Copper bismuthate / copper oxide conformal morphology heterojunction film and preparation method thereof

Abstract

The invention belongs to the technical field of preparation of photoelectric catalytic materials, and particularly provides a copper bismuthate / copper oxide conformal morphology heterojunction film and a preparation method thereof.The preparation method comprises the steps that a bismuth oxyiodide film is prepared and placed in a copper source solution, primary deposition is conducted for a certain time, and a pure-phase copper bismuthate film is obtained after sintering; a copper nanocrystal solution is prepared through laser beam irradiation, thiourea molecules are dissolved in the copper nanocrystal solution, and a mixed solution is obtained; spin-coating the mixed solution on the outer surface of a pure-phase copper bismuthate thin film, drying the thin film in a heating stage, placing the thin film in a copper source solution, carrying out secondary deposition for a certain time, and sintering again to obtain a copper oxide second phase attached to the outer surface of the pure-phase copper bismuthate thin film, so as to obtain a copper bismuthate / copper oxide conformal morphology heterojunction thin film; the pure-phase copper bismuthate film and the copper oxide second phase are obtained in sequence through two times of electro-deposition, and the preparation process is simple and easy to regulate and control; and the surface dynamics and the surface carrier extraction efficiency of the prepared thin film are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of photoelectrocatalytic materials, and particularly relates to a copper bismuthate / copper oxide conformal heterojunction thin film and a preparation method thereof. Background Art

[0002] Photoelectrochemical (PEC) water splitting for hydrogen production is a low-cost hydrogen production technology. The core of this technology is to search for and develop excellent photoelectrode materials. Copper bismuthate (CuBi2O4) is a natural mineral, which is inexpensive, easy to obtain and chemically stable. At the same time, due to its suitable band gap and band edge position as well as good light absorption ability, it is considered to be a very promising photoelectrode material.

[0003] Under simulated light of AM 1.5G, the theoretical photocurrent density of CuBi2O4 is 19.7 - 29 mA / cm 2 , however, the experimental photocurrent density is far less than this theoretical value. This is mainly due to the slow surface reaction kinetics and serious surface carrier accumulation and recombination of CuBi2O4. Finding a suitable material to form a heterojunction structure with CuBi2O4 is an effective strategy to solve the above problems.

[0004] Copper oxide (CuO) has a suitable bandwidth and conduction band position as well as better light absorption ability, and becomes a suitable material to form a heterojunction structure with CuBi2O4. At present, most of the copper bismuthate / copper oxide heterojunctions or other types of heterojunctions are single structures with a layered "mechanical" stack, and this structure limits the function of the heterojunction. Therefore, according to the morphology of the substrate material, what strategy to adopt to maximize the function of the heterojunction structure is worthy of in-depth study. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a copper bismuthate / copper oxide conformal heterojunction thin film and a preparation method thereof.

[0006] The present invention provides a preparation method of a copper bismuthate / copper oxide conformal heterojunction thin film, and the preparation method includes, Step 1: Prepare a bismuth iodide oxide thin film, place it in a copper source solution, deposit for a certain time once, and obtain a pure-phase copper bismuthate thin film after sintering; Step 2: Prepare a copper nanocrystal solution by laser beam irradiation, and dissolve thiourea molecules in the copper nanocrystal solution to obtain a mixed solution; Step 3: Spin-coat the mixed solution in Step 2 on the outer surface of the pure-phase copper bismuthate thin film in Step 1, dry it on a hot stage, then place it in a copper source solution, deposit for a certain time twice, and sinter again to obtain a second-phase copper oxide attached to the outer surface of the pure-phase copper bismuthate thin film, thereby obtaining a copper bismuthate / copper oxide conformal heterojunction thin film.

