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

Abstract

The invention discloses a W-WN heterojunction composite material based on in-situ growth on carbon and a preparation method of the W-WN heterojunction composite material, and belongs to the technical field of counter electrode materials of dye-sensitized solar cells. The preparation method comprises the following steps: stirring and mixing NH3.H2O, deionized water and ethanol to form a uniform mixed solution; (NH4) 10H2 (W2O7) 6 is dissolved in the uniform mixed solution, and the uniform mixed solution is formed through stirring; adding dopamine hydrochloride powder into the uniformly mixed solution, uniformly stirring, and carrying out hydrothermal reaction; after the hydrothermal reaction is finished, cooling to room temperature, washing the precipitate, and drying; and calcining in a tubular argon atmosphere, and then cooling to room temperature to form the W-WN heterojunction composite material growing on carbon in situ. The composite material can be used as a counter electrode material for a dye-sensitized solar cell, and has more excellent photoelectric conversion efficiency.

Description

Technical Field

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

[0002] Solar energy is a clean and sustainable energy source. 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, research on dye-sensitized solar cells (DSSC) has made significant progress. It has a simple structure (a sandwich structure consisting of a photoanode, an electrolyte, and a counter electrode (CE)), is easy to install, and has low production costs. It can be used to power small electronic devices, and can also be combined with other energy storage technologies to build a hybrid energy system. The role of the counter electrode is to conduct electrons and at the same time transfer the Restore to / - . Therefore, the counter electrode usually exhibits the characteristics of low resistance and high catalytic activity, minimizing energy loss during electron transfer. Usually, the best choice for commercial counter electrode materials is the precious metal platinum (Pt), which has excellent charge transport and catalytic capabilities and can achieve high photoelectric conversion efficiency. However, the high cost and low reserves of platinum limit its widespread application. Therefore, it is of great value to explore low-cost and efficient counter electrodes. For this purpose, a W-WN heterojunction composite material based on in-situ growth on carbon and a preparation method thereof are proposed. Summary of the invention

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

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for preparing a W-WN heterojunction composite material based on in-situ growth on carbon comprises the following steps:

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

[0007] NH4 10 H2(W2O7)6 is dissolved in the uniform mixed solution, and stirred to form a uniform mixed solution;

[0008] Add dopamine hydrochloride powder to the uniform mixture, stir evenly, and then perform a hydrothermal reaction;

[0009] After the hydrothermal reaction is completed, the mixture is cooled to room temperature, and the precipitate is washed and dried;

[0010] After calcination in an argon atmosphere and then cooling to room temperature, a W-WN heterojunction composite material grown in situ on carbon was formed.

[0011] Furthermore, the heating temperature of the hydrothermal reaction was 160° C. and the temperature was kept for 8 hours.

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

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

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

[0015] Furthermore, the calcination temperature was 3 °C·min -1 The temperature was raised at a slow heating rate and kept at 850 °C for 2 h.

[0016] Furthermore, (NH4) 10 The stirring temperature when H2(W2O7)6 was dissolved and when dopamine hydrochloride powder was added to the mixture was 30°C.

[0017] The W-WN heterojunction composite material based on in-situ growth on carbon is prepared using the above-mentioned method for preparing the W-WN heterojunction composite material based on in-situ growth on carbon.

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

[0019] The above-mentioned W-WN heterojunction composite material based on in-situ growth on carbon is used as a counter electrode in the preparation of dye-sensitized solar cells.

[0020] Beneficial effects of the present invention:

[0021] 1. The present invention can intuitively find through the transmission electron microscope (TEM) of the cross section that the W-WN heterojunction composite material grown in situ on the prepared carbon is conducive to the rapid transmission of charge, and the iodine electrolyte can fully contact the counter electrode material. In addition, nitrogen-doped carbon can accelerate the overall charge transmission and help reduce I 3- The adsorption barrier of I - / I 3- Circulate the catalytic process to speed up the reaction kinetics.

[0022] 2. The present invention uses the prepared W-WN heterojunction composite material based on in-situ growth on carbon as a dye-sensitized solar cell counter electrode (CE) to study its catalytic reduction activity (IRR) of triiodide. The results show that the W-WN@NC counter electrode exhibits a high power conversion efficiency (PCE) of 8.87%, exceeding the commercial Pt electrode (7.91%). The mechanism is to enhance the catalytic ability at the interface through the synergistic effect of the W-WN heterojunction and nitrogen-doped carbon, which not only accelerates the reaction kinetics, but also accelerates the catalytic redox reaction of triiodide. The present invention is based on the W-WN heterojunction composite material grown in situ on carbon as the counter electrode material to maximize the active sites on the interface and accelerate the electron transfer of the heterojunction. Therefore, the strategy of combining the W-WN heterojunction with nitrogen-doped carbon effectively improves the photoelectric conversion performance of the DSSC and further opens up the research prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

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

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

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

[0028] Figure 5 is the JV curve of the photocurrent density test of the composite material prepared in Example 1 and the comparative material under the solar simulator;

