Photocatalytic hybrid systems based on cobalt-oxime molecular catalysts and applications thereof

Abstract

The application relates to a photocatalytic hybrid system based on a cobalt oxime molecular catalyst and application thereof, and belongs to the field of energy materials and catalysis technology. The cobalt oxime catalyst is synthesized by an organic method, and is obtained by adding cobalt chloride hexahydrate and butanedione oxime in an acetone solution, stirring at normal temperature, taking the precipitate, and stirring at normal temperature after adding 4-methoxypyridine to obtain the catalyst. The photocatalytic hybrid system is constructed by taking semiconductor powder bismuth vanadate as an optical component, sodium persulfate as a sacrificial electron acceptor, and the cobalt oxime molecular catalyst as a water oxidation catalyst. In a water solution with pH=7, oxygen is successfully generated after 3h of light irradiation, and the oxygen generation rate is 2099.9 mu mol g ‑1 h ‑1 , which is 2.5 times that of the system without the cobalt oxime. In three-cycle photocatalytic tests, the catalyst shows good stability. The catalyst is simple to synthesize, cobalt is abundant in the earth's crust, and has wide application prospects in the fields of renewable energy production and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical energy, and particularly relates to simulating natural light and action, and oxidizing water into oxygen under light conditions. BACKGROUND

[0002] At present, the use and combustion of fossil fuels have led to a series of energy and environmental problems, which directly affect the sustainable development of human society. Therefore, people have begun to turn their attention to renewable energy and hope to solve the energy crisis and environmental problems by using abundant renewable natural resources. Renewable energy such as solar energy, wind energy and biomass energy plays an important role in conversion and utilization, and can achieve adjustment of energy structure, energy saving and protection of social and economic and environmental health development. Among them, solar energy is considered as one of the most ideal renewable energy sources due to its wide distribution, no pollution, large reserves and low price. However, solar energy also has the disadvantages of uneven distribution, discontinuous supply and low utilization rate, and faces the problems of conversion and storage. The proposal of artificial photosynthesis brings a new opportunity for the solar energy conversion problem that plagues us. In this field, the water oxidation half-reaction is considered as the main bottleneck restricting the development of artificial photosynthesis, and it is urgent for us to explore and break through.

[0003] The two key problems in the artificial photosynthesis system are the selection of catalyst and the determination of light absorption component. For the selection of catalyst, molecular catalysts have won the widespread attention and favor of scientific workers due to their clear catalytic mechanism, easy to control, excellent high selectivity and high atomic utilization rate. When selecting molecular catalysts, the difficulty of synthesizing catalysts, the harm to the environment, economy and the like should be considered. In addition, the selection of light absorption component is also very important. It must be ensured that it has the characteristics of thermodynamic matching with the water oxidation catalyst, and its stability and light absorption range should also be fully considered.

[0004] In summary, there are the following problems in the current construction of efficient photocatalytic water oxidation system:

[0005] (1) Artificial photosynthesis can effectively convert solar energy into chemical energy, but the water oxidation reaction has a high thermodynamic energy barrier and involves four-electron / four-proton transfer, which has become a bottleneck for the development of artificial photosynthesis.

[0006] (2) Preliminary results have been achieved in the study of molecular catalysts, but most of them are still focused on molecular complexes based on noble metals such as ruthenium and iridium. Therefore, it is particularly important to develop and design molecular catalysts with environmental friendliness and easy synthesis using the abundant first-row transition metal elements on earth.

[0007] (3) For the first row transition metal element metal organic complex, it is easy to degrade to form oxide in the process of water oxidation, and the oxide formed also has catalytic activity for water oxidation. Therefore, it is necessary to find a molecular catalyst that can maintain molecular properties during water oxidation.

[0008] (4) In the photocatalytic system, another important part is the light absorption component, and the biggest challenge for the light absorption component is to match the thermodynamic properties with the water oxidation catalyst, and to have the characteristics of simple preparation method, abundant element reserves in the earth's crust, safety, non-toxicity and no pollution.

