Preparation method and application of high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film

Abstract

The present invention discloses a preparation method and application of a high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film. Iron salt and urea are dissolved in deionized water, an ethanol solution of TiCl4 is added, and a precursor Ti-FeOOH is grown on a conductive glass FTO by a hydrothermal method. The precursor film is taken out and calcined to obtain a Ti-Fe2O3 nanofilm. Then, selenium powder is dissolved in a strong alkaline solution, cobalt salt and disodium ethylenediaminetetraacetate are added, and the solution is hydrothermally heated at 180°C for 16 hours. The precipitate is centrifuged and dried to obtain CoSe2 powder. CoSe2 is loaded on the Ti-Fe2O3 film by an impregnation method, and finally calcined to obtain a Ti-Fe2O3 / CoSe2 heterojunction film. The Ti-Fe2O3 / CoSe2 photoelectrode film prepared by the method of the present invention can effectively improve the photoelectrochemical performance of Fe2O3 and its ability to decompose water and produce hydrogen as a photoanode.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectrochemistry, and in particular relates to a high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film and a preparation method and application thereof. Background Art

[0002] With the continuous growth of global energy demand, environmental problems and energy crisis make it imperative to develop sustainable and renewable energy technologies. Among them, solar-driven PEC water splitting technology is considered to be an effective way to directly convert solar energy into clean and storable fuel (H2), which is of great significance to solve the intermittent nature of solar energy.

[0003] Hematite (Fe2O3) has a good optical band gap (1.9-2.2 eV), excellent chemical stability in oxidizing environments, is rich in rare earth elements, and is inexpensive, so it has been widely studied as a photoanode for water oxidation. Theoretically, the theoretical photocurrent of hematite at 1.23 V (vs. RHE) is 12.6 mA / cm 2 , a high solar-to-hydrogen conversion efficiency of 15.5% can be achieved. Although a variety of doping and nano-sizing methods have been explored to overcome the problems of long solar light absorption depth and extremely short carrier lifetime of hematite, the actual photoelectric conversion performance of hematite is still far from the expected level, which is mainly due to the limitations of factors such as short excited state carrier lifetime (~10-12s), short hole diffusion length (2-4nm), abundant surface states, and especially the low conductivity of its surface. Therefore, it is very desirable to develop a universal method to solve the above problems simultaneously. Applied Catalysis B: Environmental reported a Z-type photoanode system consisting of Ti-Fe2O3 nanowire arrays and In2O3 layers, which improved the photoelectrochemical water splitting performance; Nature Communications reported a core-shell structure of tantalum-doped hematite homojunction nanorods prepared by a combination of hydrothermal regrowth and hybrid microwave annealing, which improved the photocurrent density and reduced the turn-on voltage; Chemical Engineering Journal reported a two-step hydrothermal method to introduce intrinsic (oxygen vacancies, V o ) and extrinsic (Cu 2+ ) dopant and then annealing to prepare a homogeneous pn junction on Fe2O3. The results show that the composite film photoanode has good PEC photolysis water performance.

[0004] In recent years, metal selenides have attracted great attention in water splitting due to their good electrical conductivity and high catalytic activity. In addition, since the valence band formed by Se 4p orbitals is shallower than that formed by O 2p and S 3p orbitals, their band gaps are narrower than those of the corresponding metal (oxy) sulfides, allowing for wider absorption of sunlight wavelengths. Among them, cobalt diselenide (CoSe2) is a typical p-type semiconductor that exhibits excellent catalytic performance as a catalyst for photo / electrocatalytic water splitting. Fe2O3 is an n-type semiconductor, and CoSe2 forms a heterojunction with Fe2O3, which can improve the separation of electrons and holes and accelerate the diffusion of carriers under the internal electric field, thereby achieving more efficient water splitting performance. Therefore, Ti-Fe2O3 / CoSe2 photoanode film is a very promising material for photoelectrochemical water splitting. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a method for preparing a high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film and its application. The method has the advantages of simple preparation method, convenient operation, and easy control of experimental conditions.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a method for preparing a high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film, comprising the following steps:

[0007] 1) dissolving iron salt and urea in deionized water, adding ethanol solution of TiCl4, and stirring to obtain a precursor solution; placing the precursor solution and FTO conductive glass in a hydrothermal reactor, growing precursor Ti-FeOOH on the conductive glass FTO through a hydrothermal reaction, and obtaining a Ti-FeOOH photoelectrode film; calcining the Ti-FeOOH photoelectrode film under air conditions to obtain a Ti-Fe2O3 photoelectrode film;

[0008] 2) dissolving selenium powder in a strong alkaline solution, adding cobalt salt and disodium ethylenediaminetetraacetate, and hydrothermally reacting at 180° C. for 16 h. The precipitate is centrifuged and dried to obtain CoSe2 powder;

[0009] 3) Dissolving CoSe2 and polyethylene glycol in ethanol, and preparing CoSe2 impregnation solution by ultrasound; immersing the Ti-Fe2O3 photoelectrode film obtained in step 1) in the CoSe2 impregnation solution, and calcining in an inert gas to obtain a Ti-Fe2O3 / CoSe2 photoelectrode film.

[0010] Furthermore, in the above preparation method, in step 1), the iron salt is ferric chloride hexahydrate or ferric sulfate.

[0011] Furthermore, in the above preparation method, the molar ratio of iron salt to urea is 1-2:1.

[0012] Furthermore, in the above-mentioned preparation method, in step 1), the hydrothermal reaction is carried out at 90-120° C. for 8-12 hours.

[0013] Furthermore, in the above preparation method, in step 1), the calcination is performed at 400-600° C. for 1-3 h, with a heating rate of 1-10° C. / min.

[0014] Furthermore, in the above preparation method, in step 2), the cobalt salt is cobalt nitrate hexahydrate or cobalt chloride hexahydrate.

[0015] Furthermore, in the above preparation method, the molar ratio of the cobalt salt to the selenium powder is 0.5:1-2.

[0016] Furthermore, in the above-mentioned preparation method, in step 2), the strong alkaline solution is a 20 mol / L sodium hydroxide solution or potassium hydroxide solution.

[0017] Furthermore, in the above preparation method, in step 2), the drying is performed at 50-100° C. for 10-24 hours.

[0018] Furthermore, in the above-mentioned preparation method, in step 3), the immersion treatment is performed at an immersion rate of 1 cm / min and the immersion treatment time is 0.5-5 min.

[0019] Furthermore, in the above preparation method, in step 3), the calcination is performed at 300-500° C. for 1-2 h.

[0020] Furthermore, in the above preparation method, the inert gas is nitrogen.

[0021] The high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film provided by the invention is applied in photoelectrochemical water decomposition to produce hydrogen.

[0022] The beneficial effects of the present invention are:

[0023] 1. The Ti-Fe2O3 / CoSe2 photoelectrode film provided by the present invention is a pn heterojunction structure, which makes it easier to effectively separate photogenerated electrons and holes, reduce the recombination rate, and effectively improve the photoelectrochemical performance and the ability to decompose water to produce hydrogen.

[0024] 2. The Ti-Fe2O3 / CoSe2 photoelectrode film provided by the present invention has a preparation method with cheap and readily available raw materials, simple and convenient operation, provides a new catalytic material for water decomposition, alleviates the current energy shortage situation, and has good application prospects.

[0025] 3. The Ti-Fe2O3 / CoSe2 photoelectrode film provided by the present invention has a hydrogen production rate under visible light that is about twice that of Ti-Fe2O3. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a comparison chart of XRD of the Ti-Fe2O3 / CoSe2 photoelectrode film, Ti-Fe2O3 film and CoSe2 powder prepared in Example 1.

[0027] Figure 2 This is a comparison chart of the photocurrents of the Ti-Fe2O3 / CoSe2 photoelectrode film prepared in Example 1, the Ti-Fe2O3 film, and the film prepared from pure CoSe2 powder.

