Copper niobate photocathode material, preparation method and application thereof in photocatalytic hydrogen production

Abstract

The application belongs to the field of advanced material technology, and relates to a copper niobate photocathode material, a preparation method thereof and application of the copper niobate photocathode material in photocatalytic hydrogen production. First, an ammonium niobate oxalate hydrate solution is used to prepare a first precursor film on a substrate surface by a spray pyrolysis method, then a copper nitrate solution is used to prepare a second precursor film on the surface of the first precursor film by the spray pyrolysis method, and finally, the substrate with the first precursor film and the second precursor film is annealed in an air atmosphere, and the copper niobate photocathode material is obtained. The m-CuNb2O6 film prepared by the application does not contain CuO, Nb2O5 and other copper niobate phases, has high purity, high density, strong adhesion and other characteristics, and has high PEC efficiency, and can be used as a photocathode material for solar water splitting.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of advanced materials technology, and relates to a copper niobate photocathode material, a preparation method thereof and application of the copper niobate photocathode material in photocatalytic hydrogen production. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of generally presenting the context of the application. The information disclosed in this Background section is not to be taken as an acknowledgement or any form of suggestion that this information forms prior art.

[0003] Copper niobate is a metal oxide semiconductor material with a suitable band gap, a high theoretical photocurrent density and excellent stability. The known copper niobate at present includes CuNbO3, CuNb3O8, m-CuNb2O6, o-CuNb2O6 and Cu3Nb2O8. According to the research of the inventors, the preparation of m-CuNb2O6 thin film and photoelectrochemical properties are rarely studied. The main reason is that m-CuNb2O6 will produce Nb2O5 and CuO impurities when there is enough Cu, Nb and oxygen during the annealing process, and the preparation of m-CuNb2O6 thin film requires an annealing temperature higher than the limit temperature of FTO, so that it is difficult to prepare a pure-phase m-CuNb2O6 thin film. SUMMARY

[0004] In order to solve the problems of the prior art, the application aims to provide a copper niobate photocathode material, a preparation method thereof and application of the copper niobate photocathode material in photocatalytic hydrogen production. The m-CuNb2O6 thin film prepared by the application has no CuO, Nb2O5 and other copper niobate phases, has high purity and high PEC efficiency.

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0006] On the one hand, a preparation method of a copper niobate photocathode material is provided. First, an ammonium niobate oxalate hydrate (C4H4NNbO2·nH2O) solution is used to prepare a first precursor thin film on the surface of a substrate by a spray pyrolysis method. Then, a copper nitrate solution is used to prepare a second precursor thin film on the surface of the first precursor thin film by a spray pyrolysis method. Finally, the substrate with the first precursor thin film and the second precursor thin film is annealed in an air atmosphere to obtain the copper niobate photocathode material.

[0007] The application forms a precursor film on the surface of a substrate by spraying and pyrolyzing copper nitrate solution and ammonium niobate oxalate hydrate (C4H4NNbO2.nH2O) solution in two steps, in the process of spraying and pyrolyzing, the precursor solution is atomized to form atomized small droplets, which is not only conducive to controlling the size of the precursor particles deposited on the substrate, but also conducive to reducing the thickness of the film, and further research shows that the precursor after further annealing treatment can obtain m-CuNb2O6 with higher purity, and XRD characterization shows that there is no CuO, Nb2O5 and other copper niobate phases in the film layer.

[0008] In the research process of the application, if the copper nitrate solution and the ammonium niobate oxalate hydrate are directly made into a mixed solution, precipitation will occur and the spraying and pyrolysis cannot continue, if the copper nitrate solution is first sprayed and pyrolyzed and then the ammonium niobate oxalate hydrate solution is sprayed and pyrolyzed, it will result in poor density of the m-CuNb2O6 film, and poor adhesion between the m-CuNb2O6 film and the substrate, and the m-CuNb2O6 film cannot be attached to the surface of the substrate, and the method of first spraying and pyrolyzing the ammonium niobate oxalate hydrate solution and then spraying and pyrolyzing the copper nitrate solution can make the prepared m-CuNb2O6 film have better density and better adhesion on the surface of the substrate.

[0009] On the other hand, a copper niobate photocathode material is obtained by the above preparation method.

