One-dimensional iron oxide nanorod heterojunction composite material, and preparation method and application thereof

Abstract

The application provides a one-dimensional iron oxide nanorod heterojunction composite material and a preparation method and application thereof, and belongs to the technical field of photoelectrocatalytic water splitting hydrogen production. The composite material provided by the application comprises: one-dimensional iron oxide nanorods, cuprous sulfide nanoparticles loaded on the one-dimensional iron oxide nanorods, and cobalt hydroxide nanosheets coated on the surfaces of the one-dimensional iron oxide nanorods and the cuprous sulfide nanoparticles. On one hand, the Fe2O3 / Cu2S p-n heterojunction is introduced to accelerate the separation of photo-generated carriers in the Fe2O3 nanorod array, and on the other hand, the Co(OH) x The surface OECs accelerate the kinetics process of interfacial water oxidation, the rapid depletion of photo-generated holes further improves the charge separation of the photoanode surface, and the synergistic effect between the Fe2O3 / Cu2S p-n heterojunction and the OECs significantly improves the PEC water splitting performance of the iron oxide nanorod array composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrocatalytic water decomposition and hydrogen production, and in particular to a one-dimensional iron oxide nanorod heterojunction composite material, a preparation method and an application thereof. Background Art

[0002] With economic and social development, energy and environmental crises are increasingly hindering human progress. Photoelectrocatalytic water splitting provides a promising solution. This technology utilizes solar energy, the most abundant natural resource, to decompose Earth's vast water reserves into clean, environmentally friendly hydrogen with extremely high energy density. Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photoelectrochemical cell.

[0003] Among the many semiconductor photoanode materials, iron oxide (Fe2O3) has become one of the most widely used composite materials due to its excellent stability, low toxicity and low cost. The band gap of Fe2O3 is 2.0-2.2eV, so its light absorption range exceeds 600nm, which has sufficient visible light absorption. Theoretical calculations show that at 100mW / cm 2 Under (AM1.5G) solar radiation, the ideal hematite (α-Fe2O3) composite material can generate up to 12.6 mA / cm at 1.23 V (vs. RHE). 2 The photocurrent density is 2.5 nm, and its solar-to-hydrogen (STH) efficiency can reach 16.8%, which is higher than the 10% required for practical applications. However, the actual PEC performance of hematite (α-Fe2O3) is far lower than the theoretical value due to its fast carrier recombination velocity, short hole diffusion length (only 2-4 nm), and short excited state lifetime. These shortcomings seriously hinder its application. Various modification strategies have been used to alleviate the shortcomings of hematite, such as doping, heterojunction / homojunction formation, and surface modification.

[0004] Constructing a pn junction has been shown to optimize the PEC performance of composite arrays. With the help of a built-in electric field, photogenerated carriers can be quickly separated at the pn junction interface and the degree of bulk recombination is reduced. These advantages improve the PEC water splitting performance of the composite array. Notably, loading oxygen evolution catalysts (OECs) is considered to be a particularly effective method to enhance the surface reaction kinetics of α-Fe2O3 films. The OECs used in PEC systems are generally derived from excellent electrocatalysts, among which many low-cost transition metal-based OECs have been shown to have the ability to achieve low overpotentials for electrochemical OER. However, the simultaneous improvement of charge separation and surface oxygen evolution kinetics of iron oxide nanorod array composites through the synergistic effect between pn heterojunctions and OECs has not yet been achieved, which limits the improvement of the performance of the composite.

[0005] Therefore, how to achieve the synergistic effect between the pn heterojunction and OECs in the composite material, thereby improving the performance of the composite material, has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0006] The purpose of the present invention is to provide a one-dimensional iron oxide nanorod heterojunction composite material, a preparation method and application thereof. The one-dimensional iron oxide nanorod heterojunction composite material provided by the present invention realizes the synergistic effect between the Fe2O3 / Cu2Sp-n heterojunction and OECs, so that the PEC water splitting performance of the composite material is significantly improved.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The invention provides a one-dimensional iron oxide nanorod heterojunction composite material, comprising: one-dimensional iron oxide nanorods, cuprous sulfide nanoparticles loaded on the one-dimensional iron oxide nanorods, and cobalt hydroxide nanosheets coated on the surfaces of the one-dimensional iron oxide nanorods.

[0009] Preferably, the diameter of the one-dimensional iron oxide nanorod heterojunction composite material is 80 to 120 nm.

[0010] The present invention provides a method for preparing the one-dimensional iron oxide nanorod heterojunction composite material described in the above technical solution, comprising the following steps:

[0011] (1) mixing iron salt, sodium salt and water, and then adding concentrated hydrochloric acid to obtain a hydrothermal precursor solution;

[0012] (2) adding a titanium sheet to the hydrothermal precursor solution obtained in step (1), then performing a hydrothermal reaction to obtain Ti / FeOOH, and finally performing a first annealing on the Ti / FeOOH to obtain one-dimensional iron oxide nanorods;

[0013] (3) soaking the one-dimensional iron oxide nanorods obtained in step (2) in a saturated CuCl solution and a Na2S anion solution, repeating the above operation 3 to 30 times, and finally performing a second annealing to obtain a Ti / Fe2O3 / Cu2S heterostructure;

[0014] (4) Covering the surface of the Ti / Fe2O3 / Cu2S heterostructure obtained in step (3) with Co(OH) x Nanosheets were prepared to obtain one-dimensional iron oxide nanorod heterojunction composite materials.

[0015] Preferably, the concentration of the iron salt in the hydrothermal precursor solution in step (1) is 0.075-0.3 mol / L, and the concentration of the sodium salt in the hydrothermal precursor solution is 0.5-2 mol / L.

[0016] Preferably, the temperature of the hydrothermal reaction in step (2) is 180-220° C., the time of the hydrothermal reaction is 4-6 hours, and the heating rate to the hydrothermal reaction temperature is 0.5-2° C. / min.

[0017] Preferably, the holding temperature of the first annealing in step (2) is 400-600°C, the holding time of the first annealing is 1-3h, the heating rate to the first annealing holding temperature is 1-5°C / min, and the atmosphere of the first annealing is air.

[0018] Preferably, in step (3), the time for the one-dimensional iron oxide nanorods to be immersed in the CuCl saturated solution and the Na2S anion solution is independently 30 to 120 seconds.

[0019] Preferably, the holding temperature of the second annealing in step (3) is 150-250°C, the holding time of the second annealing is 1-3h, the heating rate to the second annealing holding temperature is 3-7°C / min, and the atmosphere of the second annealing is argon.

