CN113649056A

CN113649056A - Photocatalytic carbon dioxide reduction catalyst and preparation method and application thereof

Info

Publication number: CN113649056A
Application number: CN202111048167.1A
Authority: CN
Inventors: 秦玉梅; 徐倩鑫; 朱彪
Original assignee: Guangxi Normal University
Current assignee: Guangxi Normal University
Priority date: 2021-09-08
Filing date: 2021-09-08
Publication date: 2021-11-16

Abstract

The invention discloses a photocatalytic carbon dioxide reduction catalyst, a preparation method and application thereof, and belongs to the technical field of carbon dioxide reduction. The reduction catalyst is a NiAl-LDH/porous carbon nitride foam three-dimensional heterojunction composite material. The preparation method includes preparing a three-dimensional network structure of melamine porous carbon nitride foam, preparing an aqueous solution of hydrotalcite precursor, and placing the three-dimensional network structure of porous carbon nitride foam in the aqueous solution of hydrotalcite precursor to react to prepare porous carbon nitride foam/hydrotalcite three-dimensional Heterojunction materials. The photocatalytic synergy of the heterojunction can be used to effectively improve the photocatalytic performance of the composite material. The CO yield can reach 159.62 μmol/g, which is about 4.2 times that of the pure LDHs powder material, which greatly improves the photocatalytic _CO reduction reaction. Yield.

Description

Photocatalytic carbon dioxide reduction catalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of carbon dioxide reduction, in particular to a photocatalytic carbon dioxide reduction catalyst and a preparation method and application thereof.

Background

Photocatalytic CO₂The reduction means that the semiconductor catalyst with photocatalytic activity is driven by light energy to generate photo-generated electrons and holes, and water molecules are oxidized by oxygenConversion to provide hydrogen protons to CO₂Reducing the carbon-based compound into a carbon-based compound, and simultaneously realizing environmental protection and resource reutilization. Noble metals such as Pt and Pd are difficult to oxidize, have low overpotential, stable performance and the like, and are considered to be ideal catalytic materials. However, the storage of precious metals is limited, the cost is too high, and the industrial use of the precious metals in large quantities is not easy to realize, so the research on photochemical catalysts with low cost and excellent catalytic performance is urgent.

Transition metal nitrides, transition metal carbides and transition metal chalcogenides have the characteristics of low cost, good catalytic stability and the like, and have been applied as electrocatalytic cathode materials. The band gap of the two-dimensional layered transition metal chalcogenide is mainly distributed in a range of 1-2eV, is located in a visible light region, has high-efficiency electron mobility and low overpotential, and has good application prospect.

Chinese patent ZL01127860.9 describes a method for photocatalytic reduction of carbon dioxide to formic acid and formaldehyde using tetravalent and trivalent titanium composite oxides as catalysts under ultraviolet irradiation. The catalyst material is easy to agglomerate, so that the number of effective active sites is reduced, and the catalytic efficiency is reduced. Therefore, it is necessary to develop a new catalyst and a method which have higher efficiency and are less likely to cause a decrease in catalytic activity.

Disclosure of Invention

The invention aims to provide a photocatalytic carbon dioxide reduction catalyst, a preparation method and application thereof, and solves the technical problem that a carbon dioxide reduction material is easy to agglomerate.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a photocatalytic carbon dioxide reduction catalyst is a NiAl-LDH/porous carbon nitride foam three-dimensional heterojunction composite material.

A preparation method of a photocatalytic carbon dioxide reduction catalyst comprises the following steps:

step 1: preparing a three-dimensional network structure of the melamine porous carbon nitride foam;

step 2: preparing a hydrotalcite precursor aqueous solution;

and step 3: and putting the porous carbon nitride foam three-dimensional network structure into a hydrotalcite precursor aqueous solution for reaction to prepare the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction material.

Further, the specific process of step 1 is,

heating melamine sponge to 600 ℃ at a heating rate of 10 ℃/min in nitrogen atmosphere, roasting for 100min, naturally cooling to room temperature, alternately washing with deionized water and ethanol, and drying to obtain the product rich in g-C₃N₄The melamine porous carbon nitride foam has a smooth three-dimensional network structure.

Further, the specific process of step 2 is,

0.872-3.488g of Ni (NO) are weighed₃)₂·9H₂O, 0.375-1.5g Al (NO)₃)₃·6H₂O, 2.402g of CO (NH)₂)₂And 0.593g of NH₄F was dissolved in 70mL of deionized water and stirred to form a homogeneous hydrotalcite precursor aqueous solution.

