阅读说明：本技术 一种N空位掺杂型g-C3N4-WO3异质结光催化产氢催化剂及其制法 (N-vacancy doped g-C3N4-WO3Heterojunction photocatalytic hydrogen production catalyst and preparation method thereof ) 是由 訾孟涛 于 2020-07-16 设计创作，主要内容包括：本发明涉及光催化技术领域,且公开了一种N空位掺杂型g-C<Sub>3</Sub>N<Sub>4</Sub>-WO<Sub>3</Sub>异质结光催化产氢催化剂,包括以下配方原料及组分：N空位的Cl掺杂g-C<Sub>3</Sub>N<Sub>4</Sub>多孔纳米片、聚乙烯醇、钨酸、过氧化氢、草酸、尿素。该一种N空位掺杂型g-C<Sub>3</Sub>N<Sub>4</Sub>-WO<Sub>3</Sub>异质结光催化产氢催化剂,氮空位可以作为光生电子的捕获陷阱,减少载流子的重组和复合,同时盐酸在高温过程中挥发逸出,在g-C<Sub>3</Sub>N<Sub>4</Sub>晶体内部和表面形成大量的孔道和裂纹,Cl掺杂在g-C<Sub>3</Sub>N<Sub>4</Sub>的3p电子轨道形成新的杂质能级,减小了g-C<Sub>3</Sub>N<Sub>4</Sub>的禁带宽度,表现出优异的光化学活性,纳米花瓣状WO<Sub>3</Sub>均匀修饰g-C<Sub>3</Sub>N<Sub>4</Sub>多孔纳米片中,两者的能带匹配,形成异质结结构,促进了光生电子和空穴的分离,具有优异的光催化产氢活性。(The invention relates to the technical field of photocatalysis, and discloses N-vacancy doped g-C 3 N 4 ‑WO 3 The heterojunction photocatalytic hydrogen production catalyst comprises the following formula raw materials and components: cl doping of N-vacancies g-C 3 N 4 Porous nano-sheets, polyvinyl alcohol, tungstic acid, hydrogen peroxide, oxalic acid and urea. The N-vacancy doped g-C 3 N 4 ‑WO 3 The nitrogen vacancy of the heterojunction photocatalytic hydrogen production catalyst can be used as a capture trap of photo-generated electrons, so that carriers are reducedAt the same time, hydrochloric acid volatilizes and escapes in the high-temperature process and is in g-C 3 N 4 A large number of channels and cracks are formed inside and on the surface of the crystal, and Cl is doped in g-C 3 N 4 The 3p electron orbital forms a new impurity energy level, and the g-C is reduced 3 N 4 Shows excellent photochemical activity, and is in the shape of nano-petal WO 3 Homogeneously modifying g-C 3 N 4 In the porous nanosheet, the energy bands of the porous nanosheet and the porous nanosheet are matched to form a heterojunction structure, so that the separation of photogenerated electrons and holes is promoted, and the photocatalytic hydrogen production activity is excellent.)

1. N-vacancy doped g-C₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: comprises the following raw materials and components, g-C doped with Cl of N vacancy₃N₄Porous nano-sheets, polyvinyl alcohol, tungstic acid, hydrogen peroxide, oxalic acid and urea.

2. An N-vacancy doped g-C as defined in claim 1₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: the N-vacancy doped type g-C₃N₄-WO₃The preparation method of the heterojunction photocatalytic hydrogen production catalyst comprises the following steps:

(1) adding melamine into a dilute hydrochloric acid solution, reacting for 1-4h, distilling under reduced pressure to remove a solvent, washing and drying to obtain melamine hydrochloride;

(2) placing melamine hydrochloride into a distilled water solvent, adding 1-ethyl-3-methylimidazole chloride, uniformly stirring, then distilling the solution under reduced pressure and drying, placing a solid mixed product into an atmosphere resistance furnace, heating to 540-fold 560 ℃ in the air atmosphere, carrying out heat preservation and calcination for 2-4h, grinding the calcined product into fine powderPowder preparation to obtain Cl-doped g-C of N-vacancy₃N₄A porous nanosheet;

