Preparation method of composite material for photo-anode, photo-anode and battery

Abstract

The invention provides a preparation method of a composite material for a photo-anode, the photo-anode and a battery, the preparation method of the composite material comprises the following steps: (1) mixing citric acid, urea and ethylene glycol, stirring, heating, filtering and dialyzing, and freeze-drying a solution obtained after dialyzing to obtain carbon quantum dot powder; (2) dissolving thioacetamide and cobalt chloride pentahydrate into an aqueous solution of ethanol, adding the carbon quantum dot powder obtained in the step (1), stirring, carrying out hydrothermal treatment to obtain a precipitate, washing with absolute ethyl alcohol, and then centrifuging and drying to obtain carbon quantum dot doped cobalt sulfide powder; and (3) adding titanium dioxide and the carbon quantum dot doped cobalt sulfide powder obtained in the step (2) into an ethanol aqueous solution, stirring, carrying out hydrothermal treatment to obtain a precipitate, washing, centrifuging and drying to obtain a carbon quantum dot-cobalt sulfide-titanium dioxide composite material, namely the composite material for the photo-anode. According to the invention, higher photoelectric conversion efficiency is obtained.

Description

Technical Field

[0001] This invention belongs to the field of solar cells, and in particular relates to a method for preparing a composite material for a photoanode, as well as the photoanode and the cell. Background Technology

[0002] A solar cell is a device that directly converts light energy into electrical energy through a photoelectric conversion process. Its principle is based on the photovoltaic effect, which generates electron-hole pairs under illumination, subsequently forming an electromotive force and photocurrent. As a third-generation solar cell, dye-sensitized solar cells (DSSCs) utilize organic dye molecules to absorb light energy and excite electrons, mimicking the natural photosynthesis process to convert solar energy into electrical energy. Compared to first-generation silicon solar cells and second-generation compound thin-film solar cells, DSSCs have advantages such as abundant material sources, low cost, and good stability in low-light environments. A DSSC consists of four parts: a photoanode, a dye sensitizer, an electrolyte, and a counter electrode. The photoanode, as its core component, is commonly made of TiO2. However, because it can only absorb high-energy ultraviolet light, its utilization and conversion efficiency of sunlight is limited. Improving photoelectric conversion efficiency has become an urgent problem to be solved. Summary of the Invention

[0003] In view of this, the present invention aims to propose a method for preparing a composite material for photoanodes, as well as a photoanode and battery, to overcome the shortcomings of the prior art. The present invention involves doping carbon quantum dots onto the surface of cobalt sulfide, followed by compositing with titanium dioxide to obtain a composite material for photoanodes with a continuous band structure. Carbon quantum dots can serve as channels for rapid electron transport. Combined with the suitable bandgap structure of cobalt sulfide, photoexcited N719 ruthenium dye electrons are rapidly transported to the cobalt sulfide via carbon quantum dots, effectively avoiding recombination with holes. Furthermore, carbon quantum doped cobalt sulfide has a large specific surface area, which can better facilitate the contact and mass transfer process between the photoanode and the electrolyte, providing a rapid diffusion channel and facilitating electrolyte recycling and regeneration, thereby achieving higher photoelectric conversion efficiency.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] A method for preparing a composite material for photoanodes includes the following steps:

[0006] (1) Mix citric acid, urea and ethylene glycol and stir, heat, filter and dialyze, freeze dry the solution obtained after dialyze to obtain carbon quantum dot powder;

[0007] (2) Thioacetamide and cobalt chloride pentahydrate were dissolved in an aqueous ethanol solution, and carbon quantum dot powder obtained in step (1) was added. The mixture was stirred and hydrothermally heated to obtain a precipitate. The precipitate was washed with anhydrous ethanol, and then centrifuged and dried to obtain carbon quantum dot-doped cobalt sulfide powder.

[0008] (3) Add titanium dioxide and the carbon quantum dot-doped cobalt sulfide powder obtained in step (2) into an ethanol aqueous solution, stir, and hydrothermally heat to obtain a precipitate. Wash, centrifuge and dry to obtain a carbon quantum dot-cobalt sulfide-titanium dioxide composite material, which is a composite material used for photoanodes.

[0009] Preferably, in step (1), the mass ratio of citric acid, urea and ethylene glycol is 2:(1~2):(40~120); the hydrothermal heating temperature is 120~200℃ and the heating time is 2~12h; the dialysis bag used for dialysis has a molecular weight cutoff of 500~2000Da and the dialysis time is 8~48h; the freeze-drying temperature is -50~-60℃, the pressure is 1~20Pa, and the freeze-drying time is 24~36h.

