α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on NiFe-LDH surface and its preparation method and application

Abstract

The invention provides a preparation method of an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The method comprises the following steps: placing an FTO / β-FeOOH photoelectrode in a muffle furnace for annealing to obtain an FTO / α-Fe2O3 photoelectrode; dissolving nickel nitrate hexahydrate, ferric nitrate nonahydrate, ammonium fluoride and urea in a mixed solvent of ethylene glycol and N'N-dimethylformamide to obtain a precursor solution; placing the FTO / α-Fe2O3 photoelectrode in a hydrothermal reactor with its conductive surface facing upward, injecting the precursor solution, sealing the reactor and reacting to obtain an α-Fe2O3 photoanode material modified with NiFe-LDH; and adding cobalt chloride hexahydrate into a sodium borohydride solution, stirring the solution, and injecting the solution into the hydrothermal reactor to react with the NiFe-LDH modified α-Fe2O3 photoanode material to obtain an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The FTO / α-Fe2O3 photoelectrode of the present invention obtains a more stable crystal form after high-temperature annealing; the present invention adopts a hydrothermal method to prepare the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The preparation method is simple, low-cost, reproducible, and has uniform size and consistent morphology.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrocatalytic materials, and in particular to an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH, as well as a preparation method and application thereof. Background Art

[0002] Nowadays, the demand for efficient and high-performance catalytic systems for environmentally friendly energy sources is increasing. As hydrogen energy holds the greatest promise as a clean and sustainable energy source, solar-powered hydrogen production has attracted considerable attention. However, the low conversion efficiency of solar-powered hydrogen production has significantly limited its practical application. Metal oxide photoanodes, with their excellent electrochemical properties, simple synthesis, and low cost, are attractive candidates for photoelectrochemical water oxidation. Hematite (α-Fe2O3) is particularly well-recognized as a suitable photoanode material due to its excellent chemical stability, resistance to photocorrosion, ease of synthesis, low toxicity, and natural abundance. However, the photocatalytic efficiency of pure hematite is limited due to its rapid recombination rate, low electron and hole mobility, short asymmetric carrier paths, and sluggish photoelectrolyte interface kinetics, which restrict its practical application. Therefore, loading a cocatalyst on the surface of α-Fe2O3 is an effective method to improve the PEC (photoelectrocatalytic) performance of α-Fe2O3.

[0003] Two-dimensional layered double hydroxides (LDHs) have been considered promising materials for scalable water oxidation and decomposition (OER). Edge sites are the primary active sites in 2D LDHs, but their densely packed basal planes severely limit the exposure of active sites. Therefore, activation of internal functional regions is expected to enhance their catalytic activity for water splitting (Doi.org / 10.1016 / j.apcatb.2019.118559). Existing research reports indicate that the incorporation of a third transition metal atom, such as V, Cr, Ce, Mo, Ta, or W (Doi.org / 10.1016 / j.cej.2021.130768), into NiFe-LDH can effectively modulate the electronic structure of the 3D metal matrix, further overcoming the limitation of poor activity. However, the catalytic water oxidation activity of NiFe-LDH using transition metal incorporation remains less than ideal. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to provide an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH with excellent catalytic water oxidation performance and a preparation method thereof.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] The first aspect of the present invention provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH, comprising the following steps:

[0007] S1 annealed the FTO / β-FeOOH photoelectrode in a muffle furnace and then treated it with an ozone cleaner to obtain the FTO / α-Fe2O3 photoelectrode;

[0008] S2: dissolving nickel nitrate hexahydrate, ferric nitrate nonahydrate, ammonium fluoride and urea in a mixed solvent of ethylene glycol and N'N-dimethylformamide to obtain a precursor solution;

[0009] S3: Place the FTO / α-Fe2O3 photoelectrode with the conductive surface facing upward in a hydrothermal reactor, inject the precursor solution, seal it, and react. After the reaction is completed, cool it to room temperature to obtain NiFe-LDH-modified α-Fe2O3 photoanode material;

[0010] S4 adds cobalt chloride hexahydrate to sodium borohydride solution and stirs it, and injects it into a hydrothermal reactor to react with NiFe-LDH modified α-Fe2O3 photoanode material in a sealed manner. The reaction is carried out in an incubator. After the reaction is completed, it is cooled to room temperature to obtain α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH.