[0007] Preferably, the process of preparing the bismuth oxyiodide thin film in step 1 is as follows: potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate are dissolved in water to obtain solution A, p-benzoquinone is dissolved in ethanol to obtain solution B, solution A and solution B are mixed to obtain mixed solution C, and the conductive glass substrate is placed in mixed solution C and deposited for 400 - 800 seconds to obtain the bismuth oxyiodide thin film.

[0008] Preferably, the copper source solution in step 1 is a copper acetate monohydrate solution with a concentration of 0.2 mol / L. During the first deposition process, the deposition voltage is -0.3 V, the deposition time is 50 - 80 seconds, the sintering temperature is 450 °C, the heating rate is 2 °C / min, and the sintering time is 3 h.

[0009] Preferably, the concentration of the thiourea molecules in step 2 is 1 - 3 mmol / L.

[0010] Preferably, the process of preparing the copper nanocrystal solution by laser beam irradiation in step 2 is as follows: under ultrasonic assistance, the metal material is placed in the solvent and irradiated under the laser beam. After irradiation, the metal material is taken out to obtain the copper nanocrystal solution.

[0011] Preferably, the laser used is a non - focused laser with an output wavelength of 1064 nm, a pulse frequency of 10 Hz, an output spot diameter of 10 mm, and a laser irradiation energy of 800 mJ / cm 2 , and the irradiation time is 5 - 60 seconds.

[0012] Preferably, the metal material is copper and the solvent is dimethyl sulfoxide solvent.

[0013] Preferably, the hot stage temperature in step 3 is 120 - 150 °C, and the drying time is 10 - 15 min.

[0014] Preferably, the concentration of the copper source solution in step 3 is 0.2 mol / L. During the second deposition process, the deposition voltage is -0.3 V, the deposition time is 40 - 70 seconds. During the second sintering process, the sintering temperature is 450 °C, the heating rate is 2 °C / min, and the sintering time is 3 h.

[0015] The present invention also provides a copper bismuthate / copper oxide conformal morphology heterojunction thin film prepared by the above method. The heterojunction thin film is composed of a pure - phase copper bismuthate thin film and a second - phase copper oxide attached to the outer surface of the pure - phase copper bismuthate thin film, and the pure - phase copper bismuthate thin film and the second - phase copper oxide have a conformal morphology.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention uses two - step electrodeposition to obtain a pure - phase copper bismuthate thin film and a second - phase copper oxide successively, and the preparation process is simple and easy to control.

[0017] 2. The present invention uses liquid phase pulsed laser irradiation technology to obtain copper nanocrystals with a size less than 10 nm, which are difficult to synthesize, and then mixes thiourea molecules with them and evenly spin-coates them on the surface of a pure phase copper bismuthate film. The two work together to regulate a copper bismuthate / copper oxide heterojunction film with a conformal morphology.

[0018] 3. The realization of the coplanar morphology in the present invention enables the copper bismuthate / copper oxide heterojunction structure to play the maximum role. Performance tests on the film showed that the photocurrent density was increased by 5.3 times compared with the pure phase copper bismuthate film, and the photocurrent density was increased by 2.1 times compared with the traditional morphology copper bismuthate / copper oxide heterojunction film, and the surface dynamics and surface carrier extraction efficiency of the film were greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. It should be noted that the drawings described below only relate to some embodiments of the present disclosure, but are not intended to limit the present disclosure, wherein: Figure 1 It is a scanning electron micrograph provided in Example 1 of the present invention; wherein A is the scanning electron micrograph of Example 1, and B is a high-magnification image selected and enlarged from Figure A.

[0020] Figure 2 It is the scanning electron micrograph provided by Examples 2-4 of the present invention; wherein A is the scanning electron micrograph of Example 2, B is the scanning electron micrograph of Example 3, and C is the scanning electron micrograph of Example 4.

[0021] Figure 3 It is a scanning electron micrograph provided by Examples 5-6 of the present invention; wherein A is the scanning electron micrograph of Example 5, and B is the scanning electron micrograph of Example 6.

