CN115254091B - Indium oxyhydroxide/biomass porous carbon composite photocatalyst, and preparation method and application thereof - Google Patents

Abstract

An indium oxyhydroxide/biomass porous carbon composite photocatalyst, a preparation method and application thereof, and relates to the technical fields of composite material preparation and photocatalysis application. Firstly, preparing Biomass Porous Carbon (BPC) by utilizing orange peel through hydrothermal reaction and KOH activation and high-temperature calcination treatment, and then, reacting on the Biomass Porous Carbon (BPC) to generate indium hydroxide (InOOH) nanocrystalline. In the structure, inOOH nanocrystalline uniformly grows on the surface of BPC, the BPC presents a three-dimensional honeycomb structure, and the particle size of the InOOH nanocrystalline grown on the BPC is between 10 and 20nm. The indium oxyhydroxide/biomass porous carbon composite photocatalyst prepared by the invention has rich active sites and large specific surface area, is favorable for separation of photogenerated carriers, enhances the photocatalytic activity, and has excellent effect in preparing methane by photocatalytic reduction of carbon dioxide.

Description

An indium oxyhydroxide/biomass porous carbon composite photocatalyst and its preparation method and application

Technical field

The invention relates to the technical field of composite material preparation and photocatalytic application, and specifically relates to an indium oxyhydroxide/biomass porous carbon composite photocatalyst and its preparation method and its application in the production of methane through photocatalytic carbon dioxide reduction reaction.

Background technique

High degree of industrialization has accelerated human consumption of fossil energy. The massive burning of fossil energy such as oil and natural gas has caused a sharp increase in greenhouse gases, mainly _CO2 , in the atmosphere, exacerbating the energy crisis and the greenhouse effect. Through photocatalytic reduction technology, solar energy can be directly used to convert CO ₂ into renewable chemical fuels, such as CO, CH ₄ and C _x H _y O _z , achieving high value-added conversion of CO ₂ while solving the energy crisis and mitigating the Environmental problems caused by the greenhouse effect. Although TiO ₂ is used as a commonly used photocatalyst, the conversion efficiency in photocatalytic reduction of CO ₂ is still low in practical applications. Therefore, technology that efficiently converts CO ₂ into hydrocarbons under sunlight has attracted much attention.

InOOH is a wide bandgap n-type semiconductor material. InOOH with different structures can be synthesized through solvothermal method, chemical precipitation method, sol-gel method and microemulsion method. In past research, InOOH was usually used as the precursor of In ₂ O ₃ and was mostly used in gas sensing research. However, there has been less research on its own properties and photocatalytic performance applications. Li et al. synthesized InOOH nanocrystals with a particle diameter of approximately 20 nm from indium nitrate and ethylenediamine through a simple solvothermal method, and used the prepared InOOH to photocatalytically degrade benzene vapor under 300 nm ultraviolet radiation. The results found that InOOH has comparable catalytic activity to P25, has higher salinity, and is more stable than P25 during long-term operation, demonstrating excellent photocatalytic degradation performance for benzene. (Li Z, Xie Z, Zhang Y, et al. Wide band gap p-block metaloxyhydroxide InOOH: A new durable photocatalyst for benzene degradation. Journal of Physical Chemistry C, 2007, 111(49): 18348-18352.).

The invention introduces agricultural waste as raw material and processes it into porous carbon materials. Porous carbon materials have a large specific surface area, and their unique porous structure not only increases the utilization of light energy, but also has excellent electrical conductivity, which is beneficial to the conduction of photogenerated electrons. An indium oxyhydroxide/biomass porous carbon composite photocatalyst was prepared using a one-step microwave liquid phase synthesis reaction. The obtained photocatalyst has a novel microstructure. Indium oxyhydroxide nanocrystals grow uniformly on the surface of the three-dimensional honeycomb porous carbon. The composite Photocatalysts have high photocatalytic activity and can significantly improve the efficiency of photocatalytic reduction of _CO2 to methane. There are currently no reports on the photocatalytic reduction of carbon dioxide to methane in composite experiments of indium oxyhydroxide and biomass porous carbon.

Contents of the invention

The purpose of this invention is to provide an indium oxyhydroxide/biomass porous carbon (InOOH/BPC) composite photocatalyst with high catalytic activity in view of the technical problems such as low reaction efficiency in the reaction of catalytic reduction of carbon dioxide to generate methane in the existing technology. , the invention also provides a simple, fast and efficient preparation method.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

An indium oxyhydroxide/biomass porous carbon composite photocatalyst. In its structure, indium oxyhydroxide (InOOH) nanocrystals grow uniformly on the surface of biomass porous carbon (BPC), and the biomass porous carbon (BPC) appears three-dimensional. Honeycomb structure, the particle size of indium oxyhydroxide (InOOH) nanocrystals grown on biomass porous carbon (BPC) is between 10-20nm.