[0020] Preferably, in step (4), the surface of the Ti / Fe2O3 / Cu2S heterostructure is covered with Co(OH) x The nanosheets are prepared by adding a Ti / Fe2O3 / Cu2S heterostructure into a cobalt nitrate solution and then performing electrochemical deposition; the concentration of the cobalt nitrate solution is 1 to 4 mmol / L, and the cathode current density of the electrochemical deposition is 0.5 to 2 mA / cm 2 , the electrochemical deposition time is 30 to 120 s.

[0021] The present invention provides the use of the one-dimensional iron oxide nanorod heterojunction composite material described in the above technical solution or the one-dimensional iron oxide nanorod heterojunction composite material prepared by the preparation method described in the above technical solution in hydrogen production in photoelectrocatalytic water decomposition.

[0022] The present invention provides a one-dimensional iron oxide nanorod heterojunction composite material, comprising: one-dimensional iron oxide nanorods, cuprous sulfide nanoparticles loaded on the one-dimensional iron oxide nanorods, and cobalt hydroxide nanosheets coated on the surfaces of both. The one-dimensional iron oxide nanorod heterojunction composite material provided by the present invention accelerates the separation of photogenerated carriers in the Fe2O3 nanorod array by introducing the Fe2O3 / Cu2S pn heterojunction, and also accelerates the separation of photogenerated carriers in the Fe2O3 nanorod array by introducing the Co(OH) x Surface OECs accelerate the kinetics of interfacial water oxidation, and the rapid depletion of photogenerated holes further improves charge separation on the photoanode surface. The synergistic effect between the Fe2O3 / Cu2S pn heterojunction and the OECs significantly enhances the PEC water splitting performance of the iron oxide nanorod array composite. The results of the examples demonstrate that the one-dimensional iron oxide nanorod heterojunction composite provided by the present invention achieves a synergistic effect between the Fe2O3 / Cu2S pn heterojunction and the OECs, significantly improving the composite's PEC water splitting performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of preparing one-dimensional iron oxide nanorod heterojunction composite materials according to the present invention;

[0024] Figure 2 This is the SEM image of the Ti / Fe2O3 nanorods prepared in Example 1;

[0025] Figure 3 This is the SEM image of the Ti / Fe2O3 / Cu2S heterostructure prepared in Example 1;

[0026] Figure 4 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SEM images of the composite material;

[0027] Figure 5 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x TEM images of the composite materials;

[0028] Figure 6 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x EDS diagram of the composite material;

[0029] Figure 7 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x Co(OH) in composite materials x SAED pattern of

[0030] Figure 8 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SAED pattern of Cu2S in the composite material;

[0031] Figure 9 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SAED pattern of Fe in the composite material;

[0032] Figure 10 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SAED pattern of O in the composite material;

[0033] Figure 11 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SAED pattern of Cu in the composite material;

[0034] Figure 12 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SAED pattern of S in the composite material;

[0035] Figure 13 Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x SAED pattern of Co in the composite material;

[0036] Figure 14 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XRD patterns of the composite materials;

[0037] Figure 15 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XRD detailed pattern of composite materials;

[0038] Figure 16 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XPS pattern of Fe 2P in the composite material;

[0039] Figure 17The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XPS pattern of O1s in the composite material;

[0040] Figure 18 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XPS pattern of Cu2P in the composite material;

[0041] Figure 19 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XPS pattern of S2P in the composite material;

[0042] Figure 20 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XPS pattern of Co 2P in the composite material;

[0043] Figure 21 The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) prepared in Example 1 x XPS patterns of elements in composite materials;

[0044] Figure 22 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x Photocurrent density of the composite material under AM 1.5G irradiation;

[0045] Figure 23 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x and composite materials Ti / Fe2O3 / Co(OH) x The composite material was irradiated with visible light of λ>420nm and the light intensity was 66.7mW / cm 2 The photocurrent density at ;

[0046] Figure 24Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x ABPE diagram of the composite material under AM 1.5G irradiation;

[0047] Figure 25 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x The composite material was irradiated with visible light of λ>420nm and the light intensity was 66.7mW / cm 2 ABPE diagram at ;

[0048] Figure 26 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x It test curve of composite materials;

[0049] Figure 27 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x Photovoltaic hydrogen production performance diagram of the composite material;

[0050] Figure 28 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x Constant potential wavelength scanning photocurrent density curve of the composite material;

[0051] Figure 29 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x Photocurrent density curves of composite materials under different potential and wavelength scanning;

[0052] Figure 30Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x IPCE diagram of composite materials at constant potential wavelength;

[0053] Figure 31 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x IPCE diagrams of composite materials at different potential wavelengths;

[0054] Figure 32 is the Mott-Schottky curve of Ti / Fe2O3 nanorods;

[0055] Figure 33 Ti / Fe2O3 / Co(OH) x Mott-Schottky plot of the composite material;

[0056] Figure 34 Mott-Schottky plot of Ti / Fe2O3 / Cu2S heterostructure;

[0057] Figure 35 Ti / Fe2O3 / Cu2S / Co(OH) x Mott-Schottky plot of the composite material;

[0058] Figure 36 is the Mott-Schottky curve of Cu2S powder;

[0059] Figure 37 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x carrier concentration of the composite material;

[0060] Figure 38 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) x Nyquist plot of the composite material obtained in a dark environment at open circuit potential;

[0061] Figure 39 Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) xNyquist plot of the composite material obtained in a dark environment at 1.23 V (vs. RHE). DETAILED DESCRIPTION

[0062] The invention provides a one-dimensional iron oxide nanorod heterojunction composite material, comprising: one-dimensional iron oxide nanorods, cuprous sulfide nanoparticles loaded on the one-dimensional iron oxide nanorods, and cobalt hydroxide nanosheets coated on the surfaces of the one-dimensional iron oxide nanorods.

[0063] In the present invention, the diameter of the one-dimensional iron oxide nanorod heterojunction composite material is preferably 80 to 120 nm, more preferably 100 nm. The nanometer-scale diameter of the composite material provided by the present invention provides a higher specific surface area, thereby further improving the catalytic performance of the composite material.

[0064] The one-dimensional iron oxide nanorod heterojunction composite material provided herein preferably also includes a titanium sheet. In the present invention, the titanium sheet is preferably the substrate material for the composite material. By using the titanium sheet as the substrate material, the present invention not only enables the one-dimensional iron oxide nanorods to grow normally on the titanium sheet, but also provides electrical conductivity, forming a conductive current collector.