Further, the specific process of step 3 is,

immersing the three-dimensional network structure of the melamine porous carbon nitride foam into the reaction liquid of a high-pressure reaction kettle, carrying out ultrasonic treatment for 30min, sealing, placing in a 120 ℃ oven for hydrothermal treatment for 8h, naturally cooling to room temperature after the reaction is finished, taking out, respectively cleaning for 3 times by using deionized water and absolute ethyl alcohol to remove impurities adsorbed on the surface of the composite material, and drying in the oven at 60 ℃ to obtain the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction material.

The application of a photocatalytic carbon dioxide reduction catalyst is used for reducing carbon dioxide into carbon monoxide under the photocatalysis.

Further, the specific process of the reduction is,

placing the reduction catalyst in a reactor, heating in a water bath to generate water vapor, and passing CO₂Introducing steam and CO into the reactor₂The mixed gas is carried into the reactor, purged for a certain time, and then light is applied to the outside of the reactor from the reaction chamber every hour1 ml of gaseous product was sampled and then analyzed using gas chromatography equipped with FID and TCD detectors.

Further, before introducing the mixed gas, introducing CO₂And (3) purging with gas for 1.5h to remove air in the reactor, wherein the aeration speed is 10mL/min, the reactor is a transparent quartz reactor, a 300W xenon lamp is used for simulating sunlight, the distance between the xenon lamp and the catalytic reduction material is 8cm, the volume of the reactor is 200mL, and the mixed gas is subjected to atmosphere equilibrium for 30min to ensure that gas molecules are completely adsorbed.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

the invention takes simple and easily obtained substances as raw materials and has simple synthesis steps. Photocatalytic CO of porous carbon nitride foam on composite material compared to traditional hydrotalcite powder photocatalyst₂The improvement of the reducing performance has good promoting effect. The catalyst not only can be used as a carrier, improves the dispersibility of LDH, enables the NiAl-LDH catalyst to be uniformly distributed in a composite material, solves the problem that hydrotalcite is easy to agglomerate, but also has good air permeability and light transmittance, enables the catalyst to expose more active sites, most importantly, the catalyst is rich in g-C3N4 semiconductor material, can construct a heterojunction material with the hydrotalcite, can effectively improve the photocatalytic performance of the composite material by utilizing the photocatalytic synergistic effect of the heterojunction, can achieve a CO yield of 159.62 mu mol/g which is about 4.2 times of that of a pure LDHs powder material, and greatly improves the photocatalytic CO₂Yield of the reduction reaction.

Drawings

FIG. 1 is a comparison Raman spectrum and an X-ray photoelectron spectrum of the present invention;

FIG. 2 is an XRD spectrum of NCA-3 obtained in example 3;

FIG. 3 shows the photocatalytic reduction of CO for the materials obtained in comparative examples 1 to 2 and examples 1 to 4₂And (6) performance graphs.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings by way of examples of preferred embodiments. It should be noted, however, that the numerous details set forth in the description are merely for the purpose of providing the reader with a thorough understanding of one or more aspects of the present invention, which may be practiced without these specific details.

Example 1: preparation of NiAl-LDH/CF (NAC-1)

1) Heating melamine sponge to 600 ℃ at a heating rate of 10 ℃/min in nitrogen atmosphere, roasting for 100min, naturally cooling to room temperature, alternately washing with deionized water and ethanol, and drying to obtain the product rich in g-C₃N₄CF for short.

The following table shows the elemental analysis data of the melamine foam before carbonization and after carbonization.