[0010] In a third aspect, the application provides the use of the copper niobate photocathode material in photocatalytic hydrogen production.

[0011] In a fourth aspect, the application provides a photocatalytic water splitting device, which comprises a water splitting tank, a photoanode and a photocathode arranged in the water splitting tank, and the active material of the photocathode is the copper niobate photocathode material.

[0012] The application has the following advantages:

[0013] 1. The application adopts the method of first spraying and pyrolyzing the ammonium niobate oxalate hydrate solution and then spraying and pyrolyzing the copper nitrate solution to prepare the m-CuNb2O6 film with higher purity, better density and better adhesion on the surface of the substrate, and the structure characterization shows that there is no CuO, Nb2O5 and other copper niobate phases in the m-CuNb2O6 film layer.

[0014] 2. The m-CuNb2O6 film prepared by the application is composed of 50-200 nm nano-particle phases connected to each other and has a thickness of not more than 300 nm. Experiments show that the photocurrent density of the copper niobate photocathode material prepared by the application can reach 0.25 mA / cm 2 at 0.4 V vs.RHE, which is conducive to accelerating the rate of photocatalytic decomposition of water to produce hydrogen, and thus can be better applied in photocatalytic hydrogen production. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 The XRD pattern of the m-CuNb2O6 thin film prepared in Example 1 of this invention;

[0017] Figure 2 The images show the morphological characteristics of the m-CuNb2O6 thin film prepared in Example 1 of this invention. a is a surface SEM of the m-CuNb2O6 thin film, and b is a cross-sectional SEM of the m-CuNb2O6 thin film.

[0018] Figure 3 Optical images of the m-CuNb2O6 thin film prepared in Example 1 of this invention are shown, where a is the ultraviolet absorption spectrum and b is the Tauc diagram.

[0019] Figure 4 The it curve is the photocurrent response curve of the m-CuNb2O6 thin film prepared in Example 1 of this invention.

[0020] Figure 5 The image shows the linear scanning voltammetry (LSV) curve of the m-CuNb2O6 thin film prepared in Example 1 of this invention. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Given that existing methods are difficult to prepare pure-phase m-CuNb2O6 films, and considering that the preparation of m-CuNb2O6 films by spray pyrolysis has problems such as poor density and low adhesion, this invention proposes a copper niobate photocathode material and its preparation method, as well as its application in photocatalytic hydrogen production.

[0024] In an embodiment of the present application, a preparation method of a copper niobate photocathode material is provided. First, an ammonium niobate oxalate hydrate solution is used to prepare a first precursor film on a substrate surface by a spray pyrolysis method. Then, a copper nitrate solution is used to prepare a second precursor film on the surface of the first precursor film by the spray pyrolysis method. Finally, the substrate with the first and second precursor films is annealed in an air atmosphere to obtain the copper niobate photocathode material.

[0025] Research shows that the copper niobate photocathode film prepared by the above method has the characteristics of high purity, good density, and strong adhesion.

[0026] In some embodiments, the solvent of the copper nitrate solution is deionized water.

[0027] In some embodiments, the solvent of the ammonium niobate oxalate hydrate solution is deionized water.

[0028] In some embodiments, the molar ratio of copper nitrate to ammonium niobate oxalate hydrate is 0.8-1:1.

[0029] In some embodiments, the driving gas source of the spray pyrolysis is nitrogen gas with a pressure of 0.1-0.4 MPa.

[0030] In some embodiments, the temperature of the heating plate of the spray pyrolysis is 300-450℃.

[0031] In some embodiments, the heating rate of the annealing process is 3-10℃ / min.

[0032] In some embodiments, the temperature of the annealing process is 500-650℃.

[0033] In some embodiments, the annealing process lasts for 1-6h.

[0034] In another embodiment of the present application, a copper niobate photocathode material is provided, which is obtained by the above preparation method.

[0035] In a third embodiment of the present application, the above copper niobate photocathode material is applied in photocatalytic hydrogen production.

[0036] In a fourth embodiment of the present application, a photocatalytic water hydrolysis hydrogen production device is provided, which comprises a hydrolysis tank, a photoanode and a photocathode arranged in the hydrolysis tank, and the active material of the photocathode is the above copper niobate photocathode material.

