A method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles

Abstract

The application discloses a method for photocatalytic reduction of CO2 by protein-modified hollow nanocarbon nitride, which comprises the following steps: synthesizing a catalyst by inducing rapid phase transition of a protein through a disulfide bond reducing agent and assembling the protein on hollow nanocarbon nitride in the form of a nanofilm, and then using the catalyst for photocatalytic reduction of CO2; different types of groups are exposed on the surface of the nanofilm on the catalyst, which can not only promote efficient adsorption of CO2, but also improve the hydrophobicity of the catalyst, thereby being beneficial to improving the activity and selectivity of photocatalytic reduction of CO2. The catalyst used in the method has the characteristics of simple preparation method, mild reaction condition, environmental protection, low cost and the like, is universally applicable to different proteins and different hollow nano-structured materials, and can provide a new idea for improving the activity and selectivity of photocatalytic reduction of CO2.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology, specifically relating to the application of a protein-modified hollow nano-carbon nitride catalyst in improving the activity and selectivity of photocatalytic reduction of CO2. Background Technology

[0002] Photocatalytic CO2 reduction to fuel or value-added chemicals offers a new avenue for the development of low-carbon economy and sustainable renewable energy technologies. Extensive research has been conducted on photocatalytic CO2 conversion, and numerous photocatalysts have been reported. Among these, hollow nanomaterials (hollow nanospheres, hollow nanotubes, hollow nanocages, hollow polyhedra, etc.) are currently the most attractive and promising material type due to their ability to provide spatially separated redox sites, enhance light scattering within the cavity, shorten the transport distance of photogenerated carriers, increase specific surface area, and provide richer surface active sites. However, in the CO2 reduction reaction (CO2RR) in a solid-liquid system, the overwhelming adsorption of water on the catalyst surface leads to a competing reaction—the hydrogen evolution reaction (HER). Poor CO2 mass transfer in water results in poor catalyst adsorption capacity for CO2. Furthermore, unfavorable thermodynamic and kinetic processes in CO2RR cause the catalyst's photogenerated electrons to primarily reduce water to H2, resulting in low CO2 reduction efficiency and poor selectivity. Therefore, developing a material on hollow nanomaterials that can adjust the hydrophobicity of the material surface, improve CO2 mass transfer, and enhance CO2 adsorption performance is key to achieving improved photocatalytic CO2 reduction activity and selectivity.

[0003] In recent years, many studies have explored various modification methods to improve photocatalytic efficiency, including metal / non-metal doping, metal / metal oxide / metal complex co-catalyst loading, heterojunction construction via coupling with semiconductors such as metal-organic frameworks, metal oxides, and sulfides, and defect engineering. However, these modification methods are complex, involve the use of metals and harmful gases, and rely on high temperatures and time-consuming steps, resulting in poor manufacturability, high cost, and environmental unfriendliness, thus limiting their applications. Proteins are widely distributed natural and highly specific functional biopolymers with abundant active groups, which are beneficial for adsorbing reactants. Their structure and functional groups are similar to those of biocatalysts used in natural photosynthesis, and they also have advantages such as being non-toxic, inexpensive, and easy to modify on the surface, making them worthy of consideration for use in photocatalysis. Therefore, developing a universal protein-modified hollow nanomaterial suitable for photocatalytic CO2 reduction, and effectively improving its photocatalytic activity and selectivity, is of great significance for the development of photocatalytic selective reduction of CO2 into sustainable renewable energy technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a universally applicable method for the photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles.

[0005] To achieve the above objectives, the technical solution adopted by the present invention consists of the following steps:

[0006] Step 1: Proteins are rapidly phase-transformed by disulfide reducing agents and assembled on hollow carbon nitride nanofilms in the form of nanofilms to obtain protein-modified hollow carbon nitride nanofilm photocatalysts.

[0007] Step 2: Add the protein-modified hollow carbon nitride nanoparticle photocatalyst to the reaction tube, along with 2,2'-bipyridine, cobalt chloride, acetonitrile, triethanolamine, and deionized water. Irradiate the reaction tube with visible light under a CO2 atmosphere for 7–11 hours to reduce CO2 to CO.

