CN106362807A - Visible light driven photocatalysis hydrogen production catalyst as well as preparation method and application thereof - Google Patents

Abstract

The invention discloses a photocatalytic hydrogen production catalyst driven by visible light, a preparation method and application thereof. The main points of the technical scheme of the present invention are: using isopropyl titanate and tantalum-containing polyacid Ta-POMs-1 as precursors, preparing photocatalytic hydrogen production catalyst Ta-POM-1/ _TiO2 by sol-gel method; through optimization And select the type and amount of the dye molecule, the type and amount of the sacrificial reagent and the amount of the catalyst to optimize the reaction conditions for the catalyst to catalyze hydrogen production under visible light. Compared with the parent TiO ₂ and POMs, the prepared Ta‑POM‑1/TiO ₂ composite photocatalytic material exhibits better visible light absorption and higher photocatalytic hydrogen production activity, so it has a better application in the field of photocatalysis. Application prospects.

Description

A photocatalytic hydrogen production catalyst driven by visible light and its preparation method and application

technical field

The invention belongs to the technical field of synthesis of composite photocatalytic materials, and in particular relates to a photocatalytic hydrogen production catalyst driven by visible light and its preparation method and application.

Background technique

Since entering the 21st century, while enjoying the comfort and convenience brought by the development of science and technology, human beings are facing two major survival crises: the depletion of fossil energy such as coal and oil; the gradual deterioration of the living environment, and the burning of fossil resources. The released CO ₂ , SO ₂ and other harmful gases have brought many environmental problems such as greenhouse effect and acid rain. Finding clean and renewable energy is an urgent need to achieve sustainable development and improve the quality of human life. The thermal efficiency of hydrogen is three times that of ordinary gasoline, and the combustion products have no pollution to the environment, so it is an ideal clean energy. It is of great economic and social significance to develop cost-effective methods to achieve rapid hydrogen production.

Due to its high efficiency, low cost and stability, TiO ₂ has been used in the fields of solar cells, pollutant degradation, air purification and hydrogen production by photolysis of water, and has become one of the most potential photocatalytic materials. However, _TiO2 has a wide band gap and can only absorb ultraviolet light, so it cannot effectively utilize solar energy. Moreover, the photogenerated electrons and holes generated by _TiO2 are easily recombined during the photocatalytic process, which greatly reduces its photocatalytic efficiency. The above two problems seriously restrict the further development of _TiO2 .

Polyoxometalates (POMs) have reversible redox properties and are also a class of excellent photocatalytic materials. However, these compounds often have high solubility in water or organic solvents, making them difficult to recycle. TiO ₂ /POMs is a class of porous TiO ₂ loaded polyacid composites (Y. Guo Et.al. J. Mol. Catal. A 2007, 136–148). Compared with the parent TiO ₂ and POMs, this type of composite material has a larger specific surface and porosity, and has a lower band gap energy level, which can enhance the absorption of visible light, and is an excellent class of heterogeneous photocatalysts. . In the photocatalytic process of such composites, POMs can effectively store and transfer photogenerated electrons, and can effectively inhibit the recombination of electrons and holes in TiO ₂ , so the catalytic efficiency is greatly improved. Many studies have been done on the photocatalytic degradation of organic pollutants by TiO ₂ /POMs (Y. Yang et.al.J. Mol. Catal. A 2005, 203–207), but the research on photocatalytic water splitting has not been reported .

In 2012, the inventor successfully obtained a tantalum-containing polyacid catalyst Ta-POM-1 with high-efficiency photolytic water-splitting activity, the molecular formula is H ₄ K ₈ Na ₈ [P ₈ W ₆₀ Ta ₁₂ (H ₂ O) ₄ (OH ) ₈ O ₂₃₆ ] nH ₂ O. Due to the hybridization of Ta5d orbital and W5d orbital, the LUMO level of the whole molecule is increased, and the H ₂ production capacity of the catalyst is greatly improved (J. Am. Chem. Soc., 2012, 134, 19716–19721). However, these tantalum-containing polyacid Ta-POMs, like other polyacid compounds, are easily soluble in water, difficult to recycle and reuse, and only have ultraviolet light activity in solution state. Therefore, preparing tantalum-containing polyacids with high photocatalytic activity into insoluble materials is an effective way to solve this problem. This patent uses the sol-gel method to prepare the novel Ta-POM into a composite material, code-named Ta-POM-1/TiO ₂ , to solve the problems of its recycling and visible light response, and further optimize the composite material Conditions for photocatalytic hydrogen production.

Contents of the invention

The technical problem solved by the present invention is to provide a photocatalytic hydrogen production catalyst driven by visible light and its preparation method and application.

