A copper bismuth oxide / copper oxide conformal morphology heterojunction thin film and a preparation method thereof

Abstract

The application belongs to the technical field of photoelectric catalytic material preparation, and specifically provides a copper bismuthate / copper oxide conformal morphology heterojunction film and a preparation method thereof. The preparation method comprises the following steps: preparing a bismuth oxyiodide film, placing the bismuth oxyiodide film in a copper source solution, depositing for a certain time, sintering to obtain a pure-phase copper bismuthate film; preparing a copper nanocrystal solution through laser beam irradiation, dissolving thiourea molecules in the copper nanocrystal solution to obtain a mixed solution; spin-coating the mixed solution on the outer surface of the pure-phase copper bismuthate film, placing the pure-phase copper bismuthate film on a hot table for drying, placing the pure-phase copper bismuthate film in the copper source solution, depositing for a certain time again, sintering again to obtain a copper oxide second phase attached to the outer surface of the pure-phase copper bismuthate film, and obtaining the copper bismuthate / copper oxide conformal morphology heterojunction film. The pure-phase copper bismuthate film and the copper oxide second phase are obtained through two-time electrodeposition in sequence, the preparation process is simple and easy to control, and the surface dynamics and the surface carrier extraction efficiency of the prepared film are greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photoelectric catalytic material preparation, in particular to a copper bismuthate / copper oxide conformal morphology heterojunction film and a preparation method thereof. BACKGROUND

[0002] Photoelectrochemical (PEC) water splitting for hydrogen production is a low-cost hydrogen production technology, and the core of the technology is to find and develop a photoelectrode material with excellent performance. Copper bismuthate (CuBi2O4) is a natural mineral, which is cheap and easy to obtain and has stable chemical properties. At the same time, because it has a suitable band gap and band edge position and good light absorption capacity, it is considered to be a very potential photoelectrode material.

[0003] Under the simulated light of AM 1.5G, the theoretical photocurrent density of CuBi2O4 is 19.7-29mA / cm 2 However, the experimental photocurrent density is much smaller than the theoretical value, which is mainly due to the slow surface reaction kinetics of CuBi2O4 and the serious surface carrier accumulation and recombination. 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 band width and a conduction band position and a more excellent light absorption capacity, and becomes a suitable material for forming a heterojunction structure with CuBi2O4. At present, copper bismuthate / copper oxide heterojunction or other kinds of heterojunctions are mostly single structures stacked in layers. This structure limits the role of the heterojunction. Therefore, according to the morphology of the substrate material, it is worth being deeply researched that what strategy is adopted to maximize the role of the heterojunction structure. SUMMARY

[0005] The application aims at overcoming the shortcomings of the prior art and providing a copper bismuthate / copper oxide conformal morphology heterojunction film and a preparation method thereof.

[0006] The application provides a preparation method of a copper bismuthate / copper oxide conformal morphology heterojunction film, and the preparation method comprises the following steps.

[0007] Step 1: preparing an iodine bismuth oxide film and placing it in a copper source solution, depositing for a certain time at a time, and obtaining a pure-phase copper bismuthate film after sintering;

[0008] 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;

[0009] Step 3: spin-coating the mixed solution in Step 2 on the outer surface of the pure-phase cupric bismuthate film in Step 1, drying on a hot stage, placing it in a copper source solution, 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 cupric bismuthate film, thereby obtaining a cupric bismuthate / copper oxide conformal morphology heterojunction film.

[0010] Preferably, the process for preparing the bismuth oxyiodide film in Step 1 is dissolving potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate in water to obtain solution A, dissolving p-benzoquinone in ethanol to obtain solution B, mixing solution A and solution B to obtain mixed solution C, and placing a conductive glass substrate in mixed solution C for deposition of 400-800 seconds to obtain a bismuth oxyiodide film.