[0008] In step 1 above, preferably, the pH of a 5-100 mM disulfide reducing agent solution is adjusted to 3-9 with NaOH, then hollow carbon nitride nanoparticles are added and ultrasonically dispersed evenly. Next, a 1-20 mg / mL protein solution is added, and the mixture is incubated at 20-40°C for 1-3 hours. The mixture is then washed with deionized water and dried to obtain a protein-modified hollow carbon nitride nanoparticle photocatalyst. More preferably, the pH of a 10-50 mM disulfide reducing agent solution is adjusted to 4-7 with NaOH, then hollow carbon nitride nanoparticles are added and ultrasonically dispersed evenly. Next, a 1-10 mg / mL protein solution is added, and the mixture is incubated at 20-40°C for 1-3 hours. The mixture is then washed with deionized water and dried to obtain a protein-modified hollow carbon nitride nanoparticle photocatalyst. The disulfide reducing agent solution and the protein solution are prepared using a 5-20 mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution. Preferably, the volume ratio of the disulfide bond reducing agent solution to the protein solution is 1:1, and the mass ratio of the hollow nano carbon nitride powder to the protein is 1:0.1 to 1.

[0009] In step 2 above, the preferred mass ratio of the protein-modified hollow nano carbon nitride photocatalyst, 2,2'-bipyridine, cobalt chloride, and triethanolamine is 1:0.4-1.6:0.06-0.45:35-40, and the volume ratio of triethanolamine, deionized water, and acetonitrile is 1:1-1.5:2-4.

[0010] The protein mentioned above is any one of bovine serum albumin, lysozyme, and ovalbumin; the disulfide bond reducing agent is any one of tris(2-carboxyethyl)phosphonic acid hydrochloride, cysteine, and glutathione.

[0011] The aforementioned hollow carbon nitride nanospheres are carbon nitride hollow nanospheres with an average particle size of 350–550 nm.

[0012] The beneficial effects of this invention are as follows:

[0013] This invention involves inducing a rapid phase transition in proteins using a disulfide reducing agent, followed by assembly into a nanofilm on hollow carbon nitride nanoparticles. This results in a protein phase transition nanofilm on the surface of the hollow carbon nitride nanoparticles, enhancing CO2 adsorption and hydrophobicity, thereby improving the selectivity and activity of photocatalytic CO2 reduction. During the photocatalytic CO2 reduction process, the protein acts as an insulating layer, which can be injected into the surface cocatalyst via electron tunneling, promoting the migration of photogenerated electrons from the semiconductor conduction band to surface active species. The unfolding of the high-energy α-helix structure of the protein into a β-sheet structure exposes hydrophobic groups, enhancing hydrophobicity, reducing water-catalyst contact, weakening hydrogen evolution competition, and promoting CO2 adsorption through the exposed -NH2 groups on the protein surface, thus better facilitating CO2 reduction. The catalyst preparation method of this invention is simple, low-cost, and universally applicable. Furthermore, this method provides a new approach to improving the selectivity of photocatalytic CO2 reduction products. Attached Figure Description

[0014] Figure 1 These are SEM images of PTL@CN-HS(a) in Example 1, PTB@CN-HS(b) in Example 2, and PTO@CN-HS(c) and CN-HS(d) in Example 3.

[0015] Figure 2 These are TEM images of PTL@CN-HS(a) in Example 1, PTB@CN-HS(b) in Example 2, and PTO@CN-HS(c) in Example 3.

[0016] Figure 3 This is a dark field STEM (a) and elemental mapping (b) diagram of C, N, O, Si, P, and S of PTL@CN-HS in Example 1.

[0017] Figure 4 These are FTIR plots of CN-HS, PTL@CN-HS in Example 1, and PTL in Comparative Example 1.

[0018] Figure 5 These are the FTIR plots of CN-HS, PTB@CN-HS in Example 2, and PTB in Comparative Example 2.

[0019] Figure 6 These are FTIR plots of CN-HS, PTO@CN-HS in Example 3, and PTO in Comparative Example 3.

