A bismuth-doped carbon nitride photocatalyst, a preparation method thereof and application thereof in NADH regeneration

Abstract

The application discloses a kind of bismuth-doped carbon nitride photocatalyst and its preparation method and application in NADH regeneration, comprising the following steps: bismuth salt is dissolved with vanadate in concentrated nitric acid, then deionized water is added, and bismuth vanadate precursor solution is formed by stirring violently;Vanadium bismuth precursor solution is transferred to microwave synthesis instrument to carry out microwave synthesis to obtain bismuth vanadate;Synthesized bismuth vanadate and carbon-nitrogen precursor are transferred to porcelain boat, put into tube furnace, slowly heated and calcined under Ar atmosphere, after calcination is finished, the obtained solid product is ground into powder for standby;The obtained powder is added to anhydrous ethanol, washed several times, then centrifugal separation solid, after drying, it is the bismuth-doped carbon nitride photocatalyst prepared.The application is prepared by using the above technology, and the prepared bismuth-doped carbon nitride photocatalyst has good performance in regenerating coenzyme NADH, and has the characteristics of simple preparation method, wide raw material source, good catalytic effect, safety and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material preparation, and particularly relates to a bismuth-doped carbon nitride photocatalyst, a preparation method thereof and application thereof in NADH regeneration. BACKGROUND

[0002] Nicotinamide adenine dinucleotide (NADH) is a key coenzyme in biological catalytic reactions, widely involved in the synthesis of drug intermediates, the preparation of biofuels, and the reduction of carbon dioxide, etc. However, NADH is easily oxidized to NAD + + in the reaction, and the regeneration efficiency directly restricts the economy and sustainability of the reaction. Traditional regeneration methods rely on chemical reducing agents (such as formate) or electrochemical systems, which have problems such as high cost, by-product pollution, and high energy consumption. Therefore, developing green and efficient light-driven NADH regeneration technology has become a research hotspot.

[0003] Photocatalysis uses solar energy to drive reactions, which has the advantages of environmental friendliness and mild conditions. Early studies mostly used noble metal catalysts (such as platinum, ruthenium complexes), which can achieve NADH regeneration, but the cost of noble metals is high and they are easily photo-corroded. Non-metallic semiconductor materials (such as TiO2) have limited efficiency due to the need for ultraviolet light excitation and high carrier recombination rate. In recent years, visible light-responsive carbon nitride (g-C3N4) has become an ideal candidate material, and its unique π-conjugated structure, high chemical stability, and low cost have attracted much attention. However, the visible light absorption range of pure g-C3N4 is narrow (<460 nm), and the photo-generated electron-hole recombination is fast, resulting in low quantum efficiency.

[0004] To overcome the defects of g-C3N4, researchers have improved its performance through element doping, heterostructure construction, or morphology regulation. Among them, metal doping can effectively adjust the energy band structure and introduce defect sites. Bismuth (Bi) has potential in the field of photocatalysis due to its unique lone pair and gradient energy level structure: (1) Energy band engineering: Bi 3+ doping can narrow the band gap of g-C3N4, extending the light response to the near-infrared region and improving the utilization of sunlight; (2) Charge separation: the interface effect between Bi and g-C3N4 forms an internal electric field, accelerating electron-hole separation and prolonging the lifetime of carriers; (3) Active sites: Bi species (such as Bi 0 or Bi-O bonds) can act as electron traps, promoting the selective reduction of NAD + to NADH. In addition, the low toxicity and environmental friendliness of bismuth are superior to those of cadmium and lead, which is in line with the concept of green chemistry. Bismuth-doped carbon nitride solves the problems of low efficiency and dependence on noble metals of traditional photocatalysts through energy band regulation and interface synergistic effect, providing a new idea for large-scale NADH regeneration. Future research can focus on precise regulation of doping sites and in-depth analysis of reaction mechanisms to promote its practical application in biological manufacturing and energy conversion. SUMMARY

[0005] In view of the problems existing in the prior art, the purpose of the present application is to provide a bismuth-doped carbon nitride photocatalyst, a preparation method thereof and an application thereof in NADH regeneration, which has the characteristics of good catalytic effect, simple preparation method, wide and safe and environmentally friendly raw material sources.