[0009] Therefore, it is particularly important to develop a non-noble metal-based photocatalytic water oxidation hybrid system with simple synthesis and preparation method, abundant element reserves, high stability and high activity. SUMMARY

[0010] The purpose of the present application is to overcome the above technical problems, and a preparation method of a cobalt oxime molecular catalyst is provided, which is applied to photocatalytic water oxidation. The catalyst can improve the catalytic activity of the blank bismuth vanadate photocatalytic system for water oxidation, and has good photocatalytic stability. And in the process of water oxidation, the cobalt oxime molecular catalyst always maintains its molecular properties and does not degrade to form oxide. At the same time, the preparation method of the catalyst and the light absorption component is simple, the raw materials are cheap and easy to obtain, non-toxic and harmless, and has high application value.

[0011] The specific technical scheme adopted by the present application is as follows:

[0012] The photocatalytic hybrid system based on the cobalt oxime molecular catalyst, the reaction solution in the photocatalytic hybrid system includes the cobalt oxime molecular catalyst, the light absorption component bismuth vanadate, the electron sacrificial acceptor sodium persulfate and deionized water;

[0013] The preparation method of the cobalt oxime molecular photocatalyst includes the following steps:

[0014] (1) Dissolve cobalt chloride hexahydrate and butanedione oxime into acetone solution, stir at room temperature, filter the dark green solution, stand to precipitate green solid, filter the solid, wash and dry to obtain cobalt oxime complex;

[0015] The mass ratio of the cobalt chloride hexahydrate and butanedione oxime is 1:2;

[0016] (2) Add the cobalt oxime complex into chloroform, fully dissolve after stirring, add 4-methoxypyridine and stir at room temperature, take the filtrate and distill under reduced pressure to obtain solid crude product, add dichloromethane, filter the filtrate after ultrasonic oscillation, and distill under reduced pressure to obtain solid product, which is the cobalt oxime molecular catalyst;

[0017] The molar ratio of the cobalt oxime complex and 4-methoxypyridine is 1:0.9;

[0018] The preparation method of the light-absorbing component bismuth vanadate is:

[0019] The anhydrous bismuth nitrate and cetyltrimethylammonium bromide are added into ethylene glycol, after stirring, sodium metavanadate is added, after stirring, the reaction solution is transferred to a hydrothermal reactor, and then placed in an oven for reaction; after the reaction is completed, bismuth vanadate powder is obtained by centrifugation, purification and drying;

[0020] The molar ratio of the anhydrous bismuth nitrate, cetyltrimethylammonium bromide and sodium metavanadate is 1:4:2;

[0021] The ratio of cobalt oxime molecular catalyst, bismuth vanadate, sodium persulfate and deionized water in the reaction solution is 0.023mM:10mg:60mM:10ml.

[0022] The photocatalytic hybrid system is applied to photocatalytic water oxidation reaction.

[0023] The photocatalytic hybrid system uses photocatalytic oxidation of water, and the target product is oxygen.

[0024] The light source condition is 450nm 100mW cm -2 Monochromatic light.

[0025] A preparation method of a cobalt oxime molecular photocatalyst, comprising the following steps:

[0026] (1) Dissolve cobalt chloride hexahydrate and dimethylglyoxime into an acetone solution, stir at room temperature, filter the dark green solution, let the green solid precipitate, filter the solid, wash and dry to obtain a cobalt oxime complex;

[0027] The molar ratio of the cobalt chloride hexahydrate and dimethylglyoxime is 1:2;

[0028] Further, 0.021 mol of cobalt chloride hexahydrate and 0.042 mol of dimethylglyoxime are respectively dissolved into 100 ml of acetone solution, stirred at room temperature for 15 min, filtered to obtain a dark green solution, let the green solid precipitate for 24 h, filtered and washed with acetone, and then the product is vacuum dried to obtain a cobalt oxime complex;