A method for preparing indium oxyhydroxide/biomass porous carbon composite photocatalyst. First, orange peels are used to prepare biomass porous carbon (BPC) through hydrothermal reaction, KOH activation and high-temperature calcination, and then in the biomass porous carbon (BPC) The above reaction generates indium oxyhydroxide (InOOH) nanocrystals. The specific preparation steps are as follows:

①. Preparation of biomass porous carbon

First, grind and sieve the dried orange peel with a grinder, then add an appropriate amount of distilled water and pore aid, stir evenly, and then perform a hydrothermal reaction. After the reaction is complete, wash and dry to obtain product A; add an appropriate amount of KOH and pore aid to product A. Distilled water, stir evenly and put it into an oven to dry to obtain product B; place product B in a tube furnace for calcination, cool to room temperature, wash and dry, and the resulting sample is biomass porous carbon (BPC);

②. React on biomass porous carbon to generate indium oxyhydroxide (InOOH) nanocrystals

Ultrasonically disperse 50-100 mg of porous carbon with an appropriate amount of distilled water and DMF, then add 0.1-0.5 mmol of InNO ₃ ·4H ₂ O, stir and dissolve; then place the reaction solution in a microwave oven and heat it under microwave to react, and cool it down after the reaction is completed. Leave it overnight, and finally undergo solid-liquid separation, washing, and drying to obtain the indium oxyhydroxide/biomass porous carbon (InOOH/BPC) composite photocatalyst.

As a preferred technical solution for the above preparation method, ammonium chloride is used as a pore aid in the hydrothermal process in step ①, and its addition amount is 3-8% of the weight of the sieved orange peel powder. The reaction temperature of the hydrothermal process is 140-180°C, and the reaction time is 3-8h. Add KOH and distilled water, stir evenly, and then place it in an oven at 90-110°C to dry for 3-5 hours. Product B is placed in a tube furnace for calcination under _N2 atmosphere, the temperature rise rate is 4~6°C/min, the calcination temperature is 600~800°C, and the calcination time is 50~100min.

As the preferred technical solution of the above preparation method, the mixed solution in step ② is placed in an 800W household microwave oven and heated at low heat for 20-40 minutes.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1). The microstructure of the indium oxyhydroxide/biomass porous carbon composite photocatalyst prepared by the present invention is that InOOH nanocrystals grow uniformly on the surface of BPC in a three-dimensional honeycomb shape. The particle size of the InOOH nanocrystals grown on BPC is between 10-20nm. This InOOH/BPC composite photocatalyst has abundant active sites and a large specific surface area, which is conducive to the separation of photogenerated carriers, enhances photocatalytic activity, and has excellent effects in photocatalytic reduction of carbon dioxide to methane.

2). The preparation method of the indium oxyhydroxide/biomass porous carbon composite photocatalyst of the present invention has simple process equipment, easy operation, good repeatability, cheap and easily available raw materials, and is suitable for industrial production.

3). The present invention uses cheap and easy-to-obtain biomass orange peels as the carbon source, achieving rational utilization of waste and saving resources.

Description of the drawings

Figure 1 is an X-ray diffraction analysis (XRD) spectrum of pure indium oxyhydroxide prepared in step ② in Example 1 and the indium oxyhydroxide/biomass porous carbon composite photocatalyst prepared in Examples 1, 2, and 3.

Figure 2 is a field emission scanning electron microscope (FE-SEM) photo of the porous carbon prepared in step ① in Example 1.

Figures 3, 4, and 5 are field emission scanning electron microscope (FE-SEM) photos of the indium oxyhydroxide/biomass porous carbon composite photocatalyst prepared in Examples 1, 2, and 3 respectively.

Figure 6 is a methane production diagram (a) and the corresponding methane production rate diagram (b) of the _{photocatalytic} CO reduction of pure indium oxyhydroxide and indium oxyhydroxide/biomass porous carbon composite photocatalyst in Example 4.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

①. Preparation of porous carbon

First, grind the dried orange peel with a grinder, and pass the resulting powder through a 100-mesh sieve. Weigh 5g of orange peel powder, add 45 mL of distilled water and 0.25 g of ammonium chloride, stir evenly, and then incubate the reaction at 160°C for 5 hours, and wait until it is cooled to After washing and drying at room temperature, product A is obtained; add twice the mass of KOH to product A, then add an equal volume of distilled water to the powder, stir, and then place it in a 100°C oven for 3 hours to dry to obtain product B; place product B in a tube In a furnace, heat up to 700°C at a heating rate of 5°C/min under _N2 atmosphere, calcine for 1 hour, take it out after the reaction is completed and return to room temperature, wash with deionized water, and dry. The resulting sample is biomass porous Carbon(BPC).