[0011] Beneficial effects: The photoelectrode of the present invention is subjected to high-temperature annealing to obtain a more stable FTO / α-Fe2O3 photoelectrode, and after being treated by an ozone cleaning machine, no other organic matter is attached to the surface of the FTO / α-Fe2O3 photoelectrode, making it easier to load catalysts; the present invention adopts a hydrothermal method to prepare an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The preparation method is simple in process, low in cost, and has good repeatability, and the size and morphology are uniform.

[0012] Preferably, in S1, the annealing temperature is 800° C. and the time is 2 hours; the ozone cleaning machine treatment time is 0.5 hours.

[0013] Preferably, in S2, the volume ratio of N'N-dimethylformamide to ethylene glycol is 1:1.

[0014] Preferably, in S2, the molar ratio of the nickel nitrate hexahydrate, the ferric nitrate nonahydrate, the ammonium fluoride and the urea is 2.5:1:1:1.

[0015] Preferably, in S3, the reaction temperature is 130-160° C., and the reaction time is 16-18 h.

[0016] Preferably, in S4, the pH of the sodium borohydride solution is 10-14, and the molar ratio of cobalt chloride hexahydrate to sodium borohydride in the sodium borohydride solution is 3:(1-1.5).

[0017] Preferably, in S4, the reaction temperature is 100-140° C., and the reaction time is 3-6 h.

[0018] Preferably, in S1, the preparation method of the FTO / β-FeOOH photoelectrode includes the following steps: dissolving ferric chloride hexahydrate, sodium nitrate and concentrated hydrochloric acid in water to form a mixed solution; transferring the mixed solution and FTO to a polytetrafluoroethylene reactor, placing the polytetrafluoroethylene in a stainless steel hydrothermal reactor and sealing it for reaction; after the reaction is completed, cooling to room temperature, washing and drying the obtained product to obtain the FTO / β-FeOOH photoelectrode.

[0019] The second aspect of the present invention provides an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH, which is prepared using the above-mentioned method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH.

[0020] The third aspect of the present invention provides the use of an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH as a photoelectrocatalyst for catalyzing water oxidation reactions.

[0021] The principle of the invention is to use the hydrothermal method to take FTO / α-Fe2O3 nanoarray as the substrate and pass the anion CO3 2- NH3 - with Ni 2+ 、Fe 3+ The coordination is carried out to form NiFe-LDH, and then cobalt atoms are immobilized on the surface to grow directly in situ on the FTO / α-Fe2O3 nanosubstrate to form an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The obtained product has consistent morphology and uniform size, and exhibits excellent catalytic performance in catalyzing water oxidation reactions as a photoelectrocatalyst.

[0022] The advantages of the present invention are:

[0023] The NiFe-LDH surface-supported cobalt atom-modified α-Fe2O3 photoanode catalyst prepared by the present invention is used for photoelectrocatalytic water oxidation, and exhibits a catalytic performance much higher than that of FTO / α-Fe2O3 for photoelectrocatalytic water oxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the SEM image of the FTO / α-Fe2O3 photoelectrode obtained in Example 1;

[0025] Figure 2The SEM images of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 at different magnifications are shown;

[0026] Figure 3 Transmission electron microscopy (TEM) images of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH (right) and the FTO / α-Fe2O3 photoelectrode (left) obtained in Example 1;

[0027] Figure 4 X-ray photoelectron spectroscopy (XPS) of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH, the NiFe-LDH catalyst, and the FTO / α-Fe2O3 photoelectrode obtained in Example 1; wherein a, b, c, d, and e are XPS spectra of the full element spectrum, Ni, Fe, Co, and O elements, respectively;

