A dual-light-metal-doped modified carbon nitride photocatalyst and a preparation method thereof

Abstract

The application discloses a kind of double light metal doped modified carbon nitride photocatalyst and preparation method thereof, comprising the following steps: (1) the pretreatment of precursor, according to certain mass ratio, two metal salts are mixed with carbon and nitrogen-containing organic matter and are uniformly ground;(2) preparation is carried out using high-temperature thermal polycondensation method, and constant temperature calcination is carried out under certain conditions;(3) the sample prepared by calcining is washed, centrifuged and dried to obtain double metal co-doped polymer carbon nitride.The method is simple, low in cost, uniform in morphology and high in catalytic activity.The application uses cheap main group light metal to dope and modify carbon nitride (Na-Mg / CN), and the solar conversion quantum yield of the composite material is high, the selectivity of photocatalytic preparation of hydrogen peroxide (H2O2) is good, the efficiency is high, and it can be applied to the field of artificial photosynthesis to prepare important chemicals.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a carbon nitride photocatalyst modified with two light metals and its preparation method. Background Technology

[0002] hydrogen peroxide ( Anthraquinone is a highly promising carbon-free energy carrier and a green, multifunctional oxidant with wide applications in fuel cells, energy conversion, environmental remediation, electronics manufacturing, and pharmaceuticals. However, the traditional anthraquinone process, widely used in industry, suffers from high energy consumption and the generation of harmful byproducts. Therefore, there is an urgent need to develop efficient, sustainable, and environmentally friendly methods. Synthesis technology. Photocatalytic synthesis is achieved through solar-driven oxygen reduction reaction (ORR) and water oxidation reaction (WOR). This provides a sustainable and green pathway for utilizing solar energy in chemical production. In recent years, the solar-driven two-electron oxygen reduction reaction (2... ORR) synthesis This process has attracted widespread attention. However, it still faces challenges such as slow electron transfer to adsorbed oxygen, severe recombination of photogenerated carriers, insufficient oxygen adsorption sites, and limited proton supply capacity, which restrict the formation of key intermediates and thus result in low overall efficiency. Therefore, constructing highly efficient photocatalytic materials with rapid charge transport capabilities and abundant oxygen adsorption and protonation sites is crucial. Among various photocatalysts, graphitic carbon nitride (g- Due to its excellent stability and structural tunability, it has applications in photocatalysis. It has enormous potential in terms of production. However, most g- The excitons are tightly bound, and the long-range crystallization order is poor, hindering the separation of photoexcited electron-hole pairs and disrupting carrier migration pathways. Meanwhile, g- right The efficiency of photosynthesis is also affected by its The limitations of poor adsorption capacity and insufficient local protons have led researchers to prepare Na and K co-doped g- urea precursors by heating the urea precursor using the KCl or / and NaCl molten salt method. This leads to improved light absorption and more efficient charge transfer, increasing g- Crystallinity and photocatalytic performance. Studies have shown that anchoring to g- The Mg single-atom catalyst on the surface enables visible light-driven, sacrificial agent-free [process / treatment]. Production was improved, and efficiency was increased. Importantly, the integration of Mg single atoms modulated the g- The electronic structure, particularly the enhanced valence band oxidation potential, significantly improved WOR kinetics and proton generation capacity, thereby greatly enhancing photocatalysis. Production. Although regarding g- While some progress has been made in photocatalytic synthesis, several key challenges remain. This invention employs a Na-Mg dual-light metal co-doping strategy to synergistically enhance g-... The intralayer and interlayer charge migration was improved, and proton supply was enhanced by introducing –C≡N groups, which significantly improved the efficiency. Yield. Currently, there are few reports on Na-Mg dual-light metal co-doping modified carbon nitride. Summary of the Invention

[0003] To overcome the problems existing in the prior art, this invention develops a high-performance novel visible light polymer carbon nitride photocatalyst.

[0004] This invention provides a method for preparing a carbon nitride photocatalyst modified with dual light metal doping, comprising the following steps: (1) Weigh a certain amount of carbon and nitrogen organic precursors and grind them thoroughly and mix them evenly with a certain proportion of alkali metal salts and alkaline earth metal salts in an agate mortar. (2) The sample after grinding and mixing is placed in a covered alumina crucible, placed in a muffle furnace and heated at a certain temperature gradient for a certain time, cooled to room temperature, dried and ground to obtain a yellow powder; (3) The prepared product is washed, centrifuged and dried at a certain temperature to obtain a carbon nitride photocatalyst modified by doping with two light metals.