Referring to Figure 2, the prepared biomass porous carbon mainly presents a three-dimensional honeycomb structure with a smooth surface and no other particles.

②. React on biomass porous carbon to generate InOOH nanocrystals

Take an Erlenmeyer flask, add 50 mg porous carbon, 1 mL distilled water and 29 mL DMF, disperse ultrasonically for 15 min, then add 0.1 mmol InNO ₃ ·4H ₂ O, stir at room temperature for 4 h; transfer the reaction solution to a household microwave oven (800W). Use low heat setting (power 18%) to microwave for 30 minutes, then filter while hot, wash, dry, and collect the sample to form the InOOH/BPC composite photocatalyst, labeled InOOH/BPC-1;

Using the same method, pure InOOH samples were prepared without adding porous carbon.

Refer to Figure 1. The peak positions of the spectral lines in the figure correspond one-to-one with all the diffraction crystal planes of the JCPDF standard card (71-2277), indicating orthorhombic phase InOOH crystal, space group P2 ₁ /nmm, lattice constant

Referring to Figure 3, it can be clearly seen that a large number of InOOH nanocrystals have grown on the originally smooth surface of the biomass porous carbon, and the particle size of the InOOH nanocrystals is about 10-20 nm. InOOH nanocrystals grow basically uniformly on the surface of the nanosheet, but the surface is partially exposed and not covered by InOOH nanocrystals.

Example 2

Take an Erlenmeyer flask, add 50 mg porous carbon prepared by the method in step ① of Example 1, 1 mL distilled water and 29 mL DMF, disperse with ultrasonic for 15 min, then add 0.3 mmol InNO ₃ ·4H ₂ O, stir at room temperature for 4 h; transfer the reaction solution In a household microwave oven (800W), microwave at low heat (power 18%) for 30 minutes, then filter while hot, wash, dry, and collect the sample to become the InOOH/BPC composite photocatalyst, labeled InOOH/BPC-2.

Referring to Figure 1, it can be seen that all spectral peaks are also consistent with the X-ray powder diffraction analysis (XRD) spectra of pure InOOH and InOOH/BPC-1 composite photocatalysts prepared according to the steps described in Example 1. consistent.

Referring to Figure 4, it can be clearly seen that a large number of InOOH nanocrystals have completely grown on the surface of the originally smooth biomass porous carbon. The InOOH nanocrystals have grown more uniformly and almost completely uniformly on the surface of the porous carbon. .

Example 3

Take an Erlenmeyer flask, add 50 mg of porous carbon prepared by the method in step ① of Example 1, 1 mL of distilled water and 29 mL of DMF, disperse with ultrasonic for 15 min, then add 0.5 mmol of InNO ₃ ·4H ₂ O, and stir at room temperature for 4 h; Transfer to a household microwave oven (800W), microwave at low heat (power 18%) for 30 minutes, then filter while hot, wash, dry, and collect the sample to form the InOOH/BPC composite photocatalyst, labeled InOOH/BPC-3 .

Referring to Figure 1, it can be seen that all spectral peaks are also consistent with the X-ray powder diffraction analysis (XRD) spectra of pure InOOH and InOOH/BPC-1 composite photocatalysts prepared according to the steps described in Example 1. consistent.

Referring to Figure 5, it can be clearly seen that a large number of InOOH nanocrystals have completely grown on the surface of the originally smooth porous carbon, but the particle size of the InOOH nanocrystals has increased, and there is aggregation and accumulation.

Example 4 (Indium oxyhydroxide/biomass porous carbon composite photocatalyst photocatalytic _CO2 reduction)

The photocatalytic _CO reduction activity of the catalyst prepared above was tested in an online photocatalytic reaction system (MC-SPB10-AG) designed by Beijing Meridian Company. Add 10 mg of catalyst and 1 mL of distilled water into the centrifuge tube, and continue ultrasonic for 15 min until the catalyst is completely dispersed and evenly distributed. Then drop it evenly on the sieve plate, place it in a glass reactor and connect it to the photocatalytic reaction system, and feed high-purity CO ₂ (99.999%) as the reaction gas. Stop feeding CO ₂ when the air pressure indicates 15kpa. , repeat air purging three times until the system pressure stabilizes. Use a 300W xenon lamp (MC-XF300) as the light source. During the entire photoreaction stage, the reactor temperature is controlled at about 6°C by a circulating condensate water device, and the production of reducing gas products is analyzed every 1 hour by an online gas chromatograph (GC9790II) equipped with an FID detector and a TCD detector.