[0029] (2) Add the cobalt oxime complex into chloroform, fully dissolve after stirring, add 4-methoxypyridine and stir at room temperature, filter the filtrate under reduced pressure to obtain a solid crude product, add dichloromethane, filter the filtrate after ultrasonic oscillation, and distill the solid product under reduced pressure to obtain a cobalt oxime molecular catalyst;

[0030] The molar ratio of the cobalt oxime complex and 4-methoxypyridine is 1:0.9;

[0031] Further, 1.0 mmol of the cobalt oxime complex was dissolved in 25 ml of chloroform solution, after stirring for 10 min, 0.9 mmol of 4-methoxypyridine was added, and then stirred at room temperature for 2 h. After the reaction was completed, the solvent was removed by rotary evaporation, dichloromethane was added, and ultrasonic was performed for 10 min, then the filtrate was obtained by filtration, and the solvent was removed by rotary evaporation to obtain the product cobalt oxime molecular catalyst.

[0032] A preparation method of a semiconductor bismuth vanadate as a light absorption component of a photocatalytic hybrid system, comprising the following steps:

[0033] (1) Anhydrous bismuth nitrate and cetyltrimethylammonium bromide were added to 60 ml of ethylene glycol, and after stirring vigorously for 40 min, sodium metavanadate was added, and after stirring for 5 min, the reaction solution was transferred to a 140 ml stainless steel hydrothermal reactor, and then placed in an oven for reaction; after the reaction was completed, the bismuth vanadate powder was obtained by centrifugation, purification and drying.

[0034] The molar ratio of the anhydrous bismuth nitrate, cetyltrimethylammonium bromide and sodium metavanadate is 1:4:2.

[0035] (2) The reaction conditions of the bismuth vanadate powder are as follows: heating at a rate of 3 ℃ / min to 160 ℃, and then keeping at 160 ℃ for 3 h. After the reaction was completed, the reaction solution was cooled naturally, and the powder obtained by centrifugation at a speed of 10,000 rpm for 5 min was washed with ethanol and water three times each to obtain the product, which was dried in an oven at 80 ℃ overnight.

[0036] The composition of the photocatalytic hybrid system includes the following parts: cobalt oxime molecular water oxidation catalyst, bismuth vanadate semiconductor powder as light absorption component, sodium persulfate as sacrificial electron acceptor, reaction raw materials and solvent deionized water.

[0037] The process of applying cobalt oxime molecules to photocatalytic water decomposition is as follows: 0.023 mM of cobalt oxime molecular catalyst, 10 mg of BiVO4, 60 mM of sodium persulfate and 10 ml of deionized water were added to a 34 ml sealed Schlenk bottle, and bubbled for 30 min under an argon atmosphere before the reaction. The photocatalytic reaction was carried out under mechanical stirring, and the photocatalytic reaction was carried out under 450 nm 100 mW cm -2 of monochromatic light for 3 h, and then the reaction products were detected using a gas chromatograph.

[0038] The specific steps of detecting the reaction products using a gas chromatograph are as follows: first, the syringe is washed in an argon-filled single-neck flask, then 0.5 ml of gas is taken from the photoreactor using the syringe and injected into the gas chromatograph for detection, and the peak area corresponding to the gas is obtained. The amount of oxygen produced in the reaction is calculated by the peak area and the standard curve of the gas chromatograph.

[0039] The calibration of the gas chromatography standard curve comprises the following steps: calibration of the gas chromatography standard curve. The standard curve of the peak area of hydrogen, oxygen and nitrogen in the gas chromatography to the amount of substance of the gas is calibrated by using standard gas containing known concentrations of hydrogen, oxygen and nitrogen. First, the syringe is washed in an argon-filled single-necked bottle, then 0.5ml of standard gas is taken out of the syringe and injected into the gas chromatography for detection, and the peak area corresponding to the gas is obtained, and finally the relationship between the peak area and the amount of substance of the gas is calculated. Three data are collected and averaged. The obtained standard curve is: standard curve Y = 3.516 * 10 X; standard curve Y = 3.204 * 10 X; standard curve Y = 3.336 * 10 X. H2 -6 O2 -5 N2 -5

[0040] The light source condition is 100mW cm -2 The incident light power intensity is 100mW cm

[0041] The light source condition is 450nm for monochromatic light wavelength.

