Preparation methods and applications of polyacid-modified Cu2MoS4 electrode materials

Abstract

This application relates to a method for preparing multi-acid modified Cu₂MoS₄ electrode materials, belonging to the field of new energy materials and photoelectric conversion technology. An in-situ synthesis method is employed, using a one-step solvothermal preparation technique to dope Cu₂MoS₄ materials with SiW. 11 Co; includes the following steps: S1. Dissolve sodium molybdate and thioacetamide in ethylene glycol, and then add SiW to the solution. 11 Co is dissolved, and finally Cu2O is added. The above mixed solution is ultrasonically treated at room temperature for 10-15 min to obtain a uniform dark brown suspension. S2. After stirring for another 5 min, the precursor suspension is transferred to a high-pressure reactor for a solvothermal process of 22-24 h. S3. The reactor is cooled to room temperature, and the final product is washed three times each with deionized water and anhydrous ethanol by centrifugation, and then vacuum dried to obtain SiW. 11 Co / Cu2MoS4 composite material. This invention utilizes an appropriate amount of SiW... 11 The introduction of Co creates a rough structure on the surface of Cu₂MoS₄, increasing the number of active sites and the specific surface area. This results in catalytic performance and stability that are far superior to those of traditional Cu₂S counter electrodes and unmodified Cu₂MoS₄ counter electrodes.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and photoelectric conversion technology, specifically relating to a method for preparing a polyacid-modified Cu2MoS4 electrode material and its application in quantum dot-sensitized solar cells. Background Technology

[0002] Quantum dot-sensitized solar cells (QDSSCs) have become a research hotspot in the photovoltaic field due to their advantages such as low fabrication cost, tunable bandgap, multi-exciton generation effect, and high theoretical conversion efficiency. Their core components include a semiconductor oxide photoanode, quantum dot sensitizer, electrolyte, and counter electrode (CE). The counter electrode acts as a catalyst for reducing the oxidized electrolyte (such as S in a polysulfide electrolyte) in QDSSCs. n The counter electrode (²⁻) is a key component that directly affects the battery's power conversion efficiency (PCE) and stability. Currently, the mainstream counter electrode technologies are as follows:

[0003] (1) Noble metal-based counter electrodes: represented by platinum (Pt), which have certain catalytic performance, but are easily corroded in polysulfide electrolytes and are expensive, making them unsuitable for large-scale applications. (2) Binary metal sulfide counter electrodes: such as Cu2S, MoS2, CoS, etc. Cu2S counter electrodes prepared by sulfidation of brass foil have a PCE of about 4.06% in CdS / CdSe / ZnS sensitized QDSSCs, but Cu2S has relatively poor resistance to polysulfide electrolyte corrosion and is easy to dissolve. In addition, the prepared electrode film has problems such as easy detachment and difficult encapsulation, resulting in insufficient long-term cycle stability. (3) Unmodified ternary metal sulfide counter electrodes: such as CuCo2S4, NiCo2S4, MnCo2S4, FeCo2S4, etc., which have adjustable chemical states and better electrochemical activity than binary metal sulfide counter electrodes. However, it has problems such as small specific surface area, relatively low electron transport rate, and slow catalytic reduction kinetics of polysulfide electrolytes, which limit the further improvement of battery performance. (4) Other modified (composite) counter electrodes: Some studies use carbon materials such as graphene and carbon nanotubes to modify metal sulfides. Although they can improve conductivity, the interface between carbon materials and metal sulfides is poor, and agglomeration is easy to occur. Moreover, it is impossible to effectively control the electronic structure of the material to suppress charge recombination.

[0004] Therefore, developing a low-cost counter electrode material with good catalytic performance is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a polyacid-modified Cu2MoS4 counter electrode, thereby overcoming the shortcomings of the prior art.