[0028] Figure 5 This is a surface scanning element distribution map (Mapping) of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1; the left figure is the surface scanning element distribution area, and the right figures ad correspond to the element distribution maps of Ni, Fe, Co, O, respectively;

[0029] Figure 6 This is a confocal Raman microscopic spectrum (RAMAN) of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1;

[0030] Figure 7 The UV spectra a of the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1 and the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1, and their indirect band gap spectra b calculated by UV;

[0031] Figure 8 The LSV curves of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 and the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1 in 1M KOH solution; wherein α-Fe2O3 represents the FTO / α-Fe2O3 photoanode catalyst, and the FTO / α-Fe2O3 photoanode catalyst is used as the standard catalyst;

[0032] Figure 9It curves of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 and the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1 in 1M KOH solution, where α-Fe2O3 represents the FTO / α-Fe2O3 photoanode catalyst, and the FTO / α-Fe2O3 photoanode catalyst is used as the standard catalyst;

[0033] Figure 10 The chopping curves of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 and the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1 in 1M KOH solution, where α-Fe2O3 represents the FTO / α-Fe2O3 photoanode catalyst, and the FTO / α-Fe2O3 photoanode catalyst is used as the standard catalyst;

[0034] Figure 11 Schematic diagram of the preparation method of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH in Examples 1-7;

[0035] Figure 12 Schematic diagram of the working principles of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 and the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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 making creative efforts shall fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0038] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0039] Example 1

[0040] Reference Figure 11 This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH, comprising the following steps:

[0041] (1) Dissolve ferric chloride hexahydrate, sodium nitrate, and concentrated hydrochloric acid in deionized water to form a mixed solution. In the mixed solution, the concentration of ferric chloride hexahydrate is 0.149M, the concentration of sodium nitrate is 2M, and the concentration of concentrated hydrochloric acid is 12M. Transfer the mixed solution and FTO conductive glass to a polytetrafluoroethylene reactor, seal it with a stainless steel hydrothermal reactor, and react at 120°C for 48 hours. After the reaction is completed, cool it to room temperature, wash and dry the obtained product to obtain an FTO / β-FeOOH photoelectrode;

[0042] (2) The FTO / β-FeOOH photoelectrode was annealed at 800°C in a muffle furnace for 2 h, and then treated with an ozone cleaner for 0.5 h to obtain the FTO / α-Fe2O3 photoelectrode;

[0043] (3) 25 mL of N,N-dimethylformamide and 25 mL of ethylene glycol were mixed uniformly, and then 0.0363 g of nickel nitrate hexahydrate, 0.0202 g of ferric nitrate nonahydrate, 0.0019 g of ammonium fluoride, and 0.0030 g of urea were added thereto, and the mixture was uniformly stirred by ultrasonic stirring to obtain a precursor solution;

[0044] (4) The FTO / α-Fe2O3 photoelectrode was placed in a polytetrafluoroethylene reactor with the conductive surface facing upward, and the precursor solution was slowly injected along the inner wall of the polytetrafluoroethylene reactor. After sealing with a stainless steel hydrothermal reactor, the reaction was carried out at 160°C for 18 hours. After the reaction was completed, it was cooled to room temperature. The obtained product was washed 5 times with a mixed solution of N,N-dimethylformamide and ethanol and dried at 60°C to obtain the NiFe-LDH modified α-Fe2O3 photoanode material.

[0045] (5) 0.0214 g of cobalt chloride hexahydrate was added to a sodium borohydride solution and stirred. The sodium borohydride solution was prepared by dissolving 0.0011 g of sodium borohydride in 30 mL of deionized water. The pH of the sodium borohydride solution was 14. The stirred solution was then injected into a polytetrafluoroethylene liner and mixed with the NiFe-LDH-modified α-Fe2O3 photoanode material. The mixture was sealed and placed in a 120°C oven for reaction for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of the NiFe-LDH.