[0042] The photocatalytic reactor is a 34ml closed Schlenk bottle.

[0043] The continuous stirring refers to using mechanical stirring or magnetic stirring.

[0044] Compared with the prior art, the present application has the following characteristics and beneficial effects:

[0045] (1) The present application selects a classic hydrogen production catalyst cobalt oxime molecule as a water oxidation catalyst. Cobalt is the first row transition metal, and its reserves are more abundant than those of noble metals such as ruthenium and iridium. The synthesis method of cobalt oxime molecule is simple, the synthesis conditions are mild, and the central metal has high utilization rate and good activity.

[0046] (2) The electrochemical method, X-ray photoelectron spectroscopy and EDX energy spectrum analysis prove that the cobalt oxime molecule plays a catalytic role in the photocatalytic oxygen production and still maintains the molecular form.

[0047] (3) The cobalt oxime molecule, semiconductor powder bismuth vanadate and sacrificial electron acceptor sodium persulfate together construct a photocatalytic water oxidation system based on non-noble metal catalyst, which successfully improves the oxygen production activity of water oxidation. By adjusting the concentration of cobalt oxime molecule and the pH of the reaction system, the catalytic performance of photocatalytic water oxidation is optimized. The conclusion is that when the pH is 7 and the concentration is 0.023mM, the best oxygen production effect can be obtained; after 3h of illumination, the oxygen production rate can reach 2099.9μmol g -1 h -1 ​​​​​​This is 2.5 times that of the photocatalytic system without cobalt oxime molecules. The amount of oxygen produced in the experiment was quantified, with a TON value estimated based on cobalt oxime molecules of 154.2 and a TOF value of 0.86 min. -1 . Attached Figure Description

[0048] Figure 1 The images shown are scanning electron microscope (SEM) images (ab) of bismuth vanadate powder in this invention; and elemental mapping images (cd) of bismuth vanadate powder.

[0049] Figure 2 This is the XRD pattern of the bismuth vanadate powder used in this invention.

[0050] Figure 3 This is an electrochemical rinsing experiment to verify the molecular properties in this invention; Example 3.

[0051] Figure 4 This is an X-ray photoelectron spectroscopy (XPS) image used to verify molecular properties in this invention; Example 4.

[0052] Figure 5 X-ray diffraction (EDX) test for verifying molecular properties in this invention; Example 4.

[0053] Figure 6 Example 5, Comparative Example 1, compares the oxygen production from photocatalytic water oxidation under different electron sacrificial acceptor conditions in this invention.

[0054] Figure 7 Example 6, Comparative Example 2, compares the oxygen production from photocatalytic water oxidation under different cobalt oxime molecule concentrations in this invention.

[0055] Figure 8 Example 7, Comparative Example 3, compares the oxygen production of photocatalytic water oxidation under different pH conditions in this invention.

[0056] Figure 9 This is an example of photocatalytic water oxidation for oxygen production in this invention; Example 8, Comparative Example 4.

[0057] Figure 10 Example 9 illustrates the photocatalytic water oxidation photocycle in this invention.

[0058] Figure 11 This is a schematic diagram of photocatalytic water oxidation in this invention. Detailed Implementation Plan

[0059] The present application is further described below in conjunction with the accompanying drawings and specific examples. The specific examples described herein are intended for purposes of illustration and explanation only and are not intended to limit the present application. In the following examples, unless otherwise indicated, the specific operation methods and testing methods designed are conventional techniques, and the reagents, drugs, materials, and instruments used can be obtained through commercial means. Example 1

[0060] The preparation of cobalt oxime molecular photocatalyst, the specific steps are as follows:

[0061] (1) Take 5.0 g of cobalt chloride hexahydrate (0.021 mol) and 4.9 g of butanedione oxime (0.042 mol) respectively and dissolve them in 100 ml of acetone solution. Stir at room temperature for 15 min, then filter to obtain a dark green solution. Let it stand for 24 h to precipitate green solid. Filter and wash with acetone, then vacuum dry to obtain cobalt oxime complex with a yield of 86%.