[0065] The one-dimensional iron oxide nanorod heterojunction composite material provided by the present invention accelerates the separation of photogenerated carriers in the Fe2O3 nanorod array by introducing the Fe2O3 / Cu2S pn heterojunction, and on the other hand, accelerates the separation of photogenerated carriers in the Fe2O3 nanorod array by introducing the Co(OH) x Surface OECs accelerated the kinetics of interfacial water oxidation, and the rapid depletion of photogenerated holes further improved the charge separation on the photoanode surface. The synergistic effect between the Fe2O3 / Cu2S pn heterojunction and OECs significantly improved the PEC water splitting performance of the iron oxide nanorod array composite material.

[0066] The present invention provides a method for preparing the one-dimensional iron oxide nanorod heterojunction composite material described in the above technical solution, comprising the following steps:

[0067] (1) mixing iron salt, sodium salt and water, and then adding concentrated hydrochloric acid to obtain a hydrothermal precursor solution;

[0068] (2) adding a titanium sheet to the hydrothermal precursor solution obtained in step (1), then performing a hydrothermal reaction to obtain Ti / FeOOH, and finally performing a first annealing on the Ti / FeOOH to obtain one-dimensional iron oxide nanorods;

[0069] (3) soaking the one-dimensional iron oxide nanorods obtained in step (2) in a saturated CuCl solution and a Na2S anion solution, repeating the above operation 3 to 30 times, and finally performing a second annealing to obtain a Ti / Fe2O3 / Cu2S heterostructure;

[0070] (4) Covering the surface of the Ti / Fe2O3 / Cu2S heterostructure obtained in step (3) with Co(OH) x Nanosheets were prepared to obtain one-dimensional iron oxide nanorod heterojunction composite materials.

[0071] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art.

[0072] The invention mixes iron salt, sodium salt and water, and then adds concentrated hydrochloric acid to obtain a hydrothermal precursor solution.

[0073] In the present invention, the iron salt preferably includes any one of ferric chloride hexahydrate and ferric nitrate nonahydrate, more preferably ferric chloride hexahydrate; the sodium salt preferably includes any one of sodium chloride and sodium nitrate, more preferably sodium nitrate. In the present invention, the addition of the sodium salt provides a high ionic strength environment to the hydrothermal precursor solution, which, combined with the low pH environment of the system (around 1.5), reduces the interfacial energy of the reaction system, facilitates the formation of a single hematite phase iron oxide, avoids the formation of a mixed phase, and is more conducive to the formation of nanorod morphology, making the generated iron oxide nanorods relatively more regular and having relatively better photoelectric properties.

[0074] In the present invention, the concentration of iron salt in the hydrothermal precursor solution is preferably 0.075-0.3 mol / L, more preferably 0.1-0.275 mol / L, and further preferably 0.15-0.25 mol / L; the concentration of sodium salt in the hydrothermal precursor solution is preferably 0.5-2 mol / L, more preferably 1-1.5 mol / L.

[0075] In the present invention, the water is preferably distilled water or ultrapure water. The present invention uses distilled water or ultrapure water as a solvent to reduce the content of impurities and thus improve the purity of the composite material.

[0076] The present invention has no particular limitation on the operation of mixing the iron salt, sodium salt and water, as long as the iron salt, sodium salt and water can be mixed uniformly.

[0077] In the present invention, the concentration of the concentrated hydrochloric acid is preferably 37 wt.%; the volume of the concentrated hydrochloric acid is preferably 0.1 to 0.6% of the water, more preferably 0.1 to 0.5%. The present invention adjusts the pH of the hydrothermal precursor solution to a strongly acidic pH (around 1.5) by adding concentrated hydrochloric acid, and the high ionic strength environment of the system reduces the interfacial energy of the reaction system, which is conducive to the formation of a single hematite phase of iron oxide, avoids the formation of a mixed phase, and is more conducive to the formation of nanorod morphology, resulting in relatively more regular iron oxide nanorods and relatively better photoelectric properties.

[0078] After obtaining the hydrothermal precursor solution, the present invention adds titanium sheets to the hydrothermal precursor solution, then performs a hydrothermal reaction to obtain Ti / FeOOH, and finally performs a first annealing on the Ti / FeOOH to obtain one-dimensional iron oxide nanorods.

[0079] In the present invention, the hydrothermal reaction is preferably carried out in a hydrothermal kettle. The present invention has no particular limitation on the specific model of the hydrothermal kettle, and a commercially available hydrothermal kettle well known to those skilled in the art can be used.

[0080] In the present invention, the thickness of the titanium sheet is preferably 0.05 to 0.3 mm. In the present invention, the titanium sheet is added to the hydrothermal precursor solution, and the titanium sheet can serve as a matrix material, so that the FeOOH formed during the hydrothermal reaction grows vertically on the titanium sheet to form nanorods.

[0081] In the present invention, the titanium sheet is preferably pretreated before use; the pretreatment method is preferably ultrasonic cleaning using a mixture of hydrochloric acid, ethanol, acetone, and deionized water; the ultrasonic cleaning time is preferably 0.5 to 1 hour. The present invention does not specifically limit the amount of hydrochloric acid, ethanol, acetone, and deionized water in the mixture, nor the ultrasonic power, and can be determined based on the common knowledge of those skilled in the art. This pretreatment of the titanium sheet can remove organic contaminants and dust from the surface of the titanium sheet.

[0082] In the present invention, the temperature of the hydrothermal reaction is preferably 80-120°C, more preferably 95-110°C, and even more preferably 105°C; the time of the hydrothermal reaction is preferably 4-6 hours, more preferably 5 hours; and the heating rate to the hydrothermal reaction temperature is preferably 0.5-2°C / min, more preferably 1-1.5°C / min. By controlling the parameters of the hydrothermal reaction, the present invention can ensure that the iron in the solution is converted into FeOOH for precipitation.

[0083] After the hydrothermal reaction is completed, the product of the hydrothermal reaction is preferably rinsed with deionized water. The specific operation of the deionized water rinse is not particularly limited in the present invention, and a cleaning method familiar to those skilled in the art can be used. The present invention can remove residual FeOOH by rinsing with deionized water.

[0084] In the present invention, the holding temperature of the first annealing is preferably 400-600°C, more preferably 450-550°C, and even more preferably 500°C; the holding time of the first annealing is preferably 1-3 hours, more preferably 2 hours; the heating rate to the holding temperature of the first annealing is preferably 1-5°C / min, more preferably 2-4°C / min, and even more preferably 3°C / min; and the atmosphere of the first annealing is preferably air. In the present invention, by subjecting Ti / FeOOH to high-temperature annealing, FeOOH is converted into iron oxide during this process, thereby obtaining one-dimensional iron oxide nanorods.

