggregation problem caused by explosive precipitation in high-concentration systems. This ensures that the nickel-containing mixed solution can maintain a homogeneous and stable dispersion state while accommodating extremely high nickel content, laying a key foundation for the subsequent construction of a high-loading and highly dispersed three-dimensional catalyst structure. In other embodiments, if both the first surfactant and the second surfactant are P123, F127 or P40 as template agents, these template agents are bulky and lack the ability to chemically complex high concentrations of nickel ions. Once the nickel source concentration is too high, these template agents cannot suppress the explosive aggregation of nickel ions. Therefore, the prior art can only achieve a low nickel loading and cannot achieve the high loading and high dispersion effect of the present invention.

[0028] In step S200, the nickel source is selected from any one of nickel nitrate, nickel acetate, and nickel chloride. The molar concentration of nickel ions in the nickel source alcohol solution is any value between 0.1 mol / L and 0.3 mol / L, for example, it can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or 0.3 mol / L, or any other value between 0.1 mol / L and 0.3 mol / L. The alcohol solvent in the nickel source alcohol solution is any one of methanol, ethanol, n-propanol, or isopropanol. The alcohol solvent can not only dissolve the nickel source well, but also promote the micro-mixing of the nickel source with the active solution under the action of ultrasound.

[0029] In step S300, the silicon source is selected from any one of tetraethoxysilane, methyl orthosilicate, and propyl orthosilicate. The molar ratio of nickel source to silicon source in the nickel source alcohol solution can be, for example, 1:0.8, 1:1, 1:1.5, or 1:1.2, or any other value of 1:(0.8-1.2). Setting the molar ratio of nickel source to silicon source to 1:(0.8-1.2) can ensure that, with a relatively small amount of silicon source compared to nickel source, a high loading of metallic nickel in the nickel-nickel silicate catalyst can be achieved through the setting of the first surfactant, the second surfactant, and the reduction temperature.

[0030] Figure 2 yes Figure 1 The diagram shows a schematic flow chart for the formation of a suspension. Figure 2 As shown, step S300 further includes the following steps: Step S310: Add a pH adjuster to the nickel-containing mixed solution to adjust the pH value to 10-14, and sonicate to obtain an alkaline nickel-containing mixed solution. The pH adjuster is ammonia or urea. Step S320: Add an alcohol solvent to an alkaline nickel-containing mixed solution, and prepare an alkaline nickel-containing alcohol-water system after ultrasonic treatment. The alcohol solvent is at least one of methanol, ethanol, n-propanol, isopropanol or n-butanol. Step S330: Add a silicon source to an alkaline nickel-containing alcohol-water system and prepare a suspension after stirring for 20-60 minutes.

[0031] In step S310, the mass fraction of ammonia or urea is 25%-28%, for example, 25%, 26%, 27%, or 28%, or any other value within the 25%-28% range. The pH value of the alkaline nickel-containing mixed solution is, for example, 10, 12, 13, or 14, or any other value within the 10-14 range. In step S200, the second surfactant achieves preliminary complexation and stabilization of nickel ions. Combined with the cooperative coordination mechanism of ammonia molecules, it transforms the originally weakly complexed or equilibrium free state of nickel ions into more stable nickel-ammonia complex ions under strongly alkaline conditions, providing dual protection against strong alkaline precipitation of nickel ions and ensuring the successful preparation of the subsequent nickel-nickel silicate catalyst.

[0032] In step S320, although some alcohol solvent was introduced in step S200 to dissolve the nickel source, the aqueous pH adjuster added in step S310 introduced a large amount of water, causing the alkaline nickel-containing mixed solution to become a water-rich solution. The alcohol concentration of the alkaline nickel-containing mixed solution was diluted to a level that could not meet the requirements of subsequent processes. Therefore, by adding alcohol solvent again in step S320, not only can the stratification or emulsification of the silicon source after entering the water-rich system be prevented, but the solvation effect of alcohol can also be used to moderately suppress the hydrolysis rate of the silicon source under strong alkaline conditions. Adding alcohol solvent to the alkaline nickel-containing mixed solution is a necessary process condition to ensure that the nickel-nickel silicate catalyst can form a regular spherical morphology and not agglomerate.