[0062] (2) Take 0.36 g of cobalt oxime complex (1.0 mmol) and dissolve it in 25 ml of chloroform solution. Stir for 10 min, then add 0.098 g of 4-methoxypyridine (0.9 mmol). Stir at room temperature for 2 h. After the reaction is completed, remove the solvent by rotary evaporation, add dichloromethane, and ultrasonic for 10 min. Then filter and take the filtrate part. Remove the solvent by rotary evaporation to obtain the final product with a yield of 47%. Example 2

[0063] The preparation of light-absorbing component bismuth vanadate powder, the specific steps are as follows:

[0064] Take 2.76 g of anhydrous bismuth nitrate (0.007 mol) and 1.05 g of cetyltrimethylammonium bromide (0.0028 mol) and add them to a 100 ml conical flask. Add 60 ml of ethylene glycol and stir vigorously for 40 min. Add 2.8 g of sodium metavanadate (0.015 mol) and stir for 5 min. Then transfer the reaction solution to a stainless steel hydrothermal reactor with a volume of 140 ml. Assemble the hydrothermal reactor and place it in an oven. Heat it to 160°C at a rate of 3°C / min, then keep it at 160°C for 3 h. After the reaction is completed, cool it naturally. Centrifuge the reaction solution at a speed of 10,000 rpm for 5 min. Wash the powder obtained by centrifugation with ethanol and water three times each to obtain the product. Dry it in an oven at 80°C overnight to obtain 1.6 g of yellow solid powder. Example 3

[0065] In the process of water oxidation, the cobalt oxime molecular characteristics are verified by electrochemical flushing method, the specific conditions are as follows:

[0066] The molecular property test was carried out in a homogeneous system of cobalt oxime molecules, and the electrochemical workstation used was a CHI 660E electrochemical workstation from Shanghai Chenhua Company. The reference electrode was an Ag / AgCl electrode, the counter electrode was a platinum wire, and the working electrode was a glassy carbon electrode. The solution measured was a 5 mM cobalt oxime molecule, a 50 mM tetrabutylammonium hexafluorophosphate acetonitrile and deionized water mixed solution (acetonitrile / water = 4 / 1; volume ratio). The test steps were as follows: a clean glassy carbon electrode was scanned in a cyclic voltammetry curve (CV) in an electrolyte without cobalt oxime molecules; then the glassy carbon electrode was cleaned and scanned in a cyclic voltammetry curve for 20 times in an electrolyte containing cobalt oxime molecules. The scanned glassy carbon electrode was washed with deionized water and acetonitrile, and scanned in a cyclic voltammetry curve in an electrolyte without cobalt oxime molecules (conditions: scan rate 50 mV s -1 , 0-1.5 V vs . Ag / AgCl). Example 4

[0067] In the process of water oxidation, the cobalt oxime molecule property verification: X-ray photoelectron spectroscopy (XPS) and X-ray spectrum test (EDX), the specific steps are as follows:

[0068] Take the mixed solution after the photocatalytic oxygen production experiment, centrifuge and take the BiVO4 solid part, wash the solid part with water and acetonitrile, and then dry it, and perform XPS and EDX tests. Example 5

[0069] Cobalt oxime molecule photocatalytic water oxidation, using sodium persulfate as a sacrificial electron acceptor, the specific steps are as follows:

[0070] 0.023 mM cobalt oxime molecule catalyst, 10 mg bismuth vanadate, 60 mM sodium persulfate and 10 ml deionized water were added to the photocatalytic reactor, and the reactor was bubbled under argon atmosphere for 30 min before reaction. The photocatalytic reaction was carried out under continuous stirring; the reaction was carried out at room temperature, and the closed photocatalytic reactor was placed under 450 nm 100 mW cm -2 monochromatic light for 2 h, and then the reaction products were detected using a gas chromatograph. Comparative Example 1