[0085] After obtaining the one-dimensional iron oxide nanorods, the present invention sequentially soaks the one-dimensional iron oxide nanorods in a CuCl saturated solution and a Na2S anion solution, repeats the above operation 3 to 30 times, and finally performs a second annealing to obtain a Ti / Fe2O3 / Cu2S heterostructure.

[0086] In the present invention, the concentration of the Na2S anion solution is preferably 2.5 to 10 mmol / L, more preferably 4 to 8 mmol / L, and even more preferably 5 to 6 mmol / L. By controlling the concentration of the Na2S anion solution, the amount of Na2S loaded during the soaking process can be controlled.

[0087] In the present invention, the time for the one-dimensional iron oxide nanorods to be immersed in the CuCl saturated solution and the Na2S anion solution is preferably 30 to 120 seconds, more preferably 60 to 90 seconds. By controlling the immersion time, the loading amount of CuCl and Na2S during the immersion process can be controlled.

[0088] In the present invention, after soaking in the CuCl saturated solution or the Na2S anion solution, the soaked product is preferably rinsed; the rinsing time is independently preferably 30 to 120 seconds, more preferably 60 to 90 seconds.

[0089] In the present invention, the number of repetitions is 3 to 30 times, preferably 3 times, 5 times, 10 times, 15 times or 30 times. By controlling the number of repeated immersions, the amount of Cu2S deposited in the final heterostructure can be controlled.

[0090] In the present invention, the holding temperature of the second annealing is preferably 150-250°C, more preferably 200°C; the holding time of the second annealing is preferably 1-3 hours, more preferably 2 hours; the heating rate to the second annealing holding temperature is preferably 3-7°C / min, more preferably 4-6°C / min; and the atmosphere of the second annealing is preferably argon. Through the second annealing treatment, the present invention utilizes a continuous ion layer adsorption reaction to form a Cu2S nanofilm from CuCl and Na2S adsorbed on the surface of the one-dimensional iron oxide nanorods at high temperature.

[0091] After obtaining the Ti / Fe2O3 / Cu2S heterostructure, the present invention covers the surface of the Ti / Fe2O3 / Cu2S heterostructure with Co(OH) x Nanosheets were prepared to obtain one-dimensional iron oxide nanorod heterojunction composite materials.

[0092] In the present invention, the surface of the Ti / Fe2O3 / Cu2S heterostructure is covered with Co(OH) x The nanosheet method is preferably: adding a Ti / Fe2O3 / Cu2S heterostructure to a cobalt nitrate solution, and then performing electrochemical deposition to obtain a one-dimensional iron oxide nanorod heterojunction composite material. In the present invention, the concentration of the cobalt nitrate solution is preferably 1-4 mmol / L, more preferably 2-3 mmol / L; the cathode current density of the electrochemical deposition is preferably 0.5-2 mA / cm 2 , more preferably 1 to 1.5 mA / cm 2 The electrochemical deposition time is preferably 30 to 120 seconds, more preferably 30 seconds, 60 seconds, 90 seconds or 120 seconds. The present invention can deposit Ti / Fe2O3 / Cu2S heterostructure onto ultrathin Co(OH) x nanosheets, thereby realizing Co(OH) x Nanosheet covering. The present invention covers the surface of Ti / Fe2O3 / Cu2S heterostructure with Co(OH) x Nanosheets can improve their photoelectric properties and thus their catalytic performance; by controlling the parameters of electrochemical deposition, the catalytic performance of the composite material can be optimized.

[0093] The present invention first grows rod-shaped iron oxide on a titanium sheet through a hydrothermal reaction to obtain Ti / Fe2O3 nanorods, then synthesizes a Ti / Fe2O3 / Cu2S heterostructure by a successive ionic layer adsorption and reaction (SILAR) method, and finally covers the surface of the Ti / Fe2O3 / Cu2S heterostructure with Co(OH) xThe nanosheets achieved a synergistic effect between the Fe2O3 / Cu2S pn heterojunction and OECs, which significantly improved the PEC water splitting performance of the composite material.

[0094] The present invention also provides the use of the one-dimensional iron oxide nanorod heterojunction composite material described in the above technical solution in hydrogen production by photoelectrocatalytic water splitting. The present invention does not specifically limit the specific operation of the application, and the application method familiar to those skilled in the art can be used.

[0095] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0096] Example 1

[0097] The preparation method of the one-dimensional iron oxide nanorod heterojunction composite material comprises the following steps:

[0098] (1) 182.4 mg of ferric chloride hexahydrate and 383 mg of sodium nitrate were mixed with 4.5 mL of ultrapure water and stirred continuously for 2 h, and then 20 μL of 37 wt.% concentrated hydrochloric acid was added to obtain a hydrothermal precursor solution; the concentration of the iron salt in the hydrothermal precursor solution was 0.15 mol / L, and the concentration of the sodium salt in the hydrothermal precursor solution was 1 mol / L;

[0099] (2) The hydrothermal precursor solution obtained in step (1) is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and then a titanium sheet is added to completely immerse it, followed by a hydrothermal reaction to obtain Ti / FeOOH, and after washing with deionized water, the Ti / FeOOH is subjected to a first annealing to obtain one-dimensional iron oxide nanorods, which are recorded as Ti / Fe2O3 nanorods; the titanium sheet is ultrasonically cleaned for 0.5 h with a mixture of hydrochloric acid, ethanol, acetone and deionized water before use; the temperature of the hydrothermal reaction is 105°C, the time of the hydrothermal reaction is 5 h, and the heating rate to the hydrothermal reaction temperature is 0.5°C / min; the holding temperature of the first annealing is 550°C, the holding time of the first annealing is 2 h; the heating rate to the first annealing holding temperature is 5°C / min, and the atmosphere of the first annealing is air;

[0100] (3) soaking the one-dimensional iron oxide nanorods obtained in step (2) in a saturated CuCl solution for 60 seconds, then rinsing with deionized water for 60 seconds, then soaking in a Na2S anion solution for 60 seconds, and then rinsing with deionized water for 60 seconds, repeating the above operation 5 times, and finally performing a second annealing to obtain a Ti / Fe2O3 / Cu2S heterostructure; the concentration of the Na2S anion solution is 5 mmol / L; the holding temperature of the second annealing is 200°C, the holding time of the second annealing is 2 hours, the heating rate to the second annealing holding temperature is 5°C / min, and the atmosphere of the second annealing is argon;

[0101] (4) adding the Ti / Fe2O3 / Cu2S heterojunction structure obtained in step (3) into a cobalt nitrate solution and then performing electrochemical deposition to obtain a one-dimensional iron oxide nanorod heterojunction composite material, which is recorded as Ti / Fe2O3 / Cu2S / Co(OH) x Composite material; the concentration of the cobalt nitrate solution is 2mmol / L; the cathode current density of the electrochemical deposition is 1mA / cm 2 ; The electrochemical deposition time is 60s.