[0033] In step S330, under alkaline conditions and continuous mechanical stirring, the added silicon source rapidly undergoes hydrolysis and condensation reactions to generate active silicate ions as a structural framework. These ions capture and chemically anchor complexed nickel ions in the alkaline nickel-containing alcohol-water system in situ, thereby achieving uniform co-precipitation of nickel and silicon at the molecular level and preparing a suspension. The stirring time is any value between 20 min and 60 min, such as 20 min, 40 min, 50 min, or 60 min, or any other value between 20 min and 60 min, ensuring a precursor suspension with excellent dispersibility and uniform particle size, and effectively avoiding agglomeration caused by excessively long reaction time.

[0034] In step S400, the suspension is centrifuged to remove the reaction mother liquor, and then washed repeatedly with water and ethanol alternately. After drying, a pure and well-dispersed precursor powder is obtained.

[0035] In step S500, the calcination temperature is any value between 300℃ and 500℃, for example, 300℃, 400℃, or 500℃, or any other value between 300℃ and 500℃. The heating rate is any value between 5℃ / min and 10℃ / min, for example, 5℃ / min, 7℃ / min, or 10℃ / min, or any other value between 5℃ / min and 10℃ / min. The treatment time is any value between 1h and 4h, for example, 1h, 2h, 3h, or 4h, or any other value between 1h and 4h. The precursor powder is calcined in air at 300℃-500℃, causing dehydration and shrinkage within the powder. This brings the previously loosely connected nickel and silicate ions closer together, forming silicon-oxygen-nickel bonds. Simultaneously, oxygen in the air is used as a strong oxidant to thoroughly remove residual organic impurities from the precursor powder, yielding a nickel silicate nanosphere intermediate. This intermediate possesses a stable nickel silicate framework capable of withstanding subsequent high-temperature reduction. Furthermore, the target product, the nickel silicate nanosphere intermediate, is chemically stable in air and requires no oxidation prevention. Direct air treatment not only ensures the purity of the intermediate but also eliminates the need for complex inert gas protection equipment, effectively reducing production costs.

[0036] In step S600, the temperature range of the reduction treatment is set to 500℃-600℃, for example, it can be 500℃, 520℃, 550℃, 580℃ or 600℃, or any other value in the range of 500℃-600℃. As the reduction temperature is appropriately increased within this range, more nickel ions are reduced and precipitated in situ as catalytically active metallic nickel, increasing the number of active sites, thereby directly improving the catalytic performance of the nickel-nickel silicate catalyst. The higher the reduction temperature, the more metallic nickel is reduced. However, when the reduction temperature exceeds 600℃, the generated metallic nickel particles undergo violent thermal motion and fuse with each other, resulting in agglomeration, which reduces the catalytic activity of the nickel-nickel silicate catalyst. In addition, the loading of metallic nickel in the nickel-nickel silicate catalyst is any value between 40wt% and 50wt%, for example, it can be 40wt%, 43wt%, 45wt%, 48wt% or 50wt%, or any other value between 40wt% and 50wt%, indicating that the metallic nickel in the nickel-nickel silicate catalyst has a high loading.

[0037] In step S600, the reducing atmosphere can be selected from pure hydrogen or a mixture of hydrogen and argon, depending on the actual process requirements. Using pure hydrogen facilitates completing the reduction process in a shorter time, making it suitable for industrial scenarios with high requirements for production efficiency and cost control. When using a mixture of hydrogen and argon, argon acts as an inert dilution medium, effectively reducing the partial pressure of hydrogen, thus playing a role in the slow-release regulation of the reduction reaction kinetics. This prevents localized overheating and agglomeration of metal particles caused by excessively fast reaction rates or concentrated heat release, making it suitable for precision manufacturing scenarios with extremely high requirements for the microstructure of nickel-nickel silicate catalysts. The heating rate of the reduction treatment is any value between 5℃ / min and 10℃ / min, for example, 5℃ / min, 7℃ / min, 9℃ / min, or 10℃ / min, and the reduction duration is any value between 2h and 3h, for example, 2h, 2.5h, or 3h.

