A photoanode resistant to photocorrosion and its preparation method

Abstract

The present invention combines the technology of two-dimensional material MXene with semiconductor material technology to obtain a new photocorrosion-resistant nanorod array photoanode material. This material can increase the transmission rate of photogenerated carriers, inhibit carrier recombination, and enhance photoelectric performance. Specifically, the present invention provides a method for preparing a novel photocorrosion-resistant nanorod array photoanode, characterized by comprising the following steps: step S1, preparing indium tin oxide conductive glass grown with CdS nanorod arrays; step S2, preparing a few-layer Nb2C nanosheet layer; step S3, using the CdS nanorod array and the few-layer Nb2C nanosheet layer to prepare a Nb2C nanosheet / CdS nanorod composite photoanode as a novel photocorrosion-resistant nanorod array photoanode.

Description

Technical Field

[0001] The invention belongs to the field of photoelectrochemical materials and relates to nanomaterials, in particular to a photocorrosion-resistant nanorod array photoanode and a preparation method thereof. Background Art

[0002] Energy shortage is a major problem that needs to be solved urgently for the development of human society. Solar energy, as an ideal energy source, is the main target to be developed and utilized. In the development and utilization of solar energy, photoelectrochemical materials that can convert light energy into electrical energy, especially photoelectrochemical materials that can achieve efficient and stable conversion and are easy to prepare, are indispensable.

[0003] Cadmium sulfide (CdS) is a typical direct bandgap semiconductor material in the II-VI group. The bandgap width of CdS at room temperature is 2.42 eV. Due to its relatively low work function, good electron transport, strong visible light absorption and high capacitance, CdS is an excellent photoelectrochemical material and can be widely used in solar cells, light-emitting diodes, catalyst supports and other fields. Among them, CdS nanorods with a one-dimensional structure can provide channels for photogenerated electrons, which is conducive to the transmission of photogenerated electrons and has good application prospects. However, existing studies have shown that the S in CdS 2- It is easily oxidized by photogenerated holes and photocorrosion occurs, and its stability is poor. In addition, CdS is easy to dissociate into toxic Cd during the photocatalytic process due to its inherent photocorrosion characteristics. 2+ , causing the problem of secondary pollution, which seriously hinders its practical application. Summary of the Invention

[0004] The present invention is designed to solve the above-mentioned problems. By combining the technology of forming two-dimensional materials MXene from transition metal (M) carbides and nitrides (X) with semiconductor material technology, a new photocorrosion-resistant nanorod array photoanode material is obtained. This material can increase the transmission rate of photogenerated carriers, inhibit carrier recombination, and enhance photoelectric performance.

[0005] Specifically, the present invention provides a method for preparing a photocorrosion-resistant nanorod array photoanode, which is characterized in that it includes the following steps: step S1, preparing indium tin oxide conductive glass with a CdS nanorod array grown thereon; step S2, preparing a few-layer Nb2C nanosheet layer; step S3, using the CdS nanorod array and the few-layer Nb2C nanosheet layer to prepare a Nb2C nanosheet / CdS nanorod composite photoanode as a photocorrosion-resistant nanorod array photoanode.

[0006] Furthermore, in the above-mentioned method for preparing the photocorrosion-resistant nanorod array photoanode, step S1 may include the following steps: step S1-1, cleaning the indium tin oxide conductive glass, testing the conductive surface, and drying the conductive surface upward for standby use; step S1-2, dissolving cadmium nitrate tetrahydrate, thiourea, and reduced glutathione in ultrapure water, and ultrasonically mixing them to obtain a precursor solution; step S1-3, placing the conductive surface of the indium tin oxide conductive glass downward on the polytetrafluoroethylene-lined side wall of a stainless steel autoclave, and then pouring the precursor solution into the autoclave, and performing a hydrothermal reaction in an oven. After cooling to room temperature, the glass is taken out, cleaned, and dried to obtain the indium tin oxide conductive glass with CdS nanorod arrays grown thereon.

[0007] Furthermore, in the above-mentioned method for preparing the photocorrosion-resistant nanorod array photoanode, the cleaning process in step S1-1 can be: placing the indium tin oxide conductive glass in acetone, anhydrous ethanol and ultrapure water in sequence for ultrasonic cleaning, each ultrasonic cleaning lasting 30 minutes.

[0008] In addition, in the precursor solution of step S1-2, the concentration of cadmium nitrate tetrahydrate is preferably 1 mM, the concentration of thiourea is preferably 3 mM, and the concentration of glutathione is preferably 0.6 mM.

[0009] In addition, the hydrothermal reaction conditions of step S1-3 are preferably 200° C., and the reaction duration is preferably 3.5 h.