[0102] The flow chart of the present invention for preparing one-dimensional iron oxide nanorod heterojunction composite material is as follows Figure 1 As shown. Figure 1 It can be seen that the present invention first grows rod-shaped iron oxide on a titanium sheet through a hydrothermal reaction to obtain Ti / Fe2O3 nanorods, and then synthesizes Ti / Fe2O3 / Cu2S heterostructures by using a successive ionic layer adsorption and reaction (SILAR) method. Finally, Co(OH)2O3 is coated on the surface of the Ti / Fe2O3 / Cu2S heterostructures by electrochemical deposition. x Nanosheets, to obtain a one-dimensional iron oxide nanorod heterojunction composite material, namely Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials.

[0103] Comparative Example 1

[0104] A method for preparing a one-dimensional iron oxide nanorod composite material comprises the following steps:

[0105] (1) 182.4 mg of ferric chloride hexahydrate and 383 mg of sodium nitrate were mixed with 4.5 mL of ultrapure water and stirred continuously for 2 h, and then 20 μL of 37 wt.% concentrated hydrochloric acid was added to obtain a hydrothermal precursor solution; the concentration of the iron salt in the hydrothermal precursor solution was 0.15 mol / L, and the concentration of the sodium salt in the hydrothermal precursor solution was 1 mol / L;

[0106] (2) The hydrothermal precursor solution obtained in step (1) is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and then a titanium sheet is added to completely immerse it, followed by a hydrothermal reaction to obtain Ti / FeOOH. After washing with deionized water, the Ti / FeOOH is subjected to a first annealing to obtain a one-dimensional iron oxide nanorod composite material, which is recorded as Ti / Fe2O3 nanorods; the titanium sheet is ultrasonically cleaned for 0.5 h with a mixture of hydrochloric acid, ethanol, acetone and deionized water before use; the temperature of the hydrothermal reaction is 105°C, the time of the hydrothermal reaction is 5 h, and the heating rate to the hydrothermal reaction temperature is 0.5°C / min; the holding temperature of the first annealing is 500°C, the holding time of the first annealing is 2 h, the heating rate to the first annealing holding temperature is 5°C / min, and the atmosphere of the first annealing is air.

[0107] Comparative Example 2

[0108] The preparation method of the one-dimensional iron oxide nanorod heterojunction composite material comprises the following steps:

[0109] (1) 182.4 mg of ferric chloride hexahydrate and 383 mg of sodium nitrate were mixed with 4.5 mL of ultrapure water and stirred continuously for 2 h, and then 20 μL of 37 wt.% concentrated hydrochloric acid was added to obtain a hydrothermal precursor solution; the concentration of the iron salt in the hydrothermal precursor solution was 0.15 mol / L, and the concentration of the sodium salt in the hydrothermal precursor solution was 1 mol / L;

[0110] (2) The hydrothermal precursor solution obtained in step (1) is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and then a titanium sheet is added to completely immerse it, followed by a hydrothermal reaction to obtain Ti / FeOOH, and after washing with deionized water, the Ti / FeOOH is subjected to a first annealing to obtain one-dimensional iron oxide nanorods, which are recorded as Ti / Fe2O3 nanorods; the titanium sheet is ultrasonically cleaned for 0.5 h with a mixture of hydrochloric acid, ethanol, acetone and deionized water before use; the temperature of the hydrothermal reaction is 105°C, the time of the hydrothermal reaction is 5 h, and the heating rate to the hydrothermal reaction temperature is 0.5°C / min; the holding temperature of the first annealing is 550°C, the holding time of the first annealing is 2 h; the heating rate to the first annealing holding temperature is 5°C / min, and the atmosphere of the first annealing is air;

[0111] (3) The one-dimensional iron oxide nanorods obtained in step (2) are immersed in a saturated CuCl solution for 60 seconds, then rinsed with deionized water for 60 seconds, then immersed in a Na2S anion solution for 60 seconds, and then rinsed with deionized water for 60 seconds. The above operation is repeated 5 times, and finally a second annealing is performed to obtain a Ti / Fe2O3 / Cu2S heterostructure; the concentration of the Na2S anion solution is 5 mmol / L; the holding temperature of the second annealing is 200°C, the holding time of the second annealing is 2 hours, the heating rate to the second annealing holding temperature is 5°C / min, and the atmosphere of the second annealing is argon.

[0112] Comparative Example 3

[0113] The preparation method of the one-dimensional iron oxide nanorod heterojunction composite material comprises the following steps:

[0114] (1) 182.4 mg of ferric chloride hexahydrate and 383 mg of sodium nitrate were mixed with 4.5 mL of ultrapure water and stirred continuously for 2 h, and then 20 μL of 37 wt.% concentrated hydrochloric acid was added to obtain a hydrothermal precursor solution; the concentration of the iron salt in the hydrothermal precursor solution was 0.15 mol / L, and the concentration of the sodium salt in the hydrothermal precursor solution was 1 mol / L;

[0115] (2) The hydrothermal precursor solution obtained in step (1) is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and then a titanium sheet is added to completely immerse it, followed by a hydrothermal reaction to obtain Ti / FeOOH, and after washing with deionized water, the Ti / FeOOH is subjected to a first annealing to obtain one-dimensional iron oxide nanorods, which are recorded as Ti / Fe2O3 nanorods; the titanium sheet is ultrasonically cleaned for 0.5 h with a mixture of hydrochloric acid, ethanol, acetone and deionized water before use; the temperature of the hydrothermal reaction is 105°C, the time of the hydrothermal reaction is 5 h, and the heating rate to the hydrothermal reaction temperature is 0.5°C / min; the holding temperature of the first annealing is 550°C, the holding time of the first annealing is 2 h; the heating rate to the first annealing holding temperature is 5°C / min, and the atmosphere of the first annealing is air;

[0116] (3) adding the one-dimensional iron oxide nanorods obtained in step (2) into a cobalt nitrate solution, and then performing electrochemical deposition to obtain a one-dimensional iron oxide nanorod composite material, which is recorded as Ti / Fe2O3 / Co(OH) x Composite material; the concentration of the cobalt nitrate solution is 2mmol / L; the cathode current density of the electrochemical deposition is 1mA / cm 2 ; The electrochemical deposition time is 60s.

