A dehumidification and formaldehyde removal device and method based on photovoltaic-photoelectric catalysis

Abstract

The present invention discloses a dehumidification and formaldehyde removal device and method based on photovoltaic-photoelectrocatalysis. The present invention relates to the technical field of dehumidification and formaldehyde removal. The device includes a photoanode, a hydrogel and a cathode sheet, the hydrogel is sandwiched between the photoanode and the cathode sheet, and the photoanode and the cathode sheet are respectively connected to a power source. A method for dehumidification and formaldehyde removal, placing the above-mentioned dehumidification and formaldehyde removal device based on photovoltaic-photoelectrocatalysis under a light source, and the light source is irradiated on the photoanode to dehumidify and remove formaldehyde. The present invention uses polyvinyl alcohol hydrogel to better help capture water and formaldehyde in the air, uses the hydrogel as a solid electrolyte and adsorbent, and utilizes a semiconductor photoanode thin film to photoelectrocatalyze the degradation of water and formaldehyde adsorbed by the polyvinyl alcohol hydrogel, and prevents secondary pollution caused by desorption, thereby achieving true oxidation degradation of indoor pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of dehumidification and formaldehyde removal, and in particular to a dehumidification and formaldehyde removal device and method based on photovoltaic-photoelectrocatalysis. Background Art

[0002] Currently, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) has classified formaldehyde as a Class 1 carcinogen. Although formaldehyde volatilization is mainly related to temperature, the impact of humidity on formaldehyde volatilization cannot be ignored. Within a certain range, the higher the humidity, the more severe the formaldehyde volatilization. Generally speaking, the humidity does not exceed 80%. The higher the humidity, the greater the water vapor content in the air. Formaldehyde is easily soluble in water, which will also accelerate the volatilization of formaldehyde in various furniture. Moreover, an environment with suitable humidity is also beneficial to physical health. It can effectively reduce the growth of bacteria caused by humid air and reduce the risk of respiratory infections. Therefore, purifying indoor air has become an urgent need for people to protect their health. The current method for indoor air purification, dehumidification and formaldehyde removal is activated carbon adsorption: activated carbon adsorption of formaldehyde is a passive adsorption method. It can only absorb formaldehyde molecules in the air when they float into the pores of activated carbon. CN110681353A discloses a method for producing modified activated carbon for formaldehyde removal. The modified carbon is modified with hydrogen peroxide, potassium hydroxide, and copper nitrate to increase its surface porosity and specific surface area. Molecular sieves are also added to enhance the activated carbon's adsorption capacity. The formaldehyde-removing activated carbon produced by this invention increases its specific surface area to physically adsorb formaldehyde. However, this method fails to eliminate formaldehyde and easily becomes saturated, requiring timely replacement, making it unreusable. Failure to promptly replace the activated carbon can lead to concentrated release of desorbed formaldehyde, causing secondary pollution. Summary of the Invention

[0003] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a reusable, green and efficient photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device and method.

[0004] The present invention discloses a dehumidification and formaldehyde removal device based on photovoltaic-photoelectrocatalysis, comprising a photoanode, a hydrogel and a cathode sheet, wherein the hydrogel is sandwiched between the photoanode and the cathode sheet, and the photoanode and the cathode sheet are respectively connected to a solar cell.

[0005] Furthermore, the hydrogel is polyvinyl alcohol hydrogel.

[0006] Furthermore, the photoanode is one of BiVO4 photoanode, TiO2 photoanode, and αFe2O3 photoanode.

[0007] Furthermore, the cathode sheet is a graphite sheet.

[0008] Furthermore, the preparation method of the polyvinyl alcohol hydrogel is as follows: dissolving polypropylene alcohol in ultrapure water and potassium phosphate solution, stirring and dissolving to form a sol, pouring it into a mold and cooling it to room temperature to form a gel; then sealing the surface with plastic wrap, placing it in an oven to dry so that the hydrogel loses water for later use.

[0009] Furthermore, the photoanode is a BiVO4 photoanode, and the preparation method of the BiVO4 photoanode comprises: S1, using a three-electrode system to perform constant potential deposition in the above-mentioned iodine oxybismuth mixed solution, with an FTO glass plate as a working electrode, Ag / AgCl as a reference electrode, and a Pt sheet as a counter electrode, to obtain an iodine oxybismuth layer by electrodeposition on the FTO surface;

[0010] S2. Prepare a vanadyl acetylacetonate / dimethyl sulfoxide solution and drop it onto the deposited bismuth oxyiodide layer, then anneal it in a muffle furnace and cool it naturally;

[0011] S3. Soak the sample in the muffle furnace in a sodium hydroxide solution for 5 to 10 minutes to remove excess vanadium pentoxide on the surface, rinse it with deionized water, and dry it in an oven to obtain a BiVO4 photoanode.