[0022] Figure 4 It is the scanning electron micrograph provided by comparative examples 1-2 of the present invention, wherein A is the scanning electron micrograph of comparative example 1, and B is the scanning electron micrograph of comparative example 2.

[0023] Figure 5 It is the scanning electron micrograph provided by comparative examples 3-4 of the present invention, wherein A is the scanning electron micrograph of comparative example 3, and B is the scanning electron micrograph of comparative example 4.

[0024] Figure 6 It is a voltammetric graph provided by Examples 1-4 of the present invention.

[0025] Figure 7 It is a volt-ampere curve diagram provided by Examples 1, 5 and 6 of the present invention.

[0026] Figure 8 are the volt-ampere characteristic curves provided in Example 1 and Comparative Examples 1-2 of the present invention.

[0027] Figure 9 are the volt-ampere characteristic curves provided in Example 1 and Comparative Examples 3-4 of the present invention.

[0028] Figure 10 are the X-ray diffraction and Raman spectra provided in Example 1 and Comparative Examples 3-4 of the present invention; wherein, A is the X-ray diffraction pattern and B is the Raman spectrum.

[0029] Figure 11 are the hydrogen evolution activity and photoluminescence spectra of Example 1 and Comparative Examples 3-4 of the present invention; wherein, A is the hydrogen evolution activity graph and B is the photoluminescence spectrum. Detailed implementation manners

[0030] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art without creative efforts based on the described embodiments of the present disclosure also fall within the scope of protection of the present disclosure.

[0031] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the subject matter of the present disclosure belongs. Further, it will be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless expressly defined herein otherwise. As used herein, the statement of joining or coupling two or more parts together shall mean that these parts are directly joined together or joined through one or more intermediate components.

[0032] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0033] Selecting CuO and CuBi2O4 to construct a heterojunction structure is an effective strategy to solve the problems of slow surface reaction kinetics and severe surface carrier accumulation and recombination of CuBi2O4. Most of the known heterojunction morphologies are single structures with a layered "mechanical" stacking. When encountering substrates with morphologies such as porous or vertically stacked sheets, this structure can only play a limited role. Therefore, according to the specific morphology of the substrate material, what strategy should be adopted to construct a conformal heterojunction film to maximize the role of the heterojunction structure is worthy of in-depth study. On the other hand, when a single regulator cannot meet the required requirements, what substances should be added continuously and how to achieve the synergistic regulation effect between the two are also worthy of exploration and research.

[0034] Based on the solution of the above problems, the present invention provides a method for preparing a copper bismuthate / cupric oxide conformal heterojunction film, and the preparation method includes, Step 1: Prepare a bismuth oxyiodide (BOI) film, place it in a copper source solution, deposit for a certain time once, and obtain a pure-phase copper bismuthate film after sintering; During the preparation of the bismuth oxyiodide (BOI) film, potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate are dissolved in water to obtain solution A, p-benzoquinone is dissolved in ethanol to obtain solution B, the two solutions A and B are mixed to obtain a mixed solution C, and the conductive glass substrate is placed in the mixed solution C. The deposition time is preferably 400 - 800 seconds. For example, it can be 400 seconds, 500 seconds, 600 seconds, 700 seconds, 800 seconds to obtain the bismuth oxyiodide (BOI) film; wherein, the concentration of potassium iodide is 0.4M, the volume of concentrated nitric acid is 80 μl, the concentration of bismuth nitrate pentahydrate is 0.02M, the concentration of p-benzoquinone is 0.22M, and the deposition voltage is -0.1V; In some embodiments of the present invention, the copper source solution in Step 1 is a copper acetate monohydrate solution with a concentration of 0.2M. During the single deposition process, the deposition voltage is -0.3V, the deposition time is preferably 50 - 80 seconds. For example, it can be 50 seconds, 60 seconds, 70 seconds, 80 seconds, the sintering temperature is 450 °C, the heating rate is 2 °C / min, and the sintering time is 3h.