[0117] The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructures obtained in step (3) and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were observed using a scanning electron microscope. x The composite materials were observed separately, and the results were as follows: Figure 2 、 Figure 3 and Figure 4 As shown. Figures 2 to 4 It can be seen that Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures and Ti / Fe2O3 / Cu2S / Co(OH) x The composite materials all exhibit semi-inverted rod-like structures, which are one-dimensional nanomaterials. From the side view, it can be seen that the size of these rod-like structures is about 700nm.

[0118] The Ti / Fe2O3 / Cu2S / Co(OH)2O3 obtained in Example 1 was observed using a transmission electron microscope. x The composite materials were observed and the results were as follows Figure 5 As shown. Figure 5 It can be clearly seen that Ti / Fe2O3 / Cu2S / Co(OH) x Rod-like structures in composite materials.

[0119] The Ti / Fe2O3 / Cu2S / Co(OH)2O3 obtained in Example 1 was analyzed using an X-ray energy dispersive spectrometer. x The composite material is observed and the obtained X-ray energy dispersion spectrum surface scan is as follows Figure 6 As shown. Figure 6 The calculated lattice spacing was compared with the standard XRD spectrum, indicating that the (102) crystal plane of Cu2S is on the left side of the figure, while the (202) crystal plane of Fe2O3 is on the right side of the figure. In high-resolution mode, the phase interface between Fe2O3 and Cu2S can be observed, and a heterojunction structure is formed between the two. In addition, there is an ultra-thin layer of Co(OH) x The film wraps the two together, forming Co(OH) x Covered p-Cu2S / n-Fe2O3 structure.

[0120] The Ti / Fe2O3 / Cu2S / Co(OH)2O3 obtained in Example 1 was observed using a transmission electron microscope. x The composite material was observed and the selected area electron diffraction pattern was obtained as shown in Figures 7-8 As shown. Figures 7-8 It can be seen that the (001) and (002) crystal planes of Cu2S and Co(OH) x(010) crystal planes, Cu2S and Co(OH) x The main peak of the crystal; in addition, the SAED pattern corresponds to the (300) and (006) crystal planes in the α-Fe2O3 crystal, and these two crystal planes are the main peaks of α-Fe2O3.

[0121] The Ti / Fe2O3 / Cu2S / Co(OH)2O3 obtained in Example 1 was observed by electron microscopy. x The composite material was observed, and the distribution of Fe, O, Cu, S and Co on the nanorods was shown in the following order: Figures 9 to 13 As shown. Among them, Figure 9 is the distribution of Fe on the nanorods, Figure 10 is the distribution of O on the nanorods, Figure 11 is the distribution of Cu on the nanorods, Figure 12 is the distribution of S on the nanorods, Figure 13 is the distribution of Co on the nanorods. Figures 9 to 13 It can be seen that Ti / Fe2O3 / Cu2S / Co(OH) x The composite material contains Fe, O, Cu, S and Co at the same time, and the distribution of these five elements on the nanorods is relatively uniform.

[0122] The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructures obtained in step (3) and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were analyzed by X-ray diffractometer. x The composite materials were observed separately, and the obtained X-ray diffraction patterns were as follows Figure 14 shown. Figure 14 In the standard card (PDF#44-1294) and (PDF#33-0664) are the characteristic X-ray diffraction peaks of metal Ti and Fe2O3 respectively. Figure 14 It can be seen that the three composite materials mentioned above have characteristic X-ray diffraction peaks of metallic Ti and Fe2O3.

[0123] Figure 15 The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructures obtained in step (3) and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) are shown in FIG. x The X-ray diffraction pattern of the composite material from 32.5° to 34.0°. Figure 15 It can be seen that a small amount of Cu2S and Co(OH) x The characteristic X-ray diffraction peaks of Fe2O3 and metallic Ti were not moved.

[0124] The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructures obtained in step (3) and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were respectively x The composite materials were subjected to X-ray photoelectron spectroscopy analysis, and the results were as follows: Figures 16 to 21 shown.

[0125] Depend on Figure 16 It can be seen that the two main peaks at about 724eV and 711eV prove that the main components of these three composites are Fe 3+ The main peak is accompanied by two satellite peaks at about 733eV and 718eV, which also belong to Fe 3+ ; The XPS peaks of these three composites did not shift.

[0126] Depend on Figure 17 It can be seen that the Fe-O bond peaks of the three materials are all around 529.8eV, without obvious shift. Compared with Ti / Fe2O3, Ti / Fe2O3 / Cu2S and Ti / Fe2O3 / Cu2S / Co(OH) x The high binding energy peak of the O element shifts toward the high binding energy direction, which is due to the formation of the SO bond.

[0127] Depend on Figure 18 It can be seen that for the Cu 2p spectrum, the peaks at 951.90 eV and 932.03 eV can be well assigned to Cu + Cu 2p 1 / 2 and Cu 2p 3 / 2 In addition, in Cu 2p 1 / 2 and 2p 3 / 2 The well-known jitter peaks do not appear between the peaks, indicating the absence of Cu 2+ .

[0128] Depend on Figure 19 It can be seen that, consistent with the observations in the Cu 2p spectrum, the S2p 1 / 2 (163.4 eV) and S2p 3 / 2 The appearance of two peaks at (162.3eV) confirmed the formation of Cu2S. Compared with the Ti / Fe2O3 composite materials, the prepared Ti / Fe2O3 / Cu2S and Ti / Fe2O3 / Cu2S / Co(OH) x In the composite material, a pair of weak peaks were observed at 164.3 and 162.3 eV, which were attributed to the SO bonds between Cu2S and Fe2O3.

[0129] Depend on Figure 20It can be seen that the Co 2p spectrum also shows two main peaks near 782.3 and 786.8 eV (corresponding to the Co2p 3 / 2 ) and a jittering satellite peak (about 790.7eV), corresponding to Co 3+ and Co 2+ .

[0130] Depend on Figure 21 It can be seen that Ti / Fe2O3 / Cu2S / Co(OH) x The composite materials contained five elements, while the Ti / Fe2O3 nanorods and Ti / Fe2O3 / Cu2S heterostructures also contained some elements.