[0010] Preferably, in step (2), the mass ratio of thioacetamide, cobalt chloride pentahydrate, and carbon quantum dot powder is 1:(1-5):(0.02-0.1), the concentration of thioacetamide in the aqueous ethanol solution is 1-15 mg / mL, the hydrothermal temperature is 150-220℃, the hydrothermal time is 1-16 h, the centrifugation speed is 8000-12000 rpm, the centrifugation time is 5-10 min, and the drying is done by baking at a temperature of 60-80℃ for 12-24 h.

[0011] Preferably, in step (3), the mass ratio of titanium dioxide to carbon quantum doped cobalt sulfide powder is 1:(0.1-1), the hydrothermal heating temperature is 80-150℃, the hydrothermal duration is 1-5h, the concentration of titanium dioxide in the ethanol aqueous solution is 1-15mg / mL, the centrifugation is at a speed of 8000-12000rpm for 10-20min, and the drying is at 70-90℃ for 10-20h.

[0012] A dye-sensitized solar cell photoanode includes fluorine-doped tin dioxide (FTO) conductive glass, the surface of which is coated with a composite material for photoanode prepared by the method described above.

[0013] A method for preparing the dye-sensitized solar cell photoanode as described above includes the following steps:

[0014] A) The composite material for photoanode prepared by the preparation method described above is dispersed in anhydrous ethanol, and then 5-10 wt.% Nafion solution is added. The mixture is ultrasonically dispersed to obtain a uniform film solution, which is then coated on the surface of FTO conductive glass and allowed to stand and dry to obtain FTO conductive glass coated with the composite material.

[0015] B) The FTO conductive glass coated with composite material obtained in step A) is immersed in N719 ruthenium dye solution, dyed in the dark, the residual dye is cleaned with anhydrous ethanol, and then dried to obtain the dye-sensitized solar cell photoanode.

[0016] Preferably, in step A), the coating amount of the composite material used for the photoanode on the FTO conductive glass is 0.2-2 mg / cm². 2 The volume ratio of anhydrous ethanol to 5-10 wt.% Nafion solution is 1:(0.02-0.1); the concentration of the composite material used for photoanode in the homogeneous film solution is 0.6-6 mg / mL.

[0017] Preferably, in step B), the concentration of the N719 ruthenium dye solution is 0.1–10 mM, and the dyeing time is 8–24 h.

[0018] The present invention also provides a dye-sensitized solar cell, including the dye-sensitized solar cell photoanode as described above or the dye-sensitized solar cell photoanode prepared by the preparation method described above.

[0019] Preferred, with I - / I3 - The electrolyte is used, and a platinum sheet is used as the counter electrode.

[0020] Carbon quantum dots possess excellent electron transport properties, exhibiting rapid charge transfer, long electron lifetime, and abundant surface functional groups. Their energy band structure matches that of N719 ruthenium dye. Cobalt sulfide (CoS) has a band gap of 1.1 eV, which is compatible with the energy levels of N719 ruthenium dye. Photogenerated holes from N719 ruthenium dye can be transferred to the CoS surface, effectively suppressing electron-hole pair recombination in N719 ruthenium dye. However, the lack of sufficient conductive channels makes electron transport speed a limiting factor for catalytic efficiency. Therefore, combining cobalt-based materials with carbon quantum dots, which possess excellent electron transport capabilities, yields composite photoanode materials that exhibit both high conductivity and excellent electrocatalytic activity.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] Carbon quantum dot-modified cobalt sulfide materials possess suitable band gaps, enabling the formation of continuous band gap structures with titanium dioxide and N719 ruthenium dye, which facilitates electron migration. Carbon quantum dots exhibit excellent charge transport capabilities, serving as electron transfer relay bridges between N719 ruthenium dye and cobalt sulfide, effectively achieving the separation of photogenerated carriers. The photoanode materials are chemically linked by Co-O-Ti bonds, resulting in structural stability, while cobalt sulfide provides more active sites for electrochemical reactions. Carbon quantum dot-doped cobalt sulfide titanium dioxide photoanode materials exhibit enhanced visible light absorption performance, improving the utilization rate of sunlight. Based on these characteristics, the carbon quantum dot-doped cobalt sulfide dye-sensitized solar cell photoanode material achieves a photoelectric conversion efficiency of 9.02%. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the dye-sensitized solar cell described in this invention.

[0024] Figure 2 Scanning electron microscope images of cobalt sulfide (a) and carbon quantum dot-doped cobalt sulfide (b) synthesized in Example 1.

[0025] Figure 3 The current density-voltage relationship curves of the dye-sensitized solar cells described in Example 1 and Comparative Example 1 of the present invention were measured under AM 1.5 standard sunlight.

[0026] Figure 4 Tafel curves for the photoanodic composite materials in Example 1 and Comparative Examples 1 and 2.

[0027] Figure 5 This is a diagram of the band structure of the DSSC synthesized in Example 1. Detailed Implementation

[0028] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0029] The present invention will be described in detail below with reference to embodiments.