[0071] As a comparison of Example 5, in order to compare the effect of different sacrificial electron acceptors on the oxygen production of the photocatalytic water oxidation system, the photocatalytic reaction system was prepared in the same way, except that the sacrificial electron acceptor was sodium iodate and silver nitrate. Example 6

[0072] Cobalt oxime molecule photocatalytic water oxidation, the concentration of cobalt oxime molecule water oxidation catalyst was 0.023 mM, and the specific steps were as follows:

[0073] mM of cobaloxime molecular catalyst, 10 mg of bismuth vanadate, 80 mM of sodium persulfate and 10 ml of deionized water were added into the photocatalytic reactor, and bubbled for 30 min under argon atmosphere before reaction, and the photocatalytic reaction was carried out under continuous stirring; the reaction was carried out at room temperature, and the closed photocatalytic reactor was placed under 450 nm 100 mW cm -2 of monochromatic light for 2 h, and then the reaction product was detected using a gas chromatograph. Comparative Example 2

[0074] As a comparative example of Example 6, in order to compare the effects of different concentrations of cobaloxime molecular water oxidation catalysts on the oxygen production of the photocatalytic water oxidation system, the preparation method of the photocatalytic reaction system was the same, and the difference was that the concentration of the cobaloxime molecular water oxidation catalyst was 0.0023 mM, 0.0115 mM, 0.115 mM and 0.23 mM. Example 7

[0075] The cobaloxime molecular photocatalytic water oxidation was carried out under the condition of pH = 7, and the specific steps were as follows:

[0076] Under the condition of pH = 7, 0.023 mM of cobaloxime molecular catalyst, 10 mg of bismuth vanadate, 60 mM of sodium persulfate and 10 ml of deionized water were added into the photocatalytic reactor, and bubbled for 30 min under argon atmosphere before reaction, and the photocatalytic reaction was carried out under continuous stirring; the reaction was carried out at room temperature, and the closed photocatalytic reactor was placed under 450 nm 100 mW cm -2 of monochromatic light for 2 h, and then the reaction product was detected using a gas chromatograph. Comparative Example 3

[0077] As a comparative example of Example 7, in order to compare the effects of different pH environments on the oxygen production of the photocatalytic water oxidation system, the preparation method of the photocatalytic reaction system was the same, and the difference was that the pH of the reaction liquid was 3, 4, 5 and 6, respectively. Example 8

[0078] The cobaloxime molecular photocatalytic water oxidation was carried out, and the oxygen production was 3 h, and the specific steps were as follows:

[0079] Figure 11 A schematic diagram of the cobaloxime molecular photocatalytic water oxidation process. Under the condition of pH = 7, 0.023 mM of cobaloxime molecular catalyst, 10 mg of bismuth vanadate, 60 mM of sodium persulfate and 10 ml of deionized water were added into the photocatalytic reactor, and bubbled for 30 min under argon atmosphere before reaction, and the photocatalytic reaction was carried out under continuous stirring; the reaction was carried out at room temperature, and the closed photocatalytic reactor was placed under 450 nm 100 mW cm -2The reaction product was detected using a gas chromatograph. Comparative Example 4

[0080] As a comparative example of Example 8, in order to compare the oxygen production of the photocatalytic water oxidation system only adding bismuth vanadate, the preparation method of the photocatalytic reaction system was the same, except that the cobalt iminoxyl molecule water oxidation catalyst was not added. Example 9

[0081] Exploration of the oxygen production performance of the cobalt iminoxyl molecule photocatalytic water oxidation system, the specific steps are as follows:

[0082] At pH = 7 and room temperature, 0.023 mM of cobalt iminoxyl molecule catalyst, 10 mg of bismuth vanadate, 60 mM of sodium persulfate and 10 ml of deionized water were added to the photocatalytic reactor, and the reactor was bubbled under argon atmosphere for 30 min before reaction. The closed photocatalytic reactor was placed under 450 nm 100 mW cm -2 monochromatic light for 2 h, and the reaction product was detected using a gas chromatograph; then the photocatalytic reactor was placed under argon atmosphere for 30 min to remove the oxygen produced in the first photocatalytic cycle, and placed under light source for 2 h, and the reaction product was detected using a gas chromatograph; the photocatalytic reactor was placed under argon atmosphere for 30 min to remove the oxygen produced in the second photocatalytic cycle, and placed under light source for 2 h, and the reaction product was detected using a gas chromatograph.