[0035] Step 2: Prepare a copper nanocrystal solution by laser beam irradiation, and dissolve thiourea molecules in the copper nanocrystal solution to obtain a mixed solution; The process of preparing the copper nanocrystal solution by laser beam irradiation is as follows: Under ultrasonic assistance, a metal material is placed in a solvent and irradiated under a laser beam. After irradiation, the metal material is taken out to obtain a copper nanocrystal solution; wherein, the metal material is Cu, the solvent is dimethyl sulfoxide solvent, the laser is a non-focused laser, the output wavelength of the laser is 1064 nm, the pulse frequency is 10 Hz, the output spot diameter is about 10 mm, and the laser irradiation energy is 800 mJ / cm 2, the irradiation time is preferably 5 to 60 seconds. For example, it can be 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds. The concentration of thiourea molecules is preferably 1 to 3 mM. For example, it can be 1 mM, 2 mM, or 3 mM.

[0036] Step 3: Spin-coat the mixed solution in Step 2 on the outer surface of the pure-phase copper bismuthate thin film in Step 1. After drying it on a hot stage, place it in a copper source solution and perform secondary deposition for a certain period of time. Then sinter it again to obtain a second-phase copper oxide attached to the outer surface of the pure-phase copper bismuthate thin film, thus obtaining a copper bismuthate / copper oxide conformal morphology heterojunction thin film. Among them, the temperature of the above-mentioned hot stage is 120 - 150 °C, and the drying time is 10 - 15 min; the concentration of the copper source solution in Step 3 is 0.2 mol / L. During the secondary deposition process, the deposition voltage is -0.3 V, and the deposition time is preferably 40 - 70 seconds. For example, it can be 40 seconds, 50 seconds, 60 seconds, or 70 seconds. During the re-sintering process, the sintering temperature is 450 °C, the heating rate is 2 °C / min, and the sintering time is 3 h.

[0037] The present invention also provides a copper bismuthate / copper oxide conformal morphology heterojunction thin film prepared by the above method. The heterojunction thin film is composed of a pure-phase copper bismuthate thin film and a second-phase copper oxide attached to the outer surface of the pure-phase copper bismuthate thin film, and the pure-phase copper bismuthate thin film and the second-phase copper oxide have a conformal morphology. In order to verify the effectiveness of the present invention in synergistically regulating the conformal morphology of the copper bismuthate / copper oxide heterojunction through copper nanocrystals and thiourea molecules, the effectiveness of the present invention can be verified by testing the optoelectronic properties of the thin film.

[0038] The following is illustrated with specific examples: Example 1

[0039] A method for preparing a copper bismuthate / copper oxide conformal morphology heterojunction thin film, comprising the following steps: Step 1: Dissolve potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate in water, and dissolve p-benzoquinone in ethanol. Mix the two solutions to obtain a mixed solution. Place the conductive glass substrate in the above solution and deposit it at a voltage of -0.1 V for 600 seconds to obtain a BOI thin film. Among them, the volume of water is 50 ml, the volume of ethanol is 20 ml, the concentration of potassium iodide is 0.4 M, the volume of concentrated nitric acid is 80 μl, the concentration of bismuth nitrate pentahydrate is 0.02 M, and the concentration of p-benzoquinone is 0.22 M.

[0040] Step 2: Place the BOI thin film in a copper acetate monohydrate solution, deposit it for 70 seconds, and sinter it at 450 °C for 3 h to obtain a pure-phase copper bismuthate thin film. Among them, the volume of the copper acetate monohydrate solution is 60 ml, the concentration is 0.2 M, and the heating rate is 2 °C / min.

[0041] Step 3: Under ultrasonic assistance, place the Cu target in dimethyl sulfoxide solvent and irradiate it under a laser beam with a wavelength of 1064 nm and an energy of 800 mJ / cm 2 for 15 seconds. After irradiation, take out the Cu target to obtain a copper nanocrystal solution, and dissolve thiourea molecules in the above solution to obtain a mixed solution of the two; among them, the volume of dimethyl sulfoxide is 10 ml and the concentration of thiourea molecules is 2 mM.