[0028] Figure 3 This is a comparison chart of the open circuit voltages of the Ti-Fe2O3 / CoSe2 photoelectrode film and the Ti-Fe2O3 film prepared in Example 1.

[0029] Figure 4 This is a graph of the hydrogen production rate from water decomposition of the Ti-Fe2O3 / CoSe2 photoelectrode film and the Ti-Fe2O3 film prepared in Example 1. DETAILED DESCRIPTION

[0030] Example 1 High-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film

[0031] (I) Preparation method

[0032] 1. Preparation of CoSe2 powder

[0033] Dissolve 0.1580g (0.002mol) of selenium powder in 5mL of 20mol / L KOH solution, stir magnetically for 30min, add 0.291g (0.001mol) Co(NO3)2·6H2O and 0.5952g (0.0016mol) EDTA-2Na, continue magnetic stirring for 1h, transfer to a 50mL reactor, and hydrothermally react at 180℃ for 16h. After the reaction, centrifuge and wash the precipitate, and dry it in an oven at 60℃ for 24h to obtain CoSe2 powder.

[0034] 2. Preparation of n-type Ti-Fe2O3 photoelectrode film

[0035] 0.81 g (0.003 mol) of ferric chloride hexahydrate and 0.18 g (0.003 mol) of urea were dissolved in 20 mL of deionized water, 150 μL of 5% TiCl4 ethanol solution was added dropwise, and the mixture was stirred thoroughly to prepare a precursor solution.

[0036] The precursor solution and the cleaned FTO conductive glass were placed in a 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 100 °C for 12 h to obtain a Ti-FeOOH photoelectrode film.

[0037] The Ti-FeOOH photoelectrode film was calcined at 550°C for 2h to obtain a high performance n-type photoelectrode material Ti-Fe2O3 photoelectrode film.

[0038] 3. Preparation of high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode films

[0039] 60 mg of CoSe2 powder and 0.5 mL of polyethylene glycol were dissolved in 50 mL of ethanol solution and ultrasonicated for 60 min to obtain the CoSe2 impregnation solution.

[0040] The Ti-Fe2O3 photoelectrode film was immersed in the CoSe2 impregnation solution for 2 minutes at a rate of 1 cm / min. The film was calcined at 300°C for 2 hours under nitrogen protection to obtain a high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film.

[0041] (II) Testing

[0042] Figure 1 The XRD comparison diagram of the prepared Ti-Fe2O3 / CoSe2 photoelectrode film, Ti-Fe2O3 film and CoSe2 powder. Figure 1 It can be seen that the diffraction peaks of Ti-Fe2O3 / CoSe2 correspond to the diffraction peaks of SnO2 (FTO), Fe2O3 (PDF#73-0603) and CoSe2 (PDF#053-0449), respectively, proving the successful loading of CoSe2 on the Fe2O3 surface.

[0043] Example 2 Application

[0044] The prepared CoSe2, Ti-Fe2O3, and Ti-Fe2O3 / CoSe2 photoelectrode films were tested for photocurrent, open circuit voltage (OCP), and water decomposition performance.

[0045] All electrochemical experimental tests were conducted in a three-electrode electrochemical workstation (Princeton Applied Research 2273). The sample film was used as the working electrode, the platinum sheet was used as the counter electrode, the Ag / AgCl was used as the reference electrode, the electrolyte was 1 M potassium hydroxide, and the sample light irradiation area was 1 cm 2 The water decomposition test uses GC-1690 to detect the hydrogen production in each period of time.

[0046] Photocurrent test: The light source is a 300W xenon lamp, the bias voltage is 1.23V vs. RHE, and the measured results are as follows Figure 2 As shown, the results show that the photocurrent density of the heterojunction Ti-Fe2O3 / CoSe2 film is much greater than that of Ti-Fe2O3, indicating that the photoelectrochemical performance is improved after loading CoSe2.