The present invention adopts the following technical scheme to solve the above technical problems, a photocatalytic hydrogen production catalyst driven by visible light, characterized in that the photocatalytic hydrogen production catalyst is composed of titanium dioxide _TiO2 and Ta-POMs-1 containing tantalum polyacid, The chemical formula of Ta-POMs-1 containing tantalum polyacid is H ₄ K ₈ Na ₈ [P ₈ W ₆₀ Ta ₁₂ (H ₂ O) ₄ (OH) ₈ O ₂₃₆ ]·nH ₂ O.

The preparation method of the photocatalytic hydrogen production catalyst driven by visible light of the present invention is characterized in that the specific steps are: dissolving 10mL isopropyl titanate in 30mL isopropanol to obtain solution A; POMs-1 was dissolved in 2mL deionized water to obtain solution B; under ultrasonic conditions, solution B was added dropwise to solution A, and after the addition was completed, ultrasonic treatment was continued until a gel was formed. After aging for 12 hours, the gel was placed in high pressure In the reaction kettle, the temperature was raised to 150°C at a rate of 2°C/min and kept for 12 hours. After cooling to room temperature, the sample was filtered and washed with 80°C deionized water for several times until the ultraviolet-visible absorption spectrum of the eluent was free of acid. absorption peak, and then dry and activate the obtained solid sample at 150° C. for 12 hours to obtain the target product photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ .

The application of the photocatalytic hydrogen production catalyst driven by visible light in the present invention in photocatalytic hydrogen production is characterized in that the specific process is: add 180mL deionized water and 70mL sacrificial reagent methanol to the quartz photocatalytic reactor, and then add 0.35 g photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ , 0.1 g photosensitizer rhodamine b and 8 mg cocatalyst chloroplatinic acid, blow with high-purity nitrogen for 30 minutes, then airtight and adsorb under dark conditions for 12 hours , and then irradiated with a 500W xenon lamp, the gas produced was collected by the drainage method and detected as H ₂ by gas chromatography.

The application of the photocatalytic hydrogen production catalyst driven by visible light in the present invention in photocatalytic hydrogen production is characterized in that the specific process is: add 180mL deionized water and 25mL sacrificial reagent triethanolamine to the quartz photocatalytic reactor, and then add 0.35g of catalyst Ta-POM-1/TiO ₂ , 0.1g of photosensitizer Eosin Y and 8mg of cocatalyst chloroplatinic acid were blown with high-purity nitrogen for 30 minutes, then airtight and stirred and adsorbed for 12 hours under dark conditions, and then used Irradiated by a 500W xenon lamp, the gas produced was collected by the drainage method and detected as H ₂ by gas chromatography.

Compared with the parent TiO ₂ and POMs, the Ta-POM-1/TiO ₂ composite photocatalytic material prepared by the present invention shows better visible light absorption and higher photocatalytic hydrogen production activity, so it has a comparative advantage in the field of photocatalysis Good application prospects.

Description of drawings

Fig. 1 is Ta-POM-1/TiO of the present invention synthesis ₂ and Ta-POMs-1 and anatase TiO ₂ solid diffuse reflectance spectrograms, it has better absorption in the visible region;

Fig. 2 is the Ta-POM-1/TiO of the present invention synthesis ₂ and the Raman spectrum of each raw material component;

Fig. 3 is the Ta-POM-1/TiO that the present invention synthesizes ₂ and anatase TiO ₂ The powder XRD pattern of collection;

Fig. 4 is the Ta-POM-1/ _TiO synthesized by the present invention The visible light catalytic hydrogen production activity effect figure, abscissa is time, and ordinate is hydrogen production amount;

Figure 5 is the synthesis of Ta-POM-1/TiO ₂ in the present invention in the presence of different dyes (rhodamine b, abbreviated as Rh-b and eosin Y, abbreviated as EY) and sacrificial reagents (methanol and triethanolamine) Photocatalytic hydrogen production activity.

detailed description

The above-mentioned contents of the present invention are described in further detail below through the embodiments, but this should not be interpreted as the scope of the above-mentioned themes of the present invention being limited to the following embodiments, and all technologies realized based on the above-mentioned contents of the present invention all belong to the scope of the present invention.

Example

Preparation of Ta-POM-1/TiO ₂ Composite Photocatalytic Material

1. The precursor contains tantalum polyacid H ₄ K ₈ Na ₈ [P ₈ W ₆₀ Ta ₁₂ (H ₂ O) ₄ (OH) ₈ O ₂₃₆ ]·nH ₂ O, marked as Ta-POM-1, synthesized according to the literature : J. Am. Chem. Soc., 2012, 134, 19716−19721.