[0012] Furthermore, in step S1, a bismuth iodide layer is obtained by electroplating on the FTO surface using a chronoamperometry method. First, -0.35V vs. Ag / AgCl is set to deposit for 30 to 90 seconds to form a thin bismuth iodide seed layer on the FTO surface. Then, -0.35V vs. Ag / AgCl is set to deposit for 1200 to 1500 seconds to electroplated the bismuth iodide layer.

[0013] Furthermore, in step S2, the temperature is maintained at 420-450° C. in a muffle furnace for 120-150 min, the heating rate is controlled at 2-5° C. / min, and the temperature is naturally cooled.

[0014] A method for dehumidification and formaldehyde removal is provided, wherein the above-mentioned dehumidification and formaldehyde removal device based on photovoltaic-photoelectrocatalysis is placed under a light source, and the light source is irradiated on the photoanode to dehumidify and remove formaldehyde.

[0015] Furthermore, after a period of time, the hydrogel is washed with water and then dried, and then assembled into the photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device to continue irradiating with light to dehumidify and remove formaldehyde.

[0016] The present invention uses polyvinyl alcohol hydrogel to better help capture water and formaldehyde in the air, uses hydrogel as a solid electrolyte and adsorbent, and utilizes semiconductor photoanode film (BiVO4, TiO2, αFe2O3) to photoelectrocatalytically degrade water and formaldehyde adsorbed by the polyvinyl alcohol hydrogel, and prevents desorption causing secondary pollution, thereby achieving true oxidative degradation of indoor pollutants.

[0017] This device uses solar cells as an external power source and only requires solar energy to drive it, which is green and environmentally friendly. It produces a water oxidation reaction through the photoelectric effect to reduce indoor humidity, achieve better dehumidification and oxygenation effects, and remove harmful substances such as formaldehyde. The solar cell and photoelectric catalytic technology are connected in series to achieve complete solar energy-driven operation, achieving the green dual functions of efficient dehumidification and formaldehyde removal.

[0018] The present invention uses a hydrogel with a large specific surface area to better adsorb formaldehyde and water in the air, and utilizes photoelectrocatalytic technology to oxidize the adsorbed water and formaldehyde to prevent secondary pollution. After work, the hydrogel can be dried and other post-processed to remove the reaction products of water and formaldehyde, and can be reused.

[0019] The device has a simple structure, mild conditions for removing water and formaldehyde, low cost, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device of the present invention simulates the indoor air formaldehyde degradation experimental system;

[0021] Figure 2 This is a diagram of the formaldehyde removal reaction mechanism of the photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device of the present invention;

[0022] Figure 3 The photocurrent density of the photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device of the present invention in an environment with or without formaldehyde;

[0023] Figure 4 This is a graph showing the relationship between the relative humidity in the experimental cabin and time;

[0024] Figure 5 This is a graph showing the relationship between the relative concentration of formaldehyde in the experimental chamber and time;

[0025] 1- cathode graphite sheet; 2- photoanode; 3- hydrogel; 4- solar cell; 5- simulated sunlight lamp;

[0026] a-Photovoltaic-photoelectric catalytic experimental cabin; b-Dehumidification and formaldehyde removal device; c-Cabin environment detection system; d-Formaldehyde generator; e-Humidification generator. DETAILED DESCRIPTION

[0027] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0028] Preparation of polyvinyl alcohol hydrogel

[0029] Dissolve 0.5g of polypropylene alcohol (PVA) in 5mL of ultrapure water and 4.5mL of 1M potassium phosphate solution (K2PO4). Stir at 120°C and 400-500 rpm until a sol forms. Pour the solution into a polytetrafluoroethylene mold measuring 5cm long, 5cm wide, and 1.5cm high and allow to cool to room temperature to form a gel. Seal the surface with plastic wrap and dry in an oven until the hydrogel loses approximately 50% of its water content. This yields an adsorbent for absorbing water and formaldehyde. Because the hydrogel is dehydrated and its porous structure makes it more susceptible to capturing water and formaldehyde from the air.

[0030] Preparation of photoanode

[0031] Preparation of Bismuth Vanadate (BiVO4)

[0032] First, prepare 50 mL of a mixed solution with a molar concentration of 0.4 M potassium iodide (KI) and 0.03 M lactic acid, add concentrated nitric acid (HNO3) dropwise to adjust the solution pH to 1.2-2.0, add bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) to obtain a molar concentration of 0.018 M, and stir at 400-500 r / min for 20 minutes; then, add 20 mL of an ethanol solution with a molar concentration of 0.032 M p-benzoquinone, mix the above two solutions to obtain bismuth oxyiodide (BiOI), and stir vigorously for 20-30 minutes.