[0010] In the preparation method of the above-mentioned anti-photocorrosion nanorod array photoanode provided by the present invention, step S2 may include: step S2-1, uniformly mixing Nb2AlC and NaBF4 in an HCl solution, and transferring the obtained solution to a polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction to obtain a suspension after the reaction; step S2-2, filtering, washing, and drying the suspension obtained in step S2-1 to obtain a multilayer Nb2C nanosheet; step S2-3, adding the multilayer Nb2C nanosheet to ultrapure water with N2 gas continuously introduced to perform ultrasonic exfoliation; step S2-4, centrifuging, filtering, and drying the solution after the ultrasonic exfoliation in step S2-3 to obtain a few-layer Nb2C nanosheet.

[0011] Furthermore, the hydrothermal reaction temperature in step S2-1 is preferably 180°C, and the duration is preferably 24 hours; and the duration of ultrasonic stripping in step S2-3 is preferably 1 hour.

[0012] In the preparation method of the above-mentioned anti-photocorrosion nanorod array photoanode provided by the present invention, step S3 may include: step S3-1, ultrasonically dispersing a few-layer Nb2C nanosheet layer in ethanol to form a few-layer Nb2C nanosheet layer dispersion liquid; step S3-2, taking a predetermined amount of the few-layer Nb2C nanosheet layer dispersion liquid and dropping it on an indium tin oxide conductive glass grown with a CdS nanorod array, and naturally drying it to form a film to obtain a Nb2C nanosheet / CdS nanorod composite photoanode.

[0013] In addition, the present invention also provides a photocorrosion-resistant nanorod array photoanode, characterized in that it is composed of a Nb2C nanosheet / CdS nanorod composite photoanode, and the Nb2C nanosheet / CdS nanorod composite photoanode is prepared using any of the preparation methods above.

[0014] Functions and effects of the invention

[0015] As described above, according to the photocorrosion-resistant nanorod array photoanode provided by the present invention, a Nb2C nanosheet / CdS nanorod composite photoanode is prepared by using a CdS nanorod array and a few-layer Nb2C nanosheet layer, wherein the CdS is in the shape of a vertical hexagonal nanorod. After being compounded with the two-dimensional Nb2C nanosheet, a "one-dimensional + two-dimensional" interface design is constructed, which enables the two to be effectively compounded, thereby suppressing the photocorrosion phenomenon of the CdS material, improving the transmission path of the photogenerated charge, and optimizing the catalytic performance of the photoelectrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 These are actual photos of ITO glass with CdS nanorod arrays grown thereon and a Nb2C nanosheet / CdS nanorod composite photoanode according to an embodiment of the present invention.

[0017] Figure 2 This is a top-down photograph of an ITO glass grown with a CdS nanorod array under a scanning electron microscope according to an embodiment of the present invention.

[0018] Figure 3 This is a top-down scanning electron microscope photograph of the Nb2C nanosheet / CdS nanorod composite photoanode according to an embodiment of the present invention.

[0019] Figure 4 It is an X-ray diffraction pattern of ITO glass with CdS nanorod arrays and Nb2C nanosheet / CdS nanorod composite photoanode according to an embodiment of the present invention.

[0020] Figure 5 4 is a graph showing the relationship between the photocurrent and time of the photoanode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is described in detail below with reference to embodiments and drawings.

[0022] This embodiment provides a method for preparing a photocorrosion-resistant nanorod array photoanode, which specifically includes the following steps:

[0023] Step S1: Prepare indium tin oxide conductive glass with CdS nanorod arrays. The specific operation includes the following steps:

[0024] In step S1-1, the indium tin oxide conductive glass (hereinafter referred to as ITO glass) is cleaned, the conductive surface is tested with a multimeter, and the conductive surface is placed upward for drying and set aside. The cleaning operation involves ultrasonically cleaning the ITO glass in acetone, anhydrous ethanol, and ultrapure water, sequentially for 30 minutes each time.

[0025] Step S1-2: Dissolve cadmium nitrate tetrahydrate, thiourea, and reduced glutathione in ultrapure water and mix them evenly by ultrasonication to obtain a precursor solution, wherein the concentration of cadmium nitrate tetrahydrate is 1 mM, the concentration of thiourea is 3 mM, and the concentration of glutathione is 0.6 mM.

[0026] In step S1-3, the conductive surface of the ITO glass is placed face-down against the Teflon-lined sidewall of a stainless steel autoclave. The precursor solution obtained in step S1-2 is then poured into the autoclave and subjected to a hydrothermal reaction in an oven at 200°C. After 3.5 hours of reaction, the reaction is terminated. After cooling to room temperature, the glass is removed, cleaned, and dried to obtain the ITO glass with the CdS nanorod arrays grown thereon. Step S2 is then performed.