[0042] Step 4: Take out 80 μl of the mixed solution in Step 3, spin-coat it evenly on the surface of the pure-phase copper bismuthate thin film, and then place it on a hot stage at 150 °C to dry for 10 min.

[0043] Step 5: Place the pure-phase copper bismuthate thin film treated in Step 4 in a copper acetate monohydrate solution again, deposit for 60 seconds, and sinter at 450 °C for 3 h to obtain a copper bismuthate / copper oxide conformal heterojunction thin film.

[0044] Among them, the volume of the copper acetate monohydrate solution is 60 ml, the concentration is 0.2 M, and the heating rate is 2 °C / min.

[0045] Among them, the copper bismuthate / copper oxide conformal heterojunction thin film prepared by this method is denoted as CuNC / THI-CBO / CuO-1.

[0046] Example 2: The preparation steps are the same as those in Example 1, except that: the laser irradiation time in Step 3 is 60 seconds.

[0047] Among them, the copper bismuthate / copper oxide conformal heterojunction thin film prepared by this method is denoted as CuNC / THI-CBO / CuO-2.

[0048] Example 3

[0049] The preparation steps are the same as those in Example 1, except that: the laser irradiation time in Step 3 is 30 seconds.

[0050] Among them, the copper bismuthate / copper oxide conformal heterojunction thin film prepared by this method is denoted as CuNC / THI-CBO / CuO-3.

[0051] Example 4

[0052] The preparation steps are the same as those in Example 1, except that: the laser irradiation time in Step 3 is 5 seconds.

[0053] Among them, the copper bismuthate / copper oxide conformal heterojunction thin film prepared by this method is denoted as CuNC / THI-CBO / CuO-4.

[0054] Example 5

[0055] The preparation steps are the same as those in Example 1, except that: in step three, the concentration of thiourea molecules is 3 mM.

[0056] Among them, the copper bismuthate / cupric oxide conformal heterojunction thin film prepared by this method is denoted as CuNC / THI-CBO / CuO-5.

[0057] Example 6

[0058] The preparation steps are the same as those in Example 1, except that: in step three, the concentration of thiourea molecules is 1 mM.

[0059] Among them, the copper bismuthate / cupric oxide conformal heterojunction thin film prepared by this method is denoted as CuNC / THI-CBO / CuO-6.

[0060] Comparative Example 1: The preparation steps are the same as those in Example 1, except that: in step three, the mixed solution becomes a copper nanocrystal solution containing only 15 seconds of laser irradiation.

[0061] Among them, the copper bismuthate / cupric oxide heterojunction thin film prepared by this method is denoted as CuNC-CBO / CuO.

[0062] Comparative Example 2: The preparation steps are the same as those in Example 1, except that: in step three, the mixed solution becomes a solution containing only 0.2 mM thiourea molecules.

[0063] Among them, the copper bismuthate / cupric oxide heterojunction thin film prepared by this method is denoted as THI-CBO / CuO.

[0064] Comparative Example 3: Step 1: Dissolve potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate in water, dissolve p-benzoquinone in ethanol, mix the two solutions to obtain a mixed solution, place the conductive glass substrate in the above solution, and deposit for 600 seconds at -0.1 V voltage to obtain a BOI thin film.

[0065] Among them, the volume of water is 50 ml, the volume of ethanol is 20 ml, the concentration of potassium iodide is 0.4 M, the volume of concentrated nitric acid is 80 μl, the concentration of bismuth nitrate pentahydrate is 0.02 M, and the concentration of p-benzoquinone is 0.22 M.

[0066] Step 2: Place the BOI thin film in a copper acetate monohydrate solution, deposit for 130 seconds, and sinter at 450 °C for 3 h to obtain a copper bismuthate / cupric oxide heterojunction thin film.

