A S, Na, B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst and its preparation method and application

Abstract

A S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst, a preparation method, and an application thereof. The catalyst uses 10 g of urea with a purity of 99.9 wt%, 0.2-1 g of CH4N2S, and 0.1-0.5 g of NaBH4 as raw materials. A multi-element co-doped precursor material is first prepared; the prepared multi-element co-doped precursor is then calcined to prepare an S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst; the synergistic effect between the cyanide and (S, Na, and B) atomic doping broadens the light absorption range of g-C3N4, increases the specific surface area, and reduces the carrier recombination rate, thereby improving the catalytic performance; the g-C3N4 photoresponsive catalyst material obtained under optimal optimization conditions has a specific surface area of ​​50.8 m 2 ·g ‑1 , which is 1.8 times that of the original g‑C3N4; the catalytic hydrogen production activity in the wavelength range of 380-500nm is 3637.9μmol·h ‑1 ·g ‑1 , which is 7.6 times that of the original g‑C3N4, and the reduction rate of CO2 to CO is 779.2 μmol·h ‑1 ·g ‑1 , which is 2.9 times that of the original g-C3N4; the present invention is simple to operate, has good repeatability, and can improve the efficiency of water decomposition to produce hydrogen and the efficiency of CO2 reduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysis, and in particular relates to a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of science and technology and the advancement of global industrialization, the limited and rapid consumption of fossil energy has led to a serious energy crisis. At the same time, its development and utilization has also brought about serious environmental pollution problems, posing a huge threat to the survival and development of human society. Therefore, promoting the low-carbon transformation of the global energy industry and society and developing clean and efficient renewable energy have become ideal ways to promote the healthy and harmonious development of human society, and are also strategic goals in the field of energy technology in my country. Hydrogen energy has always been regarded as an ideal clean and renewable energy source with the characteristics of high energy density, excellent combustion performance, easy storage and transportation, and no pollution. The use of solar energy to photocatalytically decompose water to produce hydrogen is a clean energy technology that converts solar energy into hydrogen energy and is expected to achieve a sustainable "hydrogen economy". Among them, the preparation of non-toxic, inexpensive, efficient and stable visible light photocatalysts is one of the keys to this technology.

[0003] The reaction principle of photocatalytic hydrogen production involves three main steps. First, the generation of photogenerated carriers. When light strikes the photocatalyst surface, valence band electrons absorb photons with energy greater than the band gap energy and transition to the conduction band to become photogenerated electrons. Photogenerated holes form in the valence band. These electron-hole pairs are called photogenerated carriers. Photogenerated electrons have reducing power and participate in the hydrogen evolution reaction, while photogenerated holes have oxidizing power and participate in the oxygen evolution reaction. The second step is the transfer of photogenerated carriers. Some photogenerated carriers migrate to the surface and participate in the reaction. Only those that successfully migrate and do not recombine can effectively participate in the reaction. The final step is the redox reaction. Some photogenerated carriers migrate to the surface and bind to substances in the solution, participating in the redox reaction. In photocatalytic water splitting to produce hydrogen, photogenerated electrons combine with hydrogen ions in water to produce hydrogen gas, while photogenerated holes oxidize the sacrificial agent into organic matter. In actual reactions, a series of intermediate products may be produced. To ensure the photocatalytic splitting of water to produce hydrogen, the photocatalyst's energy band structure must meet certain requirements, allowing photogenerated electrons to participate in the hydrogen evolution reaction and photogenerated holes to participate in the oxygen evolution reaction. Photocatalysts absorb energy, and the shortest wavelength of sunlight corresponds to a band gap energy of 4.2 eV. Based on the energy band structure of photocatalysts, the band gap energy of currently common photocatalysts ranges from 1.23 to 4.2 eV.

