Bismuth-doped carbon nitride photocatalyst as well as preparation method and application thereof in NADH (Nicotinamide Adenine Dinucleotide Hydrocarbon) regeneration

Abstract

The invention discloses a bismuth-doped carbon nitride photocatalyst and a preparation method and application thereof in NADH regeneration, and the preparation method comprises the following steps: dissolving bismuth salt and vanadate in concentrated nitric acid, then adding deionized water, and violently stirring to form a bismuth vanadate precursor solution; transferring the bismuth vanadate precursor solution into a microwave synthesizer for microwave synthesis to obtain bismuth vanadate; transferring the synthesized bismuth vanadate and a carbon-nitrogen precursor into a porcelain boat, putting the porcelain boat into a tubular furnace, slowly heating and roasting in an Ar atmosphere, and after roasting is finished, grinding an obtained solid product into powder for later use; adding the obtained powder into absolute ethyl alcohol, cleaning for multiple times, then centrifugally separating solids, and drying to obtain the bismuth-doped carbon nitride photocatalyst to be prepared. By the adoption of the technology, the prepared bismuth-doped carbon nitride photocatalyst regenerated coenzyme NADH is good in performance, and the preparation method has the advantages of being simple, wide in raw material source, good in catalytic effect, safe and environmentally friendly.

Description

Technical Field

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

[0002] Nicotinamide adenine dinucleotide (NADH) is a key coenzyme in biocatalytic reactions and is widely involved in processes such as the synthesis of pharmaceutical intermediates, the preparation of biofuels, and the reduction of carbon dioxide. However, NADH is easily oxidized to NAD + , and its 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, the development of green and efficient light-driven NADH regeneration technology has become a research hotspot.

[0003] Photocatalysis uses solar energy to drive reactions and has the advantages of environmental friendliness and mild conditions. Early studies mostly used noble metal catalysts (such as platinum and ruthenium complexes). Although NADH regeneration could be achieved, the cost of noble metals was high and they were prone to photocorrosion. Non-metallic semiconductor materials (such as TiO2) were limited in efficiency due to the need for ultraviolet light excitation and high carrier recombination rates. 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 and easy-to-obtain characteristics have attracted much attention. However, pure g-C3N4 has a narrow visible-light absorption range (<460 nm) and fast photo-generated electron-hole recombination, resulting in low quantum efficiency.

[0004] Aiming at 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) shows potential in the field of photocatalysis due to its unique lone electron pair and gradient energy level structure: (1) Energy band engineering: Bi 3+ doping can narrow the band gap of g-C3N4, extend the light response to the near-infrared region, and improve the utilization rate of sunlight; (2) Charge separation: The interfacial effect between Bi and g-C3N4 forms a built-in electric field, accelerating electron-hole separation and prolonging the carrier lifetime; (3) Active sites: Bi species (such as Bi 0 or Bi-O bonds) can act as electron traps to promote the selective reduction of NAD + to NADH. In addition, the low toxicity and environmental friendliness of bismuth are superior to metals such as cadmium and lead, which conform to 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 interfacial synergistic effects, providing new ideas for large-scale NADH regeneration. Future research can focus on the precise regulation of doping sites and the in-depth analysis of reaction mechanisms to promote its practical application in biomanufacturing and energy conversion. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention 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 source of raw materials, and safety and environmental protection.

[0006] To achieve the above object, the technical solution of the present invention is as follows: The present invention provides a preparation method of a bismuth-doped carbon nitride photocatalyst, comprising 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) Transfer the bismuth vanadate synthesized in step (1) and the carbon nitride precursor to a porcelain boat, place it in a tubular furnace, and slowly heat and roast it under an Ar atmosphere. After the roasting is completed, grind the obtained solid product into powder for standby; (3) Add the powder obtained in step (2) to absolute ethanol, wash it several times, then centrifuge to separate the solid, and dry it to obtain the bismuth-doped carbon nitride photocatalyst to be prepared.

[0007] Further, in step (1), the bismuth salt is at least one of bismuth chloride, bismuth bromide, bismuth nitrate, bismuth acetate, and bismuth subnitrate.