[0067] Among them, the volume of the copper acetate monohydrate solution is 60 ml, the concentration is 0.2 M, and the heating rate is 2 °C / min.

[0068] Among them, the copper bismuthate / copper oxide heterojunction film prepared by this method is denoted as CBO / CuO.

[0069] Comparative Example 4: The preparation steps are the same as those in Comparative Example 3, except that: in Step 2, the deposition time is changed to 70 seconds.

[0070] Among them, the copper bismuthate film prepared by this method is denoted as CBO.

[0071] To illustrate the actual effect of the copper bismuthate / copper oxide conformal morphology heterojunction film prepared by the present invention, the films prepared in Specific Example 1 and Comparative Examples 3 and 4 were subjected to scanning electron microscopy and X-ray diffraction and Raman spectroscopy tests for morphology and phase analysis. The results are as Figure 1 、 5 、10 shown; as can be seen from Figure 5 B, the pure-phase copper bismuthate film prepared in Comparative Example 4 shows a morphology of vertical stacking of flake structures; as can be seen from Figure 5 A, the copper bismuthate / copper oxide heterojunction film prepared in Comparative Example 3 shows a morphology of layered stacking of copper bismuthate and copper oxide, and the copper oxide crystal size is large and unevenly distributed; as can be seen from Figure 1 A, the copper bismuthate / copper oxide conformal morphology heterojunction film prepared in Specific Example 1 shows a conformal morphology in which small copper oxide particles grow on the outer surface of copper bismuthate, and as can be seen from Figure 1 the local enlarged view of B, the small copper oxide particles densely and uniformly cover the outer surface of copper bismuthate; as can be seen from Figure 10 A and Figure 10 B, it can be seen that Example 1 and Comparative Example 3 contain obvious corresponding peaks of copper oxide, while Comparative Example 4 only has a single corresponding peak of copper bismuthate. The above analysis shows the feasibility of preparing the copper bismuthate / copper oxide conformal morphology heterojunction film in Example 1.

[0072] To illustrate the effect of the copper nanocrystals and thiourea molecules in the present invention in synergistically regulating the copper bismuthate / copper oxide heterojunction film to achieve a conformal morphology, the films prepared in Specific Example 1 and Comparative Examples 1 and 2 were subjected to scanning electron microscopy and photocurrent density tests for morphology and performance analysis. The results are as Figure 1 、 4 、8 shown. As can be seen from Figure 1 A, the copper bismuthate / copper oxide conformal morphology heterojunction film prepared in Specific Example 1 shows a conformal morphology in which small copper oxide particles grow on the outer surface of copper bismuthate, and as can be seen from Figure 1 the local enlarged view of B, the small copper oxide particles densely and uniformly cover the outer surface of copper bismuthate; as can be seen from Figure 4It can be seen from A that in Comparative Example 1, under the regulation of copper nanocrystals, copper oxide particles also cover the surface of copper bismuthate and maintain the morphology of pure-phase copper bismuthate, which has the effect of fixing the morphology. However, compared with Specific Example 1, the copper oxide particles are larger and unevenly distributed. At the same time, from Figure 8 it can be seen that there is still a large gap in the photocurrent density of the thin film prepared in Comparative Example 1 compared with that in Example 1; from Figure 4 It can be seen from B that in Comparative Example 2, under the regulation of thiourea molecules, a layer of copper oxide crystals covers the surface of copper bismuthate. Like Comparative Example 3, copper bismuthate and copper oxide belong to a stacked structure. However, in Comparative Example 2, the copper oxide crystals are smaller and more evenly distributed, which has the effect of refining the grain size. At the same time, from Figure 8 it can be seen that there is still a large gap in the photocurrent density of the thin film prepared in Comparative Example 2 compared with that in Example 1. The above analysis shows that copper nanocrystals and thiourea molecules have a good synergistic effect in regulating the copper bismuthate / copper oxide heterojunction thin film to achieve a conformal morphology.