[0020] Figure 7 These are XPS plots of CN-HS, PTL@CN-HS in Example 1, and PTL in Comparative Example 1.

[0021] Figure 8These are XPS plots of CN-HS, PTB@CN-HS in Example 2, and PTB in Comparative Example 2.

[0022] Figure 9 These are XPS plots of CN-HS, PTO@CN-HS in Example 3, and PTO in Comparative Example 3.

[0023] Figure 10 The hydrophobic contact angle measurement diagrams are for CN-HS, PTL@CN-HS in Example 1, PTB@CN-HS in Example 2, PTO@CN-HS in Example 3, PTL in Comparative Example 1, PTB in Comparative Example 2, and PTO in Comparative Example 3.

[0024] Figure 11 These are CO2 adsorption isotherms of CN-HS, PTL@CN-HS in Example 1, and PTL in Comparative Example 1.

[0025] Figure 12 These are CO2 adsorption isotherms of CN-HS, PTB@CN-HS in Example 2, and PTB in Comparative Example 2.

[0026] Figure 13 These are CO2 adsorption isotherms of CN-HS, PTO@CN-HS in Example 3, and PTO in Comparative Example 3.

[0027] Figure 14 These are the photocurrent response diagrams of CN-HS, PTL@CN-HS in Example 1, and PTL in Comparative Example 1.

[0028] Figure 15 These are the photocurrent response diagrams of CN-HS, PTB@CN-HS in Example 2, and PTB in Comparative Example 2.

[0029] Figure 16 These are the photocurrent response diagrams of CN-HS, PTO@CN-HS in Example 3, and PTO in Comparative Example 3.

[0030] Figure 17 This is a comparison chart of the photocatalytic CO2 reduction activity and selectivity of CN-HS and PTL@CN-HS in Example 1 with that of PTL in Comparative Example 1.

[0031] Figure 18 This is a comparison chart of the photocatalytic CO2 reduction activity and selectivity of CN-HS and PTB@CN-HS in Example 2 with that of PTB in Comparative Example 2.

[0032] Figure 19 This is a comparison chart of the photocatalytic CO2 reduction activity and selectivity of CN-HS and PTO@CN-HS in Example 3 with that of PTO in Comparative Example 3. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0034] In the examples below, the carbon nitride hollow nanospheres used were synthesized using the method disclosed in the reference “Sun, J., Zhang, J., Zhang, M. et al. Bioinspired hollow semiconductor nanospheres as photosynthetic nanoparticles. Nat Commun 3, 1139 (2012).”

[0035] Example 1

[0036] Step 1: Prepare a 10mM TCEP solution by adding tris(2-carboxyethyl)phosphonic acid hydrochloride (TCEP) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution, and adjust the pH to 7 with 5M NaOH aqueous solution; prepare a 5mg / mL lysozyme solution by adding 50mg of lysozyme (PTL) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution; then weigh 100mg of carbon nitride hollow nanospheres (CN-HS) powder with a particle size of approximately 500nm, add it to 10mL of 10mM TCEP solution at pH=7, disperse it evenly by ultrasonication, add 10mL of 5mg / mL lysozyme solution, and incubate at 30℃ for 2h. Finally, centrifuge the solid, wash it three times with ultrapure water, and obtain the lysozyme-modified carbon nitride hollow nanosphere photocatalyst, denoted as PTL@CN-HS.

[0037] Step 2: Add 30 mg PTL@CN-HS to the reaction tube, along with 15 mg 2,2'-bipyridine, 2.38 mg cobalt chloride, 3 mL acetonitrile, 1 mL (1.124 g) triethanolamine, and 1 mL deionized water. Seal the reaction tube with a rubber stopper. While stirring vigorously, purge the reaction tube with CO2 gas to expel the air inside. After sealing, irradiate the tube with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction is complete, extract 400 μL of the gas produced using a syringe and test the gas yield using a gas chromatograph.