[0033] Potentiostatic deposition was performed in the above-mentioned mixed solution using a three-electrode system, with a FTO glass plate as the working electrode, an Ag / AgCl plate as the reference electrode, and a Pt plate as the counter electrode. Using chronoamperometry, a thin BiOI seed layer was first deposited at -0.35V vs. Ag / AgCl for 30-90 seconds. Subsequently, a BiOI layer was electrodeposited at -0.35V vs. Ag / AgCl for 1200-1500 seconds.

[0034] A 0.17M solution of vanadyl acetylacetonate was dissolved in 2mL of dimethyl sulfoxide solution and stirred for 10-20 minutes until uniformly mixed. Using a syringe, 0.14mL of this solution was then dripped onto the deposited bismuth oxyiodide layer. The sample was then annealed in a muffle furnace at 420-450°C for 120-150 minutes at a controlled heating rate of 2-5°C / min, followed by natural cooling. Finally, a 1M sodium hydroxide (NaOH) solution was prepared and the sample in the muffle furnace was soaked in this solution for 5-10 minutes to remove excess vanadium pentoxide (V2O5) from the surface. The sample was then rinsed with deionized water and dried in an oven to obtain bismuth vanadate (BiVO4).

[0035] "Sandwich" photovoltaic-photoelectric catalytic dehumidification and formaldehyde removal device

[0036] The prepared polyvinyl alcohol hydrogel in a dehydrated state is placed on the dried BiVO4 photoanode, and the graphite sheet is used as the cathode to reduce costs. The hydrogel not only acts as an adsorbent to capture water and formaldehyde in the air, but also acts as a solid electrolyte, constructing a "sandwich" photocatalytic dehumidification and formaldehyde removal system: BiVO4 photoanode-hydrogel electrolyte-graphite cathode, which can achieve dehumidification and formaldehyde removal applications under external photovoltaic devices and light conditions.

[0037] Construction of photovoltaic-photoelectrocatalytic tandem device for dehumidification and formaldehyde removal

[0038] like Figure 1 As shown, a solar cell 4 is selected, and the positive and negative electrodes of the battery are connected via wires. A "sandwich" photoelectrocatalytic dehumidification and formaldehyde removal device b is placed on a stainless steel platform, with the cathode graphite sheet 1 in close contact with the stainless steel platform. The photoanode 2 is then placed on the top layer, and the hydrogel 3 is sandwiched between the cathode graphite sheet 1 and the photoanode 2. A copper tape about 3 cm long and 0.5 cm wide is applied to the BiVO4 glass surface, and a portion of the tape is connected to the positive electrode of the solar cell 4 with a wire clamp. A copper tape about 3 cm long and 0.5 cm wide is also applied to the stainless steel platform, and a portion of the tape is connected to the negative electrode of the solar cell with a wire. This forms a closed loop for the entire device. When driven by a simulated sunlight lamp 5, it can be placed in a simulated indoor environment to purify the air and remove formaldehyde.

[0039] Performance Testing

[0040] Under light conditions, the device was placed in a sealed simulated indoor air formaldehyde degradation test chamber (such as Figure 1 After formaldehyde or moisture is introduced into the actual indoor environment through the formaldehyde generator d and the humidification generator e, the cabin environment detection system c tests the indoor humidity and formaldehyde content, mainly through electrochemical methods, ultraviolet-visible spectrophotometry methods or gas chromatography. Different indoor environmental parameters (relative humidity of air, initial formaldehyde concentration) and light source characteristics (light source power, light source wavelength, light source irradiation mode) are used to evaluate its ability to purify, dehumidify and remove formaldehyde in the air. The system reaction mechanism diagram is shown in the figure below. Figure 2 As shown:

[0041] Other key experimental conditions in the cabin are controlled as follows:

[0042] Air temperature T=23±2℃, initial humidity Initial formaldehyde concentration C0 = 0 or 1.0 ± 0.2 mg / m 3 , simulates single-sided sunlight irradiation, light intensity is 100mW / cm -2 .like Figure 3As shown in the figure, the photocurrent density of the photovoltaic-photoelectrocatalytic tandem device was tested. The BiVO4 / polypropylene alcohol hydrogel electrolyte was placed in the presence of (C0 = 1.0 ± 0.2 mg / m 3 ) / none (C0=0mg / m 3 ) formaldehyde environment, it was found that the photocurrent density of BiVO4 after formaldehyde was introduced at the same humidity increased from 1.10 mA cm -2 Increased to 1.52 mA cm -2 , proving that the device can not only decompose water, but also effectively oxidize formaldehyde. Therefore, BiVO4 / polypropylene alcohol hydrogel can not only achieve the function of dehumidification, but also degrade formaldehyde.