[0030] Example 1: Preparation steps of carbon quantum dot-cobalt sulfide-titanium dioxide composite material, photoanode and DSSC (1): Preparation of carbon quantum dot powder

[0031] Weigh 3 mmol of citric acid and 6 mmol of urea, dissolve them in 30 mL of ethylene glycol, and stir magnetically for 2 h. Then place the mixture in a stainless steel reactor and heat at 180 °C for 7 h. After cooling to room temperature, filter the black product obtained by heating through a 0.22 μm filter membrane to remove large particles. Place the filtrate in a regenerated cellulose dialysis bag with a molecular weight cutoff of 1000 Da, and use deionized water as the dialysis fluid. Dialyze continuously for 48 h, changing the dialysis fluid 3 times every 24 h during dialysis. After dialysis, collect the liquid in the bag, freeze it, and place it in a freeze dryer at -55 °C and 10 Pa for 30 h to obtain black carbon quantum dot powder.

[0032] Step (2): Preparation of carbon quantum dot-doped cobalt sulfide powder

[0033] 0.15 g of thioacetamide and 0.385 g of cobalt chloride pentahydrate were dissolved in 30 mL of an aqueous ethanol solution (ethanol to water volume ratio of 1:1). 5 mg of the carbon quantum dot powder prepared in step (1) was added, and the mixture was magnetically stirred for 1 h. Then, it was placed in a stainless steel reactor and heated at 180 °C for 12 h. After natural cooling, it was washed three times with deionized water and anhydrous ethanol, centrifuged at 10000 rpm for 10 min, and dried at 65 °C for 12 h. After drying, carbon quantum dot-doped cobalt sulfide powder was obtained.

[0034] Step (3): Preparation of carbon quantum dot-cobalt sulfide-titanium dioxide composite material

[0035] Weigh 0.1g of titanium dioxide powder and 0.1g of carbon quantum dot-doped cobalt sulfide powder prepared in step (2), mix and disperse them in 30mL of an aqueous solution of ethanol (the volume ratio of ethanol to water is 1:1), place them in a stainless steel reactor and heat them in an oven at 100°C for 2 hours. After natural cooling, wash them three times with deionized water and anhydrous ethanol, centrifuge them at 12000rpm for 15min, and then transfer them to an oven at 80°C and dry them for 12 hours. Then collect the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder.

[0036] Step (4): Preparation of photoanode

[0037] Weigh 3.6 mg of the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder prepared in step (3), disperse it in 950 μL of anhydrous ethanol, add 50 μL of 5 wt.% Nafion solution, sonicate for 30 min, and then coat it onto a 3 cm² area. 2 The FTO conductive glass is left to dry to obtain FTO conductive glass coated with composite material.

[0038] The FTO conductive glass plate coated with the composite material was immersed in a 3mM N719 ruthenium dye solution and placed in the dark for 12 hours to fully sensitize the catalyst film of the photoanode. After the photoanode color changed from colorless and transparent to a uniform purplish-red, it was taken out, washed with anhydrous ethanol, and then air-dried naturally.

[0039] Step (5): Preparation of DSSC

[0040] Take I - / I3 - Electrolyte, 1*1cm 2 Platinum sheets were used as counter electrodes to assemble a DSSC.

[0041] Example 2: Preparation steps of carbon quantum dot-cobalt sulfide-titanium dioxide composite material, photoanode and DSSC (1): Preparation of carbon quantum dot powder

[0042] Weigh 3 mmol of citric acid and 6 mmol of urea, dissolve them in 30 mL of ethylene glycol, stir magnetically for 2 h, then place in a stainless steel reactor and heat at 180 °C for 7 h. After cooling to room temperature, filter the black product obtained by heating through a 0.22 μm filter membrane to remove large particles. Place the filtrate in a regenerated cellulose dialysis bag with a molecular weight cutoff of 1000 Da, use deionized water as the dialysis fluid, and continue dialysis for 48 h. During dialysis, change the dialysis fluid 3 times every 24 h. After dialysis, collect the liquid in the bag and continuously freeze-dry at -52 °C and 10 Pa for 30 h to obtain black carbon quantum dot powder.

[0043] Step (2): Preparation of carbon quantum dot-doped cobalt sulfide

[0044] 0.15 g of thioacetamide and 0.385 g of cobalt chloride pentahydrate were dissolved in 30 mL of an aqueous ethanol solution (ethanol to water volume ratio of 1:1). 5 mg of carbon quantum dot powder prepared in step (1) was added, and the mixture was magnetically stirred for 1 h. Then, it was placed in a stainless steel reactor and heated at 180 °C for 12 h. After natural cooling, it was washed three times with deionized water and anhydrous ethanol, centrifuged at 9000 rpm for 8 min, and dried at 70 °C for 16 h to obtain carbon quantum dot-doped cobalt sulfide powder.

