W-wn heterojunction composite material based on in-situ growth on carbon and preparation method thereof

Abstract

The application discloses a W-WN heterojunction composite material based on in-situ growth on carbon and a preparation method thereof, and belongs to the technical field of dye-sensitized solar cell counter electrode materials. 10 H2(W2O7)6 is dissolved in the uniform mixed solution, and stirring is performed to form a uniform mixed solution; dopamine hydrochloride powder is added into the uniform mixed solution, and stirring is uniformly performed, and then hydrothermal reaction is performed; after the hydrothermal reaction is completed, cooling is performed to room temperature, the precipitate is washed and then dried; calcination is performed under a tube argon atmosphere, and then cooling is performed to room temperature, so that the W-WN heterojunction composite material based on in-situ growth on carbon is formed. The composite material can be used as a counter electrode material for a dye-sensitized solar cell, and has excellent photoelectric conversion efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of dye-sensitized solar cell counter electrode materials, and particularly relates to a W-WN heterojunction composite material based on in-situ growth on carbon and a preparation method thereof. BACKGROUND

[0002] Solar energy is a clean and sustainable energy. Large-scale utilization of solar energy can effectively alleviate the world's energy shortage and pollution problems. Therefore, research on solar cells is in full swing. At present, the research on dye-sensitized solar cells (DSSC) has made great progress. It has a simple structure (a sandwich structure composed of a photoanode, an electrolyte and a counter electrode (CE)), is easy to install and has low production cost. It can be used to power small electronic devices or combined with other energy storage technologies to build a hybrid energy system. The role of the counter electrode is to conduct electrons and simultaneously reduce the electrolyte to / - Therefore, the counter electrode usually exhibits low resistance and high catalytic activity, which minimizes energy loss during electron transfer. Generally, the best choice of commercial counter electrode material is the noble metal platinum (Pt), which has excellent charge transport capacity and catalytic capacity, and can achieve high photoelectric conversion efficiency. However, the high cost and low reserves of platinum limit its wide application. Therefore, it is of great value to explore low-cost and efficient counter electrodes, and for this purpose, a W-WN heterojunction composite material based on in-situ growth on carbon and a preparation method thereof are proposed. SUMMARY

[0003] In view of the deficiencies of the prior art, the purpose of the present application is to provide a W-WN heterojunction composite material based on in-situ growth on carbon and a preparation method thereof, which solves the problems in the prior art.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] The preparation method of the W-WN heterojunction composite material based on in-situ growth on carbon comprises the following steps:

[0006] Stir and mix NH3·H2O, deionized water and ethanol to form a uniform mixed solution;

[0007] Dissolve (NH4) 10 H2(W2O7)6 in the uniform mixed solution and stir to form a uniform mixed solution;

[0008] Add dopamine hydrochloride powder to the above uniform mixed solution, stir uniformly, and then perform a hydrothermal reaction;

[0009] After the hydrothermal reaction is completed, cool to room temperature, wash the precipitate and dry.

[0010] After calcination under the argon atmosphere, the W-WN heterojunction composite material in-situ grown on carbon is formed after being cooled to room temperature.

[0011] Further, the heating temperature of the hydrothermal reaction is 160 DEG C, and the holding time is 8 hours.

[0012] Further, the hydrothermal reaction is carried out in a Teflon-lined stainless steel autoclave.

[0013] Further, the precipitate is washed with deionized water and ethanol.

[0014] Further, the drying temperature is 50 DEG C, and the vacuum degree is 60 Pa.

[0015] Further, the slow heating rate is 3 DEG C per minute during calcination, and the holding time is 2 hours at 850 DEG C. -1

[0016] Further, the stirring temperature is 30 DEG C when (NH4) 10 H2(W2O7)6 is dissolved and when the dopamine hydrochloride powder is added into the mixture.

[0017] The W-WN heterojunction composite material in-situ grown on carbon is prepared by using the above-mentioned preparation method of the W-WN heterojunction composite material in-situ grown on carbon.

[0018] The dye-sensitized solar cell has the above-mentioned W-WN heterojunction composite material in-situ grown on carbon as the counter electrode.

[0019] The above-mentioned W-WN heterojunction composite material in-situ grown on carbon is applied as the counter electrode in the preparation of the dye-sensitized solar cell.

