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CN-121972204-A - Modified Na-PHI carbon nitride catalyst with high photocatalytic performance, synthesis method and application of photocatalytic hydrogen production

CN121972204ACN 121972204 ACN121972204 ACN 121972204ACN-121972204-A

Abstract

The invention discloses a modified Na-PHI carbon nitride catalyst with high photocatalytic performance, a synthesis method and application of photocatalytic hydrogen production. Firstly, calcining urea raw materials and various carbon doping agents at high temperature to synthesize an intermediate product, and then, mixing and calcining sodium chloride, sodium oxalate and the intermediate product in a certain proportion, and finally obtaining a series of modified Na-PHI carbon nitride. The preparation method has the advantages of low raw material cost, simple operation flow, green and stable sample, and can be recycled for a plurality of times. The modified Na-PHI has excellent photocatalytic hydrogen production efficiency in the photocatalytic electrolytic water production hydrogen reaction, wherein the hydrogen production efficiency of a modified Na-PHI sample with the most excellent activity is respectively 20.6 times of that of ordinary carbon nitride PCN at the wavelength lambda of more than or equal to 420 nm and 4.2 times of that of ordinary Na-PHI, and the hydrogen production efficiency of the modified Na-PHI sample at the wavelength lambda of more than or equal to 500 nm is 35.4 times of that of ordinary Na-PHI (ordinary carbon nitride PCN is inactive).

Inventors

  • YU YUXIANG
  • HUANG LIHONG
  • XU YANGSEN

Assignees

  • 华南理工大学

Dates

Publication Date
20260505
Application Date
20260228

Claims (10)

  1. 1. The synthesis method of the modified Na-PHI carbon nitride catalyst is characterized by comprising the following steps of: (1) Mixing urea and a carbon doping agent into a sample bottle, and wrapping the sample bottle by aluminum foil paper; (2) Placing the sample bottle wrapped by the aluminum foil paper in the step (1) into a muffle furnace for calcination to obtain a transition sample; (3) Respectively wet-grinding the transition sample obtained in the step (2) and sodium composite salt into slurry through absolute ethyl alcohol, and drying the slurry material into powder; (4) Transferring the powder obtained in the step (3) into a sample bottle, and wrapping the sample bottle by aluminum foil paper; (5) And (3) placing the sample bottle obtained in the step (4) into a muffle furnace for calcination and post-treatment to obtain the modified Na-PHI carbon nitride catalyst.
  2. 2. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the carbon dopant in step (1) is one of 2-methylimidazole, 2,4, 6-triaminopyrimidine, terephthalic acid, succinic acid.
  3. 3. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the mass ratio of urea to carbon dopant in step (1) is 10:0.05-2, depending on the dopant type.
  4. 4. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the calcining temperature in step (2) is 500 to 650 ℃, the calcining time is 3 to 6 h, and the temperature rising rate is 3 to 10 ℃ per minute.
  5. 5. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the sodium complex salt of step (3) is 4 g NaCl and 0.05 to 0.2 g Na 2 C 2 O 4 .
  6. 6. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the mass ratio of the transition sample to the sodium complex salt in step (3) is 1:4-10.
  7. 7. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the drying temperature in step (3) is 40 to 100 ℃ and the drying time is 0.5 to 2 h.
  8. 8. The method for synthesizing a modified Na-PHI carbon nitride catalyst according to claim 1, wherein the calcination temperature in step (5) is 500 to 650 ℃, the calcination time is 3 to 6 h, and the temperature rising rate is 3 to 10 ℃ per minute.
  9. 9. A modified Na-PHI carbon nitride catalyst synthesized by the method of any one of claims 1-8.
  10. 10. The modified Na-PHI carbon nitride catalyst of claim 9 for photocatalytic decomposition of water to produce hydrogen.