[0043] Figure 4 、 Figure 5 This is the relationship between the relative humidity and the relative concentration of formaldehyde in the experimental chamber over time. Figure 4 It can be seen that when BiVO4 photoanode-polypropylene alcohol hydrogel electrolyte-graphite cathode is used as the purification material in the cabin, the relative humidity in the cabin drops from the initial 80.1% to 45.7%. Figure 5 The relative concentration of formaldehyde in the air also showed a significant downward trend with time, proving that the photovoltaic-BiVO4 photoanode-polypropylene alcohol hydrogel electrolyte-graphite cathode device can adsorb water and formaldehyde gas in the air through physical adsorption and chemical oxidation.

[0044] Any matters not mentioned above shall be subject to the existing technology.

[0045] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dehumidification and formaldehyde removal device based on photovoltaic-photoelectric catalysis, characterized in that: It includes a photoanode, a hydrogel and a cathode sheet, wherein the hydrogel is sandwiched between the photoanode and the cathode sheet, and the photoanode and the cathode sheet are respectively connected to a solar cell; The hydrogel is a polyvinyl alcohol hydrogel; The preparation method of the polyvinyl alcohol hydrogel is as follows: dissolving polypropylene alcohol in ultrapure water and potassium phosphate solution, stirring and dissolving to form a sol, pouring into a mold and cooling to room temperature to form a gel; then sealing the surface with a plastic wrap, putting it in an oven to dry so that the hydrogel loses water for later use; Polyvinyl alcohol hydrogel captures water and formaldehyde in the air, and uses the hydrogel as a solid electrolyte and adsorbent, and utilizes the photoanode to photoelectrocatalytically degrade the water and formaldehyde adsorbed by the polyvinyl alcohol hydrogel.

2. A photovoltaic-photoelectric catalytic dehumidification and formaldehyde removal device as claimed in claim 1, characterized in that: The photoanode is one of a BiVO4 photoanode, a TiO2 photoanode and an α-Fe2O3 photoanode.

3. The photovoltaic-photoelectric catalytic dehumidification and formaldehyde removal device according to claim 1, characterized in that: The cathode sheet is a graphite sheet.

4. The photovoltaic-photoelectric catalysis-based dehumidification and formaldehyde removal device according to claim 1, characterized in that: The photoanode is a BiVO4 photoanode, and the preparation method of the BiVO4 photoanode comprises: S1, using a three-electrode system to perform constant potential deposition in an iodine-oxygen-bismuth mixed solution, with an FTO glass plate as a working electrode, Ag / AgCl as a reference electrode, and a Pt sheet as a counter electrode, and electro-depositing an iodine-oxygen-bismuth layer on the FTO surface; S2, preparing vanadium oxyacetylacetonate\dimethyl sulfoxide solution and dropping it on the deposited bismuth oxyiodide layer, followed by annealing in a muffle furnace and then cooling naturally; S3. Soak the sample in the muffle furnace in a sodium hydroxide solution for 5 to 10 min to remove excess vanadium pentoxide on the surface, rinse it with deionized water, and dry it in an oven to obtain a BiVO4 photoanode.

5. The photovoltaic-photoelectric catalytic dehumidification and formaldehyde removal device according to claim 4, characterized in that: In step S1, the iodine bismuth layer is electro-deposited on the FTO surface by using a chronoamperometry method. First, -0.35V vs. Ag / AgCl is set to deposit for 30-90s to form a thin iodine bismuth seed layer on the FTO surface. Then, -0.35V vs. Ag / AgCl is set to deposit for 1200-1500s to electro-deposit the iodine bismuth layer.

6. The photovoltaic-photoelectric catalytic dehumidification and formaldehyde removal device according to claim 5, characterized in that: In step S2, the annealing is carried out in a muffle furnace at 420-450°C for 120-150 min, the heating rate is controlled at 2-5°C / min, and the temperature is naturally cooled.

7. A method for reducing humidity and removing formaldehyde, characterized in that: The photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device according to any one of claims 1 to 6 is placed under a light source, and the light source is irradiated on the photoanode to perform dehumidification and formaldehyde removal.

8. A method for dehumidifying and removing formaldehyde as claimed in claim 7, characterized in that: After a period of time, the hydrogel is washed with water and then dried, and then assembled in the photovoltaic-photoelectrocatalytic dehumidification and formaldehyde removal device to continue to illuminate, dehumidify and remove formaldehyde.

Images