[0131] Depend on Figures 16 to 21 The fitting results show that Ti / Fe2O3 / Cu2S / Co(OH) x Co in composite materials 3+ The content is relatively higher than Co 2+ , which is conducive to obtaining excellent catalytic activity of the composite material.

[0132] The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructures obtained in step (3), and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were prepared. x Composite material and Ti / Fe2O3 / Co(OH) obtained in Comparative Example 3 x The photocurrent density of the composite material was tested, and the results were as follows: Figures 22 and 23 shown.

[0133] Depend on Figure 22 It can be seen that under AM 1.5G irradiation, as the P-type Cu2S semiconductor and ultrathin Co(OH) x With the gradual introduction of nanosheets, the photocurrent density of the composite material increased significantly. Ti / Fe2O3 / Cu2S / Co(OH) x The composite material has the highest photocurrent density, which is about 4.81 mA / cm at 1.23 V. 2 (relative to RHE), which is about the original Ti / Fe2O3 composite material (1.62mA / cm 2 ) three times.

[0134] Depend on Figure 23 It can be seen that the visible light irradiation λ>420nm, the light intensity is 66.7mW / cm 2 When Ti / Fe2O3 / Cu2S / Co(OH) x The photocurrent density of the composite material is about half that of AM 1.5G irradiation. At 1.23V, the photocurrent density is about 2.39mA / cm2 (relative to RHE), which indicates that Ti / Fe2O3 / Cu2S / Co(OH) x The composite material has good visible light photocatalytic activity.

[0135] Based on the linear sweep voltammetry (LSV) results, the Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x The photoelectric conversion efficiency (ABPE) of the composite material under an applied bias voltage at the water oxidation thermodynamic potential (1.23 V vs. RHE).

[0136] Depend on Figure 24 It can be seen that Ti / Fe2O3, Ti / Fe2O3 / Cu2S and Ti / Fe2O3 / Co(OH) x Compared with Ti / Fe2O3 / Cu2S / Co(OH) x The ABPE efficiency of the composite material is significantly improved, reaching 0.48% at 1.03 V (relative to RHE), which is the highest among Ti / Fe2O3 / Cu2S / Co(OH) x 3.2 times that of composite materials.

[0137] Depend on Figure 25 It can be seen that under visible light irradiation, λ>420nm, the light intensity is 66.7mW / cm 2 ,Ti / Fe2O3 / Cu2S / Co(OH) x The composite material also has the highest ABPE, reaching 0.2%.

[0138] In order to verify the stability of the prepared composite materials, the It test was carried out, e.g. Figure 26 As shown in Figure 2, under 1h of continuous illumination, the four prepared composite materials all showed good stability and the photocurrent was basically unchanged. Under It conditions, the photocurrent of these composite materials was consistent with that under LSV conditions. In order to determine the correlation between the observed photocurrent and the solar-assisted water splitting H2 generation reaction, the actual H2 generation performance of different samples at 1.23V (vs.RHE) was also recorded, as shown in Figure 2. Figure 27 As shown. Figure 27 It can be seen that the composite material with high photocurrent density tends to have a higher hydrogen production rate under the conditions of photoelectric coupling. x The amount of H2 generated by the composite material increases linearly with time, indicating that the H2 generation rate of the sample is very stable, which also proves again that Ti / Fe2O3 / Cu2S / Co(OH) xThe composite material is stable.

[0139] In order to explore the response of the composite material to light of different wavelengths, the Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructure obtained in step (3), and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were subjected to the following tests: x Composite material and Ti / Fe2O3 / Co(OH) obtained in Comparative Example 3 x The composite material was tested for incident monochromatic photon-electron conversion efficiency (IPCE), and the results were as follows: Figures 28 to 31 During the test, the light source starts irradiating from 300nm, changes to 600nm at a constant speed, and ends at 600nm; the wavelength resolution of the spectrum analysis is 1nm. Figures 28 to 31 It can be seen that in the electrochemical noise mode, the original Ti / Fe2O3 composite material has photocurrent performance in the wavelength range of 300-600nm, which shows that the Fe2O3 material has a wide light absorption range and good visible light response. Compared with Ti / Fe2O3, Ti / Fe2O3 / Cu2S, Ti / Fe2O3 / Co(OH) x and Ti / Fe2O3 / Cu2S / Co(OH) x The photocurrent density and IPCE value of the composite material gradually increased, which indicated that Cu2S and Co(OH) x The introduction of α-Hydroxy-1-nitropropene improves the photoelectric performance of Fe₂O₃ across the entire wavelength range from 300 to 600 nm. Under potentiostatic polarization with varying applied bias voltages, the photocurrent density and IPCE values ​​of these composites increase with increasing bias voltage, demonstrating that increasing the applied bias voltage facilitates the separation of photogenerated carriers, thereby enhancing the sample's photoelectric performance.

[0140] In order to explore the Ti / Fe2O3 / Cu2S / Co(OH) x The energy band structure information of the composite material was obtained to obtain its key parameters. The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructure obtained in step (3), and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were analyzed. x Composite material and Ti / Fe2O3 / Co(OH) obtained in Comparative Example 3 x The composite materials were subjected to Mott-Schottky (MS) tests, and the results were as follows: Figures 32 to 35 As shown, Figure 32 is the Mott-Schottky curve of Ti / Fe2O3 nanorods, Figure 33 Ti / Fe2O3 / Co(OH) xMott-Schottky plot of the composite material, Figure 34 This is the Mott-Schottky curve of the Ti / Fe2O3 / Cu2S heterostructure. Figure 35 Ti / Fe2O3 / Cu2S / Co(OH) x Mott-Schottky curves of composite materials. The intersection of the longest straight line of the Mott-Schottky curve and the baseline is the flat band potential position. The intersection of the extended lines of different frequencies of the four composite materials is a point. The slopes of the tangent lines of the four composite materials are all positive, indicating the n-type nature of these composite materials. For n-type and p-type semiconductors, the flat band potential can be approximated as the conduction band potential. Figures 32 to 35 It can be seen that Cu2S and Co(OH) x The introduction of will make the conduction band potential of Ti / Fe2O3 composite material more negative, compared with Ti / Fe2O3, Ti / Fe2O3 / Cu2S and Ti / Fe2O3 / Co(OH) x ,Ti / Fe2O3 / Cu2S / Co(OH) x The conduction band potential of the composite material is the smallest, which is -0.06V (vs. RHE). The negative shift of the flat band potential means that the energy barrier for interfacial electron transfer is lower, resulting in a lower charge transfer resistance. Therefore, compared with the other three composite materials, Ti / Fe2O3 / Cu2S / Co(OH) x The conduction band potential of the composite material is the most negative, and its photocurrent and photoelectric hydrogen production performance are the best.

