CN-121972199-A - Ultrathin carbon nitride nanosheet coated titanium dioxide microsphere catalyst and photocatalytic PET plastic reforming hydrogen production method

Abstract

The invention discloses a titanium dioxide microsphere catalyst coated by ultrathin carbon nitride nanosheets and hydrogen produced by reforming photocatalytic PET (polyethylene terephthalate) plastics. The preparation method comprises the steps of preparing ultrathin g-C 3 N 4 nano sheets through urea two-step heat treatment and mixed acid etching, preparing TiO 2 microspheres through a glucose template assisted hydrothermal method and calcining, and finally obtaining the composite catalyst through solvent mixing and self-assembly. The catalyst has a core-shell heterojunction structure of g-C 3 N 4 nano sheets tightly coated with TiO 2 microspheres, and can efficiently separate photo-generated charges. The invention also provides an application method of the catalyst in hydrogen production by reforming the photocatalytic PET plastic, which is characterized in that after PET is hydrolyzed under alkaline condition, the catalyst is used for carrying out photocatalytic reaction, and high-added value chemicals such as hydrogen, glycollic acid, formic acid and the like can be synchronously produced. The catalyst has high activity, good stability and low cost, and provides a high-efficiency solution for recycling waste plastics and producing clean energy.

Inventors

• Teng Yunan
• ZHANG JIANLING
• LI MEILING
• WEI ZHENHUAN
• WANG HAOXIANG

Assignees

• 中国科学院化学研究所

Dates

Publication Date

20260505

Application Date

20260123

Claims (10)

1. 1. The preparation method of the titanium dioxide microsphere catalyst coated by the ultrathin carbon nitride nanosheets comprises the following steps: s1, carrying out primary annealing treatment on urea, cooling and grinding to obtain a sample A; S2, carrying out secondary annealing treatment on the sample A to obtain a sample B; S3, treating the sample B in a sulfuric acid-nitric acid mixed solution, and obtaining an ultrathin carbon nitride nanosheet sample C after dilution, centrifugation, washing and drying; s4, mixing a glucose aqueous solution and an ammonium fluotitanate aqueous solution for hydrothermal reaction, and centrifuging, washing and drying a reaction product to obtain a precursor sample D; s5, carrying out third annealing treatment on the sample D to obtain a titanium dioxide microsphere sample E; and S6, dispersing the sample C in a solvent, adding the sample E, stirring and mixing, and removing the solvent to obtain the ultrathin carbon nitride nanosheet coated titanium dioxide microsphere catalyst.
2. 2. The method according to claim 1, wherein in the step S1, the first annealing treatment is performed under the condition that the temperature is raised to 500-600 ℃ at a temperature raising rate of 2-10 ℃ per minute in an air atmosphere, and the temperature is kept for 2-6 hours.
3. 3. The method according to claim 1 or 2, wherein in step S2, the second annealing treatment is performed in a closed or semi-closed container under the condition that the temperature is raised to 450-550 ℃ at a temperature raising rate of 1-5 ℃ per minute, and the temperature is kept for 1-4 hours.
4. 4. The method according to any one of claims 1 to 3, wherein in the step S3, the concentration of sulfuric acid in the sulfuric acid-nitric acid mixed solution is 8-10 mol/L and the concentration of nitric acid is 3-5 mol/L, and the treatment comprises soaking and stirring for 1-15 minutes.
5. 5. The method according to any one of claims 1 to 4, wherein in step S4, the concentration of the aqueous glucose solution is 0.1 to 0.3 g/mL, the concentration of the aqueous ammonium fluorotitanate solution is 0.05 to 0.1 g/mL, and the temperature of the hydrothermal reaction is 160 to 200 ℃ and the time is 18 to 30 hours.
6. 6. The method according to any one of claims 1 to 5, wherein in step S5, the third annealing treatment is performed under the conditions of raising the temperature to 500-600 ℃ at a rate of 2-10 ℃ per minute in an air atmosphere, and maintaining the temperature for 2-6 hours; In the step S6, the mass ratio of the sample C to the sample E is 1:1-1:5, and the solvent is at least one of methanol, ethanol and isopropanol.
7. 7. An ultrathin carbon nitride nanosheet-coated titanium dioxide microsphere catalyst prepared by the method of any one of claims 1-6.
8. 8. A method for producing hydrogen by reforming photocatalytic PET plastic, which adopts the ultrathin carbon nitride nanosheet-coated titanium dioxide microsphere catalyst according to claim 7, and comprises the following steps: SI, heating and hydrolyzing PET plastic in alkaline aqueous solution to obtain hydrolysate; and SII, adding the titanium dioxide microsphere catalyst into the hydrolysate under inert atmosphere, and carrying out photocatalytic reaction under the irradiation of a light source to generate hydrogen.
9. 9. The method according to claim 8, wherein in the step SI, the alkaline aqueous solution is an aqueous potassium hydroxide solution with a concentration of 1-10 mol/L, the temperature of the thermal hydrolysis is 60-90 ℃ and the time is 12-72 hours.
10. 10. The method according to claim 8 or 9, wherein in the step SII, the catalyst is added in an amount such that the concentration of the catalyst in the reaction system is 0.5-2 mg/mL, the inert atmosphere is an argon or nitrogen atmosphere, the light source is a xenon lamp with a power of 200-500W, and the photocatalytic reaction time is 1-12 hours.