[0037] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific examples.

[0038] Example 1

[0039] Cu(NO3)2*3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed well to prepare 20 mM Cu(NO3)2 precursor.

[0040] C4H4NNbO9*nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed well to prepare 20 mM C4H4NNbO9*nH2O precursor.

[0041] The Cu(NO3)2 precursor and the C4H4NNbO9*nH2O precursor were prepared separately in a volume ratio of 1:1.

[0042] A two-step spray pyrolysis method was used to first spray pyrolyze the prepared C4H4NNbO9*nH2O precursor solution to deposit a niobium precursor film on a substrate (FTO coated glass, square resistance of 7Ω), and then spray the Cu(NO3)2 precursor on the substrate with the niobium precursor film. Before starting the deposition, the substrate was cleaned by ultrasonic rinsing in ultrapure water, acetone and ethanol for three consecutive 15 minutes, and then the cleaned substrate was placed on a hot plate heated to 300℃ after being blown dry with a nitrogen gun. The nozzle was placed 20 cm above the hot plate and driven by 0.2 Mpa overpressure nitrogen. Spray for 5 s (~1.3 mL) each time, intermittent 50 s, and repeat the cycle for 20 times.

[0043] The precursor film was annealed in a muffle furnace in air at a rate of 5℃ / min for 2 hours at 600℃ to obtain a m-CuNb2O6 film, i.e. a copper niobate photocathode material.

[0044] Figure 1 It is shown that the m-CuNb2O6 photocathode material prepared in this embodiment has all diffraction peaks well matched with the standard value (PDF #83-0369). There are no XRD peaks from other impurity phases such as CuO and Nb2O5, indicating the purity of the crystalline m-CuNb2O6 film.

[0045] Figure 2 It is shown that the m-CuNb2O6 photocathode material prepared in this embodiment is composed of rough nanoparticles connected to each other, with a particle size of 50-200 nm and a film thickness of about 220 nm.

[0046] Figure 3 a shows that significant light absorption (photoresponse) occurs near 880 nm, corresponding to a band gap energy of 1.41 eV, which is consistent with the visible gray of the film seen in the inset. In order to quantify the band gap of the sample, the Tauc plot (αhν)2 vs hν was calculated. Figure 3b). The band gap (Eg) was estimated by calculating the intercept of the extrapolated linear fit of the experimental data, from which the indirect and direct allowed band gaps were found to be 1.94 eV and 1.41 eV, respectively.

[0047] Figure 4 The i-t curve of m-CuNb2O6 under chopped illumination (0.4 V vs. RHE) is shown. The m-CuNb2O6 thin film has a good photoelectric response.

[0048] Figure 5 It is shown that the photoelectric current density generated by the m-CuNb2O6 thin film prepared in this embodiment is 0.25 mA / cm 2 .

[0049] Example 2

[0050] Cu(NO3)2·3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare an 18 mM Cu(NO3)2 precursor.

[0051] C4H4NNbO9·nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 20 mM C4H4NNbO9·nH2O precursor.

[0052] The Cu(NO3)2 precursor and the C4H4NNbO9·nH2O precursor were prepared separately in a volume ratio of 0.9:1.

[0053] A two-step spray pyrolysis method was used. First, the prepared C4H4NNbO9·nH2O precursor solution was spray pyrolyzed to deposit a niobium precursor film on a substrate (FTO-coated glass, square resistance of 7 Ω). Then, the Cu(NO3)2 precursor was sprayed on the substrate with the niobium precursor film. Before starting the deposition, the substrate was cleaned by ultrasonic rinsing in ultrapure water, acetone, and ethanol for three consecutive 15-minute periods. The cleaned substrate was then dried using a nitrogen gas jet and placed on a hot plate heated to 300°C. The nozzle was placed 20 cm above the hot plate and was driven by an overpressure of 0.2 MPa of nitrogen gas. The spray was performed for 5 s (~1.3 mL) each time, with an intermittent period of 50 s. This cycle was repeated 20 times for each precursor.

[0054] The precursor film was annealed in a muffle furnace in air at a rate of 5°C / min for 2 hours at 600°C to obtain a m-CuNb2O6 thin film, i.e., a copper niobate photocathode material.

