CN112337496B - Method for preparing ternary composite photocatalyst by combining supercritical water/supercritical organic matter - Google Patents

Method for preparing ternary composite photocatalyst by combining supercritical water/supercritical organic matter Download PDF

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CN112337496B
CN112337496B CN202011253868.4A CN202011253868A CN112337496B CN 112337496 B CN112337496 B CN 112337496B CN 202011253868 A CN202011253868 A CN 202011253868A CN 112337496 B CN112337496 B CN 112337496B
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nitrate
water
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李菊英
张月超
钱正芳
丁腾达
钱毅光
高小中
程亚楠
黄晓桐
潘伟杰
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Shenzhen University
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/30—Treatment of water, waste water, or sewage by irradiation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2305/10—Photocatalysts

Abstract

The invention discloses a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters, and relates to the technical field of photocatalyst preparation. The method firstly utilizes supercritical hydrothermal polycondensation to prepare g-C with a porous structure 3 N 4 (ii) a Then the g-C obtained is 3 N 4 Performing supercritical hydrothermal synthesis with aqueous solution of metal salt to obtain g-C with metal oxide deposited on surface 3 N 4 A composite material; finally, reducing the noble metal salt by using a supercritical organic matter to further obtain metal oxide/g-C with highly dispersed noble metal simple substance deposited on the surface 3 N 4 Finally obtaining the noble metal/metal oxide/g-C 3 N 4 A three-way catalyst. The invention fully utilizes the different advantages of supercritical water and supercritical organic matter in the preparation of materials, and the preparation is completed in the same closed kettle body, and the yield and the purity of the materials are high. The process flow is simple, the synthesis speed is high, the organic solvent can be recycled, and the risk of environmental pollution is reduced.

Description

Method for preparing ternary composite photocatalyst by combining supercritical water/supercritical organic matter
Technical Field
The invention relates to the technical field of photocatalyst preparation, in particular to a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters.
Background
In recent years, with the rapid development of industrialization and urbanization, environmental pollution is attracting much attention. Organic pollutants, which are one of the important causes of water environment deterioration, are high in content, various in types and high in toxicity, and pose serious threats to living beings and ecological systems. The photocatalysis technology is a green technology, utilizes the energy required by the conversion of light energy into chemical reaction to generate catalysis, and has wide application prospect in the fields of environment, energy and the like. Compared with the traditional treatment method, the semiconductor photocatalytic oxidation technology has the characteristics of mild reaction conditions, high treatment efficiency, simpler operation, environmental friendliness and the like, and has unique advantages in solving the environmental problems.
Semiconductor materials such as TiO are currently being investigated and used in many applications 2 The wide band gap of ZnO and the like causes that the wavelength region of the semiconductor materials which generate the photocatalytic reaction is limited by ultraviolet light, and the radiation energy of the ultraviolet light only accounts for about 4 percent of the sunlight, thereby becoming an important factor for limiting the large-scale application of the semiconductor materials. g-C as a visible light-responsive semiconductor catalyst 3 N 4 The (graphite-like phase carbon nitride) has the advantages of unique electronic structure, high thermal stability and chemical stability, low cost, easy synthesis and the like, and gradually becomes a research hotspot in the field of photocatalysis. However, g-C 3 N 4 The problems of small specific surface area, easy recombination of photon-generated carriers, low utilization rate of visible light and the like still cause a lot of difficulties in practical application. In order to improve the photocatalytic activity of semiconductor materials, methods such as doping metals, compounding semiconductor materials, depositing noble metals on the surface, and the like are generally adopted, so that the recombination of photon-generated carriers can be inhibited, the spectral response range can be widened, and the like.
