Preparation method of bimetallic hole transport layer composite photoanode, product and application of product in solar-driven photoelectrochemical desalination

Abstract

The invention relates to the field of new energy materials, in particular to a preparation method of a bimetallic hole transport layer composite photo-anode, a product and application of the product in solar-driven photoelectrochemical desalination. The preparation method of the bimetallic hole transport layer composite photo-anode comprises the following steps: dissolving 2-methylimidazole, a Co source, a Ni source and polyvinylpyrrolidone in water to prepare a Ni-Co-MOF precursor solution; a BiVO4 thin film is soaked in the Ni-Co-MOF precursor solution to be subjected to in-situ growth, and Ni-Co-MOF / BiVO4 is obtained; and the Ni-Co-MOF / BiVO4 is calcined to obtain the bimetal hole transport layer composite photoanode. Through loading of the Ni-Co bimetallic hole transport layer, photocorrosion of the composite photo-anode is efficiently protected, effective separation and transfer of photo-generated electron-hole pairs of the photo-anode are achieved, and the photoelectric conversion efficiency and the photoelectric desalination performance are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of new energy materials, and in particular to a preparation method and product of a bimetallic hole transport layer composite photoanode and its application in solar-driven photoelectrochemical desalination. Background Art

[0002] Water is the source of life and a core element of sustainable social development. It is estimated that by 2030, about 47% of the world's population will live in areas with severe water shortages. At the same time, the pollution of freshwater resources has further exacerbated the water shortage crisis. The global water shortage and the demand for desalination technology are becoming increasingly urgent. There are currently a variety of desalination technologies, including multi-stage flash evaporation, multi-effect distillation, electrodialysis, etc. These methods generally have problems of high cost, high energy consumption and secondary pollution. For example, in reverse osmosis technology, the consumption of electricity accounts for 50% of the total cost; while the cost of electricity and heat energy in multi-step flash evaporation and multi-effect distillation accounts for ~77% and ~66% respectively.

[0003] As a clean and sustainable energy source, solar energy has great development potential. Solar-driven photoelectrochemical desalination technology, which combines solar energy with photoelectrochemistry, is an emerging desalination technology that achieves zero electricity consumption and becomes an important way to solve the above problems.

[0004] The core of solar-driven photoelectrochemical desalination technology is the photoelectrode. However, the photoelectrodes in the existing technology generally have problems such as photocorrosion, low photoelectric conversion efficiency, and low photoelectric desalination performance. Summary of the invention

[0005] Based on the above content, the present invention provides a preparation method and product of a bimetallic hole transport layer composite photoanode and its application in solar-driven photoelectrochemical desalination.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a method for preparing a bimetallic hole transport layer composite photoanode, comprising the following steps:

[0008] Dissolve 2-methylimidazole, Co source, Ni source and polyvinyl pyrrolidone in water to prepare a Ni-Co-MOF precursor solution;

[0009] Immersing the BiVO4 thin film in the Ni-Co-MOF precursor solution for in-situ growth to obtain Ni-Co-MOF / BiVO4;

[0010] The Ni-Co-MOF / BiVO4 is calcined to obtain the bimetallic hole transport layer composite photoanode.

[0011] The second technical solution of the present invention is a bimetallic hole transport layer composite photoanode prepared by the above-mentioned preparation method.

[0012] The third technical solution of the present invention is the application of the above-mentioned bimetallic hole transport layer composite photoanode in solar-driven photoelectrochemical desalination.

[0013] The fourth technical solution of the present invention is a photoelectrochemical desalination system, which uses the bimetallic hole transport layer composite photoanode as the photoanode.

