Visible light catalyst capable of efficiently producing hydrogen peroxide and preparation method of visible light catalyst

Abstract

The invention relates to the technical field of preparation of hydrogen peroxide through visible light catalysis, in particular to a visible light catalyst capable of efficiently producing hydrogen peroxide and a preparation method thereof.The preparation method comprises the following steps that S100, urea serving as a carbon and nitrogen source and yttrium nitrate serving as a yttrium source are dissolved in deionized water respectively, then the urea and the yttrium nitrate are mixed and stirred to be uniform, and a mixed solution is obtained; s200, drying the mixed solution until the solvent is completely removed to obtain a solid precursor; s300, the solid precursor is placed in a high-temperature-resistant container for high-temperature calcination, yttrium ions are introduced into crystal lattices of the generated graphite phase carbon nitride through thermal polymerization, and a calcined product is obtained; according to the preparation method disclosed by the invention, metal yttrium ions in a specific proportion are successfully and uniformly embedded into two-dimensional layered crystal lattices of graphite-phase carbon nitride through a preparation process of refined respective dissolution, titration and mixing, thermal polymerization in a semi-closed environment and alternate washing of dilute acid and ethanol matched with freeze drying.

Description

A highly efficient visible light photocatalyst for hydrogen peroxide production and its preparation method Technical Field

[0001] This invention relates to the field of visible light photocatalysis for hydrogen peroxide production, specifically to a highly efficient visible light photocatalyst for hydrogen peroxide production and its preparation method. Background Technology

[0002] Hydrogen peroxide (H2O2), as a high-value-added, environmentally friendly strong oxidant, plays a crucial role in modern chemical and energy systems. Due to its efficient oxidation reaction and clean decomposition products of only water and oxygen (H2O and O2), H2O2 is widely used in key areas such as paper and textile bleaching, water purification, organic chemical synthesis, and medical disinfection. Furthermore, compared to gaseous hydrogen energy, H2O2 exists in liquid form, possessing higher energy density and water solubility, significantly reducing safety risks and costs in storage and transportation. Therefore, it is also considered a highly promising liquid energy carrier in the fuel cell field. With the global emphasis on green and sustainable development, the market demand for H2O2 is experiencing explosive growth, and its global market size is projected to approach 5.7 million tons by 2027, indicating a promising future.

[0003] Despite the urgent demand, the industrial production of H2O2 still heavily relies on the traditional anthraquinone process. This method not only requires expensive precious metals such as palladium (Pd) or nickel (Ni) as catalysts, but also needs to be carried out in a high-pressure hydrogen atmosphere and an organic solvent system composed of aromatics and alcohols. This energy-intensive and polluting production mode has significant drawbacks: on the one hand, the introduction of flammable and explosive hydrogen and organic solvents poses a huge safety hazard; on the other hand, precious metal catalysts not only increase production costs, but also require cumbersome filtration processes to prevent them from inducing the ineffective decomposition of H2O2.

[0004] Therefore, exploring a safe, low-consumption, and environmentally friendly new route for the synthesis of H2O2 has become a research hotspot. In recent years, graphitic carbon nitride has shown great potential in the photocatalytic preparation of hydrogen peroxide. Graphitic carbon nitride possesses a graphene-like two-dimensional layered conjugated structure, endowing it with excellent chemical stability. Its bandgap is suitable, corresponding to a visible light absorption band of approximately 460 nm, enabling effective capture and utilization of visible light energy. Furthermore, graphitic carbon nitride exhibits excellent thermal stability (withstanding temperatures up to 600℃) and acid-base stability, and its preparation process is simple. However, bulk graphitic carbon nitride suffers from problems such as low specific surface area, insufficient exposure of catalytically active sites; a relatively fast recombination rate of photogenerated electrons and holes, resulting in low quantum efficiency; and a narrow visible light absorption bandgap, preventing full utilization of light resources, thus leading to lower photocatalytic reaction efficiency. Studies have shown that yttrium doping can introduce impurity energy levels, expanding the visible light absorption range; as an electron trapping center, it can significantly reduce carrier recombination rate and improve quantum efficiency; and by adjusting the band structure, it can improve specific surface area and enhance photocatalytic activity. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a highly efficient visible light catalyst for producing hydrogen peroxide and its preparation method, comprising the following steps: S100: urea as a carbon and nitrogen source and yttrium nitrate as a yttrium source are dissolved separately in deionized water, and then the two are mixed and stirred evenly to obtain a mixed solution;

[0007] S200: The mixed solution is dried until the solvent is completely removed to obtain a solid precursor;

[0008] S300: The solid precursor is placed in a high-temperature resistant container for high-temperature calcination. Yttrium ions are introduced into the lattice of the generated graphitic carbon nitride through thermal polymerization to obtain the calcined product.