[0005] Furthermore, in step (1), the carbon-nitrogen organic precursor is urea or melamine; the alkali metal is sodium, and the alkaline earth metals are magnesium, calcium, strontium, or barium, respectively; and the metal salts are all metal hydrochlorides.

[0006] Furthermore, in step (1), the mass ratio of urea to alkali metal salt is 1:4, and the mass ratio of urea to alkaline earth metal salt is approximately 36:1.

[0007] Further, in step (2), the temperature is raised at a rate of 15 °C / min and calcined at 580 °C for 2 h in an air atmosphere.

[0008] Furthermore, in step (3), the product is repeatedly washed with deionized water until no chloride ions remain, and then vacuum dried at 80 °C for 24 h.

[0009] This invention also provides a carbon nitride photocatalyst modified with dual light metal doping by the above method.

[0010] The principle of this invention: This invention uses urea as a precursor for carbon nitride, and sodium chloride and magnesium chloride as sodium and magnesium sources, respectively. These are mixed in a specific mass ratio using solid-phase mechanical mixing, followed by one-pot calcination to prepare a highly efficient sodium-magnesium co-doped carbon nitride photocatalyst. Compared to other current methods for preparing modified carbon nitride, this invention uses a Na-Mg modified carbon nitride photocatalyst (Na-Mg / CN), which exhibits higher visible light photocatalytic hydrogen peroxide production activity and chemical stability, making it suitable for artificial photocatalytic synthesis and environmental applications. Furthermore, the photocatalyst of this invention uses readily available raw materials, has low preparation costs, and a simple preparation method, overcoming the technical difficulties of high preparation costs, cumbersome steps, and unsuitability for large-scale preparation in existing technologies.

[0011] Beneficial effects of the invention The photocatalyst is prepared by a one-pot calcination method, which is simple, low-cost, and produces high-purity, uniform morphology, good dispersibility, and stable performance. The Na-Mg / CN photocatalyst prepared by this invention exhibits high solar energy utilization and quantum efficiency, and excellent photocatalytic activity for hydrogen peroxide synthesis. It can be applied in energy conversion and catalytic degradation of organic pollutants in the energy and environmental fields. Attached Figure Description

[0012] Figure 1 This is an X-ray electron diffraction (XRD) image of the photocatalytic material prepared in this invention.

[0013] Figure 2 This is the UV-Vis diffuse reflectance spectrum of the photocatalytic material prepared in this invention. Figure 3 This is a comparison chart of the photocatalytic performance of the catalyst prepared by the one-pot method of this invention in the synthesis of hydrogen peroxide.

[0014] Figure 4 This is a graph showing the performance of Na-Mg / CN prepared by the one-pot method of this invention in the photocatalytic synthesis of hydrogen peroxide from different water samples.

[0015] Figure 5 This is a performance diagram of the photocatalytic synthesis of hydrogen peroxide using the catalyst prepared by the one-pot method of this invention.

[0016] Figure 6 This is a performance graph of photocatalytic synthesis of hydrogen peroxide using catalysts prepared by other methods (post-doping). Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments, proportions, and accompanying drawings.

[0018] Example 1 The one-pot preparation method of this invention involves: weighing 5 grams of urea, 20 grams of sodium chloride, and 0.14 grams of magnesium chloride, mechanically grinding and mixing them evenly, then placing them in a covered alumina crucible and heating them in a muffle furnace at a heating rate of 15°C / min to 580°C, and calcining at this temperature for 2 hours. After cooling to room temperature, washing with deionized water multiple times and centrifuging, then vacuum drying at 80°C for 24 hours, and finally grinding to obtain the Na-Mg / CN composite photocatalyst.

[0019] Meanwhile, different catalysts (Na-Ca / CN, Na-Sr / CN, Na-Ba / CN, K-Mg / CN) were prepared using the one-pot method of this invention for subsequent comparative experiments.

[0020] Comparative Example 1 Other post-doping preparation steps: Weigh 5 g of urea and 20 g of sodium chloride, mechanically grind and mix evenly, place in a covered alumina crucible, place in a muffle furnace, heat to 580 °C at 15 °C / min, and calcine at a constant temperature for 2 h. Cool to room temperature, wash and centrifuge repeatedly, and vacuum dry overnight to obtain Na / CN photocatalyst. Then, weigh 0.2 g of Na / CN and 0.86 g of magnesium chloride, grind thoroughly and evenly, place in a covered alumina crucible, place in a muffle furnace, heat to 500 °C at 15 °C / min, and calcine at a constant temperature for 2 h. Cool to room temperature, wash and centrifuge repeatedly, and vacuum dry to obtain Na-Mg / CN photocatalyst.