[0006] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0007] The present application provides a preparation method of a bismuth-doped carbon nitride photocatalyst, comprising the following steps:

[0008] (1) Dissolve bismuth salt and vanadate in concentrated nitric acid, then add deionized water, stir to form a bismuth vanadate precursor solution; transfer the bismuth vanadate precursor solution to a microwave synthesis instrument for microwave synthesis to obtain bismuth vanadate;

[0009] (2) Transfer the bismuth vanadate synthesized in step (1) and carbon-nitrogen precursor to a porcelain boat, put it into a tube furnace, slowly heat and calcine under Ar atmosphere, after calcination is completed, grind the obtained solid product into powder for standby use;

[0010] (3) Add the powder obtained in step (2) to anhydrous ethanol, wash several times, then centrifuge the solid, dry to obtain the prepared bismuth-doped carbon nitride photocatalyst.

[0011] Further, the bismuth salt in step (1) is at least one of bismuth chloride, bismuth bromide, bismuth nitrate, bismuth acetate and bismuth subnitrate.

[0012] Further, the vanadate in step (1) is at least one of ammonium vanadate, ammonium metavanadate, vanadium acetylacetone and sodium metavanadate.

[0013] Further, the molar ratio of bismuth salt to vanadate in step (1) is 1:0.5-5, preferably 1:0.5-2.

[0014] Further, the microwave synthesis conditions in step (1) are as follows: microwave temperature is 80-120℃, preferably 90-110℃; microwave time is 10-30 min, preferably 15-20 min.

[0015] Further, the carbon-nitrogen precursor in step (2) is at least one of monocyamine, dicyanamide and melamine.

[0016] Further, the mass ratio of bismuth vanadate to carbon-nitrogen precursor in step (2) is 0.1-1:1, preferably 0.3-0.4:1.

[0017] Further, the heating rate in step (2) is 1-5 ℃ / h, preferably 2-3 ℃ / h; the calcination temperature is 450-600 ℃, preferably 500-550 ℃; and the calcination time is 2-5 h, preferably 3-4 h.

[0018] Further, the drying temperature in step (3) is 50-100 ℃, preferably 60-70 ℃.

[0019] The application provides a bismuth-doped carbon nitride photocatalyst.

[0020] The application also provides application of the bismuth-doped carbon nitride photocatalyst in NADH regeneration.

[0021] Further, the bismuth-doped carbon nitride photocatalyst and triethanolamine are added to the sodium phosphate buffer solution, ultrasonic dispersion treatment is performed, and then , NAD + to obtain a mixed solution, and then the mixed solution is transferred to a photocatalytic reactor, stirred under sealed conditions, nitrogen is introduced, and NADH is regenerated by photocatalysis under irradiation of a 300 W xenon lamp.

[0022] Further, the mass of the bismuth-doped carbon nitride photocatalyst to the volume of the sodium phosphate buffer solution is 1:0.5-2, preferably 1:1, the unit of mass is g, and the unit of volume is mL; the flow rate of the introduced nitrogen is 1-30 mL / min, preferably 10-15 mL / min; the volume ratio of triethanolamine to the sodium phosphate buffer solution is 0.1-0.5:1, preferably 0.15-0.2:1; the unit of volume is mL; the wavelength of the xenon lamp is 300-800 nm, and preferably, the wavelength is in the visible light range of 420-800 nm.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1) The bismuth-doped carbon nitride photocatalyst has high efficiency, selectivity and sustainability in NADH regeneration: the lattice defects and intermediate energy levels induced by bismuth doping significantly improve the utilization rate of sunlight; meanwhile, the Bi nanoclusters act as electron traps and cooperate with the local electric field to prolong the carrier lifetime and improve the photoelectron flux, thereby significantly improving the driving concentration of NADH regeneration.

[0025] 2) Bismuth doping realizes high selectivity of NADH under mild conditions; the stable structure is constructed by using low-cost bismuth (cost reduction of 90%), and the bismuth doping has biocompatibility and environmental friendliness, thereby providing an innovative solution for a green biological-photocatalytic coupling system. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1SEM images of catalysts prepared in Example 1-4 of the present application;

[0027] Figure 2 NADH regeneration concentration standard curve in the present application;

[0028] Figure 3 Performance chart of catalysts prepared in Example 5-8 of the present application for regenerating NADH. DETAILED DESCRIPTION

[0029] The present application is further illustrated by the following examples and figures, but the scope of the present application is not limited to the scope of the examples.