[0014] Solar-driven photoelectrochemical desalination technology, which combines solar energy with photoelectrochemistry, is an emerging desalination technology. Solar-driven photoelectrochemical desalination technology is an emerging technical method for removing salt from salt water using solar energy without an external bias. The present invention constructs a bimetallic hole transport layer composite photoanode that matches the energy level of perovskite ferroelectric (PF) semiconductor materials, promotes the separation and transfer of photogenerated electron-hole pairs through a porous bimetallic hole transport layer, and slows down the recombination of electrons and holes. The bimetallic hole transport layer can effectively protect the photoelectrode from photocorrosion. The stability of the photocurrent and desalination system is significantly improved. The efficient and stable photoelectrochemical desalination system has the ability to store energy and desalinate salt water, and has broad development prospects and application potential.

[0015] The core of solar-driven photoelectrochemical desalination technology is the photoelectrode. The present invention realizes solar-driven photoelectrochemical desalination without consuming electrical energy by constructing a bimetallic hole transport layer composite photoanode. It is a green, environmentally friendly, efficient and clean photoelectrochemical desalination method at room temperature and pressure.

[0016] The present invention discloses the following technical effects:

[0017] The present invention constructs a bimetallic hole transport layer composite photoanode (NiO@Co3O4 / BiVO4) by an in-situ growth method. The method of the present invention is simple and easy to be promoted and applied in industrialization.

[0018] The loading of the Ni-Co bimetallic hole transport layer in the bimetallic hole transport layer composite photoanode of the present invention effectively protects the composite photoanode from photocorrosion, realizes the effective separation and transfer of photogenerated electron-hole pairs in the NiO@Co3O4 / BVO photoanode, and significantly improves the photoelectric conversion efficiency and photoelectric desalination performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is the SEM image of the dual-metal hole transport layer composite photoanode BCN-120 prepared in Example 1.

[0021] Figure 2 This is a performance test diagram of the dual-metal hole transport layer composite photoanode BCN-120 prepared in Example 1. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0027] One of the technical solutions of the present invention is a method for preparing a bimetallic hole transport layer composite photoanode, comprising the following steps:

[0028] Dissolve 2-methylimidazole, Co source, Ni source and polyvinyl pyrrolidone in water to prepare a Ni-Co-MOF precursor solution;

[0029] Immersing the BiVO4 thin film in the Ni-Co-MOF precursor solution for in-situ growth to obtain Ni-Co-MOF / BiVO4;

[0030] The Ni-Co-MOF / BiVO4 is calcined to obtain the bimetallic hole transport layer composite photoanode.

[0031] In some specific embodiments of the present invention, the preparation method of the Ni-Co-MOF precursor solution is as follows:

[0032] Dissolve 2-methylimidazole in water to obtain solution A;

[0033] Dissolve the Co source and polyvinyl pyrrolidone in water, and add the Ni source to obtain solution B;

[0034] The solution A and the solution B are mixed evenly to obtain a Ni-Co-MOF precursor solution.

[0035] In a preferred embodiment of the present invention, the molar ratio of the Co source to the Ni source is 1:4-4:1 (more preferably 1:1); the molar ratio of the 2-methylimidazole to the Co source is 10:1; and the ratio of the Co source to the polyvinyl pyrrolidone is 0.002 mol:30 mg.

[0036] In a preferred embodiment of the present invention, the concentration of the Co source in the Ni-Co-MOF precursor solution is 0.025 mol / L.

[0037] In a preferred embodiment of the present invention, the Co source is Co(NO3)2·6H2O; the Ni source is Ni(NO3)2·6H2O.

[0038] In a preferred embodiment of the present invention, the in-situ growth is specifically: standing at room temperature for 80-140 minutes.

[0039] In a preferred embodiment of the present invention, the calcination is specifically: calcination at 450° C. for 2 hours under a nitrogen atmosphere.

[0040] In the present invention, if the calcination temperature is too low, Ni-Co-MOF cannot be transformed into NiO@Co3O4; if the calcination temperature is too high, the BiVO4 film decomposes. If the calcination temperature is too high or too low, the performance of the prepared bimetallic hole transport layer composite photoanode will be affected.