2. Dissolve 10mL of isopropyl titanate in 30mL of isopropanol to obtain solution A; dissolve 1g of tantalum-containing polyacid Ta-POM-1 in 2mL of deionized water to obtain solution B; under ultrasonic conditions, dissolve solution B drop by drop Add it into solution A, continue to sonicate until the gel is formed after the dropwise addition, after aging for 12 hours, put the gel in an autoclave and raise the temperature to 150°C at a rate of 2°C/min for 12 hours, then cool to room temperature Finally, the sample was filtered and washed with 80°C deionized water for several times until the eluent had no absorption peak of polyacid in the UV-Vis absorption spectrum, and then the obtained solid sample was dried and activated at 150°C for 12 hours to obtain the target photocatalyst Ta- POM-1/TiO ₂ .

As shown in the solid diffuse reflectance photometry of accompanying drawing 1, compared with Ta-POMs-1 and anatase TiO ₂ , the photocatalytic hydrogen production catalyst prepared has a significant shift in the light absorption to the long-wave direction, which can improve the photocatalytic Efficient utilization of visible light by hydrogen-producing catalysts. As shown in Figure 2, the characteristic absorption peak of polyacid at 989cm ^-1 in the Raman spectrum of the composite photocatalytic material Ta-POM-1/ _TiO2 indicates the existence of Ta-POM-1 in the composite material. The powder XRD spectrum of the composite photocatalytic material in Figure 3 is very similar to that of the matrix _TiO2 , indicating that the appearance of Ta-POM-1 did not change the lattice structure of the _TiO2 matrix, but was evenly dispersed in the pores of the frame . The nitrogen adsorption test results show that the Langmuir specific surface area of Ta-POM-1/TiO ₂ is 203m ² /g, and the BET specific surface area is 150m ² /g; the pore size distribution analysis shows that the composite photocatalytic material has typical mesopority.

Photocatalytic activity test method

Add a certain amount of deionized water and sacrificial reagent methanol to the quartz photocatalytic reactor, and then add a certain amount of photocatalyst Ta-POM-1/TiO ₂ , photosensitizer Rhodamine b (abbreviated as Rh-b) and cocatalyst Chloroplatinic acid (molecular formula is H ₂ PtCl ₆ ), gassed with high-purity nitrogen for 30 minutes, then sealed and stirred and adsorbed for 12 hours under dark conditions, and then irradiated with a 500W xenon lamp. The generated gas was collected by drainage and analyzed by gas chromatography. Detected as H ₂ .

Effect of the amount of photocatalytic hydrogen production catalyst Ta-POM-1/ _TiO2 on the catalytic performance.

Under the conditions of maintaining 180mL of deionized water, 70mL of sacrificial reagent methanol, 0.1g of photosensitizer Rh-b and 8.0mg of cocatalyst chloroplatinic acid, when changing a series of photocatalytic hydrogen production catalysts Ta-POM-1/ When the amount of TiO ₂ is used, it is found that the catalytic effect of the photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ is 0.35g, and the hydrogen production amount in 1.5 hours is 498μmol.

Catalyst dosage (g) Hydrogen production in 1.5 hours/μmol 0.20 481 0.35 498 0.50 379

The effect of the amount of sacrificial reagent on the catalytic effect.

Under the conditions of keeping 180mL of deionized water, photocatalytic hydrogen production catalyst Ta-POM-1/ _TiO Consumption of 0.35g, photosensitizer Rh-b consumption of 0.1g and cocatalyst chloroplatinic acid consumption of 8.0mg, when changing methanol It is found that the catalytic effect is the best when the methanol content in the reaction solution is 28% (methanol volume is 70mL). Before the amount of methanol used was less than 70mL, the photocatalytic efficiency increased with the increase of the amount of methanol, and the amount of hydrogen produced gradually increased. However, when the amount of methanol used was greater than 70mL, the catalytic efficiency tended to be stable, and the amount of hydrogen produced in 1.5 hours did not increase with the amount of methanol. obviously increase.

Methanol content in solution (V/V %) Hydrogen production in 1.5 hours/μmol 12 339 20 424 28 498 36 491

The effect of the amount of photosensitizer on the catalytic effect.

Under the conditions of maintaining 180mL of deionized water, 70mL of sacrificial reagent methanol, 0.35g of photocatalytic hydrogen production catalyst Ta-POM-1/ _TiO and 8.0mg of cocatalyst chloroplatinic acid, when changing the amount of photosensitizer Rh-b It was found that when the amount of Rh-b was less than 0.1g, the amount of hydrogen produced increased significantly with the increase of the amount of dye. However, when the amount of Rh-b is greater than 0.1 g, the amount of hydrogen produced decreases when the amount of Rh-b is increased. This may be because when the amount of Rh-b is small, as the concentration of the dye increases, it helps to absorb visible light and improve the quantum efficiency; but when the concentration is too large, Rh-b will hinder the absorption of light by the catalyst and weaken the catalytic effect. . Therefore, the optimal dosage of Rh-b is 0.1g.

Rh-b dosage (mmol) Hydrogen production in 1.5 hours/μmol 0.1 412 0.2 498 0.3 300

The effect of co-catalyst dosage on catalytic performance.