[0045] Step (3): Preparation of carbon quantum dot-cobalt sulfide-titanium dioxide composite material

[0046] Weigh 0.2g of titanium dioxide powder and 0.1g of carbon quantum dot-doped cobalt sulfide powder prepared in step (2), mix and disperse them in 30mL of ethanol aqueous solution (volume ratio of 1:1), place them in a stainless steel reactor and heat them in an oven at 100℃ for 2h. After natural cooling, wash them three times with deionized water and anhydrous ethanol, centrifuge them at 11000rpm for 10min and dry them at 75℃ for 12h to collect the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder.

[0047] Step (4): Preparation of photoanode

[0048] Weigh 3.6 mg of the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder prepared in step (3), disperse it in 950 μL of anhydrous ethanol, add 50 μL of 5 wt.% Nafion solution, sonicate for 30 min, and then coat it onto a 3 cm² area. 2 The FTO conductive glass is left to dry to obtain FTO conductive glass coated with composite material.

[0049] The FTO conductive glass plate coated with the composite material was immersed in a 3mM N719 ruthenium dye solution and placed in the dark for 12 hours to fully sensitize the catalyst film of the photoanode. After the photoanode color changed from colorless and transparent to a uniform purplish-red, it was taken out, washed with anhydrous ethanol, and then air-dried naturally.

[0050] Step (5): Preparation of DSSC

[0051] Take I - / I3 - Electrolyte, 1*1cm 2 Platinum sheets were used as counter electrodes to assemble a DSSC.

[0052] Example 3: Preparation steps of carbon quantum dot-cobalt sulfide-titanium dioxide composite material, photoanode and DSSC (1): Preparation of carbon quantum dots

[0053] Weigh 3 mmol of citric acid and 6 mmol of urea, dissolve them in 30 mL of ethylene glycol, and stir magnetically for 2 h. Then place the mixture in a stainless steel reactor and heat at 180 °C for 7 h. After cooling to room temperature, filter the black product obtained by heating through a 0.22 μm filter membrane to remove large particles. Place the filtrate in a regenerated cellulose dialysis bag with a molecular weight cutoff of 1000 Da, and use deionized water as the dialysis fluid. Dialyze continuously for 48 h, changing the dialysis fluid 3 times every 24 h during dialysis. After dialysis, collect the liquid in the bag, freeze it, and place it in a freeze dryer. Dry it continuously at -55 °C and 10 Pa for 30 h to obtain black carbon quantum dot powder.

[0054] Step (2): Preparation of carbon quantum dots doped with cobalt sulfide

[0055] 0.15 g of thioacetamide and 0.385 g of cobalt chloride pentahydrate were dissolved in 30 mL of an aqueous ethanol solution (ethanol to water volume ratio of 1:1). 5 mg of the carbon quantum dot powder prepared in step (1) was added, and the mixture was magnetically stirred for 1 h. Then, it was placed in a stainless steel reactor and heated at 180 °C for 12 h. After natural cooling, it was washed three times with deionized water and anhydrous ethanol, centrifuged at 9000 rpm for 10 min, and dried at 80 °C for 18 h to obtain carbon quantum dot-doped cobalt sulfide powder.

[0056] Step (3): Preparation of carbon quantum dot-cobalt sulfide-titanium dioxide composite material

[0057] Weigh 0.3g of commercially available titanium dioxide powder and 0.1g of carbon quantum dot-doped cobalt sulfide powder prepared in step (2), mix and disperse them in 30mL of an aqueous solution of ethanol (volume ratio of ethanol to water is 1:1), place them in a stainless steel reactor and heat them in an oven at 100°C for 2 hours. After natural cooling, wash them three times with deionized water and anhydrous ethanol, centrifuge them at 12000rpm for 15min, dry them at 80°C for 16h and collect the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder.

[0058] Step (4): Preparation of photoanode

[0059] Weigh 3.6 mg of the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder prepared in step (3), disperse it in 950 μL of anhydrous ethanol, add 50 μL of 5 wt.% Nafion solution, sonicate for 30 min, and then coat it onto a 3 cm² area. 2 The FTO conductive glass is left to dry to obtain FTO conductive glass coated with composite material.

[0060] The FTO conductive glass plate coated with the composite material was immersed in a 3mM N719 ruthenium dye solution and placed in the dark for 12 hours to fully sensitize the catalyst film of the photoanode. After the photoanode color changed from colorless and transparent to a uniform purplish-red, it was taken out, washed with anhydrous ethanol, and then air-dried naturally.

[0061] Step (5): Preparation of DSSC

[0062] Take I - / I3 - Electrolyte, 1*1cm 2 Platinum sheets were used as counter electrodes to assemble a DSSC.