[0038] This invention also provides a nickel-nickel silicate catalyst, prepared by the aforementioned method. The catalyst comprises a nickel silicate substrate and metallic nickel. The nickel silicate substrate has a spherical three-dimensional network framework structure, with metallic nickel supported on the surface and interior of the substrate. The loading of metallic nickel in the nickel-nickel silicate catalyst is any value between 40 wt% and 50 wt%. The nickel silicate substrate, as a supporting framework, not only endows the nickel-nickel silicate catalyst with good mechanical strength, but its abundant porous structure also provides efficient mass transfer channels for reactant molecules. Metallic nickel particles grow in situ on the surface and interior of the nickel silicate substrate in a highly dispersed form. This unique distribution utilizes the strong interaction and spatial confinement effect of the nickel silicate framework on the metal particles, effectively preventing the agglomeration of metal particles under high loading. In particular, the ultra-high metallic nickel loading of 40 wt%-50 wt% enables the nickel-nickel silicate catalyst to exhibit catalytic activity far exceeding that of conventional supported catalysts while maintaining excellent structural stability.

[0039] In some embodiments, the diameter of the nickel silicate substrate is any value between 150nm and 250nm, for example, it can be 150nm, 180nm, 200nm or 250nm, or any other value between 150nm and 250nm, and the particle size of the metallic nickel is any value between 4nm and 5nm, for example, it can be 4nm, 4.5nm or 5nm, or any other value between 4nm and 5nm.

[0040] The nickel-nickel silicate catalyst of this invention can be applied in photocatalysis and / or electrocatalysis. In electrocatalysis, the metallic nickel particles in the nickel-nickel silicate catalyst are used for the hydrogen evolution reaction (HER), while the nickel silicate substrate is used for the chlorine evolution reaction (CHE). In photocatalysis, the nickel-nickel silicate catalyst, through its unique heterostructure, achieves the directional separation and utilization of photogenerated carriers, thereby synergistically driving the HER and CHE reactions. In both photocatalysis and electrocatalysis, the CHE and OX reactions compete. This nickel silicate framework, through its special surface electronic structure and adsorption characteristics, preferentially adsorbs chloride ions and promotes their oxidation kinetics. This effectively suppresses the thermodynamically superior OX side reaction, ensuring that the nickel-nickel silicate catalyst exhibits excellent HER activity while achieving high selectivity and high efficiency for the CHE reaction. The following detailed description uses specific embodiments and comparative examples. Example 1:

[0041] This embodiment provides a method for preparing a nickel-nickel silicate catalyst, the method comprising: Step S111: Provide 15 mL of 10 mg / mL polyvinylpyrrolidone aqueous solution and 300 μL of 0.2 mol / L sodium citrate aqueous solution. The polyvinylpyrrolidone aqueous solution and the sodium citrate aqueous solution together form an active solution. The molecular weight of polyvinylpyrrolidone is 1000. Step S121: Add nickel nitrate hexahydrate [Ni(NO3)2·6H2O]ethanol solution to the ultrasonically treated active solution to obtain a nickel-containing mixed solution. The molar concentration of nickel ions in the nickel source alcohol solution is 0.2 mol / L. Step S131: Add 2.9 ml of ammonia water with a mass fraction of 25% to the nickel-containing mixed solution to adjust the pH value to 10, and sonicate for 3 min to obtain an alkaline nickel-containing mixed solution. Step S132: Add 32.5 mL of ethanol to the alkaline nickel-containing mixed solution, and then sonicate for 3 min to prepare an alkaline nickel-containing alcohol-water system. Step S133: Add 100 μL of tetraethoxysilane (TEOS) to an alkaline nickel-containing alcohol-water system, and prepare a suspension after stirring for 30 min. Step S141: The suspension is centrifuged, washed with deionized water and ethanol eight times in sequence, and dried to obtain precursor powder. Step S151: The precursor powder is calcined at 400°C for 2 hours in air atmosphere with a heating rate of 5°C / min to obtain nickel silicate nanosphere intermediate. In step S161, the nickel silicate nanosphere intermediate is reduced at 550°C for 2 hours under a hydrogen atmosphere with a heating rate of 5°C / min, so that part of the nickel silicate is reduced in situ to metallic nickel, thereby obtaining a three-dimensional supported nickel-nickel silicate (Ni / Ni2SiO4) catalyst. The loading of metallic nickel in the nickel-nickel silicate catalyst is 45wt%. The nickel-nickel silicate catalyst includes a nickel silicate substrate (Ni2SiO4) and metallic nickel (Ni).