Chinese patent CN110813354A discloses a g-C 3 N 4 Method for preparing/ZnO/GO ternary composite material and degrading methyl orange, and roasting melamine to obtain light yellow product g-C 3 N 4 Grinding, storing, collecting g-C 3 N 4 Suspending liquid, dispersing by ultrasonic wave, adding zinc acetate and sodium hydroxide in sequenceHeating in water bath for reaction, adding ammonium nonylphenol polyoxyethylene ether oxide, dropwise adding GO suspension, performing ultrasonic treatment, aging, suction filtration, water washing, alcohol washing and drying to obtain g-C 3 N 4 /ZnO/GO; chinese patent CN111408395A discloses an RGO/Cu 5 FeS 4 /g-C 3 N 4 The preparation method of the ternary composite photocatalyst comprises the steps of mixing molybdenum disulfide and carbon nitride with water, carrying out ultrasonic treatment, transferring to a dark environment, adding silver nitrate, heating, keeping the temperature, simultaneously dropwise adding a sodium phosphate solution to obtain a suspension, centrifuging, washing with water, washing with alcohol, and drying to obtain Ag 3 PO 4 /g-C 3 N 4 @MoS 2 A photocatalyst; chinese patent CN110152711A discloses CeO 2 @MoS 2 /g-C 3 N 4 The composite photocatalytic material is prepared through (1) hydrothermal treatment and calcination of the mixed solution of cerium oxide hexahydrate, butylamine and toluene to obtain CeO 2 A nanocrystal; (2) Mixing sodium molybdate dihydrate with g-C 3 N 4 The nano-sheets are ultrasonically dispersed in a mixed solution of L-cysteine and dimethyl sulfoxide, and the obtained mixed solution is subjected to hydrothermal treatment to obtain MoS 2 /g-C 3 N 4 Nanosheets; (3) CeO is added 2 Nanocrystalline and MoS 2 /g-C 3 N 4 Ultrasonically dispersing in methanol solution, and volatilizing the methanol to obtain a product CeO 2 -MoS 2 /g-C 3 N 4 The composite material is further calcined in the nitrogen atmosphere to obtain CeO 2 @CeO 2 -MoS 2 /g-C 3 N 4 A ternary composite photocatalyst.
The method for preparing the ternary composite photocatalyst has various steps and complex operation, and is not suitable for industrial production.
Disclosure of Invention
The invention aims to solve the technical problem of complex steps of the existing method for preparing the ternary composite photocatalyst, and provides a method for preparing the ternary composite photocatalyst by combining supercritical water/supercritical organic matters.
In order to solve the above problems, the present invention utilizes the excellent expansibility and fluidity of supercritical waterThe reaction activity and the characteristic of mutual solubility with gas can quickly obtain the g-C with a porous thin-layer structure 3 N 4 (ii) a Utilizes the excellent hydrolysis and diffusion capacity of supercritical water and the characteristic of rapidly precipitating inorganic salt crystals at g-C 3 N 4 Depositing nano particles on the surface; the high dispersion of the noble metal simple substance on the surface of the material is realized by utilizing the strong dispersion and reduction capability of the supercritical organic matter.
The technical scheme is as follows:
a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following steps:
(1) G to C 3 N 4 The mass ratio of the precursor to water is 1: (1.5-12) placing the mixture into a reaction kettle, sealing the reaction kettle, then heating and pressurizing the mixture to a supercritical state of water, and carrying out contact reaction for 1-5.5 hours to obtain g-C 3 N 4 (ii) a Continuously introducing a metal salt aqueous solution into the reaction kettle to ensure that the g-C 3 N 4 The mixture is contacted with the aqueous solution of metal salt for reaction for 5 to 115min, the gas-solid-liquid separation is realized by pressure relief, and the residual solid material in the kettle body is g-C 3 N 4 The composite material with metal oxide has water in supercritical state at 400-650 deg.c and pressure of 22.5-40 MPa;
(2) When the temperature of the reaction kettle in the step (1) is reduced to a set temperature, introducing an organic solvent and a noble metal salt solution, reacting for 25-120 min in a supercritical state of the organic solvent, relieving pressure and releasing air, stopping the reaction, cooling the reaction kettle to a proper temperature, disassembling the reaction kettle to obtain the product containing g-C 3 N 4 And the ternary composite photocatalyst of the metal oxide and the noble metal simple substance.
The further technical scheme is that in the step (1), oxidizing gas and/or inert gas with the flow rate of 0-18L/h is introduced into the reaction kettle.
The further technical proposal is that the oxidizing gas is at least one of oxygen and ozone; the inert gas is at least one of nitrogen, argon and helium.
The further technical scheme is that the g-C 3 N 4 The precursor is a cyano-containing groupA precursor compound of (1).