Description

Modified Na-PHI carbon nitride catalyst with high photocatalytic performance, synthesis method and application of photocatalytic hydrogen production Technical Field The invention belongs to the technical field of hydrogen production by photocatalytic electrolysis, and particularly relates to a general preparation method of a modified Na-PHI carbon nitride catalyst with high photocatalytic performance and application of the catalyst in hydrogen production by photocatalysis. Background The hydrogen energy is one of the most ideal clean energy in the future accepted by the scientific community, has the advantages of high energy density (the energy density is 2.5 times of natural gas, 5 times of coal and 3 times of gasoline), being renewable, non-toxic and pollution-free, and can be widely applied to fuel transportation, chemical synthesis, high-temperature industry, power supply and the like. However, 90% of the hydrogen in the industry is derived from the thermal reforming of traditional energy sources, such as coal gasification hydrogen production, natural gas reforming hydrogen production and the like, a small amount of hydrogen is derived from electrolyzed water, the use of traditional non-renewable energy sources is the most main cause of energy crisis and environmental pollution, and a factory for electrolyzing water by utilizing photovoltaic power is established at present. In the solar spectrum, visible light and infrared light account for about 95% of solar radiation energy, so that the direct utilization of solar energy to obtain energy to achieve the purpose of photocatalytic decomposition of water to prepare hydrogen is a very promising technology for relieving energy crisis, and can be used as one of ideal ways for producing clean energy in a large scale. The key point of the reaction for preparing hydrogen by photocatalytic decomposition of water is the performance of a semiconductor, wherein ordinary carbon nitride (PCN) is a current research hot spot, and the non-metal organic semiconductor material of ordinary carbon nitride (PCN) is easy to synthesize, can be directly obtained through heat-shrinkable melamine, thiourea, dicyandiamide, urea and other nitrogen-rich precursors, is environment-friendly, has proper band gap, unique chemical and physical properties and controllable electronic structure, so that the PCN has great advantages compared with other semiconductor photocatalysts. However, the common carbon nitride has the problems of narrow light absorption range, large carrier transmission resistance and high carrier recombination degree, and becomes a stopper for improving the photocatalytic hydrogen production efficiency. Patent CN120169407A discloses a method for improving crystallinity and catalytic water decomposition performance of a poly-heptazinyl-imine carbon nitride photocatalyst, which takes melamine as a precursor, thermally polymerizes to form an oligomer melon composed of heptazinyl units, and then carries out high-temperature fused salt calcination treatment under nitrogen atmosphere to obtain carbon nitride with a certain crystallinity, wherein the fully-hydrolyzed active hydrogen of the crystalline carbon nitride with the highest active sodium poly-heptazinyl-imine (Na-PHI) structure under full light irradiation is 370 mu mol/h. Patent CN113318765A discloses a preparation method of an ultrathin high-crystallization carbon nitride photocatalyst, which comprises the steps of placing melamine in a crucible for calcination, grinding after natural cooling to obtain block carbon nitride, placing in a porcelain boat for high-temperature air stripping, obtaining ultrathin carbon nitride after natural cooling and grinding, placing in the porcelain boat for calcination after grinding together with sodium chloride and potassium chloride to obtain carbon nitride with high crystallinity and thin thickness and having a partial Na-PHI structure, and then achieving 73.6% quantum efficiency under 420 and nm wavelength, and decomposing water with hydrogen rate of 9.7 mmol h -1g-1 under visible light. Unfortunately, although Na-PHI exhibits significant advantages in the hydrogen production efficiency of photocatalysis in the short wavelength range (λ. Gtoreq.420 nm), the hydrogen production efficiency of photocatalysis in the long wavelength range (λ. Gtoreq.500 nm) is still relatively low and the activity is almost zero, so that widening the light absorption range of Na-PHI crystalline carbon nitride is important for further improvement of the hydrogen production performance of photocatalysis. In view of the above, a general synthetic method for synthesizing modified NA-PHI with higher crystallinity, wider light absorption range and special functional group (increased active site) is sought, which can provide great reference significance for preparing hydrogen by photocatalytic water splitting. Disclosure of Invention In order to solve the problem of narrow light absorption range of the ex