[0009] S400: The calcined product is alternately washed with dilute acid solution and alcohol to etch and remove the impurity phase generated during calcination. After separation, purification, and drying, the visible light photocatalyst is obtained; wherein the yttrium loading ratio in the prepared visible light photocatalyst is limited to [specific value missing]. .

[0010] Furthermore, in step S100, the yttrium nitrate specifically used is yttrium nitrate hexahydrate. ;

[0011] Urea is dissolved in deionized water and stirred until completely dissolved to obtain a urea solution; yttrium nitrate is dissolved in deionized water to obtain a yttrium nitrate solution, and then the yttrium nitrate solution and the urea solution are mixed by stirring and titration to obtain the mixed solution;

[0012] The mass of urea added is 10g, and the mass of yttrium nitrate added is between 0.208g and 1.04g.

[0013] When preparing a visible light catalyst with an optimal doping ratio of 20 wt%, the added mass of yttrium nitrate is 0.431 g.

[0014] Further, in step S200, the drying process specifically includes transferring the mixed solution into a beaker and then placing it in a vacuum oven for drying;

[0015] The drying process continues in the vacuum oven until the solvent in the mixed solution is completely removed, resulting in the solid precursor in a completely dry state.

[0016] Furthermore, in step S300, the high-temperature resistant container is specifically a covered quartz crucible, and the high-temperature calcination process is carried out in a muffle furnace.

[0017] Further, step S300 specifically includes placing the solid precursor in the covered quartz crucible and transferring it to the muffle furnace, heating it to a high temperature according to the set heating program, and maintaining it at the high temperature for a certain period of time, so that the precursor undergoes a thermal polymerization reaction.

[0018] Further, in step S400, the dilute acid solution is a dilute hydrochloric acid solution, and the alcohol is ethanol.

[0019] Furthermore, the calcined product is alternately washed with the dilute hydrochloric acid solution and ethanol, and centrifugation is performed during the washing process to separate the solid and liquid phases, so as to etch away any impurity phases that may be generated during the calcination process.

[0020] Furthermore, the specific process for drying and post-processing the product after etching and impurity removal is as follows: the product collected after washing and centrifugation is freeze-dried, and then the dried product is ground into powder to obtain the visible light catalyst.

[0021] A highly efficient visible light catalyst for producing hydrogen peroxide, characterized in that the visible light catalyst is prepared by the preparation method according to any one of claims 1-8; the visible light catalyst is yttrium-doped graphitic carbon nitride, and the yttrium loading ratio in the catalyst is 10wt%-50wt%.

[0022] The application of a highly efficient visible light catalyst for hydrogen peroxide production in visible light catalytic hydrogen peroxide production includes the following steps: the visible light catalyst is added to an aqueous solution and dispersed evenly, stirred in the dark, oxygen is introduced into the resulting suspension, and hydrogen peroxide is catalytically synthesized under visible light with a wavelength greater than 420 nm at room temperature.

[0023] Before introducing oxygen for illumination, isopropanol is added to the aqueous solution as a hole sacrificial agent; the light source for the visible light effect is a 300W xenon lamp with a 420nm filter.