[0042] Figure 3 This is a schematic diagram of the synthesis of the nickel-nickel silicate catalyst according to Example 1 of the present invention. Figure 3 This visually demonstrates the preparation process and microstructure evolution of the nickel-nickel silicate catalyst in Example 1 of the present invention. Figure 3 The mid-section structure clearly reveals the structural features of the nickel-nickel silicate catalyst. The metallic nickel particles are not only uniformly distributed on the outer surface of the nickel silicate substrate, but are also in situ anchored in its internal channels, forming a spherical nickel-nickel silicate catalyst structure with high nickel metal loading and excellent dispersion.

[0043] Figure 4 This is a transmission electron microscope image of the nickel-nickel silicate catalyst according to Example 1 of the present invention. Figure 4 As shown, Figure 4 The scale bar in the lower left corner is 10nm. It can be observed that dark-colored metallic nickel particles are uniformly dispersed on the surface of the nickel silicate substrate, exhibiting good monodispersity and no obvious agglomeration. The particle size of the metallic nickel is 4nm-5nm. Figure 4 The magnified view of the area selected by the white box clearly shows the orderly arranged lattice stripes. The measurement shows that the spacing between adjacent crystal planes is 0.2 nm, which is consistent with the standard spacing between the (111) crystal planes of metallic nickel. This confirms that after reduction treatment, metallic nickel was successfully reduced and stably anchored on the nickel silicate substrate in a highly crystalline form.

[0044] Figure 5 This is an energy-dispersive X-ray spectral elemental surface scan of the nickel-nickel silicate catalyst according to Example 1 of the present invention. Figure 5 As shown, the nickel-nickel silicate catalyst contains nickel, silicon, and oxygen elements, and these elements exhibit a highly overlapping and uniform distribution within the catalyst, without local agglomeration or element segregation.

[0045] Figure 6 This is the surface-enhanced Raman spectrum of the nickel-nickel silicate catalyst according to Example 1 of the present invention. Figure 6 As shown, terpyridine iron ions ([Fe(bpy)3]) 2+As a standard Raman probe molecule, [Fe(bpy)3] primarily utilizes its high sensitivity to electromagnetic fields to visually characterize and verify the localized surface plasmon resonance effect generated by metallic nickel particles by observing the significant increase in the intensity of its characteristic peaks. After introducing a nickel-nickel silicate catalyst, the tag molecule [Fe(bpy)3]... 2+ The characteristic Raman peak intensity showed a significant gain effect, with its signal intensity increasing by 5 to 6 times compared to the nickel-free nickel silicate catalyst. This confirms that the nickel particles supported in the nickel-silicon silicate catalyst have a strong local surface plasmon resonance effect in the 532nm band. The plasmon resonance effect not only enhances the local electromagnetic field, but also indicates that the nickel-silicon silicate catalyst has excellent light-harvesting ability and photoresponse characteristics, proving that it can efficiently utilize incident light energy to drive photocatalytic reactions.

[0046] Figure 7 This is a performance diagram of the nickel-nickel silicate catalyst according to Example 1 of the present invention for the chlorine evolution reaction. Figure 7 As shown, in a NaCl electrolyte with pH=2 and a concentration of 4M, the potential was set to 1.6V relative to the reversible hydrogen electrode. The 15min, 30min, and 60min values ​​in the figure represent the time for the chlorine evolution reaction at each light intensity. Here, 0 is defined as dark conditions, and one solar irradiance is defined as 100mW / cm². 2 Two solar irradiance values ​​are defined as 200 mW / cm². 2 The three solar irradiance values ​​are defined as 300 mW / cm². 2 The photoelectrocatalytic performance of the nickel-nickel silicate catalyst obtained in Example 1 for chlorine evolution was tested. The experimental results showed that the nickel-nickel silicate catalyst exhibited a significant enhancement in light response. When the applied light intensity increased from a dark environment to three times the intensity of sunlight, the chlorine evolution yield increased from 0.6 μmol to 1.6 μmol after 60 min of reaction, and the selectivity increased from 95% to 98%. This confirms that the nickel-nickel silicate catalyst possesses excellent photoelectrocatalytic performance in the chlorine evolution reaction and exhibits superior selectivity for chlorine evolution.