Table 1 elemental analysis data sheet

To maximize the degree of graphitization, the melamine foam (abbreviated as MF) was annealed at 400, 500, 600, 700 and 800 ℃ for 100 minutes in a nitrogen atmosphere. Raman spectra of the CF foam at different temperatures were collected as shown in fig. 1 a. Typical peaks for graphite appear at 1360(D band) and 1592cm^-1(G band), which are respectively attributed to A of the disordered graphite structure_1gBreathing pattern and E of graphite_2gA stretch mode. I of CF foams carbonized at 400, 500, 600, 700 and 800 deg.C_D/I_GThe ratios were 0.96, 1.01, 1.07, 1.03, and 1.00, respectively. In particular, CF foams show the highest I when carbonized at 600 ℃_D/I_GThe ratio indicates the highest concentration of defect sites in all CF foams. The elemental analysis data (Table 1) show that the melamine foam has a relatively high nitrogen content of 43.37 wt.%. The nitrogen content gradually decreases with increasing carbonization temperature. After charring at 600 ℃ for 100min, the nitrogen content was 25.86 wt%, indicating that half of the nitrogen element was retained. The surface composition and chemical state of the CF foam were further investigated by XPS analysis. As shown in fig. 1b, XPS full spectrum of CF foam confirmed the presence of C, N, O element. The high resolution C1s spectrum in FIG. 1C can be fittedThree main peaks centered at 284.7eV, 286.2eV and 288.4eV, belonging to sp of CF foams carbonized at 400, 500, 600, 700 and 800 ℃ respectively²Hybrid carbon (C-C), sp²Carbon hybridizes with nitrogen (C-N) and some oxygen-containing groups (C ═ O). The N1s spectrum of the CF foam had three peaks, with the 398.1eV peak due to pyridine-N, the 400.5eV peak due to pyrrole-N, and the 401eV peak due to graphite-N (FIG. 1 d). The XPS results above show that g-C rich foams were successfully synthesized by annealing MF foams in an inert atmosphere₃N₄The foam of (1).

2) 0.872g (3mmol) of Ni (NO) were weighed₃)₂·9H₂O, 0.375g (1mmol) of Al (NO)₃)₃·6H₂O, 2.402g (40mmol) of CO (NH)₂)₂And 0.593g (16mmol) of NH₄F was dissolved in 70mL of deionized water and stirred to form a homogeneous hydrotalcite precursor aqueous solution. It was transferred to a 100mL teflon lined autoclave. Subjecting the porous carbon nitride foam (3X 2 cm) treated in step 1) to³) Immersing the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material into the reaction solution, carrying out ultrasonic treatment for 30 minutes, sealing, placing in a 120 ℃ oven for hydrothermal reaction for 8 hours, naturally cooling to room temperature after reaction, taking out, washing for 3 times by deionized water and absolute ethyl alcohol to remove impurities adsorbed on the surface of the composite material, and drying in the 60 ℃ oven to obtain the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material. Denoted as NAC-1.

CO simulating sunlight under a 300W xenon lamp at a distance of about 8cm from the sample₂The reduction experiment was carried out in the bottom of a quartz reactor having a volume of about 200 ml. Before illumination, NAC-1 was placed in the bottom of the photoreactor and high purity CO was used₂The photoreactor was purged with gas for 1.5 hours to remove air from the reactor. High purity CO₂Gas passing through water bath to produce CO₂And water vapor. In CO₂/H₂And (4) balancing in an O atmosphere for 30min to ensure that gas molecules are completely adsorbed. During the light period, 1 ml of the gaseous product was sampled from the reaction chamber every hour, and the performance was characterized by gas chromatography (using Ar as a carrier gas). As shown in FIG. 3, the CO yield of NAC-1 was 76.75. mu. mol g^-1。

Example 2: preparation of NiAl-LDH/CF (NAC-2)

2) 1.744g (6mmol) of Ni (NO) were weighed out₃)₂·9H₂O, 0.75g (2mmol) of Al (NO)₃)₃·6H₂O, 2.402g (40mmol) of CO (NH)₂)₂And 0.593g (16mmol) of NH₄F was dissolved in 70mL of deionized water and stirred to form a homogeneous hydrotalcite precursor aqueous solution. It was transferred to a 100mL teflon lined autoclave. Subjecting the porous carbon nitride foam (3X 2 cm) treated in step 1) to³) Immersing the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material into the reaction solution, carrying out ultrasonic treatment for 30 minutes, sealing, placing in a 120 ℃ oven for hydrothermal reaction for 8 hours, naturally cooling to room temperature after reaction, taking out, washing for 3 times by deionized water and absolute ethyl alcohol to remove impurities adsorbed on the surface of the composite material, and drying in the 60 ℃ oven to obtain the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material. Denoted as NAC-2.