[0004] Since the energy of sunlight is mainly concentrated in the visible light region, the preparation of photocatalyst materials with visible light response has always been a hot topic and focus of research. The graphite phase carbon nitride (g-C3N4) photocatalyst has a band gap width of about 2.7eV, good acid, alkali, light and thermal stability, easy to control the morphology and energy band, and can decompose water to produce hydrogen under visible light. It has been widely used in the field of photocatalysis. In addition, the raw materials for the preparation of g-C3N4 are abundant, the preparation method is simple, and the preparation cost is low, which has great application prospects and research value. However, the efficiency of g-C3N4 in decomposing water to produce hydrogen in current research results cannot meet the requirements of industrial production, and it often shows low photocatalytic hydrogen production efficiency due to problems such as high carrier recombination rate and small specific surface area, which limits its potential application value. Summary of the Invention

[0005] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, a preparation method and application thereof, and a reliable preparation scheme for S, Na, and B co-doped cyanide-rich g-C3N4 by hydrothermally treating the original g-C3N4 with CH4N2S and NaBH4 and then calcining it again, and realizing photocatalytic decomposition of water to produce hydrogen and reduction of CO2, which is beneficial to the industrial application of photocatalytic decomposition of water to produce hydrogen and reduction of CO2, and has the characteristics of simple operation, good repeatability, cheap and easy to obtain raw materials, and the obtained product has excellent visible light catalytic decomposition of water to produce hydrogen performance.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A S, Na, and B co-doped cyanide-rich graphite phase carbon nitride light-responsive catalyst comprises raw materials including: 10g urea, 0.2-1g CH4N2S, and 0.1-0.5g NaBH4, all of which are of analytical purity of 99.9wt%.

[0008] A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, comprising the following steps:

[0009] Step 1: Prepare a multi-element co-doped precursor material using 10g urea with a purity of 99.9wt%, 0.2-1g CH4N2S and 0.1-0.5g NaBH4;

[0010] Step 2: calcining the multi-element co-doped precursor prepared in step 1 to prepare S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0011] The specific method of step 1 is: weigh 10g of 99.9wt% urea, and condense it in air at 2-5℃·min-1 The method comprises the following steps: calcining the mixture at a heating rate of 500-550°C for 2-4 hours, grinding the resultant into powder and naming it CN; weighing 0.5g CN, 0.2-1g CH4N2S of 99.9wt% and 0.1-0.5g NaBH4 of 99.9wt% and sequentially adding them into 30-50mL H2O to obtain a solution, heating the solution from room temperature to an oil bath of 100-120°C under magnetic stirring and maintaining the mixture for 2-4 hours; gradually evaporating the solution to obtain a slurry, and adding 30-50mL of a 1:1 ethanol / H2O solution to the slurry and stirring the mixture for 30-60 minutes; vacuuming the slurry for 5-15 minutes to obtain a solid compound, which was dried in air at 60-85°C for 3-5 hours to obtain a multi-element co-doped g-C3N4 precursor material.

[0012] The specific method of step 2 is: weigh 0.5-1g of material precursor, calcinate at 500-550°C for 4-6h under Ar atmosphere, and obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0013] A method for photocatalytically splitting water to produce hydrogen using S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst, the specific method being:

[0014] 20.0-50 mg of the prepared S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst was added to the reactor, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 8-16 mL was added as a sacrificial agent; 0.571-1.43 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was then added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp;

[0015] Argon was purged into the reactor for 10-20 minutes to remove oxygen and eliminate the interference of oxygen in the reactor. The reactor was maintained at a fixed temperature of 30-40°C by circulating water. A magnetic stirrer was turned on and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

[0016] A method for reducing carbon dioxide using S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst, specifically comprising:

[0017] 10.0-20.0 mg of the prepared S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst was added to a reactor, followed by 4-8 mL of deionized water, 1-2 mL of triethanolamine, and 10-20 mL of acetonitrile. Magnetic stirring was performed to obtain a uniform dispersion. 8-16 mg of [Ru(bpy))3]Cl2·6H2O was then added to the dispersion as a photosensitizer.

[0018] The reactor was purged with CO2 for 30-40 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at a fixed temperature within the range of 30-40°C. The magnetic stirrer was turned on and the xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses CH4N2S and NaBH4 for the first time in a hydrothermal modification process to synthesize S, Na, and B co-doped cyanide-rich g-C3N4. This S, Na, and B co-doped cyanide-rich g-C3N4 has a large specific surface area and good light absorption performance, effectively promoting the separation and migration of photogenerated carriers inside g-C3N4 under visible light irradiation, showing good visible light photocatalytic hydrogen production activity and carbon dioxide reduction performance, and the visible light photocatalytic hydrogen production rate reaches 3637.9 μmol·h -1 ·g -1 , and has good hydrogen production stability, and the reduction rate of CO2 to CO is 779.2μmol·h -1 ·g -1 ; The visible light photocatalytic hydrogen production rate and CO reduction rate were greatly improved.