(3) cl-doped g-C by adding N-vacancies to an aqueous solution of hydrogen peroxide₃N₄Uniformly dispersing the porous nanosheet, the polyvinyl alcohol and the tungstic acid by ultrasonic, then drying in vacuum to remove the solvent, placing in a resistance furnace, heating to 540 ℃ and 560 ℃ in the air atmosphere, and carrying out heat preservation and calcination for 2-4h to obtain the WO₃Seed crystal loading g-C₃N₄A porous nanosheet;

(4) adding tungstic acid into aqueous solution of hydrogen peroxide, stirring at 80-90 deg.C until the solution is clear, adding acetonitrile solvent, oxalic acid and urea, adding concentrated hydrochloric acid solution, stirring at room temperature for 1-3 hr, mixing the solution with WO₃Seed crystal loading g-C₃N₄Transferring the porous nano-sheets into a hydrothermal reaction kettle, heating to 190 ℃ for 170 plus materials, reacting for 2-4h, vacuum-drying the solution, placing the solid mixed product into an atmosphere resistance furnace, and calcining for 2-3h at 550 ℃ in the air atmosphere in a heat preservation manner to obtain the N-vacancy doped g-C₃N₄-WO₃A catalyst for hydrogen production by heterojunction photocatalysis.

3. An N-vacancy doped g-C as defined in claim 2₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: in the step (1), the mass ratio of HCl to melamine is controlled to be 10-20: 1.

4. An N-vacancy doped g-C as defined in claim 2₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: the mass ratio of the melamine hydrochloride to the 1-ethyl-3-methylimidazole chloride in the step (2) is 100: 2-6.

5. An N-vacancy doped g-C as defined in claim 2₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: the atmosphere resistance furnace in the step (2) comprises an atmosphere chamber, clamping rings are fixedly connected to two sides of the atmosphere chamber, air inlet pipes are movably connected to the clamping rings, and air inlet pipes are arranged on the clamping ringsThe gas pipe is movably connected with a gas guide pipe, the gas guide pipe is fixedly connected with a gas straight-flow pipe, the gas straight-flow pipe is movably connected with a throttle valve, the throttle valve is movably connected with an adjusting card, and the gas straight-flow pipe is fixedly connected with a calcining chamber.

6. An N-vacancy doped g-C as defined in claim 2₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: hydrogen peroxide, Cl-doped g-C of N vacancy in the step (3)₃N₄The mass ratio of the porous nano-sheet to the polyvinyl alcohol to the tungstic acid is 180-220:100:3-8: 8-20.

7. An N-vacancy doped g-C as defined in claim 2₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: the mass concentration of the hydrochloric acid in the total solution in the step (4) is 0.15-0.25mol/L, and the volume ratio of the acetonitrile solvent to the water solvent is 3-5: 1.

8. An N-vacancy doped g-C as defined in claim 2₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst is characterized in that: hydrogen peroxide, tungstic acid, oxalic acid, urea and WO in the step (4)₃Seed crystal loading g-C₃N₄The mass ratio of the porous nano-sheets is 40-100:10-25:0.5-1.5:0.5-1.5: 100.

Technical Field

The invention relates to the technical field of photocatalysis, in particular to N-vacancy doped g-C₃N₄-WO₃A heterojunction photocatalytic hydrogen production catalyst and a preparation method thereof.

Background

The photocatalytic water splitting hydrogen production is a new high-efficiency hydrogen production method, and the valence-band potential of the photocatalytic semiconductor material is required to be higher than the oxygen electrode potential EO in thermodynamics₂/H₂Positive and conduction band potential of O to hydrogen electrode potential EH⁺/H₂When light is radiated on a semiconductor material, the energy of the radiation is larger than the forbidden bandwidth of the semiconductor, electrons in the semiconductor are excited to jump from a valence band to a conduction band, holes are left in the valence band, the electrons and the holes are separated, then water is reduced into hydrogen or oxidized into oxygen at different positions of the semiconductor, and hydrogen production through photocatalytic decomposition of water is realized.