CO simulating sunlight under a 300W xenon lamp at a distance of about 8cm from the sample₂The reduction experiment was carried out in the bottom of a quartz reactor having a volume of about 200 ml. Before illumination, NAC-2 was placed in the bottom of the photoreactor and high purity CO was used₂The photoreactor was purged with gas for 1.5 hours to remove air from the reactor. High purity CO₂Gas passing through water bath to produce CO₂And water vapor. In CO₂/H₂And (4) balancing in an O atmosphere for 30min to ensure that gas molecules are completely adsorbed. During the light period, 1 ml of the gaseous product was sampled from the reaction chamber every hour, and the performance was characterized by gas chromatography (using Ar as a carrier gas). As shown in FIG. 3, the CO yield of NAC-2 was 106.44. mu. mol g^-1。

Example 3: preparation of NiAl-LDH/CF (NAC-3)

1) Mixing melamineHeating sponge to 600 deg.C at a heating rate of 10 deg.C/min in nitrogen atmosphere, calcining for 100min, naturally cooling to room temperature, alternately washing with deionized water and ethanol, and drying to obtain the product rich in g-C₃N₄CF for short.

2) 2.616g (9mmol) of Ni (NO) were weighed out₃)₂·9H₂O, 1.125g (3mmol) of Al (NO)₃)₃·6H₂O, 2.402g (40mmol) of CO (NH)₂)₂And 0.593g (16mmol) of NH₄F was dissolved in 70mL of deionized water and stirred to form a homogeneous hydrotalcite precursor aqueous solution. It was transferred to a 100mL teflon lined autoclave. Subjecting the porous carbon nitride foam (3X 2 cm) treated in step 1) to³) Immersing the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material into the reaction solution, carrying out ultrasonic treatment for 30 minutes, sealing, placing in a 120 ℃ oven for hydrothermal reaction for 8 hours, naturally cooling to room temperature after reaction, taking out, washing for 3 times by deionized water and absolute ethyl alcohol to remove impurities adsorbed on the surface of the composite material, and drying in the 60 ℃ oven to obtain the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material. Denoted as NAC-3.

CO simulating sunlight under a 300W xenon lamp at a distance of about 8cm from the sample₂The reduction experiment was carried out in the bottom of a quartz reactor having a volume of about 200 ml. Before illumination, NAC-3 was placed in the bottom of the photoreactor and high purity CO was used₂The photoreactor was purged with gas for 1.5 hours to remove air from the reactor. High purity CO₂Gas passing through water bath to produce CO₂And water vapor. In CO₂/H₂And (4) balancing in an O atmosphere for 30min to ensure that gas molecules are completely adsorbed. During the light period, 1 ml of the gaseous product was sampled from the reaction chamber every hour, and the performance was characterized by gas chromatography (using Ar as a carrier gas). As shown in FIG. 3, the CO yield of NAC-3 was 159.62. mu. mol g^-1. While the CO yield decreases as the concentration of the complex continues to increase (i.e., NAC-4). The possible reason is that when the amount of catalyst is too large, the supersaturated LDH forms an aggregate state in the CF itself, resulting in severe recombination of photo-generated electrons and holes, so that the CO yield decreases.

Example 4: preparation of NiAl-LDH/CF (NAC-4)

2) 3.488g (12mmol) of Ni (NO) were weighed out₃)₂·9H₂O, 1.5g (4mmol) of Al (NO)₃)₃·6H₂O, 2.402g (40mmol) of CO (NH)₂)₂And 0.593g (16mmol) of NH₄F was dissolved in 70mL of deionized water and stirred to form a homogeneous hydrotalcite precursor aqueous solution. It was transferred to a 100mL teflon lined autoclave. Subjecting the porous carbon nitride foam (3X 2 cm) treated in step 1) to³) Immersing the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material into the reaction solution, carrying out ultrasonic treatment for 30 minutes, sealing, placing in a 120 ℃ oven for hydrothermal reaction for 8 hours, naturally cooling to room temperature after reaction, taking out, washing for 3 times by deionized water and absolute ethyl alcohol to remove impurities adsorbed on the surface of the composite material, and drying in the 60 ℃ oven to obtain the porous carbon nitride foam/hydrotalcite three-dimensional heterojunction composite material. Denoted as NAC-4.

CO simulating sunlight under a 300W xenon lamp at a distance of about 8cm from the sample₂The reduction experiment was carried out in the bottom of a quartz reactor having a volume of about 200 ml. Before illumination, NAC-4 was placed in the bottom of the photoreactor and high purity CO was used₂The photoreactor was purged with gas for 1.5 hours to remove air from the reactor. High purity CO₂Gas passing through water bath to produce CO₂And water vapor. In CO₂/H₂And (4) balancing in an O atmosphere for 30min to ensure that gas molecules are completely adsorbed. During the light period, 1 ml of the gaseous product was sampled from the reaction chamber every hour, and the performance was characterized by gas chromatography (using Ar as a carrier gas). As shown in FIG. 3, the CO yield of NAC-4 was 125.5. mu. mol g^-1。

Comparative example 1: NiAl-LDH.