[0021] The present invention hydrothermally treats g-C3N4 directly obtained by calcining urea in air with CH4N2S and NaBH4 to form an S, Na, and B co-doped precursor, which is then calcined to obtain a S, Na, and B co-doped cyanide-rich g-C3N4 photoresponsive catalyst material. The synergistic effect between the cyanide and (S, Na, and B) atom doping broadens the light absorption range of the g-C3N4. The prepared g-C3N4 is modified with CH4N2S and NaBH4 to construct a novel g-C3N4 visible light responsive catalyst material having excellent properties such as a large specific surface area, low crystallinity, a narrow band gap, and a suitable carrier lifetime, thereby improving the photocatalytic efficiency.

[0022] In summary, the present invention is simple to operate, has good reproducibility, and uses inexpensive and easily available raw materials. The prepared product has excellent visible light photocatalytic water decomposition and hydrogen production performance, providing a reliable solution for the development and application of new photocatalysts that improve the efficiency of photocatalytic water decomposition and hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the X-ray diffraction (XRD) pattern of S, Na, and B co-doped cyanide-rich g-C3N4.

[0024] Figure 2This is the Fourier transform infrared (FTIR) spectrum of S, Na, and B co-doped cyanide-rich g-C3N4.

[0025] Figure 3 is an X-ray photoelectron spectrum (XPS) of S, Na, and B co-doped cyanide-rich g-C3N4: Figure 3(a) is a graph of CNS-NaB 0.5 The peak of S2p detected in the sample; Figure 3(b) is the peak of Na 1s; Figure 3(c) is the peak of B1s.

[0026] Figure 4 This is the UV-visible absorption spectrum of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B.

[0027] Figure 5(a) is the N2 adsorption-desorption isotherm of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B.

[0028] Figure 5(b) is the BJH pore size distribution of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B.

[0029] Figure 6(a) is the steady-state PL spectrum of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B.

[0030] Figure 6(b) is the transient PL spectrum of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B.

[0031] Figure 7 This is the X-ray diffraction (SEM) pattern of S, Na, and B co-doped cyanide-rich g-C3N4.

[0032] Figure 8 This is a transmission electron microscope (TEM) photo of S, Na, and B co-doped cyanide-rich g-C3N4.

[0033] Figure 9(a) is a graph showing the visible light photocatalytic hydrogen production rate of cyanide-rich g-C3N4 co-doped with S, Na, and B.

[0034] Figure 9(b) is a test graph of the visible light catalytic hydrogen production stability of S, Na, and B co-doped cyanide-rich g-C3N4.

[0035] Figure 10(a) is a graph showing the visible light photocatalytic reduction rate of carbon dioxide by cyanide-rich g-C3N4 co-doped with S, Na, and B.

[0036] Figure 10(b) is a test graph of the stability of visible light catalytic reduction of carbon dioxide by S, Na, and B co-doped cyanide-rich g-C3N4. DETAILED DESCRIPTION

[0037] Example 1:

[0038] A S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst comprises raw materials including 10g urea, 0.5g CH4N2S, and 0.5g NaBH4, all of which are of analytical purity of 99.9wt%.

[0039] A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, comprising the following steps:

[0040] Step 1: Weigh 10 g of urea (99.9 wt%) and add it to a ceramic crucible with a lid. -1 The mixture was calcined at 550°C for 4 h at a heating rate of 100 wt %. The resultant was ground into powder and named CN. 0.5 g CN, 0.5 g CH4N2S (99.9 wt %) and 0.5 g NaBH4 (99.9 wt %) were weighed and added to 30 mL H2O in sequence to obtain a solution. The solution was heated from room temperature to an oil bath at 120°C under magnetic stirring and maintained for 2 h. The solution was gradually evaporated to dryness to obtain a slurry. 30 mL of a 1:1 ethanol / H2O solution was added to the slurry and stirred for 30 min. The solid compound was obtained by evacuating the slurry for 10 min and dried in air at 80°C for 3 h to obtain a multi-element co-doped g-C3N4 precursor material.