[0024] Beneficial effects

[0025] This invention successfully embeds a specific ratio of yttrium ions uniformly into the two-dimensional layered lattice of graphitic carbon nitride through a refined preparation process involving "separate dissolution, titration, and mixing," "semi-closed environment thermal polymerization," and "alternating washing with dilute acid and ethanol combined with freeze-drying." On one hand, this in-situ doping strategy effectively modulates the band structure of the material by introducing impurity energy levels, significantly broadening the visible light absorption range of the catalyst. Simultaneously, yttrium ions, as efficient electron-capturing centers, effectively suppress the rapid recombination of photogenerated electrons and holes. On the other hand, the specific preparation and purification processes maximally remove inactive impurity phases while maintaining the loose porous network structure within the material, effectively improving the specific surface area and exposure of catalytically active sites. Based on the synergistic improvement in material structure and photoelectric properties, this catalyst can achieve efficient, low-cost, and environmentally friendly catalytic reduction of oxygen to hydrogen peroxide under mild conditions of ambient temperature, ambient pressure, and visible light irradiation, providing a practical and feasible technical path for the clean production of high-value-added chemicals. Attached Figure Description

[0026] Figure 1 is a flowchart of the preparation method of the present invention;

[0027] Figure 2 shows the absorbance of the supernatant of pure carbon nitride of the present invention and yttrium-doped carbon nitride photocatalysts with different loading ratios obtained in Example 2 after 60 minutes of photocatalysis under visible light, measured by a UV-Vis spectrophotometer using the DPD-POD method.

[0028] Figure 3 shows the effect of photocatalytic preparation of hydrogen peroxide under visible light using pure carbon nitride of the present invention and yttrium-doped carbon nitride photocatalysts with different loading ratios obtained in Example 2. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but includes other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings:

[0032] Example 1:

[0033] As shown in Figures 1-3, a method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production includes the following steps:

[0034] S100: Urea, which serves as a carbon and nitrogen source, and yttrium nitrate, which serves as a yttrium source, are dissolved separately in deionized water. The two are then mixed and stirred until homogeneous to obtain a mixed solution.

[0035] S200: The mixed solution is dried until the solvent is completely removed to obtain a solid precursor;

[0036] S300: The solid precursor is placed in a high-temperature resistant container for high-temperature calcination. Yttrium ions are introduced into the lattice of the generated graphitic carbon nitride through thermal polymerization to obtain the calcined product.

[0037] S400: The calcined product is alternately washed with dilute acid solution and alcohol to etch and remove the impurity phase generated during calcination. After separation, purification, and drying, the visible light photocatalyst is obtained; wherein the yttrium loading ratio in the prepared visible light photocatalyst is limited to [specific value missing]. .

[0038] Furthermore, the specific implementation process of step S100 is as follows:

[0039] Specifically, this invention preferably uses urea as the carbon and nitrogen source and yttrium nitrate hexahydrate (Y(NO3)3·6H2O) as the yttrium source. Urea is chosen not only because of its low cost and ease of acquisition, but more importantly, during the subsequent high-temperature thermal polymerization process, urea not only forms a two-dimensional layered conjugated graphitic carbon nitride structure, but also decomposes to produce a large amount of ammonia and other gas molecules. These gases can act as soft templates to expand pores and create a micro-reducing atmosphere within the system, which is beneficial for the stable introduction of yttrium ions. Simultaneously, the use of yttrium nitrate hexahydrate as the metal source utilizes its excellent solubility in deionized water, allowing it to exist in a completely free ionic state, thereby ensuring extreme dispersion of the doped metal.

[0040] In the specific mixing process, this invention does not employ the conventional, crude method of directly mixing all solid powders or adding them together to water. Instead, it adopts a refined strategy of "separate dissolution and titration mixing." First, the weighed urea and yttrium nitrate hexahydrate are separately dissolved in deionized water and continuously stirred at room temperature until completely dissolved, to obtain homogeneous and transparent urea and yttrium nitrate solutions respectively. Subsequently, under the dynamic condition of continuously stirring the urea solution, the yttrium nitrate solution is slowly added titrally until completely mixed to obtain the mixed solution. This process design from separate dissolution to titration mixing has significant technical advantages: it can effectively avoid local supersaturation or rapid aggregation of high-concentration yttrium ions when they encounter urea, allowing yttrium ions to be uniformly and slowly dispersed throughout the hydrated network of urea molecules.