As shown in FIG. 3, the CO yield of NiAl-LDH was 38.02. mu. mol g^-1。

Comparative example 2: porous carbon nitride foam (CF for short).

As shown in FIG. 3, the CO yield of CF was 45.33. mu. mol g^-1。

FIG. 2 is the XRD spectrum of NCA-3 obtained in example 3, and it can be seen that the NiAl-LDH/porous carbon nitride foam three-dimensional heterojunction material is successfully synthesized.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims

1. A photocatalytic carbon dioxide reduction catalyst, characterized in that: the reduction catalyst is a NiAl-LDH/porous carbon nitride foam three-dimensional heterojunction composite material.

2. the preparation method of a kind of photocatalytic carbon dioxide reduction catalyst according to claim 1, is characterized in that: described preparation method comprises the steps:

Step 1: prepare a three-dimensional network structure of melamine porous carbon nitride foam;

Step 2: prepare an aqueous solution of hydrotalcite precursor;

Step 3: The porous carbon nitride foam/hydrotalcite three-dimensional heterojunction material is prepared by placing the three-dimensional network structure of the porous carbon nitride foam in a hydrotalcite precursor aqueous solution for reaction.

3. the preparation method of a kind of photocatalytic carbon dioxide reduction catalyst according to claim 2, is characterized in that: the concrete process of described step 1 is,

The melamine sponge was heated to 600 °C for 100 min at a heating rate of 10 °C/min in a nitrogen atmosphere, cooled to room temperature naturally, washed alternately with deionized water and ethanol, and dried to obtain a porous carbon nitride foam rich in _gC3N4 _. , the melamine porous carbon nitride foam exhibits a smooth three-dimensional network structure.

4. the preparation method of a kind of photocatalytic carbon dioxide reduction catalyst according to claim 3, is characterized in that: the concrete process of step 2 is,

Weigh out 0.872-3.488 g of Ni(NO ₃ ) ₂ .9H ₂ O, 0.375-1.5 g of Al(NO ₃ ) ₃ .6H ₂ O, 2.402 g of CO(NH ₂ ) ₂ and 0.593 g of NH ₄ F Dissolve in 70 mL of deionized water and stir to form a homogeneous aqueous solution of the hydrotalcite precursor.

5. the preparation method of a kind of photocatalytic carbon dioxide reduction catalyst according to claim 4, is characterized in that: the concrete process of step 3 is,

The three-dimensional network structure of melamine porous carbon nitride foam was immersed in the reaction solution of the high pressure reactor and ultrasonically treated for 30min. After sealing, it was placed in a 120°C oven for 8h hydrothermal treatment. After the reaction was completed, it was naturally cooled to room temperature and taken out with deionized water. and anhydrous ethanol were washed three times to remove the impurities adsorbed on the surface of the composite material, and dried in an oven at 60 °C to obtain a porous carbon nitride foam/hydrotalcite three-dimensional heterojunction material.

6 . The application of a photocatalytic carbon dioxide reduction catalyst according to claim 1 , wherein: it is used for reducing carbon dioxide to carbon monoxide under photocatalysis. 7 .

7. the application of a kind of photocatalytic carbon dioxide reduction catalyst according to claim 6, is characterized in that: the concrete process of reduction is,

The reduction catalyst is placed in the reactor, the water bath is heated to generate water vapor, and the mixed gas of water vapor and CO ₂ is brought into the reactor by passing CO ₂ gas into the reactor. Light was applied to the outside of the chamber, and 1 ml of gaseous product was sampled from the reaction chamber per hour and analyzed using a gas chromatograph equipped with FID and TCD detectors.

8. the application of a kind of photocatalytic carbon dioxide reduction catalyst according to claim 7, it is characterized in that: before passing into mixed gas, first pass _CO gas purge 1.5h to remove the air in the reactor, the speed of ventilation 10mL/min, the reactor is a transparent quartz reactor, a 300W xenon lamp is used to simulate sunlight, the distance between the xenon lamp and the catalytic reduction material is 8cm, the volume of the reactor is 200mL, and the mixed gas is equilibrated in the atmosphere for 30min to ensure complete adsorption. gas molecules.