[0030] Example 1

[0031] A preparation method of a bismuth-doped carbon nitride photocatalyst, comprising the following steps:

[0032] (1) 2.36 g Bi(NO3)3·5H2O and 0.56 g NH4VO3 were dissolved in 32 mL concentrated nitric acid, followed by the addition of deionized water, and the mixture was stirred vigorously to form a bismuth vanadate precursor solution; the bismuth vanadate precursor solution was transferred to a microwave synthesis instrument, and microwave synthesis was performed at a microwave temperature of 90°C for 20 min to obtain bismuth vanadate;

[0033] (2) 1 g of the bismuth vanadate synthesized in step (1) and 3 g of melamine were transferred to a porcelain boat and placed in a tube furnace, and the temperature was raised to 550°C at a rate of 2°C / h under an Ar atmosphere from room temperature, and calcination was performed for 4 h; after the calcination was completed, the obtained solid product was ground into a powder for later use;

[0034] (3) The powder obtained in step (2) was added to anhydrous ethanol, washed several times, and then the solid was centrifuged and dried at 60°C to obtain the prepared bismuth-doped carbon nitride photocatalyst 1.

[0035] Example 2

[0036] A preparation method of a bismuth-doped carbon nitride photocatalyst, comprising the following steps:

[0037] (1) 2.36 g Bi(NO3)3·5H2O and 0.56 g NH4VO3 were dissolved in 32 mL concentrated nitric acid, followed by the addition of deionized water, and the mixture was stirred vigorously to form a bismuth vanadate precursor solution; the bismuth vanadate precursor solution was transferred to a microwave synthesis instrument, and microwave synthesis was performed at a microwave temperature of 90°C for 20 min to obtain bismuth vanadate;

[0038] (2) 2 g of the BiVO4 synthesized in step (1) and 3 g of melamine were transferred into a porcelain boat, which was placed in a tube furnace, and heated to 550 °C at a heating rate of 2 °C / h under Ar atmosphere, and calcined for 4 h. After the calcination was completed, the obtained solid product was ground into powder for later use;

[0039] (3) The powder obtained in step (2) was added into anhydrous ethanol, washed several times, and then the solid was separated by centrifugation and dried at 60 °C to obtain the Bi-doped carbon nitride photocatalyst 2.

[0040] Example 3

[0041] A method for preparing a Bi-doped carbon nitride photocatalyst, comprising the following steps:

[0042] (1) 2.36 g of Bi(NO3)3·5H2O and 0.56 g of NH4VO3 were dissolved in 32 mL of concentrated nitric acid, followed by the addition of deionized water, and then stirred vigorously to form a BiVO4 precursor solution. The BiVO4 precursor solution was transferred into a microwave synthesis instrument, and microwave synthesis was performed at a microwave temperature of 90 °C for 20 min to obtain BiVO4;

[0043] (2) 3 g of the BiVO4 synthesized in step (1) and 3 g of melamine were transferred into a porcelain boat, which was placed in a tube furnace, and heated to 550 °C at a heating rate of 2 °C / h under Ar atmosphere, and calcined for 4 h. After the calcination was completed, the obtained solid product was ground into powder for later use;

[0044] (3) The powder obtained in step (2) was added into anhydrous ethanol, washed several times, and then the solid was separated by centrifugation and dried at 60 °C to obtain the Bi-doped carbon nitride photocatalyst 3.

[0045] Example 4

[0046] A method for preparing a Bi-doped carbon nitride photocatalyst, comprising the following steps:

[0047] (1) 3 g of melamine was transferred into a porcelain boat, which was placed in a tube furnace, and heated to 550 °C at a heating rate of 2 °C / h under Ar atmosphere, and calcined for 4 h. After the calcination was completed, the obtained solid product was ground into powder for later use;

[0048] (2) The powder obtained in step (1) was added into anhydrous ethanol, washed several times, and then the solid was separated by centrifugation and dried at 60 °C to obtain the carbon nitride photocatalyst 4.

[0049] The above-prepared photocatalyst was tested for coenzyme NADH regeneration.

[0050] Example 5

[0051] 20 mg of bismuth-doped carbon nitride catalyst 1, 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer, ultrasonic dispersion treatment was performed, and then 1.8 mg of , 40 mg of NAD + A mixed solution was obtained, and then the mixed solution was transferred to a photocatalytic reactor, stirred under sealed conditions, and nitrogen was introduced at a flow rate of 10 mL / min. The photocatalytic regeneration reaction of coenzyme NADH was performed under irradiation of a 300 W xenon lamp light source, taking a visible light filter with a cutoff wavelength of 420 nm to control the wavelength of the light output by the xenon lamp light source to be visible light of 420-800 nm, and vertically irradiating the photocatalytic reactor.