[0046] Depend on Figure 1-2 It can be seen that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this embodiment has a heterogeneous structure and uniform size; Figure 3 and 5 It can be seen that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this embodiment successfully loaded NiFe-LDH on the FTO / α-Fe2O3 photoelectrode and successfully immobilized cobalt atoms on the surface.

[0047] Figure 4 The graph reflects the elemental composition and valence states of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the NiFe-LDH surface. a is the full spectrum, showing the presence and content of elements such as Ni, Fe, Co, and O, where the peak intensities indicate their relative contents. b, c, d, and e are the spectra of Ni, Fe, Co, and O, respectively, revealing the valence states and bonding types of these elements. Figure a shows the presence of Co in the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the NiFe-LDH surface, and Co atoms of the corresponding valence states are detected in Figure d, indicating that Co atoms were successfully immobilized on the NiFe-LDH surface.

[0048] from Figure 6 Typical NiFe-LDH peaks can be seen at 447nm and 532nm, and the overall peak shifts, indicating that the α-Fe2O3 photoanode catalyst modified with cobalt atoms was successfully immobilized on the NiFe-LDH surface.

[0049] Comparative Example 1

[0050] This comparative example provides a method for preparing an α-Fe2O3@NiFe-LDH photoanode catalyst. The specific steps are as follows:

[0051] (1) Dissolve ferric chloride hexahydrate, sodium nitrate, and concentrated hydrochloric acid in deionized water to form a mixed solution. In the mixed solution, the concentration of ferric chloride hexahydrate is 0.149M, the concentration of sodium nitrate is 2M, and the concentration of concentrated hydrochloric acid is 12M. Transfer the mixed solution and FTO conductive glass to a polytetrafluoroethylene reactor, seal it with a stainless steel hydrothermal reactor, and react at 120°C for 48 hours. After the reaction is completed, cool it to room temperature, wash and dry the obtained product to obtain an FTO / β-FeOOH photoelectrode;

[0052] (2) The FTO / β-FeOOH photoelectrode was annealed at 800°C in a muffle furnace for 2 h, and then treated with an ozone cleaner for 0.5 h to obtain the FTO / α-Fe2O3 photoelectrode;

[0053] (3) 25 mL of N,N-dimethylformamide and 25 mL of ethylene glycol were mixed uniformly, and then 0.0363 g of nickel nitrate hexahydrate, 0.0202 g of ferric nitrate nonahydrate, 0.0019 g of ammonium fluoride, and 0.0030 g of urea were added thereto, and the mixture was stirred and ultrasonically mixed to obtain a precursor solution;

[0054] (4) The FTO / α-Fe2O3 photoelectrode was placed in a polytetrafluoroethylene reactor with the conductive surface facing upward, and the precursor solution was slowly injected along the inner wall of the polytetrafluoroethylene reactor. After sealing with a stainless steel hydrothermal reactor, the reaction was carried out at 160°C for 18 hours. After the reaction was completed, it was cooled to room temperature. The obtained product was washed 5 times with a mixed solution of N,N-dimethylformamide and ethanol and dried at 60°C to obtain the α-Fe2O3@NiFe-LDH photoanode catalyst.

[0055] from Figure 7 It can be seen that the indirect band gap of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 is smaller than the band gap of the α-Fe2O3@NiFe LDH photoanode catalyst and the FTO / α-Fe2O3 photoelectrode obtained in Comparative Example 1, which is more conducive to absorbing light for water oxidation reaction.

[0056] Depend on Figure 8 It can be seen that the photocurrent density of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 reached 0.727 mA cm at a bias voltage of 1.23 VRHE. -2 , compared with 0.159 mA cm for FTO / α-Fe2O3 photoelectrode -2 The photocurrent density of the α-Fe2O3@NiFe LDH photoanode catalyst obtained in Comparative Example 1 was significantly improved at 1.23V. RHE The photocurrent density under bias voltage reaches 0.412 mA cm -2 Compared with the NiFe-LDH surface-supported cobalt atom-modified α-Fe2O3 photoanode catalyst obtained in Example 1, the photocurrent density is significantly reduced.