[0011] Preferably, the copper source solution in Step 1 is a copper acetate monohydrate solution with a concentration of 0.2 mol / L, the deposition voltage in the primary deposition process is -0.3 V, the deposition time is 50-80 seconds, the sintering temperature is 450℃, the heating rate is 2℃ / min, and the sintering time is 3h.

[0012] Preferably, the thiourea molecule concentration in Step 2 is 1-3 mmol / L.

[0013] Preferably, the process for preparing the copper nanocrystal solution by laser beam irradiation in Step 2 is placing a metal material in a solvent under ultrasonic assistance, irradiating it under a laser beam, and taking out the metal material after irradiation to obtain a copper nanocrystal solution.

[0014] Preferably, the laser uses 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 an irradiation time of 5-60 seconds.

[0015] Preferably, the metal material is copper, and the solvent is a dimethyl sulfoxide solvent.

[0016] Preferably, the hot stage temperature in Step 3 is 120-150℃, and the drying time is 10-15 min.

[0017] Preferably, the copper source solution concentration in Step 3 is 0.2 mol / L, the deposition voltage in the secondary deposition process is -0.3 V, the deposition time is 40-70 seconds, the sintering temperature in the secondary sintering process is 450℃, the heating rate is 2℃ / min, and the sintering time is 3h.

[0018] The present invention also provides a copper bismuthate / copper oxide conformal heterojunction film prepared by the above method, wherein the heterojunction film is composed 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 are conformal morphologies.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention uses two electrodeposition processes to obtain a pure-phase copper bismuthate thin film and a copper oxide second phase, which is simple and easy to control.

[0021] 2. This invention uses liquid-phase pulsed laser irradiation technology to obtain copper nanocrystals with a size of less than 10 nm, which are difficult to synthesize. Then, thiourea molecules are mixed with them and uniformly spin-coated on the surface of a pure phase copper bismuthate film. The two are synergistically controlled to produce a copper bismuthate / copper oxide heterojunction film with a conformal morphology.

[0022] 3. The realization of the common morphology in this invention allows the copper bismuthate / copper oxide heterojunction structure to play its maximum role. Performance testing of the film revealed that the photocurrent density was increased by 5.3 times compared to the pure phase copper bismuthate film, and by 2.1 times compared to the conventional morphology copper bismuthate / copper oxide heterojunction film. Furthermore, the film surface dynamics and surface carrier extraction efficiency were significantly improved. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure, wherein:

[0024] Figure 1 These are scanning electron microscope images provided in Embodiment 1 of the present invention; wherein, A is a scanning electron microscope image of Embodiment 1, and B is a high-magnification image selected from Image A.

[0025] Figure 2 These are scanning electron microscope images provided in Embodiments 2-4 of the present invention; wherein, A is a scanning electron microscope image of Embodiment 2, B is a scanning electron microscope image of Embodiment 3, and C is a scanning electron microscope image of Embodiment 4.

[0026] Figure 3 These are scanning electron microscope images provided in Embodiments 5-6 of the present invention; wherein, A is a scanning electron microscope image of Embodiment 5, and B is a scanning electron microscope image of Embodiment 6.

[0027] Figure 4 These are scanning electron microscope images provided in Comparative Examples 1-2 of the present invention, wherein A is a scanning electron microscope image of Comparative Example 1 and B is a scanning electron microscope image of Comparative Example 2.

[0028] Figure 5 These are scanning electron microscope images provided in Comparative Examples 3-4 of the present invention, wherein A is a scanning electron microscope image of Comparative Example 3 and B is a scanning electron microscope image of Comparative Example 4.

[0029] Figure 6 These are the current-voltage curves provided in Embodiments 1-4 of the present invention.

[0030] Figure 7 These are the volt-ampere curves provided in embodiments 1, 5, and 6 of this invention.

[0031] Figure 8 These are the current-voltage curves provided in Embodiment 1 and Comparative Examples 1-2 of the present invention.