[0008] Further, in step (1), the vanadate is at least one of ammonium vanadate, ammonium metavanadate, vanadyl acetylacetonate, and sodium metavanadate.

[0009] Further, the molar ratio of the bismuth salt to the vanadate in step (1) is 1:0.5 - 5, preferably 1:0.5 - 2.

[0010] Further, the microwave synthesis conditions in step (1) are: the microwave temperature is 80 - 120 °C, preferably 90 - 110 °C; the microwave time is 10 - 30 min, preferably 15 - 20 min.

[0011] Further, in step (2), the carbon nitride precursor is at least one of monocyanamide, dicyandiamide, and melamine.

[0012] Further, the mass ratio of the bismuth vanadate to the carbon nitride precursor in step (2) is 0.1 - 1:1, preferably 0.3 - 0.4:1.

[0013] Further, the heating rate in step (2) is 1 - 5 °C / h, preferably 2 - 3 °C / h; the roasting temperature is 450 - 600 °C, preferably 500 - 550 °C; the roasting time is 2 - 5 h, preferably 3 - 4 h.

[0014] Further, in step (3), the drying temperature is 50 - 100 °C, preferably 60 - 70 °C.

[0015] The present invention provides a bismuth-doped carbon nitride photocatalyst.

[0016] The present invention also provides the application of the bismuth-doped carbon nitride photocatalyst in NADH regeneration.

[0017] Further, the bismuth-doped carbon nitride catalyst and triethanolamine are added to the sodium phosphate buffer solution for ultrasonic dispersion treatment, and then , NAD + a mixed solution is obtained. Then, the mixed solution is transferred to a photocatalytic reactor, stirred under sealed conditions, nitrogen is introduced, and the reaction is carried out under the irradiation of a 300 W xenon lamp light source for photocatalytic regeneration of NADH.

[0018] Further, the mass ratio of the bismuth-doped carbon nitride catalyst to the volume of the sodium phosphate buffer solution is 1:0.5 - 2, preferably 1:1, the mass unit is g, the volume unit is mL, the nitrogen flow rate is 1 - 30 mL / min, preferably 10 - 15 mL / min, and the volume ratio of triethanolamine to the sodium phosphate buffer solution is 0.1 - 0.5:1, preferably 0.15 - 0.2:1, and the volume unit is mL. The wavelength of the xenon lamp is 300 - 800 nm, preferably in the visible light band with a wavelength of 420 - 800 nm.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The bismuth-doped carbon nitride photocatalyst integrates high efficiency, selectivity and sustainability in NADH regeneration: through the lattice defects and intermediate energy levels induced by bismuth doping, the utilization rate of sunlight is significantly improved. At the same time, the Bi nanoclusters act as electron traps and cooperate with the local electric field to prolong the carrier lifetime, improve the photocurrent flux, and significantly increase the regeneration concentration of NADH; 2) Bismuth doping realizes high selectivity of NADH under mild conditions; it abandons precious metals, constructs a stable structure with low-cost bismuth (cost reduced by 90%), and has both biocompatibility and environmental friendliness, providing an innovative solution for the green bio-photocatalytic coupling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the SEM diagram of the catalysts prepared in Examples 1 - 4 of the present invention; Figure 2 It is the standard curve of NADH regeneration concentration in the present invention; Figure 3 It is the performance diagram of the catalysts prepared in Examples 5 - 8 of the present invention for regenerating NADH. Detailed implementation manners

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the scope protected by the present invention is not limited to the described scope.