[0006] To achieve the objectives of the above invention, the present invention provides the following technical solution:

[0007] In one aspect, the present invention provides a method for preparing polyacid-modified Cu2MoS4 electrode materials, employing an in-situ synthesis method and a one-step solvothermal preparation technique to dope Cu2MoS4 materials with SiW. 11 Co; includes the following steps:

[0008] S1. Dissolve sodium molybdate and thioacetamide in ethylene glycol, then add SiW to the solution. 11 Co is dissolved, and finally Cu2O is added. The above mixed solution is ultrasonically treated at room temperature for 10-15 min to obtain a uniform dark brown suspension.

[0009] S2. After stirring for another 5 minutes, transfer the precursor suspension to a high-pressure reactor and carry out a solvothermal process for 22-24 hours.

[0010] S3. The reactor was cooled to room temperature. The final product was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then dried under vacuum to obtain SiW. 11 Co / Cu2MoS4 composite material.

[0011] In some embodiments, the mass ratio of sodium molybdate, thioacetamide, and Cu2O is 3:(6-12):(2-6).

[0012] In some embodiments, the SiW 11 The amount of Co added is 1%-3% of the mass of sodium molybdate.

[0013] In some embodiments, the temperature of the solvothermal process in S2 is 180-190 °C.

[0014] Secondly, this invention provides the application of the polyacid-modified Cu2MoS4 electrode material prepared by the above method in quantum dot-sensitized solar cells.

[0015] In some embodiments, the electrode material is fabricated into a counter electrode, specifically through the following steps:

[0016] Prepared SiW 11 Co / Cu2MoS4 composite powder was poured into a clean agate mortar, and ethyl cellulose, terpineol and anhydrous ethanol were added in sequence. The above substances were mixed evenly in the mortar and then continuously ground until the ethanol was completely evaporated to obtain a uniform viscous counter electrode slurry.

[0017] The electrode paste obtained above is coated onto the pretreated FTO by screen printing. After standing for 5 minutes, it is dried on a heating plate at 70-80 ℃. Finally, the dried electrode is placed in a high-temperature muffle furnace and annealed at 320-350 ℃ for 30-35 minutes. After cooling to room temperature, the final product is obtained.

[0018] In some embodiments, the heating rate is 1 °C min. -1 -2 ℃ min -1 .

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. High performance controllability: By changing the amount of polyacid doping, the surface morphology, Fermi level position and charge transfer resistance of the composite electrode can be flexibly controlled, adapting to different quantum dot sensitization systems, with strong universality, and the modification effect is better than existing carbon material modification schemes.

[0021] 2. Significant cost advantage: The preparation cost of polyacids and Cu2MoS4 is relatively low, and the total cost of composite counter electrodes is much lower than that of noble metal-based and carbon-based / metal compound composite counter electrodes. Moreover, it does not require expensive equipment and is suitable for large-scale production.

[0022] 3. Enhanced catalytic activity and stability: appropriate amount of SiW 11 The introduction of Co creates a rough structure on the surface of Cu2MoS4, increasing the number of active sites and the specific surface area. This results in catalytic performance and stability that are far superior to those of the unmodified Cu2MoS4 counter electrode.

[0023] 4. Simplified synthesis process: The preparation process is simplified by using a one-step solvothermal in-situ synthesis method, and uniform composite at the molecular level is achieved. Strong interactions are formed inside the composite material, and efficient electron transport channels are established, which significantly improves the efficiency of charge separation and transport. Attached Figure Description

[0024] Figure 1 SEM image of the unmodified Cu2MoS4 sample;

[0025] Figure 2 The following are SEM images of the synthesized samples in some embodiments of this application, wherein (a), (b), (c), and (d) correspond to Cu2MoS4-1, Cu2MoS4-2, Cu2MoS4-3, and Cu2MoS4-4, respectively.

[0026] Figure 3 This is a JV curve diagram based on QDSSCs with different electrode pairs. Detailed Implementation

[0027] To demonstrate the essential features and significant advancements of the present invention, the following embodiments further illustrate the implementation methods and effects.