[0073] In order to illustrate that the experimental parameters of Specific Example 1 in the present invention have the effect of enabling the copper bismuthate / copper oxide heterojunction thin film to reach an ideal conformal morphology state and performance, the present invention performs scanning electron microscopy and photocurrent density tests on the thin films of Specific Examples 1, 2, 3, 4, 5, and 6 for morphology and performance analysis. The results are as shown in Figure 1 、 2 、3、6、7. It can be seen from Figure 1 A that the copper bismuthate / copper oxide conformal morphology heterojunction thin film prepared in Specific Example 1 presents a conformal morphology in which small copper oxide particles grow attached to the outer surface of copper bismuthate. And from Figure 1 the local enlarged view of B, it can be seen that small copper oxide particles densely and evenly cover the outer surface of copper bismuthate; from Figure 2 A, it can be seen that when the irradiation time is 60 seconds, the copper oxide particles agglomerate and cover the surface of the copper bismuthate thin film. When the irradiation time is reduced to 30 seconds, from Figure 2 B, it can be seen that the agglomeration phenomenon of the copper oxide particles weakens and presents a certain degree of conformal morphology. When the irradiation time is less than 15 seconds and is 5 seconds, from Figure 2 C, it can be seen that the morphology is an obvious conformal morphology, but the coverage of copper oxide particles is relatively sparse. Therefore, we judge that when the irradiation time is 15 seconds, the content of copper nanocrystals in the solvent is appropriate, evenly dispersed, and in an equilibrium state. As the irradiation time increases, the equilibrium state is broken, and the copper nanocrystals agglomerate, resulting in the final morphology showing agglomeration of copper oxide particles and an unclear conformal effect. When the irradiation time is reduced, the content of copper nanocrystals in the solvent is appropriate, resulting in a low coverage rate of copper oxide. At the same time, from Figure 6 it can be seen that there is a large gap in the photocurrent density of the thin films prepared in Specific Examples 2, 3, and 4 compared with that in Example 1; when the thiourea concentration is increased, from Figure 3As can be seen in A, copper oxide covers the surface of copper bismuthate in a smaller size and more densely, resulting in an increase in film thickness and a decrease in the gap between lamellae, reducing the light absorption ability. When the thiourea concentration is decreased, from Figure 3 As can be seen in B, the morphology is an obvious conformal morphology. However, copper oxide particles mainly cover the inside of the lamellae, the surface of the lamellae is sparsely covered, and local agglomeration of copper oxide particles will occur. Therefore, we judge that the thiourea concentration of 2 mM is the most suitable. When the thiourea concentration increases, although the effect of refining crystal grains is more obvious, it will reduce the light absorption ability of the thin film. When the thiourea concentration decreases, the coverage rate of copper oxide particles is insufficient and the local distribution is uneven. At the same time, from Figure 7 it can be seen that there is a large gap in the photocurrent density of the thin films prepared in Specific Examples 5 and 6 compared with that in Example 1; the above analysis shows that the experimental parameters of Specific Example 1 have the effect of enabling the copper bismuthate / copper oxide heterojunction thin film to reach an ideal conformal morphology state and performance.

[0074] To further illustrate the effective application of the copper bismuthate / copper oxide conformal morphology heterojunction thin film prepared by the present invention in the field of photoelectrocatalysis, the catalytic performance of Specific Example 1 and Comparative Examples 3 and 4 of the present invention was characterized. The results are as Figure 9 and Figure 11 shown.

[0075] From Figure 9 it can be seen that whether it is a traditional morphology heterojunction thin film or a conformal morphology heterojunction thin film, their photocurrent density is much higher than that of pure-phase copper bismuthate, proving the effectiveness of constructing the heterojunction structure. The photocurrent density of the conformal morphology heterojunction thin film is 5.3 times that of the pure-phase copper bismuthate thin film and 2.1 times that of the traditional heterojunction thin film, indicating that the conformal morphology heterojunction thin film can maximize the role of the heterojunction structure and improve the photoelectrochemical performance.