[0047] Figure 8 This is a performance diagram of the nickel-nickel silicate catalyst according to Example 1 of the present invention for the hydrogen evolution reaction. Figure 8 As shown, in a 0.5M H₂SO₄ electrolyte, the potential was set to 0.6V relative to the reversible hydrogen electrode. The 15min, 30min, and 60min values ​​in the figure represent the time for the chlorine evolution reaction at each light intensity. Here, 0 is defined as dark conditions, and one solar irradiance is defined as 100mW / cm². 2 Two solar irradiance values ​​are defined as 200 mW / cm². 2 The three solar irradiance values ​​are defined as 300 mW / cm². 2The photoelectrochemical hydrogen evolution performance of the nickel-nickel silicate catalyst obtained in Example 1 was tested. The experimental results showed that the nickel-nickel silicate catalyst exhibited significant photoresponse enhancement characteristics. When the applied light intensity increased from a dark environment to three times the intensity of sunlight, the hydrogen evolution yield after 60 minutes of reaction showed an increasing trend, and the hydrogen evolution reaction rate increased from 0.4 mol·gcat. -1 ·h -1 Increased to 0.6 mol·gcat -1 ·h -1 This study confirmed that the proton reduction kinetics in acidic media were significantly improved through photoelectro-photocatalytic synergy, and that the nickel-nickel silicate catalyst exhibited excellent photoelectrocatalytic performance in the hydrogen evolution reaction.

[0048] Figure 9 This is a comparison image of the nickel-nickel silicate catalyst under light and dark conditions according to Example 1 of the present invention. Figure 9 As shown, the current density measured under illumination is significantly higher than that under darkness, indicating that illumination has a significant boosting effect on the catalytic reaction. Furthermore, during a continuous test period of up to 500 minutes, the current density of the nickel-nickel silicate catalyst under illumination remained at a relatively stable high level, and the curve did not show obvious fluctuations or attenuation trends. This confirms that the nickel-nickel silicate catalyst has excellent photoelectrochemical stability and can maintain high catalytic activity continuously during long-term operation.

[0049] Figure 10 This is a comparison diagram of the on / off state of the nickel-nickel silicate catalyst according to Example 1 of the present invention. Figure 10 As shown, blue arrows represent the addition of light and black arrows represent the removal of light. The nickel-nickel silicate catalyst exhibits a keen and reversible response to changes in light intensity and light removal, and maintains a stable and significant photocurrent gain over multiple cycles, thus demonstrating that the nickel-nickel silicate catalyst possesses excellent and efficient photoelectrocatalytic performance.

[0050] Figure 11 This is a performance diagram of the chlorine evolution reaction of a nickel-nickel silicate catalyst in seawater according to Example 1 of the present invention. Figure 11As shown, the electrochemical performance was tested using a three-electrode system. The nickel-nickel silicate catalyst underwent chlorine evolution reaction in seawater using a silver / silver chloride electrode (Ag / AgCl) as the reference electrode. In the figure, Ni / Ni₂SiO₄⁻¹ represents the nickel-nickel silicate catalyst tested under dark conditions, and Ni / Ni₂SiO₄⁻² represents the nickel-nickel silicate catalyst tested under three different solar irradiance intensities. The results show that even in a real seawater environment with relatively low chloride ion concentrations and complex ionic composition, the nickel-nickel silicate catalyst still exhibits excellent catalytic activity and reaction specificity, achieving high chlorine yields and maintaining high selectivity for the chlorine evolution reaction. This confirms that the nickel-nickel silicate catalyst possesses excellent environmental adaptability and anti-interference capabilities, demonstrating great potential for application in practical seawater direct electrolysis industries.

[0051] Figure 12 This is a statistical graph showing the yield of pure photocatalysis using the nickel-nickel silicate catalyst according to Example 1 of the present invention. Figure 12 As shown, in the reaction system driven solely by light energy, extending the irradiation time from 3 h to 8 h resulted in a synchronous and stable increase in the product yields of both the chlorine evolution reaction and the hydrogen evolution reaction. Simultaneously, the competing oxygen evolution byproduct was almost entirely absent. This indicates that the nickel-nickel silicate catalyst possesses excellent photocatalytic activity, capable of efficiently driving carrier separation solely by capturing light energy, thereby achieving highly selective co-production of chlorine and hydrogen. The diagram shows CER as the chlorine evolution reaction, HER as the hydrogen evolution reaction, and OER as the oxygen evolution reaction.