[0028] 1. K6SiW 11 O 39 Co(II)(H2O) (SiW 11 Preparation of Co):

[0029] (1) Dissolve 1.9028 g of cobalt acetate hydrate (Co(CH3COO)2·4H2O) in 5 mL of deionized water (DI) to form a 380 g / L cobalt acetate aqueous solution.

[0030] (2) 2.8782 g of silicotungstic acid hydrate (H4SiW) 12 O 40 ∙xH2O, SiW 12 Dissolve the cobalt acetate in 15 mL of deionized water and heat to 85 °C. Add 720 µL of a cobalt acetate aqueous solution dropwise to the above solution and continue heating at 85 °C for 20 min. After cooling to room temperature, add 15 mL of acetone to the resulting precipitate, dissolve, and filter. Then continue adding acetone to the filtrate (5 mL each time) until no precipitate appears. Finally, evaporate the acetone at 65 °C and dry at 50 °C for 6 h to obtain the product.

[0031] 2. Preparation of Cu2O:

[0032] 1.7048 g of copper chloride hydrate (CuCl2·2H2O) was added to 1 L of deionized water, stirred until dissolved, and then stirred for 15 min at 55 °C. Subsequently, 100 mL of 2 M NaOH and 100 mL of 0.6 M ascorbic acid solution were added dropwise to the solution. After the addition was complete, the mixture was stirred continuously at room temperature for 3 h, then allowed to stand for 2 h, centrifuged, washed three times each with DI and ethanol, and dried at 60 °C for 8 h to obtain Cu2O.

[0033] 3. SiW 11 Preparation of Co / Cu2MoS4 composite material

[0034] SiW 11 The Co / Cu2MoS4 composite material was prepared by a one-step solvothermal method, as detailed in the examples.

[0035] Example 1:

[0036] SiW 11 The preparation method of Co polyacid modified Cu2MoS4 composite material is as follows:

[0037] S1. Dissolve 120 mg sodium molybdate (Na2MoO4・2H2O) and 240 mg thioacetamide (C2H5NS) in 60 mL of ethylene glycol, then add 1.2 mg of SiW to the solution. 11 Co was dissolved, and finally 80 mg of Cu2O was added to the solution. The mixture was then sonicated at room temperature for 10 min to obtain a uniform dark brown suspension.

[0038] S2. After stirring for 5 min, the precursor suspension was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor and subjected to a solvothermal process at 180 °C for 22 h.

[0039] S3. The reactor was then cooled to room temperature. The final product was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then dried in a vacuum oven at 50 °C for 6 h to obtain SiW. 11 Co / Cu2MoS4 composite material.

[0040] Example 2:

[0041] Unlike Example 1, SiW 11 The amount of Co added was 2.4 mg.

[0042] Example 3:

[0043] Unlike Example 1, SiW 11 The amount of Co added was 3.6 mg.

[0044] Example 4:

[0045] SiW 11 The preparation method of Co polyacid modified Cu2MoS4 composite material is as follows:

[0046] S1. Dissolve 120 mg sodium molybdate (Na2MoO4・2H2O) and 480 mg thioacetamide (C2H5NS) in 60 mL of ethylene glycol, then add 2.4 mg of SiW to the solution. 11 Co was dissolved, and finally 240 mg of Cu2O was added to the solution. The mixture was then sonicated at room temperature for 15 min to obtain a uniform dark brown suspension.

[0047] S2. After stirring for another 5 minutes, the precursor suspension was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor and subjected to a solvothermal process at 190 °C for 24 hours.

[0048] S3. The reactor was then cooled to room temperature. The final product was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then dried in a vacuum oven at 50 °C for 6 h to obtain SiW. 11 Co / Cu2MoS4 composite material.

[0049] Example 5:

[0050] SiW 11 The preparation method of Co polyacid modified Cu2MoS4 composite material is as follows:

[0051] S1. Dissolve 120 mg sodium molybdate (Na2MoO4・2H2O) and 320 mg thioacetamide (C2H5NS) in 60 mL of ethylene glycol, then add 2.4 mg of SiW to the solution. 11 Co was dissolved, and finally 160 mg of Cu2O was added to the solution. The mixture was then sonicated at room temperature for 15 min to obtain a uniform dark brown suspension.