The added chloroplatinic acid was reduced to Pt at the initial stage of the photocatalytic reaction and served as a co-catalyst for the photocatalytic hydrogen production reaction. Keeping deionized water 180mL, photocatalytic hydrogen production catalyst Ta-POM-1/ _TiO Consumption 0.35g, sacrificial reagent methanol 70mL and photosensitizer Rh-b consumption 0.1g, when changing the consumption of cocatalyst chloroplatinic acid, find that, When the amount of chloroplatinic acid is 8 mg, the catalytic effect is the best; but when the amount of chloroplatinic acid is too large, the hydrogenation reaction of the dye will occur, so that the hydrogen production reaction rate is greatly reduced.

Chloroplatinic acid content in the solution (mg) Hydrogen production/μmol 4 225 8 498 12 218

After a series of comparative experiments above, the optimal catalytic conditions were finally determined as follows: the amount of deionized water was 180mL, the amount of photocatalytic hydrogen production catalyst Ta-POM-1/ _TiO2 was 0.35g, and the amount of sacrificial reagent methanol was 70mL. The amount of photosensitizer Rh-b is 0.1g and the amount of cocatalyst chloroplatinic acid is 8mg, as shown in Figure 4, under this condition, the amount of hydrogen produced in 1.5 hours reaches 498 μmol, and the catalytic efficiency is the same as that of commercially purchased anatase TiO ₂ 4.65 times.

In addition, we also tested the photocatalytic activity of the photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ when the sacrificial reagent was triethanolamine and the photosensitizer was eosin Y. As shown in accompanying drawing 5, under the condition that deionized water, photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ and cocatalyst chloroplatinic acid consumption are exactly the same, only sacrificial reagent methanol is replaced by 25mL triethanolamine and photosensitizer When the agent Rh-b was replaced by 0.1g eosin Y, the hydrogen production rate was slower but the persistence was better, and there was no obvious decrease within 90 hours.

The above embodiments are only to illustrate the technical ideas of the present invention, and cannot limit the protection scope of the present invention with this. All technical ideas proposed according to the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (4)

1. A photocatalytic hydrogen production catalyst driven by visible light, characterized in that the photocatalytic hydrogen production catalyst is composed of titanium dioxide _TiO2 and tantalum-containing polyacid Ta-POMs-1, wherein tantalum polyacid Ta-POMs-1 The chemical formula is H ₄ K ₈ Na ₈ [P ₈ W ₆₀ Ta ₁₂ (H ₂ O) ₄ (OH) ₈ O ₂₃₆ ]·nH ₂ O. 2. A preparation method of a photocatalytic hydrogen production catalyst driven by visible light according to claim 1, characterized in that the specific steps are: 10mL isopropyl titanate is dissolved in 30mL isopropanol to obtain solution A; 1g containing Tantalum polyacid Ta-POMs-1 was dissolved in 2mL of deionized water to obtain solution B; under ultrasonic conditions, solution B was added dropwise to solution A, and after the addition was completed, ultrasonic treatment was continued until a gel was formed. After aging for 12 hours, the Put the gel in a high-pressure reactor and raise the temperature to 150°C at a rate of 2°C/min and keep it for 12 hours. After cooling to room temperature, the sample is filtered and washed with 80°C deionized water for several times until the ultraviolet-visible absorption of the eluent There is no absorption peak of polyacid in the spectrum, and then the obtained solid sample is dried and activated at 150° C. for 12 hours to obtain the target product photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ . 3. The application of the photocatalytic hydrogen production catalyst driven by visible light in claim 1 in photocatalytic hydrogen production is characterized in that the specific process is: add 180mL deionized water and 70mL sacrificial reagent methanol to the quartz photocatalytic reactor, Then add 0.35g of photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ , 0.1g of photosensitizer rhodamine b and 8mg of cocatalyst chloroplatinic acid, blow it with high-purity nitrogen for 30 minutes, then seal it and stir in the dark Adsorb for 12 hours, and then irradiate with a 500W xenon lamp. The gas produced is collected by drainage method and detected as H ₂ by gas chromatography. 4. The application of the photocatalytic hydrogen production catalyst driven by visible light in claim 1 in photocatalytic hydrogen production is characterized in that the specific process is: adding 180mL deionized water and 25mL sacrificial reagent triethanolamine to the quartz photocatalytic reactor , then add 0.35g of photocatalytic hydrogen production catalyst Ta-POM-1/TiO ₂ , 0.1g of photosensitizer Eosin Y and 8mg of cocatalyst chloroplatinic acid, blow with high-purity nitrogen for 30 minutes, then airtight and store in the dark Stir and adsorb for 12 hours, and then irradiate with a 500W xenon lamp. The gas generated is collected by drainage method and detected as H ₂ by gas chromatography.