[0022] Example 1

[0023] A preparation method of a bismuth-doped carbon nitride photocatalyst includes the following steps: (1) Dissolve 2.36 g of Bi(NO3)3·5H2O and 0.56 g of NH4VO3 in 32 mL of concentrated nitric acid, then add deionized water and stir vigorously to form a bismuth vanadate precursor solution; transfer the bismuth vanadate precursor solution to a microwave synthesizer, with a microwave temperature of 90 °C and a microwave time of 20 min, and carry out microwave synthesis to obtain bismuth vanadate; (2) Transfer 1 g of the bismuth vanadate synthesized in step (1) and 3 g of melamine to a porcelain boat, place it in a tube furnace, and under an Ar atmosphere, heat from room temperature to 550 °C at a heating rate of 2 °C / h and calcine for 4 h. After the calcination is completed, grind the obtained solid product into powder for standby; (3) Add the powder obtained in step (2) to absolute ethanol, wash it several times, then centrifuge to separate the solid, and dry it at 60 °C to obtain the bismuth-doped carbon nitride photocatalyst 1 to be prepared.

[0024] Example 2

[0025] A preparation method of a bismuth-doped carbon nitride photocatalyst includes the following steps: (1) Dissolve 2.36 g of Bi(NO3)3·5H2O and 0.56 g of NH4VO3 in 32 mL of concentrated nitric acid, then add deionized water and stir vigorously to form a bismuth vanadate precursor solution; transfer the bismuth vanadate precursor solution to a microwave synthesizer, with a microwave temperature of 90 °C and a microwave time of 20 min, and carry out microwave synthesis to obtain bismuth vanadate; (2) Transfer 2 g of the bismuth vanadate synthesized in step (1) and 3 g of melamine to a porcelain boat, place it in a tube furnace, and under an Ar atmosphere, heat from room temperature to 550 °C at a heating rate of 2 °C / h and calcine for 4 h. After the calcination is completed, grind the obtained solid product into powder for standby; (3) Add the powder obtained in step (2) to absolute ethanol, wash it several times, then centrifuge to separate the solid, and dry it at 60 °C to obtain the bismuth-doped carbon nitride photocatalyst 2 to be prepared.

[0026] Example 3

[0027] A preparation method of a bismuth-doped carbon nitride photocatalyst includes the following steps: (1) Dissolve 2.36 g of Bi(NO3)3·5H2O and 0.56 g of NH4VO3 in 32 mL of concentrated nitric acid, then add deionized water and stir vigorously to form a bismuth vanadate precursor solution; transfer the bismuth vanadate precursor solution to a microwave synthesizer, with a microwave temperature of 90 °C and a microwave time of 20 min, and carry out microwave synthesis to obtain bismuth vanadate; (2) Transfer 3 g of the bismuth vanadate synthesized in step (1) and 3 g of melamine to a porcelain boat, place it in a tubular furnace, and under an Ar atmosphere, heat from room temperature to 550 °C at a heating rate of 2 °C / h and calcine for 4 h. After the calcination is completed, grind the obtained solid product into powder for standby; (3) Add the powder obtained in step (2) to absolute ethanol, wash it several times, then centrifuge to separate the solid, and dry it at 60 °C to obtain the bismuth-doped carbon nitride photocatalyst 3 to be prepared.

[0028] Example 4

[0029] A method for preparing a bismuth-doped carbon nitride photocatalyst, comprising the following steps: (1) Transfer 3 g of melamine to a porcelain boat, place it in a tubular furnace, and under an Ar atmosphere, heat from room temperature to 550 °C at a heating rate of 2 °C / h and calcine for 4 h. After the calcination is completed, grind the obtained solid product into powder for standby; (2) Add the powder obtained in step (1) to absolute ethanol, wash it several times, then centrifuge to separate the solid, and dry it at 60 °C to obtain the carbon nitride photocatalyst 4 to be prepared.

[0030] Test the prepared photocatalyst for coenzyme NADH regeneration.

[0031] Example 5

[0032] Add 20 mg of bismuth-doped carbon nitride catalyst 1 and 4.5 mL of triethanolamine to 20 mL of sodium phosphate buffer solution, carry out ultrasonic dispersion treatment, and then add 1.8 mg , 40 mg of NAD + to obtain a mixed solution. Then transfer the mixed solution to a photocatalytic reaction kettle, stir under sealed conditions, and introduce nitrogen with a flow rate of 10 mL / min. React under the irradiation of a 300 W xenon lamp source. Take a visible light filter with a cut-off wavelength of 420 nm, control the light wavelength output by the xenon lamp source to visible light with a wavelength of 420 - 800 nm, and vertically irradiate the photocatalytic reaction kettle to carry out the photocatalytic regeneration reaction of coenzyme NADH.