The existing photocatalytic hydrogen production materials mainly comprise titanium dioxide, molybdenum disulfide, cadmium disulfide and the like, wherein graphite phase carbon nitride (g-C)₃N₄) Has moderate forbidden band width, good photochemical activity, stable chemical property and environmental protection, is a photocatalytic hydrogen production material widely researched and applied, but has g-C₃N₄The conductive performance is poor, the transmission rate of photo-generated electrons is high, the photo-generated electrons and holes are easy to recombine, the photocatalytic activity is seriously influenced, and therefore, the g-C is promoted₃N₄Separation of photogenerated electrons and holes, suppression of carrier recombination, and enhancement of g-C₃N₄The specific surface area and the utilization rate of light energy of is enhanced by₃N₄Photochemical performance and photocatalytic hydrogen production activity.

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides the high-efficiency N-vacancy doping type g-C₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst and the preparation method thereof solve the problem of the traditional g-C₃N₄Is not high, and the photogenerated electrons and holes are easily recombined.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: n-vacancy doped g-C₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst comprises: comprises the following raw materialsAnd component, Cl-doped g-C of N-vacancies₃N₄Porous nano-sheets, polyvinyl alcohol, tungstic acid, hydrogen peroxide, oxalic acid and urea.

Preferably, the N-vacancy doped type g-C₃N₄-WO₃The preparation method of the heterojunction photocatalytic hydrogen production catalyst comprises the following steps:

(1) adding a dilute hydrochloric acid solution and melamine into a reaction bottle, stirring at a constant speed for reacting for 1-4h, distilling the solution under reduced pressure to remove the solvent, washing and drying to obtain melamine hydrochloride.

(2) Placing melamine hydrochloride into a distilled water solvent, adding 1-ethyl-3-methylimidazole chloride, uniformly stirring, distilling the solution under reduced pressure, drying, placing a solid mixed product into an atmosphere resistance furnace, heating to 540-fold 560 ℃ in the air atmosphere, carrying out heat preservation and calcination for 2-4h, grinding the calcined product into fine powder, and preparing the Cl-doped g-C with N vacancies₃N₄Porous nanoplatelets.

(3) Adding aqueous solution of hydrogen peroxide and Cl-doped g-C of N vacancy into a reaction bottle₃N₄Uniformly dispersing the porous nanosheet, the polyvinyl alcohol and the tungstic acid by ultrasonic, then drying the solution in vacuum to remove the solvent, placing the solution in a resistance furnace, heating to 540 and 560 ℃ in the air atmosphere, and carrying out heat preservation and calcination for 2-4h to obtain the WO₃Seed crystal loading g-C₃N₄Porous nanoplatelets.

(4) Adding aqueous solution of hydrogen peroxide and tungstic acid into a reaction bottle, stirring at a constant speed at 80-90 ℃ until the solution is clear, adding acetonitrile solvent, oxalic acid and urea, adding concentrated hydrochloric acid solution, stirring at a constant speed at room temperature for 1-3h, mixing the solution with WO₃Seed crystal loading g-C₃N₄Transferring the porous nano-sheets into a hydrothermal reaction kettle, heating to 190 ℃ for 170 plus materials, reacting for 2-4h, vacuum-drying the solution, placing the solid mixed product into an atmosphere resistance furnace, and calcining for 2-3h at 550 ℃ in the air atmosphere in a heat preservation manner to obtain the N-vacancy doped g-C₃N₄-WO₃A catalyst for hydrogen production by heterojunction photocatalysis.

Preferably, the amount ratio of HCl to melamine in the step (1) is controlled to be 10-20: 1.