[0020] The beneficial effects of the present application are as follows:

[0021] 1、The W-WN heterojunction composite material in-situ grown on carbon can be directly found by the transmission electron microscope (TEM) of the cross section, which is beneficial to the rapid transmission of the electric charge, and the iodine-based electrolyte can be fully contacted with the counter electrode material. 3- In addition, the nitrogen-doped carbon can accelerate the overall charge transmission, which helps to reduce the adsorption potential barrier of I - / I 3- cycle catalytic process and accelerate the reaction kinetics.

[0022] ​2, The application studies the catalytic reduction activity (IRR) of triiodide of the prepared W-WN heterojunction composite material based on in-situ growth on carbon as a dye-sensitized solar cell counter electrode (CE). The results show that the W-WN@NC counter electrode exhibits a high power conversion efficiency (PCE) of 8.87%, which exceeds that of a commercial Pt electrode (7.91%). The mechanism is that the W-WN heterojunction and nitrogen-doped carbon synergistically enhance the catalytic ability at the interface, which not only accelerates the reaction kinetics, but also speeds up the catalytic triiodide redox reaction. The application maximizes the active sites on the interface and accelerates the electron transfer of the heterojunction by using the W-WN heterojunction composite material based on in-situ growth on carbon as a counter electrode material, therefore, the strategy of combining W-WN heterojunction and nitrogen-doped carbon effectively improves the DSSC photoelectric conversion performance, and further opens up the research prospects. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below, and obviously, other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0024] Figure 1 is a transmission electron microscope (TEM) image of the composite material prepared in Example 1;

[0025] Figure 2 is a high-resolution transmission electron microscope (HRTEM) image of the composite material prepared in Example 1;

[0026] Figure 3 is a Mapping image of the composite material prepared in Example 1;

[0027] Figure 4 is an X-ray diffraction (XRD) pattern of the composite material prepared in Example 1;

[0028] Figure 5 is a J-V curve of the light current density test of the composite material prepared in Example 1 and a comparative material under a solar simulator;

[0029] Figure 6 is the PCE value of the composite material prepared in Example 1 and W@NC, WN@NC and Pt electrode. DETAILED DESCRIPTION

[0030] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0031] Embodiment 1

[0032] The preparation method of the W-WN heterojunction composite material grown in-situ on carbon comprises the following steps:

[0033] (1) a mixed solution of 0.5 mL of NH3·H2O, 25 mL of deionized water and 60 mL of ethanol is stirred at room temperature on a magnetic stirring table for 30 min to form a uniform mixed solution;

[0034] (2) 0.3 g of (NH4) 10 H2(W2O7)6 is dissolved in the above uniform mixed solution, and the uniform mixed solution is stirred on a magnetic table at 30℃ for 60 min;

[0035] (3) 300 mg of dopamine hydrochloride powder is added to the above uniform mixed solution, and the mixture is stirred on a magnetic table at 30℃ for 360 min;

[0036] (4) the solution obtained in step (3) is transferred to a Teflon-lined stainless steel autoclave, and hydrothermal reaction is carried out at 160℃ for 8 hours;

[0037] (5) after the hydrothermal reaction is completed, the solution is cooled to room temperature, the precipitate is washed with deionized water and ethanol several times, and drying is carried out at 50℃ under a vacuum degree of 60 Pa or less;

[0038] (6) the temperature is slowly increased at a rate of 3℃·min -1 -1 under the condition of high-purity argon (99.999%) atmosphere in a tube furnace, and the temperature is kept at 850℃ for 2 hours, and then the temperature is decreased to room temperature to form the W-WN heterojunction composite material grown in-situ on carbon.

[0039] Embodiment 2

[0040] In this embodiment, the sample prepared in embodiment 1 is characterized and the photoelectric conversion performance is studied

[0041] 1. Microscopic state of the sample

[0042] The transmission electron microscope (TEM) image of the sample prepared in embodiment 1 is as Figure 1 Figure 1 ​The sample clearly shows the morphological characteristics of the nitrogen-doped carbon-coated W-WN heterojunction, exhibiting a regular nanotube structure with a hollow internal morphology and a tube diameter of approximately 150 nm. High-resolution transmission electron microscopy (HRTEM) images of the sample are shown below. Figure 2 As shown, Figure 2 It is clearly visible that the W-WN heterostructure exhibits two different lattice fringes; the energy-dispersive X-ray (EDX) elemental mapping of the sample is as follows: Figure 3 As shown, Figure 3 The W, N, and C atoms are clearly uniformly distributed in the NC. High-resolution transmission electron microscopy (HRTEM) combined with EDX elemental diffraction can prove that W-WN@NC was successfully synthesized.