[0083] Performance analysis of the cobalt iminoxyl molecule catalyst photocatalytic hybrid system constructed in the example:

[0084] Figure 1 It was observed that the prepared bismuth vanadate had a nanosheet structure on the surface, and the specific surface area was relatively large, which was beneficial to the loading of the cocatalyst. Through the element mapping image, it can be seen that there are a large number of V, O and Bi elements, which proves the successful synthesis of bismuth vanadate.

[0085] Figure 2 The prepared bismuth vanadate was tested by X-ray diffraction (XRD), and the results showed that the prepared material had good crystallinity. The characteristic diffraction at 19.5°, 29°, 30.5° and 40° were all characteristic diffraction peaks of bismuth vanadate, and the structure was monoclinic scheelite structure.

[0086] Figure 3A rinsing experiment was conducted using a glassy carbon electrode as the working electrode in a three-electrode system. First, a blank image was obtained by cyclic voltammetry of the glassy carbon electrode. Then, the cyclic voltammetry curve was scanned 20 times in a homogeneous solution of cobalt oxime molecules. After scanning, the electrode was rinsed with deionized water and acetonitrile (cobalt oxime molecules have poor solubility in water but good solubility in acetonitrile). Cyclic voltammetry (CV) was then performed on the rinsed glassy carbon electrode. By comparison, the current decreased significantly after rinsing, and the current magnitude was almost the same as that of the blank electrode. This proves that during water oxidation, the catalytic agent is still the molecular cobalt oxime catalyst, and it has not dissociated into oxides; otherwise, the CV image after the rinsing experiment would show a large water oxidation current.

[0087] Figure 4 , Figure 5 X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy were used to measure the energy spectrum of solids after photocatalytic reaction. Figure 4 No obvious peaks were observed at the Co 2p binding energies of 795.5 eV and 780.1 eV, indicating that during the photocatalytic water oxidation process, the cobalt oxime molecules did not degrade into related cobalt oxides that adhered to bismuth vanadate. Meanwhile, Figure 5 No cobalt was detected, indicating that no cobalt oxide was deposited on the bismuth vanadate surface during the reaction. The Na shown is sodium persulfate, a sacrificial agent used in the photocatalytic reaction, while Tc, Mo, and Zr were introduced during gold sputtering for energy dispersive spectroscopy (EDS) analysis.

[0088] Figure 6 Example 5 illustrates the photocatalytic oxygen production of Comparative Example 1. When sodium persulfate was used as the sacrificial electron acceptor, the best oxygen production effect was achieved, with oxygen production amounts being 12.2 times and 8.9 times that of silver nitrate and sodium iodate, respectively. This is likely because sodium persulfate can more effectively capture photogenerated electrons during the photocatalytic reaction, thus better promoting the photocatalytic reaction.

[0089] Figure 7 Example 6 illustrates the photocatalytic oxygen production of Comparative Example 2. The optimal oxygen production effect was achieved at a cobalt oxime molecule concentration of 0.023 mM. This is likely because when the cobalt oxime molecule concentration is too low, the holes generated by the photoexcitation of bismuth vanadate cannot be effectively quenched during the photocatalytic reaction, resulting in suboptimal oxygen production. Conversely, when the concentration is too high, the holes generated by the photoexcitation of bismuth vanadate are dispersed and cannot be repeatedly transferred to individual cobalt oxime molecules, thus worsening the oxygen production effect.

[0090] Figure 8 Example 7 illustrates the photocatalytic oxygen production of Comparative Example 3. The oxygen production effect gradually increased with increasing pH, and the optimal oxygen production effect was achieved at pH=7.