[0063] Example 4: Preparation steps of carbon quantum dot-cobalt sulfide-titanium dioxide composite material, photoanode and DSSC (1): Preparation of carbon quantum dots

[0064] Weigh 3 mmol of citric acid and 6 mmol of urea, dissolve them in 30 mL of ethylene glycol, and stir magnetically for 2 h. Then place the mixture in a stainless steel reactor and heat at 180 °C for 7 h. After cooling to room temperature, filter the black product obtained by heating through a 0.22 μm filter membrane to remove large particles. Place the filtrate in a regenerated cellulose dialysis bag with a molecular weight cutoff of 1000 Da, and use deionized water as the dialysis fluid. Dialyze continuously for 48 h, changing the dialysis fluid 3 times every 24 h during dialysis. After dialysis, collect the liquid in the bag, freeze it, and place it in a freeze dryer. Dry it continuously at -50 °C and 15 Pa for 30 h to obtain black carbon quantum dot powder.

[0065] Step (2): Preparation of carbon quantum dots doped with cobalt sulfide

[0066] 0.3 g of thioacetamide and 1.25 g of cobalt chloride pentahydrate were dissolved in 30 mL of an aqueous ethanol solution (ethanol to water volume ratio of 1:1). 30 mg of the carbon quantum dot powder prepared in step (1) was added, and the mixture was magnetically stirred for 1 h. Then it was placed in a stainless steel reactor and heated at 180 °C for 12 h. After natural cooling, the mixture was washed three times with deionized water and anhydrous ethanol, centrifuged at 10000 rpm for 10 min, and dried at 65 °C for 12 h to obtain carbon quantum dot-doped cobalt sulfide powder.

[0067] Step (3): Preparation of carbon quantum dot-cobalt sulfide-titanium dioxide composite material

[0068] Weigh 0.425 g of titanium dioxide powder and 0.175 g of carbon quantum dot-doped cobalt sulfide powder prepared in step (2), mix and disperse them in 30 mL of ethanol aqueous solution (ethanol to water volume ratio of 1:1), place them in a stainless steel reactor and heat them in an oven at 100 °C for 2 h. After natural cooling, wash them three times with deionized water and anhydrous ethanol, centrifuge them at 12000 rpm for 15 min, and then transfer them to an oven at 80 °C and dry them for 12 h. Collect the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder.

[0069] Step (4): Preparation of photoanode

[0070] Weigh 3.6 mg of the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder prepared in step (3), disperse it in 950 μL of anhydrous ethanol, add 50 μL of 5 wt.% Nafion solution, sonicate for 30 min, and then coat it onto a 3 cm² area. 2The FTO conductive glass is left to dry to obtain FTO conductive glass coated with composite material.

[0071] The FTO conductive glass plate coated with the composite material was immersed in a 3mM N719 ruthenium dye solution and placed in the dark for 12 hours to fully sensitize the catalyst film of the photoanode. After the photoanode color changed from colorless and transparent to a uniform purplish-red, it was taken out, washed with anhydrous ethanol, and then air-dried naturally.

[0072] Step (5): Preparation of DSSC

[0073] Take I - / I3 - Electrolyte, 1*1cm 2 Platinum sheets were used as counter electrodes to assemble a DSSC.

[0074] Example 5: Preparation steps of carbon quantum dot-cobalt sulfide-titanium dioxide composite material, photoanode and DSSC (1): Preparation of carbon quantum dot powder

[0075] Weigh 3 mmol of citric acid and 6 mmol of urea, dissolve them in 30 mL of ethylene glycol, and stir magnetically for 2 h. Then place the mixture in a stainless steel reactor and heat at 180 °C for 7 h. After cooling to room temperature, filter the black product obtained by heating through a 0.22 μm filter membrane to remove large particles. Place the filtrate in a regenerated cellulose dialysis bag with a molecular weight cutoff of 1000 Da, and use deionized water as the dialysis fluid. Dialyze continuously for 48 h, changing the dialysis fluid 3 times every 24 h during dialysis. After dialysis, collect the liquid in the bag, freeze it, and place it in a freeze dryer. Dry it continuously at -55 °C and 10 Pa for 30 h to obtain black carbon quantum dot powder.

[0076] Step (2): Preparation of carbon quantum dot-doped cobalt sulfide powder

[0077] 0.25 g of thioacetamide and 0.75 g of cobalt chloride pentahydrate were dissolved in 30 mL of ethanol-water solution (ethanol to water volume ratio of 1:1). 25 mg of carbon quantum dot powder prepared in step (1) was added, and the mixture was magnetically stirred for 1 h. Then it was placed in a stainless steel reactor and heated at 180 °C for 12 h. After natural cooling, it was washed three times with deionized water and anhydrous ethanol, centrifuged at 10000 rpm for 10 min, and dried at 65 °C for 12 h to obtain carbon quantum dot-doped cobalt sulfide powder.