[0043] 2. Structural analysis of the sample

[0044] The X-ray diffraction pattern of the sample is as follows Figure 4 As shown in the figure, the diffraction peaks of pure W-WN@NC, pure WN@NC, and pure W@NC are displayed respectively. It can be observed that W-WN@NC contains both WN@NC and W@NC diffraction peaks. This further reflects the successful synthesis of the W-WN heterostructure. Furthermore, a distinct carbon peak is observed in the XRD pattern around 25 degrees, which further confirms the successful synthesis of W-WN@NC.

[0045] 3. Analysis of the photocurrent density curve of the sample

[0046] The photoelectric conversion process of dye-sensitized solar cells (DSSCs) is carried out under fixed illumination conditions (AM 1.5, 100mW cm⁻¹). -2 The photocurrent density-voltage (JV) curve was tested. Figure 5 This reflects the different JV curve changes produced by assembling DSSC devices with counter electrodes made of different materials (W@NC, WN@NC, W-WN@NC, and Pt). Figure 5 As can be seen, the W-WN@NC heterostructure achieves the best photoelectric conversion performance.

[0047] Figure 6 The high power conversion efficiency (PCE) of each material is shown, from highest to lowest: W-WN@NC (8.87%), WN@NC (7.20%), W@NC (6.23%), and Pt (7.91%). Therefore, W-WN@NC achieves a high PCE value as the counter electrode for DSSC, exceeding that of the given comparative materials and commercially available pure Pt electrodes.

[0048] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0049] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for preparing W-WN heterojunction composite materials based on in-situ growth on carbon, characterized in that, Includes the following steps: NH3·H2O, deionized water and ethanol are stirred and mixed to form a homogeneous mixture; (NH4) 10 H2(W2O7)6 is dissolved in the homogeneous mixture and stirred to form a homogeneous mixture; Add dopamine hydrochloride powder to the above homogeneous mixture, stir well, and then carry out a hydrothermal reaction. After the hydrothermal reaction is complete, the mixture is cooled to room temperature, and the precipitate is washed and dried. The material was calcined in a tube under an argon atmosphere and then cooled to room temperature to form a W-WN heterojunction composite material grown in situ on carbon. Calcination at 3℃·min -1 The temperature was increased at a slow rate and held at 850℃ for 2 hours.

2. The method for preparing W-WN heterojunction composite materials based on in-situ carbon growth according to claim 1, characterized in that, The hydrothermal reaction was heated to 160℃ and held at that temperature for 8 hours.

3. The method for preparing W-WN heterojunction composite materials based on in-situ carbon growth according to claim 1 or 2, characterized in that, The hydrothermal reaction was carried out in a high-pressure reactor lined with Teflon stainless steel.

4. The method for preparing W-WN heterojunction composite materials based on in-situ carbon growth according to claim 1, characterized in that, The precipitate was washed with deionized water and ethanol.

5. The method for preparing W-WN heterojunction composite materials based on in-situ carbon growth according to claim 1, characterized in that, The drying temperature is 50℃ and the vacuum degree is 60 Pa.

6. The method for preparing W-WN heterojunction composite materials based on in-situ carbon growth according to claim 1, characterized in that, (NH4) 10 The stirring temperature was 30℃ when H2(W2O7)6 was dissolved and when dopamine hydrochloride powder was added to the mixture.

7. A W-WN heterojunction composite material based on in-situ carbon growth, characterized in that, It was prepared using the preparation method of W-WN heterojunction composite material based on in-situ growth on carbon as described in any one of claims 1-6.

8. A dye-sensitized solar cell, characterized in that, Its counter electrode is the W-WN heterojunction composite material based on in-situ carbon growth as described in claim 7.

9. The application of the W-WN heterojunction composite material based on in-situ carbon growth as a counter electrode in the fabrication of dye-sensitized solar cells, as described in claim 7.

Images