[0091] Figure 9 The photocatalytic oxygen evolution of Example 8, Comparative Example 4 was carried out. After 3h of irradiation, the amount of oxygen evolved by the photocatalytic system with the addition of cobalt-oxime molecules was 6299.6μmol g -1 , with an oxygen evolution rate of 2099.9μmol g -1 h -1 . The amount of oxygen evolved by the photocatalytic system without the addition of cobalt-oxime molecules was 2482.2μmol g -1 , with an oxygen evolution rate of 827.4μmol g -1 h -1 . The oxygen evolution rate of the photocatalytic system with the addition of cobalt-oxime molecules was 2.5 times that of the system without the addition of cobalt-oxime molecules. The TON value estimated based on the photocatalytic hybrid system of cobalt-oxime molecules was 154.2, and the TOF value was 0.86min -1 . However, in the powder system, only a small fraction of the cobalt-oxime molecules can be in close contact with the surface of bismuth vanadate and participate in the reaction, so the actual TON and TOF values must be greater than the calculated results.

[0092] Figure 10 The results of the photocatalytic recycling test of Example 9. In the three-round recycling photocatalytic test, the oxygen evolution rate of the cobalt-oxime molecule photocatalytic hybrid system did not decrease significantly within 5h, and the oxygen evolution rate decreased slightly after 7.5h of reaction, showing good stability.

Claims

1. A photocatalytic hybrid system based on a cobalt oxime molecule catalyst, characterized in that: The reaction solution in the photocatalytic hybrid system includes a cobalt oxime molecular catalyst, a light-absorbing component bismuth vanadate, an electron sacrificial acceptor sodium persulfate, and deionized water; The preparation method of the cobalt oxime molecular photocatalyst includes the following steps: (1) Cobalt chloride hexahydrate and dimethylglyoxime were dissolved in acetone solution, stirred at room temperature, filtered to obtain dark green solution, allowed to stand to precipitate green solid, filtered to obtain solid, washed and dried to obtain cobalt oxime complex; The molar ratio of cobalt chloride hexahydrate to dimethylglyoxime is 1:2; (2) Add the cobalt oxime complex to chloroform, stir until fully dissolved, add 4-methoxypyridine and stir at room temperature, take the filtrate and distill under reduced pressure to obtain a solid crude product, add dichloromethane, sonicate and filter, take the filtrate and distill under reduced pressure to obtain a solid product, which is the cobalt oxime molecular catalyst. The molar ratio of the cobalt oxime complex to 4-methoxypyridine is 1:0.9; The method for preparing the light-absorbing component bismuth vanadate is as follows: Anhydrous bismuth nitrate and hexadecyltrimethylammonium bromide were added to ethylene glycol and stirred. Sodium metavanadate was then added and stirred again. The reaction solution was transferred to a hydrothermal reactor and then placed in an oven for reaction. After the reaction was completed, bismuth vanadate powder was obtained by centrifugation, purification and drying. The molar ratio of anhydrous bismuth nitrate, hexadecyltrimethylammonium bromide, and sodium metavanadate is 1:4:

2.

2. The photocatalytic hybrid system based on cobalt oxime molecular catalyst according to claim 1, characterized in that: The ratio of cobalt oxime molecular catalyst, bismuth vanadate, sodium persulfate and deionized water in the reaction solution is 0.023 mM: 10 mg: 60 mM: 10 mL.

3. The application of the photocatalytic hybrid system based on cobalt oxime molecular catalyst as described in claim 1, characterized in that: The photocatalytic hybrid system is applied to the photocatalytic water oxidation reaction.

4. The application of the photocatalytic hybrid system based on cobalt oxime molecular catalyst according to claim 3, characterized in that: The photocatalytic hybrid system utilizes photocatalytic oxidation of water, with oxygen as the target product.

5. The application of the photocatalytic hybrid system based on cobalt oxime molecular catalyst according to claim 3, characterized in that: Light source conditions: 450nm 100mW cm -2 Monochromatic light.

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