[0052] S2. After stirring for another 5 minutes, the precursor suspension was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor and subjected to a solvothermal process at 185 °C for 24 hours.

[0053] S3. The reactor was then cooled to room temperature. The final product was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then dried in a vacuum oven at 50 °C for 6 h to obtain SiW. 11 Co / Cu2MoS4 composite material.

[0054] Comparative Example 1:

[0055] Unlike Example 1, SiW 11 The amount of Co added was 0 mg.

[0056] Comparative Example 2:

[0057] Unlike Example 1, SiW 11 The amount of Co added was 4.8 mg.

[0058] With SiW 11 With the mass percentage of Co / sodium molybdate as a variable, Examples 1-3 and Comparative Examples 1-2 synthesized five different proportions of X%SiW. 11 Co / Cu2MoS4 (X = 0, 1, 2, 3, 4) composite materials are defined as Cu2MoS4 (SiW) composite materials. 11 The amount of Co added was 0 mg), Cu2MoS4-1 (SiW 11 The amount of Co added was 1.2 mg), Cu2MoS4-2 (SiW11 The amount of Co added was 2.4 mg), Cu2MoS4-3 (SiW 11 The amount of Co added was 3.6 mg), Cu2MoS4-4 (SiW 11 The amount of Co added was 4.8 mg.

[0059] like Figure 1 As shown, the unmodified Cu2MoS4 sample exhibits a relatively smooth surface and a flattened decahedral microstructure of different sizes, while the SiW... 11 With an appropriate increase in the percentage of Co, the surface morphology of the sample becomes increasingly rough.

[0060] like Figure 2 As shown in (a)-(c), a rough surface structure can increase the active sites for catalytic reactions and increase the contact area between the electrolyte and the counter electrode, which is beneficial to promoting the transfer of electrons from the counter electrode film to the electrolyte in the external circuit, thereby accelerating the interfacial catalytic reduction reaction.

[0061] like Figure 2 As shown in (d), when the addition amount increases to 4%, the excess SiW 11 The addition of Co may disrupt the main catalytic crystal planes of the material, creating "deep electron traps" within the material. These traps then act as "electron trap filling sites," causing electrons from the external circuit to be trapped for extended periods, thereby inhibiting effective electron transfer and reducing the catalytic reduction of S at the electrode. n 2- The rate.

[0062] Comparative Example 3:

[0063] SiW 11 A method for preparing Co-modified Cu2MoS4 composite materials using polyoxometalates involves non-in-situ synthesis to dope Cu2MoS4 materials with SiW. 11 Co, the steps are as follows:

[0064] Directly use pre-synthesized SiW 11 Co and Cu2MoS4 are mixed, with SiW 11 A 2% (w / w) Co / Cu2MoS4 mixture was placed in a PTFE-lined stainless steel high-pressure reactor and subjected to a solvothermal process at 180 °C for 22 h. Afterward, the reactor was cooled to room temperature, and the final product was washed three times each with deionized water and anhydrous ethanol by centrifugation. It was then dried in a vacuum oven at 50 °C for 6 h to obtain in-situ synthesized SiW. 11 Co / Cu2MoS4 composite material.

[0065] Application example:

[0066] (a) Electrode preparation:

[0067] 1. SiW 11 Preparation of Co / Cu2MoS4 composite counter electrode

[0068] Weigh 0.2 g of each of the prepared Cu2MoS4-X (X = 0, 1, 2, 3, 4) and Cu2MoS4-2 (ex-situ) powder prepared in Comparative Example 3, and pour them into a clean agate mortar. Add 0.02 g of ethyl cellulose, 0.5 g of terpineol and 10 mL of anhydrous ethanol to each mortar in sequence. After the above substances are mixed evenly in the mortar, continue grinding until the ethanol is completely evaporated to obtain a uniform viscous electrode slurry.