The further technical scheme is that the g-C 3 N 4 The precursor is urea, thiourea, cyanamide, dicyandiamide, melamine, cyanuric acid or a mixture thereof.
The further technical scheme is that in the step (1), the metal salt is zinc nitrate, manganese nitrate, magnesium nitrate, nickel nitrate, cobalt nitrate, aluminum nitrate, copper nitrate, ferric nitrate, cadmium nitrate, cerium nitrate, lanthanum nitrate or a mixture thereof, wherein the metal salt contains metal elements and g-C 3 N 4 The mass ratio of (1): (5 to 50).
The further technical scheme is that in the step (2), the noble metal salt is selected from chloroauric acid, sodium tetrachloroaurate, potassium tetrachloroaurate, platinum tetrachloride, chloroplatinic acid, sodium chloroplatinate, silver nitrate, silver sulfate, silver acetate, palladium dichloride, potassium tetrachloropalladate, sodium tetrachloropalladate, potassium hexachloropalladate, sodium hexachloropalladate, ruthenium trichloride, ammonium chlororuthenate, ruthenium nitrosyl nitrate or a mixture thereof, wherein the noble metal element and g-C contained in the noble metal salt 3 N 4 The mass ratio of (1): (10 to 100).
The further technical scheme is that in the step (2), the organic solvent is selected from methanol or ethanol.
The further technical proposal is that when the organic solvent is selected from methanol, the temperature of the supercritical state of the methanol is 244-283 ℃, and the pressure is 8.5-16 Mpa.
The further technical proposal is that when the organic solvent is selected from ethanol, the temperature of ethanol in a supercritical state is 245-285 ℃, and the pressure is 6.7-15.5 MPa.
The further technical scheme is that the step (2) further comprises the operation of recovering the organic solvent after the reaction is finished.
The principle of the invention is as follows:
(1) g-C is quickly obtained by utilizing the excellent expansibility, fluidity and reaction activity of supercritical water 3 N 4 ；
(2) By utilizing the characteristic of mutual solubility of supercritical water and gas, the expansion gas is beneficial to preparing porous g-C 3 N 4 And can also beStripping off block-shaped g-C 3 N 4 Thereby obtaining a thin layer g-C 3 N 4 When the gas is an oxidizing gas, g-C can be produced more rapidly 3 N 4 ；
(3) The excellent hydrolysis and diffusion capacity of supercritical water is utilized, and the inorganic salt active component can be quickly crystallized and separated out;
(4) The supported catalyst with high dispersion is prepared by utilizing the outstanding reducibility and dispersibility of the supercritical organic solvent.
Compared with the prior art, the invention can achieve the technical effects that:
the invention provides a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters, which comprises the step of preparing g-C with a porous structure by supercritical water thermal polycondensation 3 N 4 (ii) a Then g-C obtained 3 N 4 Performing supercritical hydrothermal synthesis with aqueous solution of metal salt to obtain g-C with metal oxide deposited on surface 3 N 4 A composite material; finally, reducing the noble metal salt by using a supercritical organic matter to further obtain metal oxide/g-C with highly dispersed noble metal simple substances deposited on the surface 3 N 4 Finally obtaining the noble metal/metal oxide/g-C 3 N 4 A three-way catalyst.
The invention utilizes supercritical water to prepare g-C by thermal condensation polymerization 3 N 4 The preparation period is short; the reaction process is completed in a closed space, g-C 3 N 4 The yield is high, and the purity of the product is high; the raw materials have no special requirements, and the applicability is strong; the water and the organic stripping agent can be recycled, so that the process cost is reduced; g-C in sequence in a closed space 3 N 4 With noble metal/metal oxide/g-C 3 N 4 In the preparation process, the purity of the product is high; after the reaction, the pressure can be directly released to realize solid-liquid-gas separation, and the residual solid in the kettle is noble metal/metal oxide/g-C 3 N 4 The ternary composite photocatalyst.