[0052] The reaction solution was taken every 5 min, 1 mL of centrifuged supernatant was taken, and then 2 mL of phosphate buffer was added for dilution. The concentration of NADH was detected at 340 nm using a UV-Vis spectrophotometer, and the relationship between the concentration of NADH and the absorbance was obtained by comparison with the standard curve (the standard curve was drawn: the absorbance of NADH with different concentrations was detected at 340 nm using a UV-Vis spectrophotometer, and the absorbance was fitted with the data of NADH with different concentrations to draw a standard curve). The calculation formula is: C[NADH]=0.187*Abs (as shown in Figure 2 ).

[0053] Example 6

[0054] 20 mg of bismuth-doped carbon nitride catalyst 2, 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer, ultrasonic dispersion treatment was performed, and then 1.8 mg of , 40 mg of NAD + A mixed solution was obtained, and then the mixed solution was transferred to a photocatalytic reactor, stirred under sealed conditions, and nitrogen was introduced at a flow rate of 10 mL / min. The photocatalytic regeneration reaction of coenzyme NADH was performed under irradiation of a 300 W xenon lamp light source, taking a visible light filter with a cutoff wavelength of 420 nm to control the wavelength of the light output by the xenon lamp light source to be visible light of 420-800 nm, and vertically irradiating the photocatalytic reactor.

[0055] The reaction solution was taken every 5 min, 1 mL of the centrifuged supernatant was taken, then 2 mL of phosphate buffer was added for dilution, the concentration of NADH was detected at 340 nm by using a UV-visible spectrophotometer, and the relationship between the concentration of NADH and the absorbance was obtained by comparing with the standard curve (the standard curve was drawn: the absorbance of different concentrations of NADH was detected at 340 nm by using a UV-visible spectrophotometer, and the absorbance was fitted with the data of different concentrations of NADH to make a standard curve). The calculation formula is: C[NADH]=0.187*Abs.

[0056] Example 7

[0057] 20 mg of bismuth-doped carbon nitride catalyst 3, 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer, ultrasonic dispersion treatment was performed, then 1.8 mg of , 40 mg of NAD + A mixed solution was obtained, and then the mixed solution was transferred to a 500 mL photocatalytic reactor, stirred under sealed conditions, and nitrogen was introduced at a flow rate of 10 mL / min. The photocatalytic regeneration reaction of coenzyme NADH was carried out under the irradiation of a 300 W xenon lamp light source, a visible light filter with a cutoff wavelength of 420 nm was used to control the wavelength of the xenon lamp light source to 420-800 nm visible light, and the photocatalytic reactor was vertically irradiated.

[0058] The reaction solution was taken every 5 min, 1 mL of the centrifuged supernatant was taken, then 2 mL of phosphate buffer was added for dilution, the concentration of NADH was detected at 340 nm by using a UV-visible spectrophotometer, and the relationship between the concentration of NADH and the absorbance was obtained by comparing with the standard curve (the standard curve was drawn: the absorbance of different concentrations of NADH was detected at 340 nm by using a UV-visible spectrophotometer, and the absorbance was fitted with the data of different concentrations of NADH to make a standard curve). The calculation formula is: C[NADH]=0.187*Abs.

[0059] Example 8

[0060] 20 mg of carbon nitride catalyst 4, 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer, ultrasonic dispersion treatment was performed, then 1.8 mg of , 40 mg of NAD +The resulting mixed solution was then transferred to a 500 mL photocatalytic reactor. Under sealed conditions, the mixture was stirred and nitrogen gas was introduced at a flow rate of 10 mL / min. The reaction was carried out under irradiation with a 300 W xenon lamp. A visible light filter with a cutoff wavelength of 420 nm was used to control the wavelength of the light output from the xenon lamp to be visible light of 420-800 nm. The light was then vertically irradiated into the photocatalytic reactor to carry out the photocatalytic regeneration reaction of coenzyme NADH.

[0061] Every 5 minutes, take 1 mL of the reaction solution from centrifugation, then dilute it with 2 mL of phosphate buffer. Detect the NADH concentration at 340 nm using a UV-Vis spectrophotometer. Compare the results with a standard curve to obtain the relationship between NADH concentration and absorbance (Standard curve plotting: Detect the absorbance of different NADH concentrations at 340 nm using a UV-Vis spectrophotometer, fit the absorbance data to the data for different NADH concentrations, and plot a standard curve). The calculation formula is: C[NADH] = 0.187 * Abs.

[0062] The catalysts prepared in Examples 1-4 were analyzed, and from... Figure 1 Scanning electron microscope (SEM) images show that the catalyst has an irregular sheet-like morphology, and the catalyst exhibits varying degrees of agglomeration as the bismuth doping content increases.