[0041] Step 2: Weigh 1 g of multi-element co-doped g-C3N4 precursor material and spread it flat in an ark (6 cm x 3 cm x 2 cm), and calcine it at 500 °C for 4 h in an Ar atmosphere in a tube furnace to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0042] An application method of S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst for photocatalytic water decomposition to produce hydrogen, specifically comprising:

[0043] 20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added to a glass side window reactor with a volume of 105 mL, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 10 mL was added; and 0.571 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp;

[0044] Argon was purged through the glass side window reactor for 15 minutes to remove oxygen and eliminate the interference of oxygen in the air in the reactor. The reactor was maintained at 35°C by circulating water, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

[0045] An application method of S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst for carbon dioxide reduction, specifically:

[0046] In a 105 mL glass side window reactor, 10.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst prepared in step 2 was added, followed by 4 mL of deionized water, 1 mL of triethanolamine, and 10 mL of acetonitrile. Magnetic stirring was performed to obtain a uniform dispersion. 8 mg of [Ru(bpy))3]Cl2·6H2O was then added to the dispersion as a photosensitizer.

[0047] The reaction was purged with CO2 for 30 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at 35°C, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

[0048] Example 2:

[0049] A S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst is characterized in that its raw materials include: 10g urea, 1g CH4N2S and 0.5g NaBH4, all of which are 99.9wt% analytically pure.

[0050] A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, comprising the following steps:

[0051] Step 1: Weigh 10 g of urea (99.9 wt%) and add it to a ceramic crucible with a lid and incubate in air at 4 °C / min. -1 The mixture was calcined at 550°C for 3 h at a heating rate of 100 wt %. The obtained yellow powder g-C3N4 was ground into powder and named CN. 0.5 g CN, 1 g CH4N2S (99.9 wt %) and 0.5 g NaBH4 (99.9 wt %) were weighed and added to 30 mL H2O in sequence to obtain a solution. The solution was heated from room temperature to an oil bath at 100°C under magnetic stirring and maintained for 4 h. The solution was gradually evaporated to dryness to obtain a slurry. 40 mL of a 1:1 ethanol / H2O solution was added to the slurry and stirred for 40 min. The solid compound was obtained by evacuating the slurry for 5 min and dried in air at 70°C for 3 h to obtain a multi-element co-doped g-C3N4 precursor material.

[0052] Step 2: Weigh 1g of multi-element co-doped g-C3N4 precursor material and spread it flat in an ark (6cm x 3cm x 2cm), and calcine it at 550℃ in a tube furnace under Ar atmosphere for 3h to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0053] An application method of S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst for photocatalytic water decomposition to produce hydrogen, specifically comprising:

[0054] 20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added to a glass side window reactor with a volume of 105 mL, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 10 mL was added; and 0.571 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp;

[0055] Argon was purged through the glass side window reactor for 10 minutes to remove oxygen and eliminate the interference of oxygen in the air in the reactor. The reactor was maintained at 36°C by circulating water, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

[0056] An application method of S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst for carbon dioxide reduction, specifically:

[0057] In a 105 mL glass side window reactor, 10.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst prepared in step 2 was added, followed by 4 mL of deionized water, 1 mL of triethanolamine, and 10 mL of acetonitrile. Magnetic stirring was performed to obtain a uniform dispersion. Then, 10 mg of [Ru(bpy)3]Cl2·6H2O was added to the dispersion as a photosensitizer.

[0058] The reaction was purged with CO2 for 40 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at 36°C, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

[0059] Example 3:

[0060] A S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst is characterized in that its raw materials include: 10g urea, 1g CH4N2S and 0.3g NaBH4, all of which are 99.9wt% analytically pure.

[0061] A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, comprising the following steps:

[0062] Step 1: Weigh 10 g of urea (99.9 wt%) and add it to a ceramic crucible with a lid and incubate in air at 5 °C / min. -1The mixture was calcined at 530°C for 3 hours at a heating rate of 100 ℃. The resulting yellow powder g-C3N4 was ground and named CN. 0.5g CN, 1g CH4N2S (99.9wt%), and 0.3g NaBH4 (99.9wt%) were weighed and added to 30mL H2O in sequence to obtain a solution. The solution was heated from room temperature to a 110°C oil bath under magnetic stirring and maintained for 3 hours. The solution was gradually evaporated to dryness to obtain a slurry, and 36mL of a 1:1 ethanol / H2O solution was added to the slurry and stirred for 30 minutes. The solid compound was obtained by vacuuming the slurry for 10 minutes and dried in air at 80°C for 3 hours to obtain a multi-element co-doped precursor material.