[0032] Figure 9 These are the current-voltage curves provided in Embodiment 1 and Comparative Examples 3-4 of the present invention.

[0033] Figure 10 These are the X-ray diffraction and Raman spectra provided in Embodiment 1 and Comparative Examples 3-4 of the present invention; wherein, A is the X-ray diffraction pattern and B is the Raman spectrum.

[0034] Figure 11 These are the hydrogen evolution activity and photoluminescence spectra of Embodiment 1 and Comparative Examples 3-4 of the present invention; wherein, A is the hydrogen evolution activity spectrum and B is the photoluminescence spectrum. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0036] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein. As used herein, the statement of “connecting” or “coupling” two or more parts together shall mean that these parts are directly joined together or joined through one or more intermediate components.

[0037] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] Choosing CuO and CuBi2O4 to construct heterojunction structures is an effective strategy to solve the problems of slow surface reaction kinetics and severe surface carrier recombination in CuBi2O4. Most known heterojunction morphologies are single structures with layered "mechanical" stacking. Such structures can only play a limited role when the substrate material is porous or has vertically stacked sheets. Therefore, it is worthwhile to study in depth which strategy to construct heterojunction films with conformal morphology according to the specific morphology of the substrate material, so as to maximize the role of the heterojunction structure. On the other hand, when a single regulator cannot meet the requirements, it is also worthwhile to explore what substances to add and how to achieve the synergistic regulation effect of the two.

[0039] To address the above problems, this invention provides a method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film, the method comprising:

[0040] Step 1: Prepare bismuth oxy iodide (BOI) thin film, place it in copper source solution, deposit it for a certain time at a time, and sinter to obtain pure phase copper bismuthate thin film;

[0041] In the preparation of bismuth oxyiodide (BOI) thin films, potassium iodide, concentrated nitric acid, and bismuth nitrate pentahydrate are dissolved in water to obtain solution A, and p-benzoquinone is dissolved in ethanol to obtain solution B. Solutions A and B are mixed to obtain mixed solution C. A conductive glass substrate is placed in mixed solution C, and the deposition time is preferably 400-800 seconds, for example, 400 seconds, 500 seconds, 600 seconds, 700 seconds, or 800 seconds, to obtain the bismuth oxyiodide (BOI) thin film. 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, the concentration of p-benzoquinone is 0.22 M, and the deposition voltage is -0.1 V.

[0042] 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, 50 seconds, 60 seconds, 70 seconds, or 80 seconds, the sintering temperature is 450℃, the heating rate is 2℃ / min, and the sintering time is 3h.

[0043] 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;

[0044] The process of preparing copper nanocrystal solution by laser beam irradiation involves placing a metal material in a solvent under ultrasonic assistance and then irradiating it with a laser beam. After irradiation, the metal material is removed, yielding the copper nanocrystal solution. The metal material is Cu, the solvent is dimethyl sulfoxide, the laser is an unfocused laser with an output wavelength of 1064 nm, a pulse frequency of 10 Hz, an output spot diameter of approximately 10 mm, and an irradiation energy of 800 mJ / cm². 2 The irradiation time is preferably 5 to 60 seconds, for example, 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds. The thiourea molecular concentration is preferably 1 to 3 mM, for example, 1 mM, 2 mM, or 3 mM.

[0045] Step 3: Spin-coat the mixed solution from Step 2 onto the outer surface of the pure phase copper bismuthate film from Step 1, dry it on a hot table, place it in a copper source solution, deposit it a second time for a certain period of time, and sinter it again to obtain a copper oxide second phase attached to the outer surface of the pure phase copper bismuthate film, thus obtaining a copper bismuthate / copper oxide conformal heterojunction film.

[0046] The hot plate temperature is 120-150℃, 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 -0.3V, and the deposition time is preferably 40-70 seconds, for example, 40 seconds, 50 seconds, 60 seconds, or 70 seconds. During the second sintering process, the sintering temperature is 450℃, the heating rate is 2℃ / min, and the sintering time is 3h.