[0141] The Mott Schottky (MS) test was performed on Cu2S powder, and the results were as follows: Figure 36 As shown. Figure 36 It can be seen that the intersection of the extended lines of the data curves of the three different frequencies is a point, and the slope of its tangent is negative, which indicates the p-type nature of the Cu2S semiconductor.

[0142] The Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Cu2S / Co(OH) x Composite materials and Ti / Fe2O3 / Co(OH) x The carrier concentration of the composite material is shown in the following figure. Figure 37 As shown. Figure 37 It can be seen that compared with Ti / Fe2O3 nanorods, Ti / Fe2O3 / Cu2S heterostructures, Ti / Fe2O3 / Co(OH) x Composite material, Ti / Fe2O3 / Cu2S / Co(OH) x The carrier concentration of the composite material is significantly higher by an order of magnitude, which is one of the reasons for its good performance.

[0143] The Ti / Fe2O3 nanorods obtained in step (2) of Example 1, the Ti / Fe2O3 / Cu2S heterostructures obtained in step (3) and the Ti / Fe2O3 / Cu2S / Co(OH)2O obtained in step (4) were analyzed by electrochemical impedance spectroscopy (EIS). x The frequency transmission characteristics and electrochemical properties of the composite material were studied. EIS measurements were performed in the frequency range of 100 mHz to 100 kHz. The Nyquist plot and equivalent circuit obtained are shown in Figures 1 and 2. Figure 38 and Figure 39 As shown in FIG, the equivalent circuit consists of a resistor (R), a capacitor (C), a constant phase element (CPE), and a Warburg impedance element (W). Figure 38 The Nyquist plots obtained were obtained in a dark environment at open circuit potential. Figure 39 The resulting Nyquist plots were obtained in a dark environment at 1.23 V (vs. RHE).

[0144] Typically, the Nyquist plot consists of a semicircle in the high-frequency region and a straight line in the low-frequency region, which are controlled by the charge transfer resistance at the working electrode / electrolyte interface and the diffusion of reactants or products of the electrode reaction, respectively. Figure 38 As can be seen from the small figure (under open circuit potential conditions), in the high frequency region (0-5KOhms) Ti / Fe2O3 / Cu2S and Ti / Fe2O3 / Cu2S / Co(OH) x The arc radius of the EIS curve is smaller than that of Ti / Fe2O3; Figure 39 As can be seen from the small figure (1.23V (vs.RHE)), in the high frequency region (0-5KOhms) Ti / Fe2O3 / Cu2S / Co(OH) x The arc radius of the EIS curve is smaller than that of Ti / Fe2O3 and Ti / Fe2O3 / Cu2S. The smaller the arc radius, the lower the charge transfer resistance of the electrode, resulting in rapid separation and transfer of photogenerated carriers. These results show that the introduction of P-type Cu2S nanoparticle semiconductors and the electrodeposition of an ultra-thin layer of Co(OH) x Improves the charge transport of iron oxide and promotes the separation and transfer of surface photogenerated carriers.

[0145] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a one-dimensional iron oxide nanorod heterojunction composite material, comprising the following steps: (1) Mixing iron salt, sodium salt and water, and then adding concentrated hydrochloric acid to obtain a hydrothermal precursor solution; (2) adding a titanium sheet to the hydrothermal precursor solution obtained in step (1), then performing a hydrothermal reaction to obtain Ti / FeOOH, and finally performing a first annealing on the Ti / FeOOH to obtain one-dimensional iron oxide nanorods; (3) soaking the one-dimensional iron oxide nanorods obtained in step (2) in a saturated CuCl solution and a Na2S anion solution, repeating the above operation 3 to 30 times, and finally performing a second annealing to obtain a Ti / Fe2O3 / Cu2S heterostructure; (4) Covering the surface of the Ti / Fe2O3 / Cu2S heterostructure obtained in step (3) with Co(OH) x nanosheets to obtain a one-dimensional iron oxide nanorod heterojunction composite material; In step (3), the time for the one-dimensional iron oxide nanorods to be immersed in the CuCl saturated solution and the Na2S anion solution is independently 30 to 120 seconds; The holding temperature of the second annealing in step (3) is 150-250°C, the holding time of the second annealing is 1-3h, the heating rate to the second annealing holding temperature is 3-7°C / min, and the atmosphere of the second annealing is argon; In the step (4), the surface of the Ti / Fe2O3 / Cu2S heterostructure is covered with Co(OH) x The nanosheets are prepared by adding a Ti / Fe2O3 / Cu2S heterostructure into a cobalt nitrate solution and then electrochemically depositing the nanosheets. The concentration of the cobalt nitrate solution is 1-4 mmol / L, and the cathode current density of the electrochemical deposition is 0.5-2 mA / cm 2 , the electrochemical deposition time is 30~120s.

2. The preparation method according to claim 1, characterized in that In the step (1), the concentration of the iron salt in the hydrothermal precursor solution is 0.075-0.3 mol / L, and the concentration of the sodium salt in the hydrothermal precursor solution is 0.5-2 mol / L.

3. The preparation method according to claim 1, characterized in that The temperature of the hydrothermal reaction in step (2) is 80-120° C., the time of the hydrothermal reaction is 4-6 h, and the heating rate to the hydrothermal reaction temperature is 0.5-2° C. / min.

4. The preparation method according to claim 1, characterized in that The holding temperature of the first annealing in step (2) is 400-600°C, the holding time of the first annealing is 1-3h, the heating rate to the first annealing holding temperature is 1-5°C / min, and the atmosphere of the first annealing is air.

5. The one-dimensional iron oxide nanorod heterojunction composite material prepared by the preparation method according to any one of claims 1 to 4, comprising: One-dimensional iron oxide nanorods, cuprous sulfide nanoparticles loaded on the one-dimensional iron oxide nanorods, and cobalt hydroxide nanosheets coated on the surfaces of the two.

6. The one-dimensional iron oxide nanorod heterojunction composite material according to claim 5, characterized in that The diameter of the one-dimensional iron oxide nanorod heterojunction composite material is 80-120 nm.

7. Use of the one-dimensional iron oxide nanorod heterojunction composite material according to any one of claims 5 to 6 in hydrogen production in photoelectrocatalytic water splitting.

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