[0041] In a preferred embodiment of the present invention, before immersing the BiVO4 film in the Ni-Co-MOF precursor solution, the step of stirring and cleaning the BiVO4 film with a 0.1M NaOH solution for 30 minutes (rotation speed 100 r / min) is also included.

[0042] The purpose of washing the BiVO4 film with 0.1M NaOH solution is to form a porous structure.

[0043] By immersing the BiVO4 film in a Ni-Co-MOF precursor solution at room temperature for in-situ growth, the Ni-Co-MOF precursor is deposited on the surface of the BiVO4 film, thereby achieving the decoration of BiVO4 with Ni-Co-MOF nanosheets.

[0044] In some specific embodiments of the present invention, the BiVO4 thin film is prepared by electrodeposition and thermal annealing, comprising the following steps:

[0045] 0.02 mol KI was dissolved in 50 mL deionized water, and the pH value was adjusted to about 1.7 by dropping HNO3 solution to obtain KI solution; 0.002 mol Bi(NO3)2·5H2O was added to the KI solution and stirred, which was marked as solution A; 0.005 mol p-benzoquinone was dissolved in 20 mL anhydrous ethanol and stirred continuously, which was solution B; solution B was added to solution A to form a uniform mixture; then nanostructured BiOI was electrochemically deposited on the surface of the FTO substrate at a potential of -0.1 V (relative to Ag / AgCl); after the deposition was completed, it was washed and dried to obtain a BiOI film; 0.0006 mol VO(acac)2 was dissolved in 3 mL DMSO and coated on the BiOI film; the BiOI film was annealed at 450°C for 2 hours and then cooled to room temperature to obtain a BiVO4 film. The BiVO4 film prepared by this method has a coral-like porous structure.

[0046] The second technical solution of the present invention is a bimetallic hole transport layer composite photoanode prepared by the above-mentioned preparation method.

[0047] The third technical solution of the present invention is the application of the above-mentioned bimetallic hole transport layer composite photoanode in solar-driven photoelectrochemical desalination.

[0048] The fourth technical solution of the present invention is a photoelectrochemical desalination system, which uses the bimetallic hole transport layer composite photoanode as the photoanode.

[0049] In the photoelectrochemical desalination system (device), the NiO@Co3O4 / BVO prepared by the present invention was used as a photoanode. Under zero bias, with light as the driving force, a 3.01 mA / cm 2 The initial photocurrent and 88.76μg / (cm 2 The salt removal rate of pure BiVO4 is 37.05μg / (cm 2 ·min). By using the current desalination system, the salt concentration of high-concentration brine can be reduced from 3227ppm to 173ppm in application, and the solar desalination capacity of the photoanode is 0.231μmol / J. The present invention provides a feasible and effective method for developing long-term stable and efficient solar-driven photoelectrochemical desalination technology.

[0050] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0051] The chemicals used in the embodiments of the present invention are all analytically pure: bismuth (III) nitrate pentahydrate (Aladdin, 99.0%), potassium iodide (Aladdin, 99.0%), p-benzoquinone (Macklin, 99.0%), nitric acid (Sinopharm, 65% to 68%), anhydrous ethanol (Macklin, 100%), vanadium acetylacetonate (Aladdin, 98%), dimethyl sulfoxide (Macklin, 99.8%), cobalt (II) nitrate hexahydrate (Macklin, 99.0%), nickel (II) nitrate hexahydrate (Macklin, 99.0%), 2-methylimidazole (Macklin, 98.0%), N-methylpyrrolidone (Macklin, 99%), polyvinylidene fluoride (Macklin, 99.0%), polyvinylpyrrolidone (PVPK-30), sodium hydroxide (Macklin, 95.0%), and sodium sulfate (Macklin, 99.0%).