[0078] Step (3): Preparation of carbon quantum dot-cobalt sulfide-titanium dioxide composite material

[0079] Weigh 0.375 g of titanium dioxide powder and 0.125 g of carbon quantum dot-doped cobalt sulfide powder prepared in step (2), mix and disperse them in 30 mL of ethanol aqueous solution (ethanol to water volume ratio of 1:1), place them in a stainless steel reactor and heat them in an oven at 100 °C for 2 h. After natural cooling, wash them three times with deionized water and anhydrous ethanol, centrifuge them at 12000 rpm for 15 min, and then transfer them to an oven at 80 °C and dry them for 12 h. Then collect the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder.

[0080] Step (4): Preparation of photoanode

[0081] Weigh 5 mg of the carbon quantum dot-cobalt sulfide-titanium dioxide composite powder prepared in step (3), disperse it in 975 μL of anhydrous ethanol, add 25 μL of 5 wt.% Nafion solution, sonicate for 30 min, and then coat it onto a 5 cm² area. 2 The FTO conductive glass is left to dry to obtain FTO conductive glass coated with composite material.

[0082] The FTO conductive glass plate coated with the composite material was immersed in a 3mM N719 ruthenium dye solution and placed in the dark for 12 hours to fully sensitize the catalyst film of the photoanode. After the photoanode color changed from colorless and transparent to a uniform purplish-red, it was taken out, washed with anhydrous ethanol, and then air-dried naturally.

[0083] Step (5): Preparation of DSSC

[0084] Take I - / I3 - Electrolyte, 1*1cm 2 Platinum sheets were used as counter electrodes to assemble a DSSC.

[0085] Comparative Example 1:

[0086] 0.2 g of thioacetamide and 0.3 g of cobalt chloride pentahydrate were dissolved in 25 mL of an aqueous ethanol solution (ethanol to water volume ratio 1:1), stirred for 1 h, and then heated in an oven at 180 °C for 8 h. After cooling to 25 °C, the mixture was washed three times with deionized water and anhydrous ethanol and dried to obtain cobalt sulfide solid. Subsequently, 0.1 g of cobalt sulfide solid powder and 0.1 g of titanium dioxide powder were weighed and dispersed in 25 mL of an aqueous ethanol solution (ethanol to water volume ratio 1:1), stirred for 1 h, and then transferred to a stainless steel reactor and heated at 120 °C for 4 h. After cooling to 25 °C, the mixture was washed three times with deionized water and anhydrous ethanol and dried to obtain a cobalt sulfide-titanium dioxide composite. 3 mg of the cobalt sulfide-titanium dioxide composite was dissolved in 950 mL of anhydrous ethanol, followed by the addition of 50 μL of 5 wt.% Nafion solution. The mixture was sonicated for 30 min and then coated onto a 3 cm thick substrate. 2 The FTO conductive glass coated with cobalt sulfide-titanium dioxide composite was immersed in a 3 mM N719 ruthenium dye solution for 12 h, with I... - and I3 - The electrolyte is used, and a platinum sheet is used as the counter electrode to construct a DSSC.

[0087] Comparative Example 2

[0088] 10 mg of carbon quantum dot powder (prepared as in Example 1) and 0.1 g of titanium dioxide were weighed and added to 25 mL of an aqueous ethanol solution (ethanol to water volume ratio 1:1). The mixture was stirred for 30 min, then heated at 120 °C for 2 h. After cooling to 25 °C, it was washed with deionized water and anhydrous ethanol, and dried to obtain the carbon quantum dot-titanium dioxide composite. 5 mg of the carbon quantum dot-titanium dioxide composite was weighed and dispersed in 950 μL of anhydrous ethanol, followed by the addition of 50 μL of 5 wt.% Nafion solution. The mixture was sonicated for 30 min and then coated onto a 3 cm thick substrate. 2 The FTO conductive glass coated with carbon quantum dot-titanium dioxide composite was immersed in a 3 mM N719 ruthenium dye solution for 12 h, with I... - and I3 - The electrolyte is used, and a platinum sheet is used as the counter electrode to construct a DSSC.

[0089] Comparative Example 3

[0090] Weigh 220 mg of titanium dioxide powder and add it to 30 mL of an aqueous ethanol solution (ethanol to water volume ratio 1:1). Stir for 30 min, then heat at 120 °C for 2 h. After cooling to 25 °C, centrifuge at 10000 rpm for 10 min, and wash with deionized water and anhydrous ethanol. Repeat three times, then dry in an oven at 75 °C for 12 h to obtain titanium dioxide powder. Weigh 5 mg of titanium dioxide powder and disperse it in 950 μL of anhydrous ethanol, then add 50 μL of 5 wt.% Nafion solution, sonicate for 30 min, and then coat it onto a 3 cm thick substrate. 2 The FTO conductive glass coated with carbon quantum dot-titanium dioxide composite was immersed in a 3 mM N719 ruthenium dye solution for 12 h, with I... - and I3 - The electrolyte is used, and a platinum sheet is used as the counter electrode to construct a DSSC.