[0041] In a specific embodiment, when the added mass of urea is fixed at 10g, the corresponding added mass of yttrium nitrate hexahydrate is strictly controlled within the range of 0.208g to 1.04g. Through extensive experimental research, the inventors discovered that the doping amount of yttrium plays a decisive regulatory role in the final photocatalytic hydrogen peroxide production performance. When the added amount of yttrium is too low (e.g., below 0.208g corresponding to a 10wt% loading ratio), the number of impurity energy levels introduced into the system is limited, failing to effectively broaden the visible light absorption range, and there are insufficient electron trapping centers, resulting in a still relatively fast recombination rate of photogenerated carriers. Conversely, if the added amount of yttrium is too high (e.g., above 1.04g corresponding to a 50wt% loading ratio), the excessive yttrium ions will inevitably agglomerate during calcination to form large impurity phases. This not only clogs the porous structure of the material surface, leading to a sharp decrease in specific surface area, but also masks catalytic active sites, significantly weakening the catalytic yield.

[0042] Experimental data conclusively show that the catalytic activity first increases and then decreases with increasing yttrium doping concentration. When 10g of urea and 0.431g of yttrium nitrate hexahydrate are weighed in step S100, the final catalyst has a yttrium loading ratio of 20wt%. At this point, the band structure of the material is optimized, the role of yttrium ions as electron trapping centers is maximized, and the recombination rate of electrons and holes is significantly reduced, resulting in the peak efficiency of visible light photocatalytic synthesis of hydrogen peroxide, which is the optimal doping ratio of this invention.

[0043] Furthermore, the specific implementation process of step S200 is as follows:

[0044] First, the mixed solution containing uniformly dispersed yttrium ions and urea molecules prepared in step S100 is physically transferred by gently pouring and completely collecting it into a clean beaker. This beaker, as an open container, provides sufficient surface area for subsequent solvent evaporation. Then, the beaker containing the mixed solution is placed stably inside the chamber of a vacuum oven.

[0045] Regarding the operation of the drying equipment and the control of material conditions, this invention explicitly employs a vacuum oven as the dehydration and drying device for the mixed solution. In actual operation, after closing the vacuum oven door, the vacuum system is activated to create a negative pressure environment inside the chamber, and the mixed solution in the beaker is continuously heated and dried under a set specific temperature condition. As the drying process progresses, solvents such as deionized water in the mixed system continuously vaporize and are extracted under the combined effects of negative pressure and heat.

[0046] The drying endpoint in this step must be strictly controlled. The drying process must be continuous and uninterrupted until the solvent in the mixed solution is completely removed. Operators or monitoring equipment must observe the morphological changes of the material inside the beaker. The drying process can be ended when it is confirmed that there is no liquid water residue at the bottom and inner wall of the container, and the internal material has completely transformed from a liquid mixed solution into a solid phase. After shutting off the heating and negative pressure systems of the vacuum oven and restoring atmospheric pressure, the physically stable, completely dried solid precursor is removed from the beaker.

[0047] Furthermore, the specific implementation process of step S300 is as follows:

[0048] The collected solid precursors are moderately physically crushed, then transferred and centrally loaded into a high-temperature resistant container. In this specific implementation, the high-temperature resistant container is explicitly a covered quartz crucible. After the solid precursors are loaded, the lid of the quartz crucible is tightly closed to create a relatively independent and semi-enclosed microenvironment within the crucible's internal physical space. Subsequently, the covered quartz crucible containing the precursors is stably placed in the central region of the heating chamber of the muffle furnace to ensure a uniform temperature field distribution during subsequent heating.

[0049] After the crucible is placed and the muffle furnace door is closed, the specific programmed heating parameters are set via the muffle furnace's temperature control panel. The entire calcination process is strictly performed dynamically according to the preset temperature curve: First, the heating program is started, allowing the temperature inside the muffle furnace to steadily rise from room temperature at a set heating rate (e.g., controlled within a uniform range of 2℃ / min to 5℃ / min). This programmed uniform heating operation aims to avoid rapid temperature changes that could cause rapid decomposition of the precursor, generating large amounts of gas and resulting in material overflow or splashing. When the furnace temperature reaches the preset high-temperature target value according to the set program, the temperature control program automatically switches and enters the constant-temperature holding stage.