[0063] Step 2: Weigh 1 g of the precursor and spread it flat in an ark (6 cm x 3 cm x 2 cm), and calcine it at 530 ° C for 3 h in an Ar atmosphere in a tube furnace to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0064] An application method of S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst for photocatalytic water decomposition to produce hydrogen, specifically comprising:

[0065] 20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added to a glass side window reactor with a volume of 105 mL, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 10 mL was added; and 0.571 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp;

[0066] Before illumination, argon was purged into the reactor for 10 minutes to remove oxygen from the system (eliminating interference from oxygen in the air in the reactor). The reactor was maintained at 34°C by circulating water, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

[0067] An application method of S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst for carbon dioxide reduction, specifically:

[0068] In a 105 mL glass side window reactor, 10.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst prepared in step 2 was added, along with 4 mL of deionized water, 1 mL of triethanolamine, and 10 mL of acetonitrile. 8 mg of [Ru(bpy)3]Cl2·6H2O was added to the dispersion as a photosensitizer.

[0069] The reaction was purged with CO2 for 35 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at 34°C, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

[0070] Example 4:

[0071] A S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst is characterized in that its raw materials include: 10g urea, 0.6g CH4N2S and 0.5g NaBH4, all of which are 99.9wt% analytically pure.

[0072] A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, comprising the following steps:

[0073] Step 1: Weigh 10 g of urea (99.9 wt%) and add it to a ceramic crucible with a lid and incubate in air at 5 °C / min. -1 The mixture was calcined at 500°C for 4 h at a heating rate of 100 ℃, and the obtained yellow powder g-C3N4 was ground and named CN; 0.5 g CN, 0.6 g CH4N2S (99.9 wt%) and 0.5 g NaBH4 (99.9 wt%) were weighed and added to 30 mL H2O in sequence to obtain a solution, which was heated from room temperature to a 120°C oil bath under magnetic stirring and maintained for 4 h; the solution was gradually evaporated to dryness to obtain a slurry, and 40 mL of a 1:1 ethanol / H2O solution was added to the slurry and stirred for 60 min; a solid compound was obtained by evacuating the slurry for 15 min, and the multi-element co-doped precursor material was obtained by drying at 60°C in air for 5 h;

[0074] Step 2: Weigh 1 g of the precursor and spread it flat in an ark (6 cm x 3 cm x 2 cm), and calcine it at 500 °C for 4 h in an Ar atmosphere in a tube furnace to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0075] An application method of S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst for photocatalytic water decomposition to produce hydrogen, specifically comprising:

[0076] 20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added to a glass side window reactor with a volume of 105 mL, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 10 mL was added; and 1.43 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp;

[0077] Before illumination, argon was purged into the reactor for 10 minutes to remove oxygen from the system (eliminating interference from oxygen in the air in the reactor). The reactor was maintained at 35° C. by circulating water, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

[0078] An application method of S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst for carbon dioxide reduction, specifically:

[0079] In a 105 mL glass side window reactor, 10.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst prepared in step 2 was added, along with 4 mL of deionized water, 1 mL of triethanolamine, and 10 mL of acetonitrile. 8 mg of [Ru(bpy)3]Cl2·6H2O was added to the dispersion as a photosensitizer.

[0080] The reaction was purged with CO2 for 40 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at 35°C, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

[0081] Example 5:

[0082] A S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst is characterized in that its raw materials include: 10g urea, 0.8g CH4N2S and 0.3g NaBH4, all of which are 99.9wt% analytically pure.

[0083] A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, comprising the following steps:

[0084] Step 1: Weigh 10 g of urea (99.9 wt%) and add it to a ceramic crucible with a lid and incubate in air at 5 °C / min. -1 The mixture was calcined at 550°C for 4 h at a heating rate of 100 ℃, and the resulting yellow powder g-C3N4 was ground and named CN. 0.5 g CN, 0.8 g CH4N2S (99.9 wt%), and 0.3 g NaBH4 (99.9 wt%) were weighed and added to 30 mL H2O in sequence to obtain a solution. The solution was heated from room temperature to a 120°C oil bath under magnetic stirring and maintained for 2 h. The solution was gradually evaporated to dryness to obtain a slurry, and 40 mL of a 1:1 ethanol / H2O solution was added to the slurry and stirred for 30 min. The solid compound was obtained by evacuating the slurry for 10 min, and dried in air at 80°C for 3 h to obtain a multi-element co-doped precursor material.