[0038] Further, 30 mg of PTL@CN-HS was added to the reaction tube, along with 45 mg of 2,2'-bipyridine, 11.9 mg of cobalt chloride, 3 mL of acetonitrile, 1 mL (1.124 g) of triethanolamine, and 1 mL of deionized water. The reaction tube was sealed with a rubber stopper, and CO2 gas was introduced into the tube during vigorous stirring to purge the air inside. After sealing, the tube was irradiated with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction was complete, 400 μL of the gas produced was extracted using a syringe and the gas yield was measured by gas chromatography.

[0039] Example 2

[0040] Step 1: Prepare a 10mM TCEP solution by adding tris(2-carboxyethyl)phosphonic acid hydrochloride (TCEP) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution, and adjust the pH to 4.5 with 5M NaOH aqueous solution; prepare a 5mg / mL bovine serum albumin (PTB) solution by adding 50mg of PTB to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution; then weigh 100mg of carbon nitride hollow nanospheres (CN-HS) powder with a particle size of approximately 500nm, add it to 10mL of 10mM TCEP solution at pH=7, disperse it evenly by ultrasonication, add 10mL of 5mg / mL bovine serum albumin solution, and incubate at 30℃ for 2h. Finally, centrifuge the solid, wash it three times with ultrapure water, and obtain the bovine serum albumin-modified carbon nitride hollow nanosphere photocatalyst, denoted as PTB@CN-HS.

[0041] Step 2: Add 30 mg PTB@CN-HS to the reaction tube, along with 15 mg 2,2'-bipyridine, 2.38 mg cobalt chloride, 3 mL acetonitrile, 1 mL (1.124 g) triethanolamine, and 1 mL deionized water. Seal the reaction tube with a rubber stopper. While stirring vigorously, purge the reaction tube with CO2 gas to expel air. After sealing, irradiate the tube with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction is complete, extract 400 μL of the generated gas using a syringe and test the gas yield using a gas chromatograph.

[0042] Example 3

[0043] Step 1: Prepare a 10mM TCEP solution by adding tris(2-carboxyethyl)phosphonic acid hydrochloride (TCEP) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution, and adjust the pH to 7 with 5M NaOH aqueous solution; prepare a 5mg / mL ovalbumin solution by adding 50mg of ovalbumin (PTO) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution; then weigh 100mg of carbon nitride hollow nanospheres (CN-HS) powder with a particle size of approximately 500nm, add it to 10mL of 10mM TCEP solution at pH=7, disperse it evenly by ultrasonication, add 10mL of 5mg / mL ovalbumin solution, and incubate at 30℃ for 2h. Finally, centrifuge the solid, wash it three times with ultrapure water, and obtain the ovalbumin-modified carbon nitride hollow nanosphere photocatalyst, denoted as PTO@CN-HS.

[0044] Step 2: Add 30 mg PTO@CN-HS to the reaction tube, along with 15 mg 2,2'-bipyridine, 2.38 mg cobalt chloride, 3 mL acetonitrile, 1 mL (1.124 g) triethanolamine, and 1 mL deionized water. Seal the reaction tube with a rubber stopper. While stirring vigorously, purge the reaction tube with CO2 gas to expel the air inside. After sealing, irradiate the tube with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction is complete, extract 400 μL of the gas produced using a syringe and test the gas yield using a gas chromatograph.

[0045] Comparative Example 1

[0046] Step 1: Prepare a 10mM TCEP solution by adding tris(2-carboxyethyl)phosphonic acid hydrochloride (TCEP) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution, and adjust the pH to 7 with 5M NaOH aqueous solution; prepare a 5mg / mL lysozyme solution by adding 50mg of lysozyme (PTL) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution; then mix 10mL of 10mM TCEP solution at pH=7 with 10mL of 5mg / mL lysozyme solution, and incubate at 30℃ for 2h. Finally, centrifuge the solid, wash three times with ultrapure water, and freeze-dry to obtain lysozyme solid, denoted as PTL.

[0047] Step 2: Add 30 mg PTL to the reaction tube, along with 15 mg 2,2'-bipyridine, 2.38 mg cobalt chloride, 3 mL acetonitrile, 1 mL (1.124 g) triethanolamine, and 1 mL deionized water. Seal the reaction tube with a rubber stopper. While stirring vigorously, purge the reaction tube with CO2 gas to expel the air inside. After sealing, irradiate the tube with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction is complete, extract 400 μL of the gas produced using a syringe and test the gas yield using a gas chromatograph.