[0091] The FTO conductive glass treated in Examples 1-5 and Comparative Examples 1-3 was subjected to I - and I3 - The method for constructing a DSSC using a platinum sheet as the counter electrode and an electrolyte includes the following steps:

[0092] 1. Fix the platinum sheet onto the FTO conductive glass, ensuring that the contact surface with the electrolyte is flat and has stable conductivity;

[0093] 2. Prepare the electrolyte by dissolving I₂ in an organic solvent to form I₂. - and I3 - A mixed solution. Concentration control is necessary; the I₂ concentration is 0.1 mol / L.

[0094] 3. Seal the treated FTO glass and platinum foil counter electrode with a sealing ring to form a sandwich structure; inject the prepared electrolyte to ensure that the electrolyte evenly covers the entire conductive glass surface.

[0095] The specific implementation method for measuring the photoelectric conversion efficiency of the solar cells prepared in Examples 1-5 and Comparative Examples 1-3 of this invention is as follows:

[0096] Specifically, a light intensity of 100 mW / cm² was used. 2 An AM 1.5 sunlight-simulated light source illuminates the surface of FTO conductive glass, which is covered with a polyester light-shielding mask to maintain an effective illumination area of ​​1*1cm. 2The current density-voltage (JV) curves were recorded using a Victor VC-8246A source meter. Detailed experimental data for Examples 1-5 and Comparative Examples 1-3 are shown in Table 1, mainly including: open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and photoelectric conversion efficiency (η).

[0097] Table 1. DSSC-related characteristic parameters of Examples 1-5 and Comparative Examples 1-3

[0098]

[0099] Table 1 shows the DSSC-related characteristic parameters of Examples 1-5 and Comparative Examples 1-3, mainly including: open circuit voltage (Voc), short circuit current (Jsc), fill factor (FF), and photoelectric conversion efficiency (η).

[0100] The formula for calculating photoelectric conversion efficiency is as follows:

[0101]

[0102] Where FF is the fill factor, and P in For the input power density, P max The maximum power density output by the battery is the power value corresponding to the maximum power point on the current density-voltage (JV) curve.

[0103] Figure 1 This is a schematic diagram of the dye-sensitized solar cell (DSSC with carbon quantum dots doped with cobalt sulfide) described in Example 1. A composite material formed by loading cobalt sulfide with carbon quantum dots onto TiO2 is coated onto an FTO conductive glass plate to form the photoanode. After wetting the dye, N719 molecules randomly attach to the composite photoanode. The electrolyte is I... - / I3 - A solution is used, and a Pt-coated FTO conductive glass plate is used as the counter electrode to form a DSSC.

[0104] Figure 2 Scanning electron microscope (SEM) images of cobalt sulfide (a) and carbon quantum dot-doped cobalt sulfide (b) synthesized in Example 1 show the morphology of the synthesized products. The prepared cobalt sulfide is granular with an average size of about 1 μm, and is composed of irregularly stacked nanosheets. In the doped cobalt sulfide, carbon quantum dots are uniformly composited on the particle surface and within the nanosheets.

[0105] Figure 3The figures show the current density-voltage relationship curves of the DSSC described in Example 1 and Comparative Example 1 under AM 1.5 standard sunlight. It can be seen from the figure that the DSSC doped with cobalt sulfide carbon quantum dots has an expanded photocurrent response range in the visible light region, which increases the short-circuit current of the battery, thereby achieving a photoelectric conversion efficiency of 9.02%.

[0106] Figure 4 The figure shows the Tafel curves of the photoanode composite materials synthesized in Example 1 and Comparative Examples 1 and 2. This curve describes the logarithmic relationship between the overpotential and the current density of the electrode reaction. The exchange current density (J0) can be directly calculated from the intercept of the Tafel curve. The larger J0 is, the easier it is for the electrode surface to react, the lower the charge recombination rate, and the better the kinetics of the reaction process. It can be seen from the figure that the J0 of the DSSC doped with cobalt sulfide by carbon quantum dots is the largest, indicating that the modification of carbon quantum dots effectively promotes the redox reaction on the electrode surface.