Description

Ultrathin carbon nitride nanosheet coated titanium dioxide microsphere catalyst and photocatalytic PET plastic reforming hydrogen production method Technical Field The invention relates to a titanium dioxide microsphere catalyst coated by an ultrathin carbon nitride nanosheet and hydrogen produced by reforming photocatalytic PET (polyethylene terephthalate) plastic, belonging to the technical field of chemistry. Background Today, where energy is increasingly exhausted, there is an urgent need to develop new energy, and light energy is one of the most widely available energy sources on earth. The use of photocatalysis to convert waste resources into usable chemicals and fuels is an economically valuable and environmentally friendly route. Compared with homogeneous photocatalysis, the heterogeneous photocatalysis system has the characteristics of easy recovery of the catalyst, easy separation of the substrate and the catalyst, and the like, thereby being widely developed. In the multiphase photocatalysis system, under the illumination condition, photo-generated electron-hole pairs are generated in the catalyst, the photo-generated electrons are separated from holes after absorbing photon transition, oxidation reaction can occur at the hole end, reduction reaction can occur at the electron enrichment end, and therefore, the photocatalysis reaction is basically oxidation-reduction reaction. Plastic materials have an irreplaceable role and position in modern production and life, but also have serious consequences for the environment. The recycling of plastics is the best way to solve environmental problems, alleviating resource and energy shortages. Polyethylene terephthalate (PET) has become one of the most widely used polyester plastics in the world today, particularly in the packaging and textile industries, due to its low cost, non-toxicity, low permeability, light weight and high resistance to contamination. The annual output of PET exceeds 3000 ten thousand tons, but of which less than 10% can be recycled. The accumulation of waste PET creates serious environmental problems, and there is an urgent need to develop new recycling methods to increase PET recovery. Photocatalytic water splitting hydrogen production is considered as an effective way to efficiently utilize solar energy. In the strategy, ethylene glycol after hydrolysis of PET can provide electrons to promote the photocatalytic water splitting to generate hydrogen, and meanwhile, the treated PET is converted into other small molecular organic matters with high added value. According to the report of the document one (ACS mate. Lett., 2023, 5, 3032-3041), the photocatalytic reforming of PET plastics and the simultaneous production of hydrogen were successfully achieved by compounding molybdenum sulfide with a carbon nitride material. Document two (appl. Catalyst. B-environ., 2022, 307, 121143) also implements the photocatalytic reforming of PET plastics to produce hydrogen using nickel molybdenum attached carbon nanotube materials. However, the hydrogen yield in these reactions is low and the choice of active center metal is limited. In order to improve the hydrogen yield and expand the catalyst selection of the reaction, the invention expects to prepare an ultrathin titanium dioxide microsphere catalyst coated by carbon nitride nanosheets so as to realize the efficient photocatalytic PET plastic reforming hydrogen production. Disclosure of Invention The invention aims to provide a titanium dioxide microsphere (g-C 3N4/TiO2) catalyst coated by an ultrathin carbon nitride nanosheet and a photocatalytic PET plastic reforming hydrogen production process, and the uniform and stable coating of the ultrathin carbon nitride nanosheet on the surface of the titanium dioxide microsphere is realized by a specific two-step annealing-acid etching-hydrothermal synthesis-compounding process, so that a heterojunction structure with high-efficiency charge separation capability is constructed, and a material foundation is provided for improving the photocatalytic performance. The invention realizes the high-value conversion of waste PET resources, which combines plastic pollution control with clean energy production, and synchronously realizes hydrogen production in the same photocatalysis system, namely, ethylene glycol generated by PET hydrolysis is used as an electron donor to efficiently catalyze water pyrolysis to generate hydrogen, and the waste PET is converted into high-added value chemicals such as glyoxal, glycollic acid, acetic acid, formic acid and the like. The invention solves the problem of insufficient performance of the existing catalyst, namely the existing catalyst for preparing hydrogen by PET photo-reforming (such as molybdenum sulfide/carbon nitride, nickel molybdenum/carbon nano tube and the like) has the technical defects of low hydrogen yield and large limitation of active center metal selection, provides a high-performance and easy-to-prepa