[0048] Comparative Example 2

[0049] Step 1: Prepare a 10mM TCEP solution by adding tris(2-carboxyethyl)phosphonic acid hydrochloride (TCEP) to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution, and adjust the pH to 4.5 with 5M NaOH aqueous solution; prepare a 5mg / mL bovine serum albumin (PTB) solution by adding 50mg of PTB to 10mL of 10mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution; then mix 10mL of 10mM TCEP solution (pH=7) with 10mL of the 5mg / mL bovine serum albumin solution and incubate at 30℃ for 2h. Finally, centrifuge the solid, wash three times with ultrapure water, and freeze-dry to obtain bovine serum albumin solid, denoted as PTB.

[0050] Step 2: Add 30 mg PTB to the reaction tube, along with 15 mg 2,2'-bipyridine, 2.38 mg cobalt chloride, 3 mL acetonitrile, 1 mL (1.124 g) triethanolamine, and 1 mL deionized water. Seal the reaction tube with a rubber stopper. While stirring vigorously, purge the reaction tube with CO2 gas to expel the air inside. After sealing, irradiate the tube with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction is complete, extract 400 μL of the gas produced using a syringe and test the gas yield using a gas chromatograph.

[0051] Comparative Example 3

[0052] Step 1: Prepare a 10mM TCEP solution by adding tris(2-carboxyethyl)phosphonic acid hydrochloride (TCEP) to 10 mL of 10 mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution, and adjust the pH to 7 with 5 M NaOH aqueous solution; prepare a 5 mg / mL ovalbumin (PTO) solution by adding 50 mg to 10 mL of 10 mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution; then mix 10 mL of 10 mM TCEP solution at pH=7 with 10 mL of the 5 mg / mL ovalbumin solution and incubate at 30 °C for 2 h. Finally, centrifuge the solid, wash three times with ultrapure water, and freeze-dry to obtain ovalbumin solid, denoted as PTO.

[0053] Step 2: Add 30 mg PTO to the reaction tube, along with 15 mg 2,2'-bipyridine, 2.38 mg cobalt chloride, 3 mL acetonitrile, 1 mL (1.124 g) triethanolamine, and 1 mL deionized water. Seal the reaction tube with a rubber stopper. While stirring vigorously, introduce CO2 gas into the reaction tube to purge the air inside. After sealing, irradiate the tube with visible light under a 300 W xenon lamp for 9 hours to carry out the photocatalytic CO2 reduction reaction. After the reaction is complete, extract 400 μL of the generated gas using a syringe and test the gas yield using a gas chromatograph.

[0054] Comparative Example 4

[0055] 30 mg of CN-HS was added to the reaction tube, along with 15 mg of 2,2'-bipyridine, 2.38 mg of cobalt chloride, 3 mL of acetonitrile, 1 mL (1.124 g) of triethanolamine, and 1 mL of deionized water. The reaction tube was sealed with a rubber stopper. CO2 gas was introduced into the reaction tube during vigorous stirring to purge air from the tube. After sealing, the tube was irradiated with visible light under a 300 W xenon lamp for 9 hours to perform a photocatalytic CO2 reduction reaction. 400 μL of the gas produced after the reaction was completed was extracted using a syringe and the gas yield was measured by gas chromatography.

[0056] The structures of CN-HS and the catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were characterized, and the results are shown in the figure. Figures 1-16 .

[0057] Depend on Figure 1 As can be seen from the SEM images, CN-HS consists of uniformly distributed spherical nanoparticles with obvious micropores on the surface, an average particle size of approximately 505 nm, and a relatively smooth surface. In Example 1, PTL@CN-HS; in Example 2, PTB@CN-HS; and in Example 3, PTO@CN-HS show significantly rougher surfaces with a distinct layer of material adhering between the microspheres, preliminarily identified as protein-based phase transition nanofilms.