[0085] Step 2: Weigh 1 g of the precursor and spread it flat in an ark (6 cm x 3 cm x 2 cm), and calcine it at 550 ° C for 4 h in an Ar atmosphere in a tube furnace to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

[0086] An application method of S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst for photocatalytic water decomposition to produce hydrogen, specifically comprising:

[0087] 20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added to a glass side window reactor with a volume of 105 mL, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 10 mL was added; and 0.571 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp;

[0088] Before illumination, argon was purged into the reactor for 20 minutes to remove oxygen from the system (eliminating interference from oxygen in the air in the reactor). The reactor was maintained at 36° C. by circulating water, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

[0089] An application method of S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst for carbon dioxide reduction, specifically:

[0090] In a 105 mL glass side window reactor, 10.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst prepared in step 2 was added, along with 4 mL of deionized water, 1 mL of triethanolamine, and 10 mL of acetonitrile. 8 mg of [Ru(bpy)3]Cl2·6H2O was added to the dispersion as a photosensitizer.

[0091] The reaction was purged with CO2 for 40 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at 36°C, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

[0092] Figure 1 This is the X-ray diffraction (XRD) pattern of S, Na, and B co-doped cyanide-rich g-C3N4. All samples have characteristic peaks of graphitic carbon nitride (g-C3N4). Except for the CNS sample, the peak intensities of the modified samples at 12.8° and 27.2° are lower, indicating that Na / B atoms are successfully incorporated into the CN structure, destroying the long-range ordered structure of the heptazine ring unit structure inside the carbon nitride, enhancing the disorder of the carbon nitride structure and increasing the interlayer spacing, which is beneficial to promoting the increase of specific surface area.

[0093] Figure 2 This is the FTIR spectrum of S, Na, and B co-doped cyanide-rich g-C3N4. After NaBH4 is introduced into CN, the peak at 2178 cm -1 A new peak appears at , which can be attributed to the asymmetric stretching vibration of cyano group (-C≡N), that is, the generation of cyano-rich structure. As an electron-withdrawing group, cyano group can promote the separation and migration efficiency of photogenerated electrons in carbon nitride and improve the utilization rate of photogenerated electrons.

[0094] Figure 3 is the X-ray photoelectron spectrum (XPS) of S, Na, and B co-doped cyanide-rich g-C3N4. Figure 3(a) is the X-ray photoelectron spectrum (XPS) of S, Na, and B co-doped cyanide-rich g-C3N4. 0.5 The S2p peak was detected in the sample; Figure 3(b) is the Na 1s peak; Figure 3(c) is the B1s peak; its atomic ratio is S (0.10%), Na (1.16%) and B (0.07%), confirming the successful co-doping of (S, Na, B).

[0095] Figure 4 The UV-visible absorption spectrum of CN and S, Na, and B co-doped cyanide-rich g-C3N4 is shown in Figure 2. The original CN has an absorption edge at 460 nm, and the co-doped CNS-NaB 0.5 The sample shows a red shift and an expanded light absorption range of up to 500 nm, indicating that the co-doping of S, Na, and B changes the electronic structure of CN, reduces the band gap, and increases the visible light absorption response.

[0096] Figure 5(a) shows the N2 adsorption-desorption isotherms of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B. Both samples show type IV isotherms and have significant H3 hysteresis loops, indicating that the samples are composed of mesoporous structures. 0.5 The BET surface areas of the samples were 27.2 and 50.8 m 2 ·g -1 , indicating that the co-doping of S, Na, and B significantly increases the specific surface area of ​​CN.

[0097] Figure 5(b) shows the BJH pore size distribution of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B. 0.5 The pore volume of the sample is 0.23 cm 3 ·g -1 , pore size of 20.22 nm, CNS-NaB 0.5 Compared with CN, it has more porous structures.