[0047] Open circuit voltage (OCP) test: Select the light source as 300W xenon lamp, bias voltage as 1.23V vs.RHE, the measured results are as follows Figure 3 As shown in the figure, after the Ti-Fe2O3 / CoSe2 photoelectrode film is loaded with CoSe2 to form a heterojunction, the OCP (OCV dark -OCV light ) value is greater than the OCP value of Ti-Fe2O3, indicating that the separation efficiency of carriers in Ti-Fe2O3 is effectively improved after the heterojunction is formed by loading CoSe2 and Ti-Fe2O3.

[0048] Water decomposition hydrogen production test: The light source is selected as 300W xenon lamp, the bias voltage is 1.23V vs. RHE, and the test results are as follows Figure 4 As shown, after loading CoSe2 and Ti-Fe2O3 to form a heterojunction, the hydrogen production rate of the Ti-Fe2O3 / CoSe2 photoelectrode film is greater than that of Ti-Fe2O3, indicating that after loading CoSe2 and Ti-Fe2O3 to form a heterojunction, the hydrogen production efficiency of Ti-Fe2O3 is effectively improved, and the Faraday efficiency also reaches 98%, proving that Ti-Fe2O3 / CoSe2 has a more effective driving force for water oxidation.

Claims

1. A method for preparing a high-performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film, characterized in that: The steps include: 1) dissolving iron salt and urea in deionized water, adding ethanol solution of TiCl4, and stirring to obtain a precursor solution; placing the precursor solution and FTO conductive glass in a hydrothermal reactor, growing precursor Ti-FeOOH on the conductive glass FTO through a hydrothermal reaction, and obtaining a precursor Ti-FeOOH photoelectrode film; calcining the precursor Ti-FeOOH photoelectrode film under air conditions to obtain a Ti-Fe2O3 photoelectrode film; 2) dissolving selenium powder in a strong alkaline solution, adding cobalt salt and disodium ethylenediaminetetraacetate, and hydrothermally reacting at 180° C. for 16 h. The precipitate is centrifuged and dried to obtain CoSe2 powder; 3) Dissolving CoSe2 and polyethylene glycol in ethanol, and preparing CoSe2 impregnation solution by ultrasound; immersing the Ti-Fe2O3 photoelectrode film obtained in step 1) in the CoSe2 impregnation solution, and calcining in an inert gas to obtain a Ti-Fe2O3 / CoSe2 photoelectrode film.

2. The preparation method according to claim 1, characterized in that In step 1), the iron salt is ferric chloride hexahydrate or ferric sulfate.

3. The preparation method according to claim 2, characterized in that: The molar ratio of iron salt to urea is 1-2:

1.

4. The preparation method according to claim 1, characterized in that: In step 1), the hydrothermal reaction is carried out at 90-120° C. for 8-12 hours; the calcination is carried out at 400-600° C. for 1-3 hours, and the heating rate is 1-10° C. / min.

5. The preparation method according to claim 1, characterized in that: In step 2), the cobalt salt is cobalt nitrate hexahydrate or cobalt chloride hexahydrate; and the molar ratio of the cobalt salt to the selenium powder is 0.5:1-2.

6. The preparation method according to claim 1, characterized in that: In step 2), the strong alkaline solution is a 20 mol / L sodium hydroxide solution or potassium hydroxide solution.

7. The preparation method according to claim 1, characterized in that: In step 2), the drying is performed at 50-100° C. for 10-24 hours.

8. The preparation method according to claim 1, characterized in that: In step 3), the immersion treatment is performed for 0.5-5 minutes.

9. The preparation method according to claim 1, characterized in that: In step 3), the calcination is performed at 300-500° C. for 1-2 hours; and the inert gas is nitrogen.

10. Application of the high performance heterojunction Ti-Fe2O3 / CoSe2 photoelectrode film prepared by the method according to any one of claims 1 to 9 in photoelectrochemical water decomposition to produce hydrogen.

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