[0076] From Figure 11 A it can be seen that compared with the pure-phase copper bismuthate and the traditional morphology heterojunction thin film, the conformal morphology heterojunction thin film has the smallest overpotential, and the hydrogen evolution activity is increased by 2.3 and 3.9 times respectively, indicating that the conformal morphology heterojunction thin film has stronger surface kinetics; from Figure 11 B it can be seen that compared with the pure-phase copper bismuthate and the traditional morphology heterojunction thin film, the conformal morphology heterojunction thin film has the smallest peak intensity, indicating that the conformal morphology heterojunction thin film more effectively reduces the accumulation and recombination of surface carriers.

[0077] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a copper bismuthate / copper oxide conformal heterojunction film, characterized in that: The preparation method comprises: Step 1: prepare a bismuth oxide iodide film and place it in a copper source solution for a certain period of time, and obtain a pure phase copper bismuthate film after sintering; Step 2: preparing a copper nanocrystal solution by laser beam irradiation, and dissolving thiourea molecules in the copper nanocrystal solution to obtain a mixed solution; Step 3: Spin-coat the mixed solution in step 2 on the outer surface of the pure phase copper bismuth oxide film in step 1, place it on a hot plate for drying, place it in a copper source solution, deposit it for a certain period of time, and sinter it again to obtain a second phase of copper oxide attached to the outer surface of the pure phase copper bismuth oxide film, thereby obtaining a copper bismuth oxide / copper oxide conformal morphology heterojunction film.

2. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that: The process for preparing the bismuth oxide iodide film described in step 1 is to dissolve potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate in water to obtain solution A, dissolve p-benzoquinone in ethanol to obtain solution B, mix solution A and solution B to obtain a mixed solution C, place a conductive glass substrate in the mixed solution C, and deposit for 400-800 seconds to obtain a bismuth oxide iodide film.

3. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that: The copper source solution in step 1 is a monohydrated copper acetate solution with a concentration of 0.2 mol / L. During one deposition process, the deposition voltage is -0.3 V, the deposition time is 50-80 seconds, the sintering temperature is 450° C., the heating rate is 2° C. / min, and the sintering time is 3 h.

4. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that: The thiourea molecular concentration in step 2 is 1-3 mmol / L.

5. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that: The process of preparing the copper nanocrystal solution by laser beam irradiation in step 2 is to place the metal material in a solvent under the assistance of ultrasound, place it under the laser beam for irradiation, and take out the metal material after the irradiation is completed to obtain the copper nanocrystal solution.

6. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 5, characterized in that: The laser is a non-focused laser with an output wavelength of 1064nm, a pulse frequency of 10Hz, an output spot diameter of 10mm, and a laser irradiation energy of 800mJ / cm 2 , the irradiation time is 5~60 seconds.

7. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 5, characterized in that: The metal material is copper, and the solvent is dimethyl sulfoxide solvent.

8. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that: In step 3, the temperature of the hot plate is 120-150° C., and the drying time is 10-15 minutes.

9. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that: The concentration of the copper source solution in step 3 is 0.2 mol / L. During the secondary deposition process, the deposition voltage is -0.3 V, the deposition time is 40-70 seconds, and during the secondary sintering process, the sintering temperature is 450° C., the heating rate is 2° C. / min, and the sintering time is 3 h.

10. A heterojunction film prepared by the method for preparing a copper bismuthate / copper oxide conformal heterojunction film according to any one of claims 1 to 9, characterized in that: The heterojunction film consists of a pure phase copper bismuthate film and a copper oxide second phase attached to the outer surface of the pure phase copper bismuthate film, and the pure phase copper bismuthate film and the copper oxide second phase have a conformal morphology.

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