[0069] The various slurries obtained above were coated onto the pretreated FTO using screen printing. After standing for 5 minutes, the electrodes were dried on a heating plate at 80 °C. Finally, the dried electrodes were placed in a high-temperature muffle furnace and heated at 320 °C (heating rate of 1 °C / min). -1 Annealing was continued for 30 minutes to further enhance the bonding between FTO and the film. After cooling to room temperature, catalysts with different counter electrodes were obtained.

[0070] 2. Preparation of FTO / TiO2 / CdS / CdSe photoanodes

[0071] (1) Weigh 2 g of titanium dioxide (P25) and place it into a clean ball mill jar containing agate grinding balls. Add 12 g of terpineol (mass ratio 1:6) and ball mill at room temperature for 10 h to obtain a viscous TiO2 slurry. Drop the obtained TiO2 slurry onto a fixed area of ​​FTO conductive glass. Use a suitable doctor blade to coat the slurry evenly and dry it on a heating plate at 70 ℃. The obtained TiO2 film is annealed in a muffle furnace at 450 ℃ for 35 min (heating rate 5 ℃ / min). -1 After cooling to room temperature, FTO / TiO2 is obtained.

[0072] (2) Deposition of quantum dots

[0073] The preparation of CdS-QDs as seed layers is usually carried out using the continuous ion layer adsorption and reaction (SILAR) technique.

[0074] First, 5 mmol of cadmium nitrate (Cd(NO3)2∙4H2O) was prepared into a 0.1 M methanol solution as the Cd... 2+ Source: Dissolve 5 mmol of sodium sulfide (Na₂S∙9H₂O) in a mixed solution of methanol and DI (volume ratio 1:1) to obtain 0.1 M S. 2-Source. Next, the calcined photoanode is vertically immersed in 0.1 M Cd... 2+ Deposited in the source for 2 min, then removed, rinsed with methanol, and dried with N2; subsequently, the film was placed vertically in a 0.1 M S... 2- The cells were immersed in the source for 2 minutes, then removed, washed with DI, and dried with N2. This process is called one SILAR deposition cycle. Finally, after multiple screenings, it was found that the assembled QDSSCs exhibited the best photoelectric performance when the above deposition cycle was 6 times.

[0075] The synthesis of CdSe-QDs was carried out by chemical bath deposition (CBD). The detailed preparation process is as follows: Anhydrous sodium sulfite (Na2SO3) and selenium powder (Se) were dissolved in DI under a N2 atmosphere at 98 °C and reacted under reflux for 10 h. After filtration, a 0.1 M Na2SeSO3 solution (solution A) was obtained. A certain amount of cadmium sulfate (CdSO4∙8 / 3H2O) and sodium hypotriacetate (N(CH2COONa)3, NTA) were weighed and prepared into a 0.03 M CdSO4∙8 / 3H2O solution (solution B) and a 0.2 M NTA solution (solution C), respectively. Solutions A, B and C were mixed evenly at a volume ratio of 1:1:1 and stirred continuously at room temperature for 20 min. The prepared FTO / TiO2 / CdS photoanode was vertically immersed in the above mixed solution and allowed to stand for deposition in a dark environment at 5 °C for 6 h. After removal, it was thoroughly rinsed with DI and dried with N2 to obtain FTO / TiO2 / CdS / CdSe.

[0076] In addition, SILAR was also used to deposit ZnS as a passivation layer for the photoanode, and the specific deposition process was similar to that of CdS. First, the FTO / TiO2 / CdS / CdSe photoanode was vertically immersed in a prepared 0.1 M zinc acetate (Zn(CH3COO)2∙2H2O) solution for 2 min. After removal, the electrode was rinsed with DI and dried with N2. Then, the electrode was vertically immersed in 0.1 M Na2S∙9H2O for 2 min. After completion, the surface residue was thoroughly rinsed with DI and dried with N2. This immersion process was defined as one cycle. After several trials, it was found that the battery assembled with the FTO / TiO2 / CdS / CdSe / ZnS photoanode exhibited optimal performance after alternating three cycles.