[0052] Comparative Example 1: The only difference between Comparative Example 1 and Example 1 is that the nickel-containing mixed solution does not include the first surfactant and the second surfactant, and the silicon source is silicon dioxide.

[0053] Figure 13 This is a performance diagram of the chlorine evolution reaction based on the nickel-silica catalyst in Comparative Example 1. Figure 13 Conditions for chlorine evolution reaction using nickel-silica catalyst and Figure 7 The chlorine evolution reaction conditions are consistent, by Figure 13 It can be seen that the yield of the nickel-silica catalyst under 1 solar irradiance for 60 min is only 0.3 μmol, and the chlorine evolution selectivity is about 76%. This indicates that the photoelectrocatalytic performance of the nickel-silica catalyst is much lower than that of the nickel-nickel silicate catalyst obtained in Example 1. This, in turn, proves the advantages and inventiveness of the nickel-nickel silicate catalyst in this application in synergistically improving photoelectrocatalytic activity and product selectivity.

[0054] Figure 14 This is a performance diagram of the hydrogen evolution reaction based on the nickel-silica catalyst in Comparative Example 1. Figure 14 Conditions for hydrogen evolution reaction using nickel-silica catalyst and Figure 8 The hydrogen evolution reaction conditions are consistent, by Figure 14 It was found that under 1 solar irradiance, the hydrogen production after 60 minutes was only about 1.0 mmol, and the hydrogen evolution performance of this nickel-silica catalyst did not improve with increasing light intensity. This confirms that a single nickel-silica catalyst lacks an effective photoelectric synergistic mechanism and cannot achieve efficient photocatalytic hydrogen evolution.

[0055] Comparative Example 2: The only difference between Comparative Example 2 and Example 1 is that the active solution does not contain a second surfactant, i.e., it does not contain sodium citrate.

[0056] Figure 15 This is based on the transmission electron microscope image of the nickel-nickel silicate catalyst in Comparative Example 2. (e.g.) Figure 15 As shown, since sodium citrate was not added during the preparation of Comparative Example 2, the resulting nickel-nickel silicate catalyst exhibited obvious agglomeration and uneven distribution characteristics, indicating that sodium citrate plays an important role in regulating the size of metallic nickel particles, inhibiting agglomeration, and increasing the density of active sites during the synthesis process.

[0057] Table 1 below shows the comparison results of the overall performance of the catalysts prepared in the examples and the comparative examples.

[0058] The nickel-nickel silicate catalyst of Example 1 exhibits superior performance in all aspects. First, in terms of chlorine evolution selectivity, Example 1 achieves 98%, far exceeding Comparative Example 1 and Comparative Example 2, demonstrating the high efficiency and excellent selectivity of the nickel-nickel silicate catalyst in the chlorine evolution reaction. Regarding photoelectrocatalytic efficiency, Example 1 achieves 90%, significantly higher than Comparative Example 1 and Comparative Example 2, indicating a significant advantage in photoelectrocatalytic activity under enhanced light. The photoresponse enhancement coefficient of Example 1 is 6.0, higher than Comparative Example 1 and Comparative Example 2, indicating that it can more effectively utilize light to enhance the reaction rate. Furthermore, Example 1 demonstrates strong durability in long-term stability, with a stability of up to 95%, while the stability of Comparative Example 1 and Comparative Example 2 is 70% and 78%, respectively, indicating that the nickel-nickel silicate catalyst of Example 1 is more reliable in long-term operation. Finally, in terms of catalytic activity retention, Example 1 has a retention rate of 92%, significantly better than Comparative Example 1 (70%) and Comparative Example 2, proving that it has a longer catalytic activity maintenance time and better reusability.