[0052] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0053] Example 1

[0054] (1) Preparation of BVO (BiVO4) photoanode

[0055] After ultrasonic treatment of FTO substrate (3.0 cm × 3.0 cm) in a mixture of acetone, ethanol and deionized water (1:1:1) for 30 min, the FTO was cleaned with deionized water and placed in anhydrous ethanol for later use. First, 0.02 mol KI was dissolved in 50 mL deionized water, and the pH value of the KI solution was adjusted to about 1.7 by dropping HNO3 solution. 0.002 mol Bi(NO3)2·5H2O was added to the KI solution and stirred, which was marked as solution A. 0.005 mol p-benzoquinone was dissolved in 20 mL anhydrous ethanol and stirred continuously, which was referred to as solution B. Solution B was added to solution A to form a uniform mixture. Secondly, nanostructured BiOI was electrochemically deposited on the surface of the FTO substrate at a potential of -0.1 V (relative to Ag / AgCl). After the deposition was completed, the formed BiOI film was rinsed three times with deionized water and anhydrous ethanol, respectively, and then dried at 80°C. Finally, 0.0006 mol VO(acac)2 was dissolved in 3 mL DMSO and coated on the BiOI film. The BiOI film was annealed at 450 °C for 2 h and then cooled to room temperature. The sample was washed with 0.1 M NaOH solution to obtain a porous BVO film.

[0056] (2) Preparation of NiO@Co3O4 / BiVO4 bimetallic hole transport layer composite photoanode

[0057] First, 0.02 mol C4H6N2 was dissolved in 40 mL of deionized water as solution A. At the same time, 0.002 mol Co(NO3)2·6H2O and 30 mg of PVP were dissolved in 40 mL of deionized water, and 0.002 mol of Ni(NO3)2·6H2O was added thereto as solution B. Solution A and solution B were mixed and stirred for 60 min to form a Ni-Co-MOF precursor solution. Secondly, the porous BVO film prepared in step (1) was immersed in the Ni-Co-MOF precursor solution for a certain period of time (80 min, 100 min, 120 min, and 140 min, respectively) at room temperature for in-situ growth to obtain sheet-like Ni-Co-MOF / BiVO4. Finally, the flaky Ni-Co-MOF / BiVO4 film was calcined at 450 °C in N2 atmosphere for 2 h to obtain the Ni-Co-MOF-derived bimetallic hole transport layer composite photoanode NiO@Co3O4 / BiVO4, labeled as BCN-x (x represents the time of in situ growth).

[0058] Figure 1 This is a SEM image of the double metal hole transport layer composite photoanode BCN-120 prepared in Example 1. Figure 1 It can be seen that the NiO@Co3O4 bimetallic hole transport layer is successfully grown on the BiVO4 surface.

[0059] Figure 2 This is a performance test diagram of the double metal hole transport layer composite photoanode BCN-120 prepared in Example 1. Figure 2 It can be seen that the BCN-120 photoanode with a bimetallic hole transport layer structure has excellent photoelectric desalination performance. The salt removal rate and solar desalination capacity of BCN-120 are 88.76 μg / (cm 2 ·min) and 0.231μmol / J, which is higher than 37.05μg / (cm 2 ·min) and 0.085μmol / J.

[0060] On the basis of Example 1, the present invention also verifies the initial photocurrent and salt removal rate of NiO@Co3O4 / BiVO4 prepared under different Ni:Co ratio conditions (that is, on the basis of Example 1, the addition amount of Co(NO3)2·6H2O is fixed at 0.002 mol, and then the addition amount of Ni(NO3)2·6H2O is adjusted to make the Ni:Co molar ratios of 1:4 and 4:1 respectively, the in-situ growth time is 120 min, and the other step parameters are the same as those in Example 1; the prepared bimetallic hole transport layer composite photoanode has the corresponding Ni:Co molar ratios marked as Co:Ni 4:1 and Co:Ni 1:4 respectively). The results show that when the Ni:Co molar ratio is 1:1, the initial photocurrent of the prepared NiO@Co3O4 / BiVO4 is 3.01 mA / cm 2 The salt removal rate was 88.76 μg / (cm 2 ·min); when the Ni:Co molar ratio is 1:4, the initial photocurrent of the prepared NiO@Co3O4 / BiVO4 is 2.86mA / cm 2 The salt removal rate was 84.21 μg / (cm 2 ·min); when the Ni:Co molar ratio is 4:1, the initial photocurrent of the prepared NiO@Co3O4 / BiVO4 is 2.76mA / cm 2 The salt removal rate was 83.18 μg / (cm 2 ·min).