Preferably, the mass ratio of the melamine hydrochloride to the 1-ethyl-3-methylimidazole chloride in the step (2) is 100: 2-6.

Preferably, the atmosphere resistance furnace in the step (2) comprises an atmosphere chamber and clamping rings fixedly connected to two sides of the atmosphere chamber, the clamping rings are movably connected with an air inlet pipe, the air inlet pipe is movably connected with a gas guide pipe, the gas guide pipe is fixedly connected with a gas direct-flow pipe, the gas direct-flow pipe is movably connected with a throttle valve, and the throttle valve is movably connected with an adjusting clamp and a calcining chamber fixedly connected with the gas direct-flow pipe.

Preferably, the hydrogen peroxide and the Cl of the N vacancy in the step (3) are doped with g-C₃N₄The mass ratio of the porous nano-sheet to the polyvinyl alcohol to the tungstic acid is 180-220:100:3-8: 8-20.

Preferably, the concentration of the hydrochloric acid in the total solution in the step (4) is 0.15-0.25mol/L, and the volume ratio of the acetonitrile solvent to the water solvent is 3-5: 1.

Preferably, the hydrogen peroxide, the tungstic acid, the oxalic acid, the urea and the WO in the step (4)₃Seed crystal loading g-C₃N₄The mass ratio of the porous nano-sheets is 40-100:10-25:0.5-1.5:0.5-1.5: 100.

(III) advantageous technical effects

Compared with the prior art, the invention has the following beneficial technical effects:

the N-vacancy doped g-C₃N₄-WO₃The heterojunction photocatalysis hydrogen production catalyst has the advantages that in the calcining process of melamine hydrochloride, a small amount of amino does not form g-C in the high-temperature polycondensation process due to the action of the amino of the melamine and the hydrochloric acid₃N₄The triazine ring structure causes the loss of nitrogen element, generates a large number of nitrogen vacancies, the nitrogen vacancies can be used as a capture trap of photo-generated electrons, reduces the recombination and recombination of current carriers, and simultaneously hydrochloric acid volatilizes and escapes in the high-temperature process and is in g-C₃N₄A large number of pore channels and cracks are formed inside and on the surface of the crystal, and the g-C is obviously improved₃N₄The specific surface area of the nano-sheet is obtained, and then 1-ethyl-3-methylimidazole chloride is used as a doping agent to obtain Cl with N vacant sitesDoping with g-C₃N₄Porous nanosheet with Cl doped in g-C₃N₄The 3p electron orbital forms a new impurity energy level, and the g-C is reduced₃N₄The gap of (A) is larger than that of (B), and Cl of N vacancy is doped with g-C under the synergistic action₃N₄The porous nanoplatelets exhibit excellent photochemical activity.

The N-vacancy doped g-C₃N₄-WO₃A heterojunction photocatalytic hydrogen production catalyst, g-C is doped with Cl of N vacancy₃N₄Porous nano-sheet as carrier, tungstic acid under the mediation of polyvinyl alcohol in g-C₃N₄Formation of WO in porous nanosheets₃Nano seed crystal is produced into nano petal-shaped WO by adopting a hydrothermal-seed termination method₃Modification of g-C₃N₄Porous nanosheet, WO₃Cl-doped g-C of nanoflower and N vacancies₃N₄The porous nano-sheet has an ultra-high specific surface area, can improve the utilization rate of the catalyst to light energy, and simultaneously WO₃g-C after doping with Cl₃N₄The energy band matching of the structure can form a heterojunction structure, and the separation of photon-generated electrons and holes is promoted through a heterojunction carrier transmission mechanism, so that the structure has excellent photocatalytic hydrogen production activity and efficiency.

Drawings

FIG. 1 is a schematic front view of an atmosphere chamber;

FIG. 2 is a schematic top view of a throttle valve;

fig. 3 is a schematic view of an adjustment card adjustment.

1-an atmosphere chamber; 2-a snap ring; 3, an air inlet pipe; 4-gas flow guide pipe; 5-gas straight-flow pipe; 6-a throttle valve; 7-adjusting the card; 8-calcining chamber.