[0033] The reaction solution was sampled every 5 min, 1 mL of the centrifuged supernatant was taken, then diluted with 2 mL of phosphate buffer solution, and the concentration of NADH was detected at 340 nm using a UV-visible spectrophotometer. By comparing with the standard curve, the relationship between the NADH concentration and absorbance was obtained (Standard curve drawing: The absorbance of NADH at different concentrations was detected at 340 nm 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 (as Figure 2 shown).

[0034] Example 6

[0035] 20 mg of bismuth-doped carbon nitride catalyst 2 and 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer solution, and ultrasonic dispersion treatment was carried out. Then 1.8 mg , 40 mg of NAD + were added to obtain a mixed solution. 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 reaction was carried out under the irradiation of a 300 W xenon lamp source. A visible light filter with a cut-off wavelength of 420 nm was taken, and the light wavelength output by the xenon lamp source was controlled to be visible light with a wavelength of 420 - 800 nm, which was perpendicularly irradiated onto the photocatalytic reactor to carry out the photocatalytic regeneration reaction of coenzyme NADH.

[0036] The reaction solution was sampled every 5 min, 1 mL of the centrifuged supernatant was taken, then diluted with 2 mL of phosphate buffer solution, and the concentration of NADH was detected at 340 nm using a UV-visible spectrophotometer. By comparing with the standard curve, the relationship between the NADH concentration and absorbance was obtained (Standard curve drawing: The absorbance of NADH at different concentrations was detected at 340 nm 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.

[0037] Example 7

[0038] 20 mg of bismuth-doped carbon nitride catalyst 3 and 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer solution, and ultrasonic dispersion treatment was carried out. Then 1.8 mg , 40 mg of NAD +A mixed solution was obtained. 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 reaction was carried out under irradiation of a 300 W xenon light source. A visible light filter with a cut-off wavelength of 420 nm was taken, and the light wavelength output by the xenon light source was controlled to visible light with a wavelength of 420 - 800 nm, which was perpendicularly irradiated onto the photocatalytic reactor to carry out the photocatalytic regeneration reaction of coenzyme NADH.

[0039] The reaction solution was sampled every 5 min. 1 mL of the centrifuged supernatant was taken, then diluted with 2 mL of phosphate buffer solution, and the concentration of NADH was detected at 340 nm using a UV-visible spectrophotometer. By comparing with the standard curve, the relationship between the NADH concentration and absorbance was obtained (Standard curve drawing: The absorbance of NADH at different concentrations was detected at 340 nm 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.

[0040] Example 8

[0041] 20 mg of carbon nitride catalyst 4 and 4.5 mL of triethanolamine were added to 20 mL of sodium phosphate buffer solution, and ultrasonic dispersion treatment was carried out. Then, 1.8 mg and 40 mg of NAD + A mixed solution was obtained. 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 reaction was carried out under irradiation of a 300 W xenon light source. A visible light filter with a cut-off wavelength of 420 nm was taken, and the light wavelength output by the xenon light source was controlled to visible light with a wavelength of 420 - 800 nm, which was perpendicularly irradiated onto the photocatalytic reactor to carry out the photocatalytic regeneration reaction of coenzyme NADH.

[0042] The reaction solution was sampled every 5 min. 1 mL of the centrifuged supernatant was taken, then diluted with 2 mL of phosphate buffer solution, and the concentration of NADH was detected at 340 nm using a UV-visible spectrophotometer. By comparing with the standard curve, the relationship between the NADH concentration and absorbance was obtained (Standard curve drawing: The absorbance of NADH at different concentrations was detected at 340 nm 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.

[0043] The catalysts prepared in Examples 1 - 4 were analyzed. From Figure 1The scanning electron microscope (SEM) images show that the morphological structures of the catalysts all exhibit irregular flakes, and different degrees of agglomeration occur as the bismuth doping amount increases.