[0058] Depend on Figure 2 As can be seen, the TEM images of PTL@CN-HS in Example 1, PTB@CN-HS in Example 2, and PTO@CN-HS in Example 3 further confirm that a protein layer (5-15 nm) is coated on the surface of CN-HS. The protein coating does not completely block the large pores of CN-HS, which is consistent with the SEM results.

[0059] Depend on Figure 3As can be seen, the dark-field STEM and elemental mapping of C, N, O, Si, P, and S in PTL@CN-HS in Example 1 detected typical O elements in the -COOH, -OH, and acylamino groups of the protein, as well as S elements with relatively low content in disulfide bonds (SS) and SH. The corresponding areas of the SEM and TEM images show that S elements are only distributed on the surface of the nanospheres, and the elemental mapping test of S also indicates that the protein-based phase transition nanofilm is coated on the carbon nitride surface.

[0060] Depend on Figure 4 It can be seen that the FTIR spectrum of CN-HS shows the characteristic peaks of carbon nitride. The FTIR spectrum of PTL in Comparative Example 1 shows -OH (3700-3400 cm⁻¹). -1 ),-NH x (3400-3100cm -1 ), alkyl and aryl (3000-2800cm) -1 ), amides and other functional groups (1750-1000cm) -1 The peaks of the protein-based phase transition nanofilm PTL coated on the surface of carbon nitride nanospheres were observed. To confirm that the PTL nanofilm was rich in β-sheet structure, the amide I and amide II bands (1490-1750 cm⁻¹) of the secondary structures (α-helix, β-sheet, and β-turn) of PTL proteins and peptides were fitted. -1 The results were compared with those of the composite sample. It was found that, in addition to the characteristic peaks of carbon nitride itself, the position peaks corresponding to the secondary structure of PTL appeared in the FTIR spectrum of PTL@CN-HS in Example 1. These results indicate that lysozyme underwent a phase transition process and was successfully coated on the CN-HS surface. Figure 5 and Figure 6 The FTIR spectra of PTB@CN-HS in Example 2 and PTO@CN-HS in Example 3 also showed the same state, further confirming that the protein underwent a phase transition process and was successfully coated on the CN-HS surface.

[0061] Depend on Figures 7-9 It can be seen that the XPS measurements of PTL@CN-HS in Example 1, PTB@CN-HS in Example 2, and PTO@CN-HS in Example 3 successfully detected the sulfur element. In the high-resolution S2p XPS spectra of PTL@CN-HS in Example 1, PTB@CN-HS in Example 2, and PTO@CN-HS in Example 3, two distinct characteristic peaks for PTL, PTB, and PTO were observed, respectively, further confirming that lysozyme, bovine serum albumin, and ovalbumin were successfully coated onto the CN-HS surface after a phase transition process.

[0062] Depend on Figure 10As can be seen from the contact angle test, the exposed hydrophobic groups on the surface of the protein-based phase transition nanofilm exhibit excellent hydrophobic properties. After coating CN-HS with the protein-based phase transition nanofilm, the contact angle of the samples increased significantly (the contact angles of PTL@CN-HS in Example 1, PTB@CN-HS in Example 2, and PTO@CN-HS in Example 3 increased to 133.4°, 110.6°, and 114.5°, respectively). For photocatalytic CO2RR, the enhanced hydrophobicity can reduce the contact between water and the catalyst, thus weakening the occurrence of the competing reaction HER.

[0063] Figures 11-13 The CO2 adsorption isotherms show that CN-HS has a very low CO2 adsorption capacity. Due to the abundance of surface groups (such as -NH2) in proteins, PTL, PTB, and PTO exhibit higher CO2 adsorption capabilities. Compared to the original carbon nitride, the protein-modified sample shows relatively higher CO2 adsorption, thus increasing the interfacial CO2 concentration.

[0064] Depend on Figures 14-16 The photocurrent response results show that, compared to the original carbon nitride, the protein-modified sample exhibits enhanced photocurrent intensity, demonstrating the promoting effect of photogenerated charge separation. Photogenerated charges in the semiconductor can be injected into the surface co-catalyst through a thin insulating layer via tunneling, thereby promoting the migration of photogenerated electrons from the semiconductor conductor to the surface-active material and improving the photocatalytic performance of CO2 and water reduction.