Detailed Description
The technical solutions in the examples will be clearly and completely described below. It is apparent that the embodiments to be described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the embodiments of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention. As used in the description of embodiments of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be noted that, in the embodiment of the present invention, the photocatalytic ability is determined by the efficiency of catalyzing and degrading organic matters under the same conditions, rhodamine B is used as a model compound, and the reaction conditions are as follows: under visible light (lambda is more than 420 nm), the using amount of the catalyst is 1g/L, the concentration of methyl orange is 10ppm, and the treatment time is 45min.
Example 1: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Putting melamine and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing a zinc nitrate aqueous solution (zinc element and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (40) for 5min of contact reaction, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with zinc oxide is in a nitrogen atmosphere of 18L/h in the whole reaction process;
(2) Waiting reaction kettleWhen the temperature is reduced to 245 ℃, ethanol and chloroauric acid (gold element and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (100) in a supercritical state (15.5 MPa) of ethanol, reacting the residual solid in the step (1) with chloroauric acid for 25min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of photocatalytic degradation of rhodamine B is 97.9%.
Example 2: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Placing dicyandiamide and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing the ferric nitrate aqueous solution (iron element and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (20) for contact reaction for 18min, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with the iron oxide is in 14L/h argon atmosphere in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 265 ℃, ethanol and chloroplatinic acid (platinum element and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (50) under the supercritical state (6.7 MPa) of ethanol, reacting the residual solid in the step (1) with chloroplatinic acid for 75min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B by photocatalysis is 98.6 percent.
Example 3: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Putting urea and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing a cerous nitrate aqueous solution (cerium element and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (20) for 45min, and releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with cerium oxide is in 12L/h helium atmosphere in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 283 ℃, methanol and silver nitrate (silver element and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (10) in a supercritical state of methanol (8.5 MPa), reacting the residual solid in the step (1) with silver nitrate for 125min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B by photocatalysis is 94.9 percent.
Example 4: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Placing cyanamide and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing lanthanum nitrate aqueous solution (lanthanum element and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (20) for contact reaction for 115min, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with lanthanum oxide is in an oxygen atmosphere of 4.8L/h in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 265 ℃, methanol and potassium tetrachloropalladate (palladium and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (20) under a supercritical state (14 MPa) of methanol, reacting the residual solid in the step (1) with potassium tetrachloropalladate for 105min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B through photocatalysis is 96.5 percent.
Example 5: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Thiourea and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing an aluminum nitrate aqueous solution (aluminum element and g-C) 3 N 4 The mass ratio of (1) to (15) for contact reaction for 95min, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with the aluminum oxide is in the ozone atmosphere of 0.6L/h in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 265 ℃, ethanol and ruthenium trichloride (ruthenium element and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (60) in a supercritical state (12.5 MPa) of ethanol, reacting the residual solid in the step (1) with ruthenium trichloride for 95min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B through photocatalysis is 98.3 percent.
Example 6: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Placing cyanuric acid and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing a nickel nitrate aqueous solution (nickel element and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (50) for 45min, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with nickel oxide is in the ozone atmosphere of 1.8L/h in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 270 ℃, ethanol and ammonium chlororuthenate (ruthenium element and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (80), in a supercritical state (14 MPa) of ethanol, reacting residual solids in the (1) with ammonium chlororuthenate for 40min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B by photocatalysis is 96.9 percent.
Example 7: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Putting urea and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing the copper nitrate aqueous solution (copper element and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (10) for 30min, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with the copper oxide is in a helium atmosphere of 7.5L/h in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 270 ℃, introducing methanol and palladium dichloride (palladium element and g-C) 3 N 4 The mass ratio of (1) to (40) under the supercritical state (11 MPa) of methanol, reacting the residual solid in (1) with palladium dichloride for 30min, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B by photocatalysis is 94.4 percent.
Example 8: a method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters comprises the following specific steps:
(1) Placing dicyandiamide and water in a mass ratio of 1 3 N 4 (ii) a Continuously introducing a cerium nitrate solution (cerium and g-C) into the reaction kettle 3 N 4 The mass ratio of (1) to (5) for 30min after contact reaction, releasing pressure to realize gas-solid-liquid separation, wherein the solid material remained in the kettle body is g-C 3 N 4 The catalyst compounded with the cerium oxide is in a nitrogen atmosphere of 16L/h in the whole reaction process;
(2) When the temperature of the reaction kettle is reduced to 258 ℃, methanol and silver acetate (silver element and g-C) are introduced into the reaction kettle 3 N 4 The mass ratio of (1) to (30), reacting the residual solid in the step (1) with silver acetate for 55min in a supercritical state (13.8 MPa) of methanol, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, and disassembling the reaction kettle to obtain g-C 3 N 4 The efficiency of degrading rhodamine B by photocatalysis is 97.8 percent.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to the related descriptions of other embodiments.