[0047] This invention also provides a copper bismuthate / copper oxide conformal heterojunction thin film prepared by the above method. The heterojunction thin film consists of a pure-phase copper bismuthate thin film and a copper oxide second phase attached to the outer surface of the pure-phase copper bismuthate thin film, and the pure-phase copper bismuthate thin film and the copper oxide second phase have a conformal morphology. To verify the effectiveness of this invention in synergistically regulating the conformal morphology of the copper bismuthate / copper oxide heterojunction through copper nanocrystals and thiourea molecules, the effectiveness of this invention can be verified by testing the photoelectric properties of the thin film.

[0048] The following is an explanation with reference to specific embodiments:

[0049] Example 1

[0050] A method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film includes the following steps:

[0051] 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 -0.1V for 600 seconds to obtain a BOI film.

[0052] The concentrations of water, ethanol, potassium iodide, concentrated nitric acid, bismuth nitrate pentahydrate, and p-benzoquinone were 50 ml, 20 ml, 0.4 M, 80 μl, 0.02 M, and 0.22 M respectively.

[0053] Step 2: Place the BOI film in a copper acetate monohydrate solution, deposit for 70 seconds, and sinter at 450℃ for 3 hours to obtain a pure phase copper bismuthate film; wherein the volume of the copper acetate monohydrate solution is 60 ml, the concentration is 0.2 M, and the heating rate is 2℃ / min.

[0054] Step 3: Under ultrasonic assistance, place the Cu target material in dimethyl sulfoxide solvent and expose it to light at a wavelength of 1064 nm and an energy of 800 mJ / cm². 2 The target material was irradiated with a laser beam for 15 seconds. After irradiation, the Cu target material was removed to obtain a copper nanocrystal solution. Thiourea molecules were dissolved in the above solution to obtain a mixed solution. The volume of dimethyl sulfoxide was 10 ml and the concentration of thiourea molecules was 2 mM.

[0055] Step 4: Take 80 μl of the mixed solution from Step 3 and spin-coat it evenly onto the surface of a pure phase copper bismuthate film. Then place it on a hot table at 150°C to dry for 10 min.

[0056] Step 5: Place the pure phase copper bismuthate film treated in Step 4 back into a copper acetate monohydrate solution, deposit for 60 seconds, and sinter at 450℃ for 3 hours to obtain a copper bismuthate / copper oxide conformal heterojunction film.

[0057] The copper acetate monohydrate solution had a volume of 60 ml, a concentration of 0.2 M, and a heating rate of 2 °C / min.

[0058] The copper bismuthate / copper oxide conformal heterojunction film prepared using this method is designated as CuNC / THI-CBO / CuO-1.

[0059] Example 2:

[0060] The preparation steps are the same as in Example 1, except that the laser irradiation time in step three is 60 seconds.

[0061] The copper bismuthate / copper oxide conformal heterojunction film prepared using this method is designated as CuNC / THI-CBO / CuO-2.

[0062] Example 3

[0063] The preparation steps are the same as in Example 1, except that the laser irradiation time in step three is 30 seconds.

[0064] The copper bismuthate / copper oxide conformal heterojunction film prepared using this method is designated as CuNC / THI-CBO / CuO-3.

[0065] Example 4

[0066] The preparation steps are the same as in Example 1, except that the laser irradiation time in step three is 5 seconds.

[0067] The copper bismuthate / copper oxide conformal heterojunction film prepared using this method is designated as CuNC / THI-CBO / CuO-4.

[0068] Example 5

[0069] The preparation steps are the same as in Example 1, except that the concentration of thiourea molecules in step three is 3 mM.

[0070] The copper bismuthate / copper oxide conformal heterojunction film prepared using this method is designated as CuNC / THI-CBO / CuO-5.