[0055] Studies have shown that the m-CuNb2O6 thin film prepared in this embodiment has a thickness of about 220 nm.

[0056] Example 3

[0057] Cu(NO3)2·3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 19 mM Cu(NO3)2 precursor.

[0058] C4H4NNbO9·nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 20 mM C4H4NNbO9·nH2O precursor.

[0059] The Cu(NO3)2 precursor and the C4H4NNbO9·nH2O precursor were prepared separately in a volume ratio of 0.95:1.

[0060] A two-step spray pyrolysis method was used to spray pyrolyze the prepared C4H4NNbO9·nH2O precursor solution to deposit a niobium precursor film on a substrate (FTO-coated glass, square resistance of 7 Ω), and then spray the Cu(NO3)2 precursor on the substrate with the niobium precursor film. Before starting the deposition, the substrate was cleaned by ultrasonic rinsing in ultrapure water, acetone, and ethanol for three consecutive 15-minute periods, and then dried by spraying with nitrogen gas. The cleaned substrate was placed on a hot plate heated to 300°C, and the nozzle was placed 20 cm above the hot plate and driven by 0.2 MPa overpressure nitrogen gas. The spray was 5 s (~1.3 mL) each time, with an interval of 50 s, and the spray was repeated 20 times in each cycle.

[0061] The precursor film was annealed in a muffle furnace in air at a rate of 5°C / min for 2 hours at 600°C to obtain a m-CuNb2O6 film, i.e., a copper niobate photocathode material.

[0062] Studies have shown that the m-CuNb2O6 film prepared in this embodiment has a thickness of about 220 nm.

[0063] Comparative Example 1

[0064] Cu(NO3)2·3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 20 mM Cu(NO3)2 precursor.

[0065] C4H4NNbO9·nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 20 mM C4H4NNbO9·nH2O precursor.

[0066] The Cu(NO3)2 precursor and the C4H4NNbO9·nH2O precursor were prepared separately in a volume ratio of 1:1.

[0067] A two-step spray pyrolysis method was used. First, the prepared Cu(NO3)2 precursor solution was spray pyrolyzed to deposit a copper precursor film on a substrate (FTO-coated glass, sheet resistance of 7 Ω). Then, the C4H4NNbO9·nH2O precursor was sprayed on the copper precursor film. Before starting the deposition, the substrate was cleaned by ultrasonic rinsing in ultrapure water, acetone, and ethanol for three consecutive 15-minute periods. The cleaned substrate was dried using a nitrogen gas spray gun and placed on a hot plate heated to 300 °C. The nozzle was placed 20 cm above the hot plate and was driven by 0.2 MPa overpressure nitrogen gas. The spray was 5 s (~1.3 mL) each time, with a 50 s pause, and the process was repeated 20 times.

[0068] The precursor film was annealed in a muffle furnace in air at 600 °C for 2 hours at a rate of 5 °C / min to obtain a m-CuNb2O6 film.

[0069] Studies have shown that the m-CuNb2O6 film prepared in this embodiment has poor compactness and cannot be attached to FTO.

[0070] Comparative Example 2

[0071] Cu(NO3)2·3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 19 mM Cu(NO3)2 precursor.

[0072] C4H4NNbO9·nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 20 mM C4H4NNbO9·nH2O precursor.

[0073] The Cu(NO3)2 precursor and the C4H4NNbO9·nH2O precursor were prepared separately in a volume ratio of 0.95:1.

[0074] A two-step spray pyrolysis method was used. First, the prepared Cu(NO3)2 precursor solution was spray pyrolyzed to deposit a copper precursor film on a substrate (FTO-coated glass, sheet resistance of 7 Ω). Then, the C4H4NNbO9·nH2O precursor was sprayed on the copper precursor film. Before starting the deposition, the substrate was cleaned by ultrasonic rinsing in ultrapure water, acetone, and ethanol for three consecutive 15-minute periods. The cleaned substrate was dried using a nitrogen gas spray gun and placed on a hot plate heated to 300 °C. The nozzle was placed 20 cm above the hot plate and was driven by 0.2 MPa overpressure nitrogen gas. The spray was 5 s (~1.3 mL) each time, with a 50 s pause, and the process was repeated 20 times.