[0044] The photocatalytic coenzyme NADH regeneration experimental performance of bismuth-doped carbon nitride catalysts (Examples 5-8) is as Figure 3 shown. When the bismuth doping amount increases from 0 to 1 g, at 30 min of the reaction, the concentration of coenzyme NADH increases from 0.27 mmol L -1 to 2.77 mmol L -1 ; when the bismuth doping amount continues to increase to 2 g, the concentration of coenzyme NADH drops to 2.70 mmol L -1 ; when the bismuth doping amount is further increased to 3 g, the concentration of coenzyme NADH drops to 1.81 mmol L -1 . This indicates that an appropriate bismuth doping amount is helpful for the regeneration of coenzyme NADH. In the appropriate doping stage (0→1 g), the introduction of bismuth may optimize the energy band structure of carbon nitride (reduce the conduction band potential and enhance 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 bismuth-nitrogen synergistic active centers, thus significantly improving the regeneration efficiency of NADH; however, when the doping amount is too high (1→3 g), the excessive bismuth elements agglomerate on the surface due to ineffective dispersion, which not only covers the original active sites, but also causes the collapse of the layered structure of carbon nitride and lattice distortion, resulting in a reduction in active interfaces, blockage of mass transfer channels, and deviation of the energy band position from the required range of the reaction. Within the measurement time range, the catalyst with a bismuth doping amount of 1 g has a significantly faster NADH regeneration rate than that with a too high doping amount, indicating that excessive doping further weakens the redox kinetics of the catalyst. The above results show that precise regulation of the bismuth doping amount can achieve a dynamic balance of the active site density, structural stability, and electron transport efficiency to achieve the best regeneration effect.

Claims

1. A preparation method of a bismuth-doped carbon nitride photocatalyst, characterized in that, It 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) Transfer the bismuth vanadate synthesized in step (1) and the carbon nitride precursor to a porcelain boat, place it in a tubular furnace, heat and roast it under an Ar atmosphere. After the roasting is completed, grind the obtained solid product into powder for standby; (3) Add the powder obtained in step (2) to absolute ethanol, wash it several times, then centrifuge to separate the solid, and after drying, it is the bismuth-doped carbon nitride photocatalyst to be prepared.

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

4. The preparation method of a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, The microwave synthesis conditions in step (1) are: the microwave temperature is 80 - 120 °C; the microwave time is 10 - 30 min.

5. The preparation method of a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, In step (2), the carbon nitride precursor is at least one of monocyanamide, dicyandiamide, and melamine; the mass ratio of bismuth vanadate to the carbon nitride precursor is 0.1 - 1:

1.

6. The preparation method of a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, In step (2), the heating rate is 1 - 5 °C / h; the roasting temperature is 450 - 600 °C; the roasting time is 2 - 5 h.

7. The preparation method of a bismuth-doped carbon nitride photocatalyst according to claim 1, characterized in that, In step (3), the drying temperature is 50 - 100 °C.

8. A bismuth-doped carbon nitride photocatalyst prepared by the preparation method according to any one of claims 1 - 7.

9. Use of the bismuth-doped carbon nitride photocatalyst as described in claim 8 in NADH regeneration, characterized in that, It includes the following steps: adding bismuth-doped carbon nitride catalyst and triethanolamine into sodium phosphate buffer solution, performing ultrasonic dispersion treatment, and then adding , NAD + to obtain a mixed solution. Then transfer the mixed solution to a photocatalytic reactor, stir under sealed conditions, introduce nitrogen, and react under the irradiation of a 300 W xenon lamp light source to perform photocatalytic regeneration of NADH.

10. The application according to claim 9, characterized in that, The mass ratio of the bismuth-doped carbon nitride catalyst to the volume of the sodium phosphate buffer solution is 1:0.5 - 2, the mass unit is g, the volume unit is mL, the nitrogen gas flow rate is 1 - 30 mL / min, the volume ratio of triethanolamine to the sodium phosphate buffer solution is 0.1 - 0.5:1, and the xenon lamp wavelength is 300 - 800 nm.

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