[0071] Example 6

[0072] The preparation steps are the same as in Example 1, except that the concentration of thiourea molecules in step three is 1 mM.

[0073] The copper bismuthate / copper oxide conformal heterojunction film prepared using this method is designated as CuNC / THI-CBO / CuO-6.

[0074] Comparative Example 1:

[0075] The preparation steps are the same as in Example 1, except that in step three the mixed solution is changed to a copper nanocrystal solution containing only 15 seconds of laser irradiation.

[0076] The copper bismuthate / copper oxide heterojunction film prepared using this method is designated as CuNC-CBO / CuO.

[0077] Comparative Example 2:

[0078] The preparation steps are the same as in Example 1, except that in step three the mixed solution is changed to a solution containing only 0.2 mM thiourea molecules.

[0079] The copper bismuthate / copper oxide heterojunction film prepared using this method is designated as THI-CBO / CuO.

[0080] Comparative Example 3:

[0081] 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 -0.1V for 600 seconds to obtain a BOI film.

[0082] The concentrations of water, ethanol, potassium iodide, concentrated nitric acid, bismuth nitrate pentahydrate, and p-benzoquinone were 50 ml, 20 ml, 0.4 M, 80 μl, 0.02 M, and 0.22 M respectively.

[0083] Step 2: Place the BOI film in a copper acetate monohydrate solution, deposit for 130 seconds, and sinter at 450℃ for 3 hours to obtain a copper bismuthate / copper oxide heterojunction film.

[0084] The copper acetate monohydrate solution had a volume of 60 ml, a concentration of 0.2 M, and a heating rate of 2 °C / min.

[0085] The copper bismuthate / copper oxide heterojunction film prepared using this method is denoted as CBO / CuO.

[0086] Comparative Example 4:

[0087] The preparation steps are the same as those in Comparative Example 3, except that the deposition time in step two is changed to 70 seconds.

[0088] The copper bismuthate thin film prepared using this method is denoted as CBO.

[0089] To illustrate the practical effect of the copper bismuthate / copper oxide conformal heterojunction thin film prepared by this invention, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy were performed on the thin films prepared in Specific Example 1 and Comparative Examples 3 and 4 for morphology and phase analysis. The results are as follows: Figure 1 , 5 As shown in Figure 10; from Figure 5 As can be seen in B, the pure-phase copper bismuthate film prepared in Comparative Example 4 exhibits a vertically stacked, sheet-like structure; from Figure 5 As can be seen in Figure A, the copper bismuthate / copper oxide heterojunction film prepared in Comparative Example 3 exhibits a morphology of layered stacking of copper bismuthate and copper oxide, with the copper oxide crystals being relatively large and unevenly distributed; from Figure 1 As can be seen in A, the copper bismuthate / copper oxide conformal heterojunction film prepared in Specific Example 1 exhibits a conformal morphology where small copper oxide particles adhere to the outer surface of copper bismuthate and grow. Figure 1 In the magnified view of B, small copper oxide particles can be seen densely and uniformly covering the outer surface of copper bismuthate; from Figure 10 A and Figure 10B shows that Example 1 and Comparative Example 3 contain obvious peaks corresponding to copper oxide, while Comparative Example 4 only has a single peak corresponding to copper bismuthate. The above analysis demonstrates the feasibility of preparing a copper bismuthate / copper oxide conformal heterojunction film in Example 1.