Detailed Description

To achieve the above object, the present invention provides the following embodiments and examples: n-vacancy doped g-C₃N₄-WO₃The heterojunction photocatalytic hydrogen production catalyst comprises: comprises the following raw materials and components, g-C doped with Cl of N vacancy₃N₄Porous nano-sheets, polyvinyl alcohol, tungstic acid, hydrogen peroxide, oxalic acid and urea.

It is preferable thatSaid N-vacancy doped g-C₃N₄-WO₃The preparation method of the heterojunction photocatalytic hydrogen production catalyst comprises the following steps:

(1) adding a dilute hydrochloric acid solution and melamine into a reaction bottle, controlling the mass ratio of HCl to melamine to be 10-20:1, stirring at a constant speed for reaction for 1-4h, distilling the solution under reduced pressure to remove the solvent, washing and drying to obtain the melamine hydrochloride.

(2) Placing melamine hydrochloride into a distilled aqueous solvent, adding 1-ethyl-3-methylimidazole chloride in a mass ratio of 100:2-6, uniformly stirring, distilling the solution under reduced pressure, drying, placing a solid mixed product into an atmosphere resistance furnace, wherein the atmosphere resistance furnace comprises an atmosphere chamber, clamping rings are fixedly connected to two sides of the atmosphere chamber, the clamping rings are movably connected with an air inlet pipe, the air inlet pipe is movably connected with an air guide pipe, the air guide pipe is fixedly connected with a gas straight-flow pipe, the gas straight-flow pipe is movably connected with a throttle valve, the throttle valve is movably connected with an adjusting clamp, the gas straight-flow pipe is fixedly connected with a calcining chamber, heating to 540-cup 560 ℃ in the air atmosphere, carrying out heat preservation calcination for 2-4h, grinding the calcined product into fine powder, and₃N₄porous nanoplatelets.

(3) Adding aqueous solution of hydrogen peroxide and Cl-doped g-C of N vacancy into a reaction bottle₃N₄Porous nanosheets, polyvinyl alcohol and tungstic acid, wherein hydrogen peroxide, Cl of N-vacancies are doped with g-C₃N₄The mass ratio of the porous nano-sheets to the polyvinyl alcohol to the tungstic acid is 180-220:100:3-8:8-20, the solution is dried in vacuum to remove the solvent after being uniformly dispersed by ultrasound, the solution is placed in a resistance furnace, the temperature is raised to 540-560 ℃ in the air atmosphere, the solution is subjected to heat preservation and calcination for 2-4h, and the WO is obtained through preparation₃Seed crystal loading g-C₃N₄Porous nanoplatelets.

(4) Adding aqueous solution of hydrogen peroxide and tungstic acid into a reaction bottle, uniformly stirring at 80-90 ℃ until the solution is clear, adding acetonitrile solvent, oxalic acid and urea, adding concentrated hydrochloric acid solution, controlling the mass concentration of hydrochloric acid in the total solution to be 0.15-0.25mol/L and the volume ratio of the acetonitrile solvent to the aqueous solution to be 3-5:1, uniformly stirring at room temperature for 1-3h, and mixing the solution and WO₃Seed crystal loading g-C₃N₄Transferring the porous nano-sheets into a hydrothermal reaction kettle, wherein hydrogen peroxide, tungstic acid, oxalic acid, urea and WO₃Seed crystal loading g-C₃N₄The mass ratio of the porous nano-sheets is 40-100:10-25:0.5-1.5:0.5-1.5:100, the mixture is heated to 170-25 ℃, reacted for 2-4h, the solution is dried in vacuum, the solid mixed product is placed in an atmosphere resistance furnace, and is calcined for 2-3h in air atmosphere at 500-550 ℃, and the N-vacancy doped g-C is prepared₃N₄-WO₃A catalyst for hydrogen production by heterojunction photocatalysis.