[0059] Comparative Example 1 lacked both the first and second surfactants, resulting in a significant decrease in its catalytic performance. Both its chlorine evolution selectivity and photoelectrocatalytic efficiency were significantly lower than those of Example 1. Meanwhile, Comparative Example 2, while retaining the first surfactant, lacked the second surfactant, leading to agglomeration of its nickel-nickel silicate catalyst, which affected its catalytic activity and stability. Therefore, the nickel-nickel silicate catalyst of Example 1 exhibits high selectivity, high catalytic efficiency, and excellent stability, verifying the innovation and practical value of the nickel-nickel silicate catalyst of this invention.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a nickel-nickel silicate catalyst, characterized in that, Includes the following steps: An active solution comprising a first surfactant and a second surfactant is provided, wherein the first surfactant is polyvinylpyrrolidone and the second surfactant is selected from any one of sodium citrate, potassium citrate, tannic acid and ascorbic acid; Add a nickel-source alcohol solution to the ultrasonically treated active solution to obtain a nickel-containing mixed solution; A pH adjuster, an alcohol solvent, and a silicon source are added sequentially to the nickel-containing mixed solution, and a suspension is obtained after the reaction; wherein the molar ratio of the nickel source to the silicon source in the nickel source alcohol solution is any value in the range of 1:(0.8-1.2); The suspension was subjected to centrifugation, washing and drying in sequence to obtain precursor powder; The precursor powder was calcined in air to obtain nickel silicate nanosphere intermediates. The nickel silicate nanosphere intermediate is reduced in a reducing atmosphere to partially reduce nickel silicate to metallic nickel in situ. The reduction temperature is any value between 500℃ and 600℃, thereby obtaining a three-dimensional supported nickel-nickel silicate catalyst. The loading of metallic nickel in the nickel-nickel silicate catalyst is any value between 40wt% and 50wt%.

2. The preparation method according to claim 1, characterized in that, The nickel source is selected from any one of nickel nitrate, nickel acetate, and nickel chloride; The molar concentration of nickel ions in the nickel source alcohol solution is any value between 0.1 mol / L and 0.3 mol / L.

3. The preparation method according to claim 2, characterized in that, The silicon source is selected from any one of tetraethoxysilane, methyl orthosilicate, and propyl orthosilicate.

4. The preparation method according to claim 3, characterized in that, The gas in the reducing atmosphere is hydrogen or a mixture of hydrogen and argon.

5. The preparation method according to claim 4, characterized in that, The heating rate of the reduction treatment is any value between 5℃ / min and 10℃ / min, and the reduction time is any value between 2h and 3h.

6. The preparation method according to claim 5, characterized in that, The calcination treatment temperature is any value between 300℃ and 500℃, the heating rate is any value between 5℃ / min and 10℃ / min, and the treatment time is any value between 1h and 4h.

7. The preparation method according to claim 6, characterized in that, The step of sequentially adding a pH adjuster, an alcohol solvent, and a silicon source to the nickel-containing mixed solution to react and form a suspension further includes the following steps: A pH adjuster is added to the nickel-containing mixed solution to adjust the pH value to 10-14, and the solution is ultrasonically treated to obtain an alkaline nickel-containing mixed solution. The pH adjuster is ammonia or urea. An alkaline nickel-containing alcohol-water system is prepared by adding an alcohol solvent to the alkaline nickel-containing mixed solution and then treating it with ultrasound. The alcohol solvent is at least one of methanol, ethanol, n-propanol, isopropanol, or n-butanol. The silicon source was added to the alkaline nickel-containing alcohol-water system, and the suspension was prepared after stirring for 20-60 minutes.

8. A nickel-nickel silicate catalyst prepared by the method according to any one of claims 1-7, characterized in that, The nickel-nickel silicate catalyst comprises a nickel silicate substrate and metallic nickel. The nickel silicate substrate has a spherical three-dimensional network framework structure, and the metallic nickel is loaded on the surface and inside the nickel silicate substrate. The loading of metallic nickel in the nickel-nickel silicate catalyst is any value between 40wt% and 50wt%.

9. The nickel-nickel silicate catalyst according to claim 8, characterized in that, The diameter of the nickel silicate substrate is any value between 150nm and 250nm, and the particle size of the metallic nickel is any value between 4nm and 5nm.

10. The application of the nickel-nickel silicate catalyst according to any one of claims 8-9 in photocatalysis and / or electrocatalysis.

Images