[0107] Figure 5 The band structure diagram of the DSSC constructed in Example 1 is shown. The positions of the valence band (VB, orange) and conduction band (CB, blue) of each component in the DSSC were calculated. The calculation results indicate that N719 ruthenium dye (… Figure 5 N719 in the middle) and carbon quantum dots ( Figure 5 CD), carbon quantum dots and TiO2 ( Figure 5 Two continuous type I band structures are formed between the TiO2 in the N719 ruthenium dye and TiO2. The carbon quantum dots act as a bridge between the N719 ruthenium dye and TiO2, which enhances the transmission of photoelectrons and reduces the recombination of electrons and holes, thereby promoting the redox process of the electrolyte.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite material for a photoanode, characterized by, The preparation method comprises the following steps: (1) mixing and stirring citric acid, urea and ethylene glycol, heating, filtering and dialyzing, and freeze-drying the solution obtained after dialysis to obtain carbon quantum dot powder; (2) dissolving thioacetamide and cobalt chloride pentahydrate into an aqueous solution of ethanol, adding the carbon quantum dot powder obtained in step (1), stirring, and hydrothermally obtaining a precipitate, washing with anhydrous ethanol, and then centrifuging and drying to obtain carbon quantum dot-doped cobalt sulfide powder; (3) adding titanium dioxide and the carbon quantum dot-doped cobalt sulfide powder obtained in step (2) into an aqueous solution of ethanol, stirring, and hydrothermally obtaining a precipitate, washing, centrifuging and drying to obtain a carbon quantum dot-cobalt sulfide-titanium dioxide composite material, i.e., a composite material for a photoanode.

2. The method for preparing a composite material for a photoanode according to claim 1, characterized by: In step (1), the mass ratio of citric acid, urea and ethylene glycol is 2:(1-2):(40-120); the heating temperature of hydrothermal treatment is 120-200 ℃, and the heating time is 2-12 h; the molecular weight cut-off of the dialysis bag used for dialysis is 500-2000 Da, and the dialysis time is 8-48 h; the temperature of freeze-drying is -50 to -60 ℃, the pressure is 1-20 Pa, and the freeze-drying time is 24-36 h.

3. The method for preparing a composite material for a photoanode according to claim 1, characterized by: In step (2), the mass ratio of thioacetamide, cobalt chloride pentahydrate and carbon quantum dot powder is 1:(1-5):(0.02-0.1), the concentration of thioacetamide in the aqueous solution of ethanol is 1-15 mg / mL, the hydrothermal temperature is 150-220 ℃, the hydrothermal time is 1-16 h, the centrifugal speed is 8000-12000 rpm, the centrifugal time is 5-10 min, the drying is performed by oven drying, the oven drying temperature is 60-80 ℃, and the oven drying time is 12-24 h.

4. The method for preparing a composite material for a photoanode according to claim 1, characterized by: In step (3), the mass ratio of titanium dioxide and the carbon quantum dot-doped cobalt sulfide powder is 1:(0.1-1), the heating temperature of hydrothermal treatment is 80-150 ℃, the hydrothermal time is 1-5 h, the concentration of titanium dioxide in the aqueous solution of ethanol is 1-15 mg / mL, the centrifugal speed is 8000-12000 rpm, the centrifugal time is 10-20 min, and the drying is performed by oven drying at 70-90 ℃ for 10-20 h.

5. A dye-sensitized solar cell photo-anode comprising fluorine-doped tin dioxide (FTO) conductive glass, characterized in that: The surface of the FTO conductive glass is coated with the composite material for a photoanode prepared by the preparation method of any one of claims 1-4.

6. A method of preparing the dye-sensitized solar cell photoanode according to claim 5, characterized in that: The preparation method comprises the following steps: A) dispersing the composite material for a photoanode prepared by the preparation method of any one of claims 1-4 in anhydrous ethanol, then adding 5-10 wt.% Nafion solution, ultrasonic dispersion to obtain a uniform film solution, coating the film solution on the surface of the FTO conductive glass, and standing to dry to obtain FTO conductive glass coated with the composite material; B) immersing the FTO conductive glass coated with the composite material obtained in step A) in a N719 ruthenium dye solution, dyeing in a dark environment, washing the residual dye with anhydrous ethanol, and then air-drying to obtain a dye-sensitized solar cell photoanode.

7. The method of claim 6, wherein: In step A), the coating amount of the composite material for the photoanode on the FTO conductive glass is 0.2-2 mg / cm 2 ; the volume ratio of anhydrous ethanol and 5-10 wt.% Nafion solution is 1:(0.02-0.1); and the concentration of the composite material for the photoanode in the uniform film solution is 0.6-6 mg / mL.

8. The method of claim 6, wherein: In step B), the concentration of the N719 ruthenium dye solution is 0.1-10 mM, and the dyeing time is 8-24 h.

9. A dye-sensitized solar cell characterized by comprising: The dye-sensitized solar cell photoanode according to claim 5 or the dye-sensitized solar cell photoanode prepared by the preparation method according to any one of claims 6 to 8.

10. The dye-sensitized solar cell according to claim 9, characterized in that: with I - / I3 - as electrolyte and platinum as counter electrode.

Images