[0061] Inductively coupled plasma emission spectroscopy was used to characterize the Bi content in the redox electrolyte, dilute solution, and concentrate after desalination. 3+ 、V 5+ 、Co 2+ and Ni 2+ The element content test is shown in Table 1. The redox electrolyte of the pure BiVO4 photoanode contains trace amounts of Bi 3+ and V 5+ Ion, V 5+and Bi 3+ The ions come from BiVO4 nanoparticles, indicating that BiVO4 photoanode is prone to photocorrosion during solar redox desalination. 3+ 、V 5+ The content is extremely low, and Bi is not detected in the dilution and concentrate. 3+ 、V 5+ 、Co 2+ and Ni 2+ , indicating that the photocorrosion resistance and stability of the BCN-120 photoanode have been significantly improved; the NiO@Co3O4 bimetallic hole transport layer protects the coral-like structure of BiVO4 as a hole transport layer. The photoelectric conversion efficiency of the photoelectrode is shown in Table 2.

[0062] Table 1 ICP data of pure BVO and BCN-120 samples.

[0063]

[0064] In the table, “ / ” means the substance is not contained, and “-” means it is not detected.

[0065] Table 2 Solar desalination capacity (photovoltaic conversion efficiency) of photoanodes.

[0066]

[0067] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a bimetallic hole transport layer composite photoanode, characterized in that: The following steps are involved: Dissolve 2-methylimidazole, Co source, Ni source and polyvinyl pyrrolidone in water to prepare a Ni-Co-MOF precursor solution; Immersing the BiVO4 thin film in the Ni-Co-MOF precursor solution for in-situ growth to obtain Ni-Co-MOF / BiVO4; The Ni-Co-MOF / BiVO4 is calcined to obtain the bimetallic hole transport layer composite photoanode.

2. The method for preparing a bimetallic hole transport layer composite photoanode according to claim 1, characterized in that: The molar ratio of the Co source to the Ni source is 1:1; the molar ratio of the 2-methylimidazole to the Co source is 10:1; and the ratio of the Co source to the polyvinyl pyrrolidone is 0.002 mol:30 mg.

3. The method for preparing a bimetallic hole transport layer composite photoanode according to claim 1, characterized in that: The concentration of the Co source in the Ni-Co-MOF precursor solution is 0.025 mol / L.

4. The method for preparing a bimetallic hole transport layer composite photoanode according to claim 1, characterized in that: The Co source is Co(NO3)2·6H2O; the Ni source is Ni(NO3)2·6H2O.

5. The method for preparing a bimetallic hole transport layer composite photoanode according to claim 1, characterized in that: The in-situ growth specifically includes: standing at room temperature for 80-140 minutes.

6. The method for preparing a bimetallic hole transport layer composite photoanode according to claim 1, characterized in that: The calcination is specifically: calcining at 450° C. for 2 h in a nitrogen atmosphere.

7. The method for preparing a bimetallic hole transport layer composite photoanode according to claim 1, characterized in that: Before immersing the BiVO4 film in the Ni-Co-MOF precursor solution, the method further includes washing the BiVO4 film with a 0.1M NaOH solution for 30 minutes.

8. A bimetallic hole transport layer composite photoanode prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the bimetallic hole transport layer composite photoanode as claimed in claim 8 in solar-driven photoelectrochemical desalination.

10. A photoelectrochemical desalination system, characterized in that: The double metal hole transport layer composite photoanode as claimed in claim 8 is used as the photoanode.

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