[0057] Depend on Figure 9 It can be seen that the photocurrent density of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 did not show obvious decay within 10 minutes under a bias of 1.23VRHE, while the photocurrent density of the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1 showed obvious decay within 10 minutes under a bias of 1.23VRHE.

[0058] Depend on Figure 10 It can be seen that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 is more sensitive to light response than the FTO / α-Fe2O3 photoelectrode and the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in Comparative Example 1 under a bias of 1.23VRHE.

[0059] Depend on Figure 12It can be seen that when the α-Fe2O3@NiFe-LDH photoanode catalyst obtained in the comparative example oxidizes water, the electron transfer rate is slow and the hole recombination rate is slightly high. However, when the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in Example 1 oxidizes water, the cobalt atoms promote rapid electron transfer, greatly reduce the hole recombination rate, and promote the oxygen evolution reaction kinetics more significantly.

[0060] Example 2

[0061] This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The steps thereof differ from those of Example 1 only in that: in step (4), the reaction temperature is 130°C and the reaction time is 16 h; the remaining steps are the same as those of Example 1.

[0062] Characterization showed that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this example had a heterogeneous structure and was consistent in size.

[0063] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in this example reached 0.691 mA cm-1 at a bias voltage of 1.23 VRHE. -2 , the photocurrent density has no obvious decay within 10 min.

[0064] Example 3

[0065] This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The steps thereof differ from those of Example 1 only in that: in step (5), the reaction temperature is 100°C and the reaction time is 4 h; the remaining steps are the same as those of Example 1.

[0066] Characterization showed that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this example had a heterogeneous structure and was consistent in size.

[0067] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in this example reached 0.684 mA cm-1 at a bias voltage of 1.23 VRHE. -2 , the photocurrent density has no obvious decay within 10 min.

[0068] Example 4

[0069] This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The steps thereof differ from those of Example 1 only in that: in step (5), the reaction temperature is 140°C and the reaction time is 5 h; the remaining steps are the same as those of Example 1.

[0070] Characterization showed that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this example had a heterogeneous structure and was consistent in size.

[0071] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in this example reached 0.688 mA cm-1 at a bias voltage of 1.23 VRHE. -2 , the photocurrent density has no obvious decay within 10 min.

[0072] Example 5

[0073] This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The steps thereof differ from those of Example 1 only in that: in step (5), the pH of the sodium borohydride solution is 10; the remaining steps are the same as those of Example 1.

[0074] Characterization showed that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this example had a heterogeneous structure and was consistent in size.

[0075] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in this example reached 0.701 mA cm-1 at a bias voltage of 1.23 VRHE. -2 , the photocurrent density has no obvious decay within 10 min.

[0076] Example 6

[0077] This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The steps thereof differ from those of Example 1 only in that: in steps (4) and (5), the reaction temperature is 140°C and the reaction time is 3 h; the remaining steps are the same as those of Example 1.

[0078] Characterization showed that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this example had a heterogeneous structure and was consistent in size.

[0079] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in this example reached 0.665 mA cm-1 at a bias voltage of 1.23 VRHE. -2 , the photocurrent density has no obvious decay within 10 min.

[0080] Example 7

[0081] This embodiment provides a method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The steps thereof differ from those of Example 1 only in that: in step (5), the mass of sodium borohydride in the sodium borohydride solution is 0.0022 g; the remaining steps are the same as those of Example 1.

[0082] Characterization showed that the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH obtained in this example had a heterogeneous structure and was consistent in size.

[0083] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in this example reached 0.698 mA cm-1 at a bias voltage of 1.23 VRHE. -2 , the photocurrent density has no obvious decay within 10 min.

[0084] Comparative Example 2

[0085] The preparation method of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH in Comparative Example 2 is similar to that in Example 1, except that the reaction temperature in step (5) is 80°C.