[0063] Experimental performance of bismuth-doped carbon nitride catalyst in photocatalytic regeneration of coenzyme NADH (Examples 5-8) Figure 3 As shown, as the bismuth doping amount increased from 0 to 1 g, the concentration of coenzyme NADH increased from 0.27 mmol / L after 30 min of reaction. -1 Increased to 2.77 mmol / L -1 When the bismuth doping level was further increased to 2 g, the concentration of coenzyme NADH decreased to 2.70 mmol / L. -1 When the bismuth doping level was further increased to 3 g, the concentration of coenzyme NADH decreased to 1.81 mmol / L. -1The results show that appropriate amount of Bi doping is helpful for the regeneration of NADH. In the appropriate doping stage (0→1 g), the introduction of Bi can optimize the band structure of carbon nitride (lowering the conduction band potential, enhancing the reduction ability), inhibit the recombination of photo-generated electron-hole pairs to prolong the carrier lifetime, and expose more active edge sites or form Bi-N synergistic active centers, thereby significantly improving the regeneration efficiency of NADH; however, when the doping amount is too high (1→3 g), the excessive Bi element occurs surface agglomeration due to the inability to effectively disperse, not only covering the original active sites, but also triggering the collapse of the carbon nitride layered structure and lattice distortion, leading to a decrease in active interface, blockage of mass transfer channels, and deviation of the energy band position from the required range for the reaction. Within the measurement time range, the NADH regeneration rate of the catalyst with a Bi doping amount of 1 g is significantly faster than that with an excessive doping amount, thus indicating that excessive doping further weakens the redox kinetics of the catalyst. The above results show that precise regulation of the Bi doping amount can achieve a dynamic balance of active site density, structural stability, and electron transport efficiency to achieve the best regeneration effect.

Claims

1. A method for preparing a bismuth-doped carbon nitride photocatalyst, characterized in that, Includes the following steps: (1) Dissolve bismuth salt and vanadate in concentrated nitric acid, then add deionized water and stir to form a bismuth vanadate precursor solution; transfer the bismuth vanadate precursor solution to a microwave synthesizer for microwave synthesis to obtain bismuth vanadate. (2) The bismuth vanadate synthesized in step (1) and the carbon-nitrogen precursor are transferred to a ceramic boat, placed in a tube furnace, and heated and calcined under an Ar atmosphere. After calcination, the obtained solid product is ground into powder for later use. (3) Add the powder obtained in step (2) to anhydrous ethanol, wash several times, then centrifuge to separate the solid, and dry it to obtain the bismuth-doped carbon nitride photocatalyst to be prepared. The microwave synthesis conditions in step (1) are: microwave temperature 80-120℃; microwave time 10-30 min; In step (2), the carbon-nitrogen precursor is at least one of cyanamide, dicyandiamide and melamine; the mass ratio of bismuth vanadate to carbon-nitrogen precursor is 0.1-1:

1.

2. The method for preparing a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, In step (1), the bismuth salt is at least one of bismuth chloride, bismuth bromide, bismuth nitrate, bismuth acetate, and bismuth subnitrate; the vanadate is at least one of ammonium vanadate, ammonium metavanadate, vanadium acetylacetonate, and sodium metavanadate.

3. The method for preparing a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, In step (1), the molar ratio of bismuth salt to vanadate is 1:0.5-5.

4. The method for preparing a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, In step (2), the heating rate is 1-5 ℃ / h; the calcination temperature is 450-600 ℃; and the calcination time is 2-5 h.

5. The method for preparing a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, The drying temperature in step (3) is 50-100 ℃.

6. A bismuth-doped carbon nitride photocatalyst prepared by the preparation method according to any one of claims 1-5.

7. The application of the bismuth-doped carbon nitride photocatalyst as described in claim 6 in NADH regeneration, characterized in that, The steps include: adding bismuth-doped carbon nitride catalyst and triethanolamine to sodium phosphate buffer, performing ultrasonic dispersion, and then adding [Cp*Rh(bpy)H2O]. 2+ NAD + The resulting mixed solution was then transferred to a photocatalytic reactor, stirred under sealed conditions, and purged with nitrogen gas. The reaction was carried out under irradiation with a 300 W xenon lamp to regenerate NADH via photocatalysis.

8. The application as described in claim 7, characterized in that, The mass ratio of bismuth-doped carbon nitride catalyst to sodium phosphate buffer is 1:0.5-2, with mass units in g and volume units in mL. The nitrogen flow rate is 1-30 mL / min, the volume ratio of triethanolamine to sodium phosphate buffer is 0.1-0.5:1, and the xenon lamp wavelength is 300-800 nm.

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