[0050] During the high-temperature isothermal holding stage, the system maintains the preset high temperature for a certain period of time (usually set to 2 to 4 hours). Under this continuous high-temperature environment and the semi-enclosed self-generated ammonia atmosphere formed by the crucible lid, the urea in the precursor gradually undergoes deep thermal condensation and thermal polymerization reactions, ultimately constructing a two-dimensional layered graphitic carbon nitride (g-C3N4) conjugated framework structure. At the same time, yttrium ions uniformly dispersed in the precursor system diffuse in situ under the drive of high-temperature thermal energy and successfully embed into the lattice of the newly generated graphitic carbon nitride, realizing the introduction of metal ions at the atomic level.

[0051] After the set isothermal holding time has elapsed, turn off the heating source of the muffle furnace and keep the furnace door closed, allowing the furnace chamber and the quartz crucible inside to cool naturally with the ambient temperature. During this stage, avoid directly opening the furnace for sudden cooling at high temperatures to prevent the quartz crucible from cracking due to severe thermal expansion and contraction. This also prevents the high-temperature product from undergoing an unexpected deep oxidation reaction with excess oxygen entering from the outside. Once the internal temperature of the furnace has dropped to room temperature or a safe operating temperature, open the muffle furnace and remove the covered quartz crucible. Opening the crucible lid reveals the blocky or coarse powdery solid inside, which is the calcination product of step S300. The main component of this calcination product is yttrium-doped graphitic carbon nitride. The system also contains a small amount of impurity phases that failed to enter the crystal lattice at high temperatures and thus aggregated. These impurity phases will be specifically etched and separated in the subsequent step S400.

[0052] Furthermore, the specific implementation process of step S400 is as follows:

[0053] First, an acid etching operation is performed: the collected calcined product is transferred to a washing container (such as a centrifuge tube or beaker), and an excess of dilute acid solution (preferably dilute hydrochloric acid solution) is added. After adding dilute hydrochloric acid, mechanical stirring or ultrasonic vibration is used to uniformly disperse and suspend the solid calcined product in the dilute acid system. This operation aims to utilize the dissolving and etching effects of dilute hydrochloric acid to fully peel off and remove impurity phases such as yttrium oxide that failed to enter the graphite phase carbon nitride lattice during high-temperature calcination and instead aggregated on the material surface, thereby purifying the internal and surface structure of the catalyst.

[0054] After thorough acid etching, solid-liquid separation is required through alternating washing and centrifugation. The acid-washed suspension is placed in a centrifuge and centrifuged at an appropriate speed. After centrifugation, the supernatant (i.e., the acidic waste liquid containing dissolved impurities) is discarded, retaining the solid precipitate at the bottom. Then, an appropriate amount of alcohol solvent (preferably ethanol in this invention) is added to the precipitate, and it is ultrasonicated or shaken again to redisperse it. The addition of ethanol effectively washes away residual acid and any attached small organic molecule byproducts. After uniform dispersion, centrifugation is performed again. In practice, the above process of "dilute hydrochloric acid washing-centrifugation-ethanol washing-centrifugation" can be repeated several times until the supernatant after centrifugation is nearly neutral and no obvious impurities are dissolved. Finally, the thoroughly washed and purified wet solid product is collected.

[0055] Next, the collected wet solid product is dried and post-processed. To avoid severe capillary shrinkage and agglomeration of nanoscale porous materials caused by conventional hot air drying, this invention specifically employs a freeze-drying process. The specific operation involves: pre-freezing the purified wet product obtained after washing and centrifugation to solidify the internal moisture and residual solvent; subsequently, the pre-frozen material is transferred to the vacuum chamber of a freeze dryer. Under the physical environment of low temperature and high vacuum, the solid solvent (ice) inside the material sublimates directly into a gaseous state and is extracted without passing through a liquid state. This freeze-drying method can maximally maintain the loose porous network formed by the material in the liquid phase, ensuring the high specific surface area and active site exposure of the catalyst.

[0056] After the freeze-drying process is completely completed, the dried product, which is spongy or loosely lumpy, is removed from the equipment. Finally, the dried product is transferred to a grinding device (such as an agate mortar or ball mill) for physical grinding to refine it thoroughly and then sieve it, ultimately obtaining a powder with uniform particle size. This completes the entire preparation process of the visible light photocatalyst, and the resulting uniform powder is a highly efficient hydrogen peroxide-producing visible light photocatalyst (Y-C3N4) with a loading ratio limited to 10wt%-50wt% (preferably 20wt%).