[0090] To illustrate the effect of copper nanocrystals and thiourea molecules synergistically regulating the conformal morphology of the copper bismuthate / copper oxide heterojunction film in this invention, scanning electron microscopy (SEM) images and photocurrent density measurements were performed on the films prepared in Specific Example 1 and Comparative Examples 1 and 2 for morphology and performance analysis. The results are as follows: Figure 1 , 4 As shown in Figure 8. From Figure 1 As can be seen in A, the copper bismuthate / copper oxide conformal heterojunction film prepared in Specific Example 1 exhibits a conformal morphology where small copper oxide particles adhere to the outer surface of copper bismuthate and grow. Figure 1 In the magnified view of B, small copper oxide particles can be seen densely and uniformly covering the outer surface of copper bismuthate; from Figure 4 As shown in Comparative Example 1, under the control of copper nanocrystals, the surface of copper bismuthate is also covered with copper oxide particles and maintains the morphology of pure-phase copper bismuthate, thus having the function of fixing the morphology. However, compared with Specific Example 1, the copper oxide particles are larger and more unevenly distributed. Meanwhile, from... Figure 8 It can be seen that the photocurrent density of the thin film prepared in Comparative Example 1 is still significantly lower than that in Example 1; from Figure 4 As shown in Comparative Example B, under the regulation of thiourea molecules, copper bismuthate in Comparative Example 2 is coated with a layer of copper oxide crystals. Similar to Comparative Example 3, copper bismuthate and copper oxide are in a stacked structure. However, the copper oxide crystals in Comparative Example 2 are smaller and more uniformly distributed, which has the effect of refining the grain size. Simultaneously, from... Figure 8 It can be seen that the photocurrent density of the film prepared in Comparative Example 2 is still significantly lower than that in Example 1. The above analysis indicates that copper nanocrystals and thiourea molecules have a good synergistic effect in regulating the conformal morphology of the copper bismuthate / copper oxide heterojunction film.

[0091] To demonstrate that the experimental parameters of Specific Example 1 of this invention achieve the desired conformal morphology and performance of the copper bismuthate / copper oxide heterojunction film, scanning electron microscopy (SEM) images and photocurrent density measurements were performed on the films of Specific Examples 1, 2, 3, 4, 5, and 6 for morphology and performance analysis. The results are as follows: Figure 1 , 2 As shown in 3, 6, and 7. From Figure 1 As can be seen in A, the copper bismuthate / copper oxide conformal heterojunction film prepared in Specific Example 1 exhibits a conformal morphology where small copper oxide particles adhere to the outer surface of copper bismuthate and grow. Figure 1 In the magnified view of B, small copper oxide particles can be seen densely and uniformly covering the outer surface of copper bismuthate; from Figure 2As shown in Figure A, when the irradiation time is 60 seconds, the copper oxide particles agglomerate and cover the surface of the copper bismuthate film. When the irradiation time is reduced to 30 seconds, from... Figure 2 As can be seen in B, the aggregation of copper oxide particles is weakened, and a certain degree of conformal morphology is observed. When the irradiation time is less than 15 seconds, specifically 5 seconds, from... Figure 2 As shown in Figure C, the morphology is clearly conformal, but the copper oxide particle coverage is relatively sparse. Therefore, we can conclude that at an irradiation time of 15 seconds, the copper nanocrystals in the solvent are at a suitable content, evenly dispersed, and in equilibrium. However, as the irradiation time increases, this equilibrium is disrupted, and the copper nanocrystals aggregate, resulting in an aggregated copper oxide particle morphology with a less pronounced conformal effect. Conversely, when the irradiation time decreases, the copper nanocrystal content in the solvent is suitable, leading to a lower copper oxide coverage. Simultaneously, from... Figure 6 It can be seen that the photocurrent density of the films prepared in specific embodiments 2, 3, and 4 differs significantly from that in embodiment 1; when the thiourea concentration is increased, from Figure 3 As shown in Figure A, copper oxide covers the copper bismuthate surface in a smaller and denser manner, resulting in increased film thickness and smaller interlayer gaps, thus reducing light absorption. However, when the thiourea concentration is reduced, [the following occurs]: Figure 3 As seen in Figure B, the morphology is clearly conformal, but the copper oxide particles mainly cover the interior of the sheets, with sparse coverage on the surface and localized aggregation of copper oxide particles. Therefore, we determine that a thiourea concentration of 2 mM is optimal. While increasing the thiourea concentration leads to more significant grain refinement, it also reduces the film's light absorption capacity. Conversely, decreasing the thiourea concentration results in insufficient copper oxide particle coverage and uneven local distribution. Figure 7 It can be seen that the photocurrent density of the films prepared in specific embodiments 5 and 6 is significantly different from that in embodiment 1; the above analysis shows that the experimental parameters of specific embodiment 1 have the effect of enabling the copper bismuthate / copper oxide heterojunction film to achieve the ideal conformal morphology and performance.