[0086] The same test method as in Example 1 was used to test the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst obtained in Comparative Example 2. The photocurrent density of the photoanode catalyst reached 0.354 mA cm at a bias voltage of 1.23 VRHE. -2 Compared with the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH in Example 1, the photocurrent density of the photoanode catalyst is reduced, and the photocurrent density has a significant decay within 10 minutes.

[0087] Comparative Example 3

[0088] The preparation method of the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH in Comparative Example 3 is similar to that in Example 1, except that the reaction temperature in step (4) is 200°C.

[0089] The same method as in Example 1 was used for testing. The photocurrent density of the NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst prepared in Comparative Example 3 reached 0.378 mA cm-1 at a bias voltage of 1.23 VRHE. -2 Compared with the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH in Example 1, the photocurrent density is reduced, and the photocurrent density decays significantly within 10 minutes.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH, characterized in that: The following steps are involved: S1: annealing an FTO / β-FeOOH photoelectrode in a muffle furnace, and then treating it with an ozone cleaner to obtain an FTO / α-Fe2O3 photoelectrode; the preparation method of the FTO / β-FeOOH photoelectrode is as follows: dissolving ferric chloride hexahydrate, sodium nitrate, and concentrated hydrochloric acid in water to form a mixed solution; transferring the mixed solution and FTO to a polytetrafluoroethylene reactor, placing the polytetrafluoroethylene in a stainless steel hydrothermal reactor, sealing it, and reacting; after the reaction is completed, cooling it to room temperature, washing, and drying the obtained product to obtain the FTO / β-FeOOH photoelectrode; S2: dissolving nickel nitrate hexahydrate, ferric nitrate nonahydrate, ammonium fluoride, and urea in a mixed solvent of ethylene glycol and N,N-dimethylformamide to obtain a precursor solution; S3: Place the FTO / α-Fe2O3 photoelectrode with the conductive surface facing upward in a hydrothermal reactor, inject the precursor solution, seal it, and react. After the reaction is completed, cool it to room temperature to obtain NiFe-LDH-modified α-Fe2O3 photoanode material. The reaction temperature is 130-160°C. S4 adds cobalt chloride hexahydrate to sodium borohydride solution and stirs it, and injects it into a hydrothermal reactor to react with NiFe-LDH modified α-Fe2O3 photoanode material in a sealed manner. The reaction is carried out in an incubator. After the reaction is completed, it is cooled to room temperature to obtain α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH. The reaction temperature is 100-140°C.

2. The method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH according to claim 1, characterized in that: In S1, the annealing temperature is 800° C. and the time is 2 hours; the ozone cleaning machine treatment time is 0.5 hours.

3. The method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH according to claim 1, characterized in that: In S2, the volume ratio of N,N-dimethylformamide to ethylene glycol is 1:

1.

4. The method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH according to claim 1, characterized in that: In S2, the molar ratio of the nickel nitrate hexahydrate, the ferric nitrate nonahydrate, the ammonium fluoride, and the urea is 2.5:1:1:

1.

5. The method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH according to claim 1, characterized in that: In S3, the reaction time is 16-18 h.

6. The method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH according to claim 1, characterized in that: In S4, the pH of the sodium borohydride solution is 10-14, and the molar ratio of cobalt chloride hexahydrate to sodium borohydride in the sodium borohydride solution is 3:(1-1.5).

7. The method for preparing the α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH according to claim 1, characterized in that: In S4, the reaction time is 3-6 h.

8. A NiFe-LDH surface-supported cobalt-modified α-Fe2O3 photoanode catalyst, characterized in that: The catalyst is prepared by the method for preparing an α-Fe2O3 photoanode catalyst modified with cobalt atoms immobilized on the surface of NiFe-LDH as described in any one of claims 1 to 7.

9. Use of the NiFe-LDH surface-supported cobalt atom-modified α-Fe2O3 photoanode catalyst as claimed in claim 8 as a photoelectrocatalyst for catalyzing water oxidation reaction.

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