[0057] Example 2:

[0058] Preparation of yttrium-doped carbon nitride materials:

[0059] 10g of urea was weighed as the carbon and nitrogen source, and 0.431g of yttrium nitrate (Y(NO3)3·6H2O) was weighed as the yttrium source. The yttrium urea was dissolved in deionized water and stirred until completely dissolved. The yttrium nitrate was dissolved in deionized water and titrated with the urea solution. The mixture was poured into a beaker and dried completely in a vacuum oven. The dried precursor was transferred to a covered quartz crucible and calcined in a muffle furnace. The obtained product was washed alternately with dilute hydrochloric acid and ethanol, centrifuged to etch and remove any impurities that might have formed during calcination, and then freeze-dried and ground into powder to obtain yttrium-doped carbon nitride with a loading of 20wt%.

[0060] Preparation of yttrium-doped carbon nitride materials:

[0061] Weigh 10g of urea as the carbon and nitrogen source, and 0.208g of yttrium nitrate (Y(NO3)3·6H2O) as the yttrium source. Dissolve the yttrium urea in deionized water and stir until completely dissolved. Dissolve the yttrium nitrate in deionized water and titrate with the urea solution. Pour the mixture into a beaker and dry it completely in a vacuum oven. Transfer the dried precursor to a covered quartz crucible and calcine it in a muffle furnace. Wash the obtained product alternately with dilute hydrochloric acid solution and ethanol, centrifuge to etch and remove any impurities that may be generated during calcination, freeze-dry and grind into powder to obtain yttrium-doped carbon nitride with a loading of 10wt%.

[0062] Preparation of yttrium-doped carbon nitride materials:

[0063] 10g of urea was weighed as the carbon and nitrogen source, and 0.831g of yttrium nitrate (Y(NO3)3·6H2O) was weighed as the yttrium source. The yttrium urea was dissolved in deionized water and stirred until completely dissolved. The yttrium nitrate was dissolved in deionized water and titrated with the urea solution. The mixed solution was poured into a beaker and dried completely in a vacuum oven. The dried precursor was transferred to a covered quartz crucible and calcined in a muffle furnace. The obtained product was washed alternately with dilute hydrochloric acid solution and ethanol, centrifuged to etch and remove any impurities that might have formed during calcination, and then freeze-dried and ground into powder to obtain yttrium-doped carbon nitride with a loading of 40wt%.

[0064] Preparation of yttrium-doped carbon nitride materials:

[0065] 10g of urea was weighed as the carbon and nitrogen source, and 1.04g of yttrium nitrate (Y(NO3)3·6H2O) was weighed as the yttrium source. The yttrium urea was dissolved in deionized water and stirred until completely dissolved. The yttrium nitrate was dissolved in deionized water and titrated with the urea solution. The mixed solution was poured into a beaker and dried completely in a vacuum oven. The dried precursor was transferred to a covered quartz crucible and calcined in a muffle furnace. The obtained product was washed alternately with dilute hydrochloric acid solution and ethanol, centrifuged to etch and remove any impurities that might have formed during calcination, and then freeze-dried and ground into powder to obtain yttrium-doped carbon nitride with a loading of 50 wt%.

[0066] Performance testing of visible light photocatalytic synthesis of hydrogen peroxide:

[0067] First, 12.5 mg of the catalysts prepared in Examples 1-4 were added to 45 mL of ultrapure water and ultrasonically dispersed. Then, 5 mL of isopropanol was added as a hole sacrificial agent. Before illumination, O2 was introduced for 30 minutes to achieve O2 saturation. A 300 W xenon lamp with a 420 nm filter was used as the visible light source, and cooling water was used to maintain the reaction temperature at room temperature. During the photocatalytic experiment, O2 was continuously introduced into the solution. After a certain time interval (sampling every 10 minutes for a total of six times), samples were taken using a 1 mL syringe, and then the photocatalyst was filtered through a 0.22 μm polyethersulfone membrane. Finally, the solution was diluted 10 times, and the H2O2 concentration was measured.

[0068] By controlling the amount of yttrium nitrate used in the above steps to be 0.431 g, 0.208 g, 0.831 g and 1.04 g respectively, a series of yttrium-doped carbon nitride catalysts with loading ratios of 20 wt%, 10 wt%, 40 wt% and 50 wt% were successfully prepared.