[0077] (II) Assembly and Performance Testing of QDSSCs

[0078] Using the Cu2MoS4-X and Cu2MoS4-2 (ex-situ) prepared above as counter electrodes, a "sandwich" type QDSSC device was assembled with FTO / TiO2 / CdS / CdSe / ZnS photoanode and polysulfide electrolyte. The photovoltaic performance (current density-voltage (JV) curve) of the QDSSCs was then tested. Photovoltaic performance was measured at AM1.5G, 100 mW / cm². 2 (Conducted under simulated sunlight conditions).

[0079] Table 1 shows the photovoltaic performance parameters of QDSSCs based on different counter electrodes.

[0080]

[0081] As shown in Table 1, the QDSSCs power conversion efficiency (PCE) of Cu2MoS4-1, Cu2MoS4-2, and Cu2MoS4-3 prepared in Examples 1-3 is increased by 8.1%, 18.3%, and 15.0% respectively compared with unmodified Cu2MoS4. This indicates that when SiW 11 When the Co addition amount is 2%, its modification effect on Cu2MoS4 is optimal, and its catalytic performance is the best, far superior to that of the unmodified Cu2MoS4 counter electrode. However, when SiW 11 When the Co addition reaches 4%, the catalytic performance decreases by 6.9% compared to the unmodified Cu2MoS4, and its catalytic performance is slightly lower than that of the unmodified Cu2MoS4 counter electrode.

[0082] If a synthesis followed by modification is adopted, SiW 11 The interaction between Co and Cu₂MoS₄ is relatively weak, resulting in relatively low electron transport efficiency and thus lower performance compared to equivalent SiW. 11 In-situ synthesis with Co addition.

[0083] Of course, the above embodiments of the present invention are merely illustrative examples and are not intended to limit the specific implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above examples. It is impossible to provide detailed examples of all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing polyacid-modified Cu2MoS4 electrode material, characterized in that, SiW was doped into Cu2MoS4 material using an in-situ synthesis method and a one-step solvothermal preparation technique. 11 Co; the SiW 11 Co specifically refers to K6SiW 11 O 39 Co(II)(H2O); Includes the following steps: S1. Dissolve sodium molybdate and thioacetamide in ethylene glycol, then add SiW 11 Co is dissolved, and finally Cu2O is added. The mixture is then ultrasonically treated at room temperature for 10-15 min to obtain a uniform dark brown suspension. The mass ratio of sodium molybdate, thioacetamide, and Cu2O is 3:(6-12):(2-6). The SiW... 11 The amount of Co added is 1%-3% of the mass of sodium molybdate; S2. After stirring for another 5 minutes, transfer the precursor suspension to a high-pressure reactor and carry out a solvothermal process for 22-24 hours. S3. The reactor was cooled to room temperature. The final product was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then dried under vacuum to obtain SiW. 11 Co / Cu2MoS4 composite material.

2. The preparation method according to claim 1, characterized in that, In S2, the temperature of the solvothermal process is 180-190°C.

3. The application of the polyacid-modified Cu2MoS4 electrode material prepared by any one of the preparation methods described in claims 1-2 in quantum dot sensitized solar cells.

4. The application as described in claim 3, characterized in that, The electrode material is fabricated into a counter electrode, and the specific steps are as follows: Prepared SiW 11 Co / Cu2MoS4 composite powder was poured into a clean agate mortar, and ethyl cellulose, terpineol and anhydrous ethanol were added in sequence. After being mixed evenly in the mortar, the mixture was continuously ground until the ethanol was completely evaporated to obtain a uniform viscous counter electrode slurry. The electrode paste obtained above is coated onto the pretreated FTO by screen printing. After standing for 5 minutes, it is dried on a heating plate at 70-80 ℃. Finally, the dried electrode is placed in a high-temperature muffle furnace and annealed at 320-350 ℃ for 30-35 minutes. After cooling to room temperature, the final product is obtained.

5. The application as described in claim 4, characterized in that, The heating rate is 1 °C / min. -1 -2 ℃ min -1 .

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