Referring to Figure 6, the InOOH/BPC composite photocatalysts prepared in the three examples have greatly improved the production of methane through photocatalytic CO ₂ reduction compared to pure InOOH (shown in Figure 6a), especially when 0.3 mmol of InNO is added. The InOOH/BPC-2 composite photocatalyst prepared with ₃ ·4H ₂ O (Example 2) has the best photocatalytic CO ₂ reduction performance. At the same time, the InOOH/BPC-2 composite photocatalyst prepared in Example 2 has the highest methane production rate (shown in Figure 6b), reaching 94.68 μmol·g ^-1 ·h ^-1 , which is approximately 122.9 times that of pure InOOH.

It is confirmed by the above examples that the present invention prepares indium oxyhydroxide/biomass porous carbon composite photocatalyst through microwave-assisted liquid phase synthesis method, which has excellent photocatalytic CO ₂ reduction to produce methane performance, and the production process is simple and has the ability to synthesize in large quantities. possibility.

The above contents are only examples and explanations of the concept of the invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or substitute them in similar ways, as long as they do not deviate from the concept of the invention. or beyond the scope defined by the claims, shall belong to the protection scope of the present invention.

Claims (2)

1. The preparation method of the indium oxyhydroxide/biomass porous carbon composite photocatalyst is characterized by comprising the following steps of:

(1) preparation of porous carbon

Firstly, grinding dried orange peel by using a grinder, sieving the obtained powder by using a 100-mesh sieve, weighing 5g of orange peel powder, adding 45mL of distilled water and 0.25g of ammonium chloride, uniformly stirring, then carrying out heat preservation reaction at 160 ℃ for 5h, cooling to room temperature, washing and drying to obtain a product A; adding KOH with the mass twice of that of the product A, adding distilled water with the same volume as powder, stirring, and then placing the mixture into a 100 ℃ oven for 3 hours to dry to obtain a product B; product B was placed in a tube furnace at N ₂ Heating to 700 ℃ at a heating rate of 5 ℃/min under the atmosphere, calcining for 1h, taking out after the reaction is finished and the temperature is reduced to room temperature, washing with deionized water, and drying to obtain a sample, namely the biomass porous carbon BPC; the prepared biomass porous carbon BPC has a three-dimensional honeycomb structure, the surface is smooth, and no other particles exist;

(2) react on biomass porous carbon to generate InOOH nanocrystalline

Taking a conical flask, adding 50mg of biomass porous carbon BPC, 1mL of distilled water and 29mL of LDMF, performing ultrasonic dispersion for 15min, and then adding 0.3mmol of InNO ₃ ·4H ₂ O, stirring at room temperature 4h; transferring the reaction solution into a household 800W microwave oven, heating for 30min by using 18% low-fire grade microwaves, filtering while the reaction solution is hot, washing, drying and collecting a sample to obtain the InOOH/BPC composite photocatalyst; a large number of InOOH nanocrystals are grown on the surface of the biomass porous carbon, the particle size of the InOOH nanocrystals is 10-20nm, and the InOOH nanocrystals uniformly grow on the surface of the nanosheets.

2. The application of the indium oxyhydroxide/biomass porous carbon composite photocatalyst prepared by the method according to claim 1 in preparing methane by photocatalytic carbon dioxide reduction reaction, wherein 10mg catalyst and 1mL distilled water are added into a centrifuge tube, and ultrasound is continued for 15min until the catalyst is completely and uniformly dispersed; then evenly dripping the mixture on a sieve plate, placing the mixture in a glass reactor, connecting the glass reactor to a photocatalytic reaction system, and introducing 99.999% high-purity CO ₂ As a reaction gas, CO was stopped when the number of barometer was 15kpa ₂ Repeating the gas washing for three times until the system pressure is stable; using a 300W xenon lamp as a light source; the reactor temperature was controlled at 6℃by a circulating condensed water device throughout the photoreaction stage, and the amount of the reducing gas product produced was analyzed by on-line gas chromatography equipped with FID and TCD detectors every 1. 1 h.