[0069] Subsequently, the performance of visible light photocatalytic hydrogen peroxide synthesis was tested on catalysts with different loading ratios, and the yields were compared and screened. Experimental results showed that the catalytic activity first increased and then decreased with increasing yttrium doping content, reaching its peak when the yttrium loading ratio was 20 wt%. Furthermore, long-term testing demonstrated that this catalyst exhibited good cycling stability.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production, characterized in that, The process includes the following steps: S100: Urea, serving as a carbon and nitrogen source, and yttrium nitrate, serving as a yttrium source, are dissolved separately in deionized water, and then the two are mixed and stirred evenly to obtain a mixed solution; S200: The mixed solution is dried until the solvent is completely removed to obtain a solid precursor; S300: The solid precursor is placed in a high-temperature resistant container for high-temperature calcination, and yttrium ions are introduced into the lattice of the generated graphitic carbon nitride through thermal polymerization to obtain the calcined product; S400: The calcined product is alternately washed with dilute acid solution and alcohol to etch and remove the impurity phase generated during calcination. After separation, purification, and drying, the visible light photocatalyst is obtained; wherein the yttrium loading ratio in the prepared visible light photocatalyst is limited to [specific value missing]. 。 2. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 1, characterized in that, In step S100, the yttrium nitrate is specifically yttrium nitrate hexahydrate. ； Urea is dissolved in deionized water and stirred until completely dissolved to obtain a urea solution; yttrium nitrate is dissolved in deionized water to obtain a yttrium nitrate solution, and then the yttrium nitrate solution and the urea solution are mixed by stirring and titration to obtain the mixed solution; the mass of urea added is 10g, and the mass of yttrium nitrate added is between 0.208g and 1.04g; when preparing a visible light photocatalyst with an optimal doping ratio of 20wt%, the mass of yttrium nitrate added is 0.431g.

3. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 2, characterized in that, In step S200, the drying process specifically includes transferring the mixed solution into a beaker and then placing it in a vacuum oven for drying; continuing the drying process in the vacuum oven until the solvent in the mixed solution is completely removed, thereby obtaining the solid precursor in a completely dry state.

4. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 3, characterized in that, In step S300, the high-temperature resistant container is specifically a covered quartz crucible, and the high-temperature calcination process is carried out in a muffle furnace.

5. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 4, characterized in that, Step S300 specifically includes placing the solid precursor in the covered quartz crucible and transferring it to the muffle furnace, heating it to a high temperature according to the set heating program, and maintaining it at the high temperature for a certain period of time, so that the precursor undergoes a thermal polymerization reaction.

6. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 3, characterized in that, In step S400, the dilute acid solution is a dilute hydrochloric acid solution, and the alcohol is ethanol.

7. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 4, characterized in that, The calcined product was washed alternately with the dilute hydrochloric acid solution and ethanol, and centrifugation was performed during the washing process to separate the solid and liquid phases, so as to etch away any impurity phases that may be generated during the calcination process.

8. The method for preparing a highly efficient visible light photocatalyst for hydrogen peroxide production according to claim 7, characterized in that, The specific process for drying and post-processing the product after etching and impurity removal is as follows: the product collected after washing and centrifugation is freeze-dried, and then the dried product is ground into powder to obtain the visible light catalyst.

9. A highly efficient visible light photocatalyst for hydrogen peroxide production, characterized in that, The visible light catalyst is prepared by the preparation method according to any one of claims 1-8; the visible light catalyst is yttrium-doped graphitic carbon nitride, and the yttrium loading ratio in the catalyst is 10wt%-50wt%.

10. The application of a highly efficient visible light photocatalyst for hydrogen peroxide production in visible light photocatalytic hydrogen peroxide production, specifically including the following steps: The visible light catalyst was added to an aqueous solution and dispersed evenly. After stirring in the dark, oxygen was introduced into the resulting suspension. Hydrogen peroxide was synthesized under visible light with a wavelength greater than 420 nm at room temperature. Isopropanol was added to the aqueous solution as a hole sacrificial agent before introducing oxygen for illumination. The visible light source was a 300W xenon lamp with a 420 nm filter.

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