[0075] The precursor thin film was annealed in a muffle furnace in air at a rate of 5°C / min at 600°C for 2 hours to obtain the m-CuNb2O6 thin film.

[0076] Studies have shown that the m-CuNb2O6 thin film prepared in this embodiment has poor compactness and cannot be attached to FTO.

[0077] Comparative Example 3

[0078] Cu(NO3)2·3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare an 18 mM Cu(NO3)2 precursor.

[0079] C4H4NNbO9·nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare a 20 mM C4H4NNbO9·nH2O precursor.

[0080] The Cu(NO3)2 precursor and the C4H4NNbO9·nH2O precursor were prepared separately in a volume ratio of 0.9:1.

[0081] A two-step spray pyrolysis method was used. First, the prepared Cu(NO3)2 precursor solution was spray pyrolyzed to deposit a copper precursor thin film on the substrate (FTO-coated glass with a square resistance of 7Ω). Then, the C4H4NNbO9·nH2O precursor was sprayed on the copper precursor thin film. Before starting the deposition, the substrate was cleaned by ultrasonic rinsing in ultrapure water, acetone, and ethanol for three consecutive 15-minute periods. The cleaned substrate was dried using a nitrogen gas spray gun and placed on a hot plate heated to 300°C. The nozzle was placed 20 cm above the hot plate and driven by 0.2 MPa overpressure nitrogen gas. The spray was 5 s (~1.3 mL) each time, with a 50 s interval, and the cycle was repeated 20 times for each.

[0082] The precursor thin film was annealed in a muffle furnace in air at a rate of 5°C / min at 600°C for 2 hours to obtain the m-CuNb2O6 thin film.

[0083] Studies have shown that the m-CuNb2O6 thin film prepared in this embodiment has poor compactness and cannot be attached to FTO.

[0084] Comparative Example 4

[0085] Cu(NO3)2·3H2O (99%, Sigma-Aldrich) was dissolved in deionized water and mixed uniformly to prepare an 18 mM Cu(NO3)2 precursor.

[0086] C4H4NNbO9«nH2O (99.99%, Sigma-Aldrich) was dissolved in deionized water and mixed well to make 20 mM C4H4NNbO9«nH2O precursor.

[0087] The Cu(NO3)2precursor was mixed with the C4H4NNbO9«nH2O precursor in a volume ratio of 0.9:1, which resulted in precipitation and the spray pyrolysis could not continue.

[0088] The above descriptions are only preferred embodiments of the present application and are not used to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a copper niobate photocathode material, characterized by, A first precursor film is prepared on a substrate surface by using a spray pyrolysis method with an ammonium niobate oxalate hydrate solution, and a second precursor film is prepared on the surface of the first precursor film by using a spray pyrolysis method with a copper nitrate solution, and then the substrate with the first and second precursor films is annealed in an air atmosphere to obtain the copper niobate photocathode material. The molar ratio of copper nitrate to ammonium niobate oxalate hydrate is 0.8-1:

1.

2. The method for preparing the copper niobate photocathode material as described in claim 1, characterized in that, The solvent of the copper nitrate solution is deionized water.

3. The method for preparing the copper niobate photocathode material as described in claim 1, characterized in that, The solvent of the ammonium niobate oxalate hydrate solution is deionized water.

4. The method for preparing the copper niobate photocathode material as described in claim 1, characterized in that, The driving gas source for the spray pyrolysis is nitrogen at 0.1-0.4 MPa.

5. The method for preparing the copper niobate photocathode material as described in claim 1, characterized in that, The temperature of the heating plate for the spray pyrolysis is 300-450 °C.

6. The method for preparing the copper niobate photocathode material as described in claim 1, characterized in that, The heating rate for the annealing process is 3-10 °C / min. The temperature for the annealing process is 500-650 °C. The time for the annealing process is 1-6 h.

7. A copper niobate photocathode material, characterized by, The copper niobate photocathode material is prepared by the method of any one of claims 1-6.

8. The use of the copper niobate photocathode material of claim 7 in photocatalytic hydrogen production.

9. A photocatalytic water splitting device for hydrogen production, comprising a water splitting cell, in which a photoanode and a cathode are disposed, characterized in that, The active material of the photocathode is the copper niobate photocathode material of claim 7.

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