[0092] To further illustrate the effective application of the copper bismuthate / copper oxide conformal heterojunction thin film prepared by this invention in the field of photoelectrocatalysis, the catalytic performance of the films in Specific Example 1 and Comparative Examples 3 and 4 of this invention was characterized. The results are as follows... Figure 9 and Figure 11 As shown.

[0093] from Figure 9 As can be seen, both conventional and conformal heterojunction films exhibit photocurrent densities significantly higher than those of pure-phase copper bismuthate films, demonstrating the effectiveness of constructing heterojunction structures. The photocurrent density of conformal heterojunction films is 5.3 times that of pure-phase copper bismuthate films and 2.1 times that of conventional heterojunction films, indicating that conformal heterojunction films can maximize the role of heterojunction structures and improve photoelectrochemical performance.

[0094] from Figure 11 As shown in Figure A, compared with pure-phase copper bismuthate and traditional morphological heterojunction films, the conformal morphological heterojunction film has the smallest excess unit and its hydrogen evolution activity is increased by 2.3 and 3.9 times, respectively, indicating that the conformal morphological heterojunction film has stronger surface dynamics; from Figure 11 As can be seen in B, compared with pure phase copper bismuthate and traditional morphology heterojunction films, conformal morphology heterojunction films have the smallest peak intensity, indicating that conformal morphology heterojunction films more effectively reduce the accumulation and recombination of surface carriers.

[0095] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film, characterized in that, The preparation method includes, Step 1: Prepare a bismuth oxyiodide thin film and place it in a copper source solution. Deposit it once for a certain period of time and sinter to obtain a pure phase copper bismuthate thin film; 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 from Step 2 onto the outer surface of the pure phase copper bismuthate film from Step 1, dry it on a hot plate, place it in a copper source solution, deposit it a second time for a certain period of time, and sinter it again to obtain a copper oxide second phase attached to the outer surface of the pure phase copper bismuthate film, thus obtaining a copper bismuthate / copper oxide conformal 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 bismuth oxyiodine 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; solutions A and B are mixed to obtain mixed solution C; a conductive glass substrate is placed in mixed solution C and deposited for 400-800 seconds to obtain bismuth oxyiodine thin 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 mentioned in step 1 is a copper acetate monohydrate solution with a concentration of 0.2 mol / L. During the single deposition process, the deposition voltage is -0.3V, the deposition time is 50-80 seconds, the sintering temperature is 450℃, the heating rate is 2℃ / min, and the sintering time is 3h.

4. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that, The concentration of thiourea molecules 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 copper nanocrystal solution by laser beam irradiation in step 2 is as follows: under ultrasonic assistance, the metal material is placed in a solvent and irradiated under a laser beam. After irradiation, the metal material is removed 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 an unfocused 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 / cm². 2 The irradiation time is 5 to 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.

8. The method for preparing a copper bismuthate / copper oxide conformal heterojunction thin film according to claim 1, characterized in that, The temperature of the heating table in step 3 is 120-150℃, 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, In step 3, the concentration of the copper source solution is 0.2 mol / L. During the secondary deposition process, the deposition voltage is -0.3V and the deposition time is 40-70 seconds. During the second sintering process, the sintering temperature is 450℃, the heating rate is 2℃ / min, and the sintering time is 3h.

10. The heterojunction film prepared by the method for preparing a copper bismuthate / copper oxide conformal heterojunction film according to any one of claims 1-9, 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.

Images