[0021] Meanwhile, a catalyst (K-Mg / CN) was prepared using a post-doping method for subsequent comparative experiments.

[0022] Application Example 1 Photocatalytic synthesis The specific experimental steps are as follows: 0.025 g of the Na-Mg / CN composite photocatalyst powder prepared in Example 1 using the one-pot method was weighed and dispersed in a beaker containing 45 mL of deionized water. 5 mL of isopropanol was added to adjust the pH to 2-2.5. Air was continuously bubbled into the suspension, and the mixture was magnetically stirred for 30 minutes under light-protected conditions to reach adsorption-desorption equilibrium. The solution was then illuminated with a 20 W LED light for 180 minutes, with samples taken every 30 minutes. The samples were filtered through a 0.22 µm filter to remove the catalyst before analysis. Quantification was performed using a UV-Vis spectrophotometer with the potassium titanium oxalate (IV) colorimetric method. concentration.

[0023] Figure 3 This is a comparison chart of the photocatalytic performance of different catalysts prepared by the one-pot method of this invention in the synthesis of hydrogen peroxide.

[0024] Application Example 2 Photocatalytic synthesis The specific experimental steps are as follows: 0.025 g of the catalyst powder sample prepared by the post-doping method in Comparative Example 1 was weighed and dispersed into a beaker containing 45 mL of aqueous solution. 5 mL of isopropanol was added to adjust the pH to 2-2.5. Air was continuously bubbled into the suspension, and the mixture was magnetically stirred for 30 minutes under light-protected conditions to reach adsorption-desorption equilibrium. The solution was then illuminated with a 20 W LED light for 180 minutes, with samples taken every 30 minutes. The samples were filtered through a 0.22 µm filter to remove the catalyst before analysis. Quantification was performed using a UV-Vis spectrophotometer with the potassium titanium oxalate (IV) colorimetric method. concentration.

[0025] Figure 6 These are performance graphs of photocatalytic synthesis of hydrogen peroxide using different catalysts prepared by other methods (post-doping).

[0026] contrast Figure 5 and Figure 6 It can be seen that the Na-Mg / CN catalyst prepared by the one-pot method of this invention has significantly higher activity than the Na-Mg / CN catalyst prepared by the post-doping method. After 180 minutes of visible light irradiation, the Na-Mg / CN photocatalytic synthesis of this invention... The yield is nearly twice that of the post-doped Na-Mg / CN method.

Claims

1. A method for preparing a carbon nitride photocatalyst modified with dual light metal doping, characterized in that, Includes the following steps: (1) Weigh a certain amount of carbon and nitrogen organic precursors and grind them thoroughly and mix them evenly with a certain proportion of alkali metal salts and alkaline earth metal salts in an agate mortar. (2) The sample after grinding and mixing is heated with a certain temperature gradient, calcined at a constant temperature for a certain time, cooled to room temperature, dried and ground to obtain a yellow powder; (3) The prepared product was washed, centrifuged, and dried at a certain temperature to obtain a carbon nitride photocatalyst modified with two light metals.

2. The preparation method of a dual-light metal doped modified carbon nitride photocatalyst as described in claim 1, characterized in that, In step (1), the carbon and nitrogen-containing organic precursors are urea or melamine; the alkali metals are sodium, and the alkaline earth metals are magnesium, calcium, strontium, or barium, respectively; and the metal salts are all metal hydrochlorides.

3. The preparation method of a dual-light metal doped modified carbon nitride photocatalyst as described in claim 2, characterized in that, Step (1) The mass ratio of urea to alkali metal salt is 1:4, and the mass ratio of urea to alkaline earth metal salt is approximately 36:

1.

4. The preparation method of a dual-light metal doped modified carbon nitride photocatalyst as described in claim 3, characterized in that, Step (2) Calcine at 580 °C for 2 h in an air atmosphere with a heating rate of 15 °C / min.

5. The preparation method of a dual-light metal doped modified carbon nitride photocatalyst as described in claim 4, characterized in that, In step (3), the product is repeatedly washed with deionized water until no chloride ions remain, and then vacuum dried at 80 °C for 24 h.

6. A carbon nitride photocatalyst modified with dual light metal doping, characterized in that, It is prepared by any of the methods described in claims 1-5.

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