[0098] Figure 6(a) shows the steady-state PL spectra of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B. 0.5 The PL intensity of the sample is weaker than that of CN, indicating that CNS-NaB0.5 The photoinduced charge carrier separation in the sample is enhanced, that is, the co-doping of S, Na, and B suppresses the recombination of the ground state, and the cyanide group can accelerate and improve the charge transfer mechanism in the photocatalytic reaction.

[0099] Figure 6(b) shows the transient PL spectra of cyanide-rich g-C3N4 co-doped with CN and S, Na, and B. 0.5 The average lifetime of the sample (1.58 ns) is shorter than that of pristine CN (5.07 ns), indicating that CNS-NaB 0.5 The electron-hole separation and transport in the sample are rapid.

[0100] Figure 7 This is a scanning electron micrograph (SEM) of cyanide-rich g-C3N4 co-doped with S, Na, and B. The ultrathin nanosheet structure of g-C3N4 is clearly visible, with uniform size distribution and distinct mesoporous channels. The increased surface area and rich pore structure increase the number of active sites, promoting substrate adsorption and facilitating mass transfer.

[0101] Figure 8 This is a transmission electron microscopy (TEM) image of cyanide-rich g-C3N4 co-doped with S, Na, and B. It further proves the ultrathin nanosheet structure of g-C3N4.

[0102] Figure 9(a) shows the visible light photocatalytic hydrogen production activity of S, Na, and B co-doped cyanide-rich g-C3N4. When the amount of NaBH4 is 0.5 g, the visible light photocatalytic water decomposition hydrogen production rate of the prepared catalyst is the highest, reaching 3637.9 μmol·h -1 ·g -1 .

[0103] Figure 9(b) is a test chart of the visible light catalytic hydrogen production stability of S, Na, and B co-doped cyanide-rich g-C3N4. After three cycles of photocatalytic reaction for a total of 15 hours, the hydrogen production rate of the catalyst did not decrease significantly, indicating that the catalyst has good stability.

[0104] Figure 10(a) shows the visible light photocatalytic reduction of CO2 activity of S, Na, and B co-doped cyanide-rich g-C3N4. When the amount of NaBH4 is 0.5 g, the visible light photocatalytic reduction rate of CO2 is the highest, reaching 779.2 μmol·h -1 ·g -1 .

[0105] Figure 10(b) is a test chart of the visible light catalytic reduction of CO2 stability of S, Na, and B co-doped cyanide-rich g-C3N4. After three cycles of testing, the CO2 reduction performance decreased within an acceptable range after adding TEOA sacrificial agent, indicating that the catalyst has good stability.

Claims

1. A method for preparing a S, Na, and B co-doped cyanide-rich graphite phase carbon nitride photoresponsive catalyst, characterized in that: The specific steps include: Step 1: Use 10 g of 99.9 wt% urea, 0.2-1 g of 99.9 wt% CH4N2S and 0.1-0.5 g of 99.9 wt% NaBH4 as catalyst raw materials to prepare multi-element co-doped precursor material; specifically: weigh 10 g of 99.9 wt% urea, incubate in air at 2-5 °C·min -1 The mixture was calcined at 500-550 °C at a heating rate of 100-200 °C for 2-4 h, and the resultant was ground into powder and named CN; 0.5 g CN, 0.2-1 g CH4N2S (99.9 wt%), and 0.1-0.5 g NaBH4 (99.9 wt%) were weighed and added to 30-50 mL H2O in sequence to obtain a solution, which was heated from room temperature to 100-120 °C in an oil bath under magnetic stirring and maintained for 2-4 h; the solution was gradually evaporated to dryness to obtain a slurry, and 30-50 mL of a 1:1 volume ratio ethanol / H2O solution was added to the slurry and stirred for 30-60 min; a solid compound was obtained by evacuating the slurry for 5-15 min, and the solid compound was dried in air at 60-85 °C for 3-5 h to obtain a multi-element co-doped g-C3N4 precursor material; Step 2: calcining the multi-element co-doped precursor prepared in step 1 to prepare S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

2. The method for preparing a S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst according to claim 1, characterized in that: The specific method of step 2 is: weighing 0.5-1 g of precursor material, calcining it at 500-550 ° C for 4-6 h under Ar atmosphere to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

3. The method for preparing a S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst according to claim 1, characterized in that 10 g of 99.9 wt% urea, 0.5 g of 99.9 wt% CH4N2S and 0.5 g of 99.9 wt% NaBH4 were used as catalyst raw materials.