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

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing a W-WN heterojunction composite material based on in-situ growth 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 was stirred on a magnetic stirring table at room temperature for 30 min to form a homogeneous mixture;

[0034] (2) 0.3 g (NH4) 10 H2(W2O7)6 was dissolved in the above homogeneous mixture and stirred on a magnetic table at a constant temperature of 30℃ for 60min to form a homogeneous mixture;

[0035] (3) adding 300 mg of dopamine hydrochloride powder to the above uniform mixture, and stirring on a magnetic table at a constant temperature of 30° C. for 360 min;

[0036] (4) transferring the solution obtained in step (3) into a Teflon-lined stainless steel autoclave, hydrothermally reacting the mixture to 160° C. and keeping the temperature for 8 hours;

[0037] (5) After the hydrothermal reaction is completed, the precipitate is cooled to room temperature, washed several times with deionized water and ethanol, and dried at 50°C with a vacuum degree maintained below 60 Pa;

[0038] (6) In a tube furnace, high purity argon (99.999%) atmosphere was used at 3 °C min -1 The temperature was raised at a slow heating rate and kept at 850°C for 2 hours and then cooled to room temperature to form a W-WN heterojunction composite material grown in situ on carbon.

[0039] Example 2

[0040] In this example, the samples prepared in Example 1 were characterized and their photoelectric conversion performance was studied.

[0041] 1. Microscopic state of the sample

[0042] The transmission electron microscope (TEM) image of the sample prepared in Example 1 is as follows: Figure 1 Place, Figure 1The morphological characteristics of nitrogen-doped carbon-coated W-WN heterojunctions are clearly shown in the figure, showing a regular nanotube structure with a hollow internal structure and a diameter of about 150nm. Figure 2 As shown, Figure 2 It can be clearly seen that there are two different lattice fringes in the W-WN heterojunction; the sample energy dispersive x-ray (EDX) element mapping is shown in Figure 3 As shown, Figure 3 It can be clearly seen that W, N, and C are evenly distributed in the nanostructured carbon nanotubes. High-resolution transmission electron microscopy (HRTEM) combined with EDX element diffraction can prove that W-WN@NC is successfully synthesized.

[0043] 2. Structural analysis of samples

[0044] The X-ray diffraction pattern of the sample is as follows Figure 4 As shown in the figure, the results show the diffraction peaks of pure W-WN@NC, pure WN@NC and pure W@NC respectively. It can be found that W-WN@NC contains two diffraction peaks of WN@NC and W@NC. This further reflects that the W-WN heterojunction has been successfully synthesized. In addition, it can be seen that there is an obvious carbon peak at about 25 degrees in the XRD spectrum, which can also further prove that W-WN@NC was successfully synthesized.

[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, 100 mW cm -2 ) was used to test the photocurrent density-voltage (JV) curve. Figure 5 This reflects the different JV curve changes of DSSC devices assembled with counter electrodes made of different materials (W@NC, WN@NC, W-WN@NC and Pt). Figure 5 It can be seen that 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 high to low, namely W-WN@NC (8.87%), WN@NC (7.20%), W@NC (6.23%) and Pt (7.91%). Therefore, W-WN@NC achieves a higher PCE value as a counter electrode of DSSC, exceeding the given comparison material and commercial pure Pt electrode.

[0048] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, 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 above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a W-WN heterojunction composite material based on in-situ growth on carbon, characterized in that: The following steps are involved: NH3·H2O, deionized water and ethanol were stirred and mixed to form a uniform mixed solution; NH4 10 H2(W2O7)6 is dissolved in the uniform mixed solution, and stirred to form a uniform mixed solution; Add dopamine hydrochloride powder to the uniform mixture, stir evenly, and then perform a hydrothermal reaction; After the hydrothermal reaction is completed, the mixture is cooled to room temperature, and the precipitate is washed and dried; After calcination in an argon atmosphere and then cooling to room temperature, a W-WN heterojunction composite material grown in situ on carbon was formed.

2. The method for preparing a W-WN heterojunction composite material based on in-situ growth on carbon according to claim 1, characterized in that: The heating temperature of the hydrothermal reaction was 160°C and the temperature was kept for 8 hours.

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

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

5. The method for preparing a W-WN heterojunction composite material based on in-situ growth on carbon according to claim 1, characterized in that: The drying temperature was 50°C and the vacuum degree was 60Pa.

6. The method for preparing a W-WN heterojunction composite material based on in-situ growth on carbon according to claim 1, characterized in that: During calcination, the temperature was 3℃·min -1 The temperature was raised at a slow heating rate and kept at 850 °C for 2 h.

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

8. A W-WN heterojunction composite material based on in-situ growth on carbon, characterized in that: The composite material is prepared by the method for preparing a W-WN heterojunction composite material based on in-situ growth on carbon as described in any one of claims 1 to 7.

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

10. Use of the W-WN heterojunction composite material based on in-situ growth on carbon as claimed in claim 8 as a counter electrode in the preparation of a dye-sensitized solar cell.

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