While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and various equivalent modifications and substitutions may be easily made by those skilled in the art within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (6)

1. A method for preparing a ternary composite photocatalyst by combining supercritical water/supercritical organic matters is characterized by comprising the following steps:
(1) G to C 3 N 4 The mass ratio of the precursor to water is 1: (1.5 to 12) placing the mixture into a reaction kettle, sealing the reaction kettle, then heating and pressurizing the mixture to a supercritical state of water, and carrying out contact reaction for 1 to 5.5 hours to obtain g-C 3 N 4 (ii) a Continuously introducing a metal salt aqueous solution into the reaction kettle to ensure that the g-C 3 N 4 The reaction is carried out for 5 to 115min by contacting with a metal salt aqueous solution, the gas-solid-liquid separation is realized by pressure relief, and the solid material remained in the kettle is g-C 3 N 4 Composite materials with metal oxides in which water is superadjacentThe temperature of the boundary state is 400 to 650 ℃, and the pressure is 22.5 to 40MPa;
(2) When the temperature of the reaction kettle in the step (1) is reduced to a set temperature, introducing an organic solvent and a noble metal salt solution, reacting for 25-120min in a supercritical state of the organic solvent, relieving pressure and air, stopping the reaction, cooling the reaction kettle to a proper temperature, disassembling the reaction kettle to obtain the product containing g-C 3 N 4 The ternary composite photocatalyst comprises a metal oxide and a noble metal simple substance;
in the step (1), oxidizing gas and/or inert gas with the flow rate of 0-18L/h is introduced into the reaction kettle;
the g to C 3 N 4 The precursor is at least one of urea, thiourea, cyanamide, dicyandiamide, melamine and cyanuric acid;
in the step (2), the organic solvent is methanol or ethanol.
2. The supercritical water/supercritical organic matter combined preparation method of the ternary composite photocatalyst of claim 1, wherein in step (1), the metal salt is at least one of zinc nitrate, manganese nitrate, magnesium nitrate, nickel nitrate, cobalt nitrate, aluminum nitrate, copper nitrate, ferric nitrate, cadmium nitrate, cerium nitrate and lanthanum nitrate, wherein the metal salt contains metal elements in combination with g-C 3 N 4 The mass ratio of (1): (5 to 50).
3. The supercritical water/supercritical organic matter combined preparation method of a composite ternary photocatalyst according to claim 1, wherein in step (2), the noble metal salt is at least one of chloroauric acid, sodium tetrachloroaurate, potassium tetrachloroaurate, platinum tetrachloride, chloroplatinic acid, sodium chloroplatinate, silver nitrate, silver acetate, palladium dichloride, potassium tetrachloropalladate, sodium tetrachloropalladate, potassium hexachloropalladate, sodium hexachloropalladate, ruthenium trichloride, ammonium chlororuthenate and ruthenium nitrosyl nitrate, wherein the noble metal element and g-C contained in the noble metal salt 3 N 4 The mass ratio of (1): (10 to 100).
4. The method for preparing the three-way composite photocatalyst by combining supercritical water/supercritical organic matters as claimed in claim 1, wherein when the organic solvent is methanol, the temperature of the supercritical state of the methanol is 244-283 ℃, and the pressure is 8.5-16900 MPa.
5. The supercritical water/supercritical organic compound joint preparation method of the ternary composite photocatalyst as claimed in claim 1, wherein when ethanol is selected as the organic solvent, the temperature of the ethanol in a supercritical state ranges from 245 ℃ to 285 ℃, and the pressure ranges from 6.7MPa to 15.5MPa.
6. The method for preparing the composite ternary photocatalyst by combining supercritical water and supercritical organic matter as defined in claim 1, wherein the step (2) further comprises an operation of recovering the organic solvent after the reaction is finished.
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