4. The method for preparing a S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst according to any one of claims 1 to 3, characterized in that: The specific steps are: Step 1: Weigh 10 g of 99.9 wt% urea and heat it in air at 5 °C·min -1 The mixture was calcined at 550 °C for 4 h at a heating rate of 100 ℃, and the resultant was ground into powder and named CN; 0.5 g CN, 0.5 g CH4N2S (99.9 wt%), and 0.5 g NaBH4 (99.9 wt%) were weighed and added to 30 mL H2O in sequence to obtain a solution, which was heated from room temperature to 120 °C in an oil bath under magnetic stirring and maintained for 2 h; the solution was gradually evaporated to dryness to obtain a slurry, and 30 mL of a 1:1 volume ratio ethanol / H2O solution was added to the slurry and stirred for 30 min; a solid compound was obtained by evacuating the slurry for 10 min, and dried at 80 °C in air for 3 h to obtain a multi-element co-doped g-C3N4 precursor material; Step 2: Weigh 1 g of multi-element co-doped g-C3N4 precursor material and calcine it at 500 °C for 4 h under Ar atmosphere to obtain S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst.

5. A method for photocatalytically splitting water to produce hydrogen using the S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst obtained by the preparation method of claim 1 or 2, characterized in that: The specific method is: 20.0-50 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added to the reactor, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 8-16 mL was added as a sacrificial agent; 0.571-1.43 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was then added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp; Argon was purged into the reactor for 10-20 minutes to remove oxygen and eliminate the interference of oxygen in the reactor. The reactor was maintained at a fixed temperature of 30-40°C by circulating water. The magnetic stirrer was turned on and the xenon lamp was turned on for illumination. The hydrogen was quantitatively detected by gas chromatography.

6. The method for producing hydrogen by photocatalytic water decomposition according to claim 5, characterized in that: The specific method is: In a 105 mL reactor, 20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 was added, and 80 mL of a triethanolamine aqueous solution with a triethanolamine content of 10 mL was added; and 0.571 mL of a hexahydrate chloroplatinic acid aqueous solution with a concentration of 0.0007 g / mL was added as a co-catalyst, and metallic platinum was photodeposited onto the S, Na, and B co-doped cyanide-rich g-C3N4 catalyst under a xenon lamp; Argon was purged into the reactor for 15 minutes to remove oxygen and eliminate the interference of oxygen in the air in the reactor. The reactor was maintained at 35°C by circulating water, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Hydrogen was quantitatively detected by gas chromatography.

7. A method for reducing carbon dioxide using the S, Na, and B co-doped cyanide-rich graphite-phase carbon nitride photoresponsive catalyst obtained by the preparation method of claim 1 or 2, characterized in that: The specific method is: Add 10.0-20.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst obtained in step 2 to the reactor, add 4-8 mL of deionized water, 1-2 mL of triethanolamine, and 10-20 mL of acetonitrile, and stir with a magnetic stirrer to obtain a uniform dispersion. Then, add 8-16 mg of [Ru(bpy))3]Cl2·6H2O as a photosensitizer to the dispersion; The reactor was purged with CO2 for 30-40 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at a fixed temperature within the range of 30-40°C. A magnetic stirrer was turned on and a xenon lamp was turned on for illumination. Gas chromatography was used for quantitative detection of the photocatalytic products.

8. The method for reducing carbon dioxide according to claim 7, characterized in that: The specific method is: In a 105 mL reactor, 10.0 mg of the S, Na, and B co-doped cyanide-rich g-C3N4 photocatalyst prepared in step 2 was added. 4 mL of deionized water, 1 mL of triethanolamine, and 10 mL of acetonitrile were added, and magnetic stirring was used to obtain a uniform dispersion. Then, 8 mg of [Ru(bpy))3]Cl2·6H2O was added to the dispersion as a photosensitizer. The reaction was purged with CO2 for 30 minutes to remove air and reach adsorption-desorption equilibrium. The reaction temperature was controlled at 35°C, a magnetic stirrer was turned on, and a xenon lamp was turned on for illumination. Gas chromatography was used to quantitatively detect the reduction rate of CO2 in the photocatalytic product to CO.

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