[0065] The results of the photocatalytic reduction activity and selectivity of Examples 1-3 and Comparative Examples 1-4 for CO2 reduction are shown in the figure above. Figures 17-19 .

[0066] Depend on Figures 17-19 It can be seen that under visible light, with cobalt chloride and 2,2'-bipyridine as co-catalysts, the photocatalytic CO2 reduction efficiency and product CO selectivity of CN-HS are low. For the photocatalytic reaction of PTL in Comparative Example 1, no carbon-containing products or hydrogen were detected, indicating that PTL is photostable and does not decompose. Compared with CN-HS (55.0 μmol g... -1 Compared to PTL@CN-HS in Example 1, PTB@CN-HS in Example 2, and PTO@CN-HS in Example 3 had CO yields of 310.6, 322.3, and 289.6 μmol g, respectively. -1 The yields were increased by 5.6, 5.9, and 5.3 times, respectively, and the CO selectivity was significantly improved to 83%, 83%, and 80%, respectively. When the amounts of cobalt chloride and 2,2'-bipyridine added were 11.9 mg and 45 mg, respectively, the CO yield and selectivity of the PTL@CN-HS system in Example 1 were 1346.5 μmol g. -1(149.6 μmol h) -1 g -1 Or 4.5 μmol h -1 The results showed that the protein-modified hollow nanocatalysts not only enhanced the activity of CO2 photocatalytic reduction but also had the versatility to selectively regulate the reduction products.

Claims

1. A method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles, characterized in that... Includes the following steps: Step 1: Adjust the pH of the 5-100 mM disulfide bond reducing agent solution to 3-9 with NaOH, then add hollow nano carbon nitride powder, disperse it evenly by ultrasonication, then add 1-20 mg / mL protein solution, incubate at 20-40 ℃ for 1-3 h, wash with deionized water, and dry to obtain protein-modified hollow nano carbon nitride photocatalyst. Step 2: Add the protein-modified hollow carbon nitride nanoparticles photocatalyst to the reaction tube, along with 2,2'-bipyridine, cobalt chloride, acetonitrile, triethanolamine, and deionized water. Irradiate with visible light under a CO2 atmosphere for 7–11 hours to reduce CO2 to CO. The protein is any one of bovine serum albumin, lysozyme, and ovalbumin; the disulfide bond reducing agent is any one of tris(2-carboxyethyl)phosphine hydrochloride, cysteine, and glutathione.

2. The method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles according to claim 1, characterized in that: In step 1, the pH of the 10-50 mM disulfide reducing agent solution is adjusted to 4-7 with NaOH, then hollow nano carbon nitride powder is added, ultrasonically dispersed evenly, and then 1-10 mg / mL protein solution is added. The mixture is incubated at 20-40 ℃ for 1-3 h, washed with deionized water, and dried to obtain protein-modified hollow nano carbon nitride photocatalyst.

3. The method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles according to claim 1, characterized in that: The disulfide bond reducing agent solution and the protein solution were prepared using a 5-20 mM 4-hydroxyethylpiperazine ethanesulfonic acid buffer solution.

4. The method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles according to claim 1, characterized in that: The volume ratio of the disulfide bond reducing agent solution to the protein solution is 1:1, and the mass ratio of the hollow nano carbon nitride powder to the protein is 1:0.1 to 1.

5. The method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles according to claim 1, characterized in that: The hollow carbon nitride nanospheres are carbon nitride hollow nanospheres with an average particle size of 350–550 nm.

6. The method for photocatalytic reduction of CO2 using protein-modified hollow carbon nitride nanoparticles according to claim 1, characterized in that: In step 2, the mass ratio of the protein-modified hollow nano carbon nitride photocatalyst, 2,2'-bipyridine, cobalt chloride, and triethanolamine is 1: 0.4-1.6: 0.06-0.45: 35-40, and the volume ratio of triethanolamine, deionized water, and acetonitrile is 1: 1-1.5: 2-4.

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