[0027] Step S2, preparing a few-layer Nb2C nanosheet. Specifically comprising the following steps:

[0028] In step S2-1, 0.5 g of Nb2AlC and 0.75 g of NaBF4 were uniformly mixed in 15 mL of a 37% by mass HCl solution. The resulting solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and subjected to a hydrothermal reaction at 180°C for 24 h to obtain a suspension after the reaction.

[0029] Step S2-2: The suspension obtained in step S2-1 is filtered and washed with deionized water, and then vacuum-dried to obtain a multilayer Nb2C nanosheet.

[0030] Step S2-3: multilayer Nb2C nanosheets are added to ultrapure water with N2 gas continuously flowing therein and subjected to ultrasonic exfoliation for 1 hour.

[0031] Step S2-4: centrifuge the solution after ultrasonic stripping in step S2-3 (8000 rpm, 20 min), take the upper suspension after centrifugation, filter it, and vacuum dry it to obtain a few-layer Nb2C nanosheet, and then proceed to step S3.

[0032] Step S3, using the CdS nanorod array prepared in step S1 and the few-layer Nb2C nanosheet layer prepared in step S2 to prepare a Nb2C nanosheet / CdS nanorod composite photoanode as a photocorrosion-resistant nanorod array photoanode. Specifically comprising the following steps:

[0033] Step S3-1: Ultrasonic dispersion of the few-layer Nb2C nanosheets in ethanol to form a few-layer Nb2C nanosheet dispersion.

[0034] Step S3-2: using a drop coating method, take a dispersion of a few-layer Nb2C nanosheet layer, and calculate the amount of the few-layer Nb2C nanosheet layer at 0.15 mg / cm 2 A few layers of Nb2C nanosheets are dispersed and dropletted onto ITO glass with CdS nanorod arrays grown thereon, and allowed to dry naturally to form a film, thereby obtaining a Nb2C nanosheet / CdS nanorod composite photoanode. The Nb2C nanosheet / CdS nanorod composite photoanode is the photocorrosion-resistant nanorod array photoanode of this embodiment.

[0035] Figure 1 This is a photo of an ITO glass with CdS nanorod arrays and a Nb2C nanosheet / CdS nanorod composite photoanode according to an embodiment of the present invention. Frame a shows the ITO glass with CdS nanorod arrays, and frame b shows the Nb2C nanosheet / CdS nanorod composite photoanode.

[0036] like Figure 1 As shown, the ITO glass with CdS nanorod arrays in frame a appears lemon yellow, demonstrating that the hydrothermal method can synthesize CdS arrays on ITO glass, which are stable hexagonal crystals at room temperature. The Nb2C nanosheet / CdS nanorod composite photoanode in frame b appears uniformly gray-black, indicating that the CdS nanorod arrays on the ITO glass are supported by a few Nb2C nanosheets and that the loading is relatively uniform.

[0037] Figure 2 This is a top-down photograph of an ITO glass grown with a CdS nanorod array under a scanning electron microscope according to an embodiment of the present invention.

[0038] like Figure 2 As shown, the CdS on the ITO glass is a nanorod array with a hexagonal cross-section, and its one-dimensional rod-like structure is densely, uniformly and vertically distributed on the entire ITO conductive glass.

[0039] Figure 3 This is a top-down scanning electron microscope photograph of the Nb2C nanosheet / CdS nanorod composite photoanode according to an embodiment of the present invention.

[0040] like Figure 3 As shown, a few-layer Nb2C nanosheet with a two-dimensional planar structure has been combined with a CdS nanorod array, which covers the surface of the CdS nanorod array.

[0041] Figure 4 This is an X-ray diffraction pattern of the Nb2C nanosheet / CdS nanorod composite photoanode according to an embodiment of the present invention.

[0042] like Figure 4 As shown, in the Nb2C nanosheet / CdS nanorod composite photoanode prepared in this embodiment, in addition to the ITO glass as the substrate, there are also diffraction peaks of CdS and Nb2C, indicating that the main crystalline phases therein are CdS and Nb2C.

[0043] Figure 5 is a graph showing the relationship between the photocurrent and time of the photoanode according to an embodiment of the present invention. Figure 5 The relationship curve was obtained by using an electrochemical workstation and a time-current mode test, where each state of the light source switch lasted for 20 seconds. Figure 5 In the figure, “CdS” indicates ITO glass with CdS nanorod arrays grown on it, and “Nb2C / CdS” indicates Nb2C nanosheets / CdS nanorod composite photoanode.

[0044] like Figure 5 As shown in the figure, when the light source is turned on, the photocurrent values ​​of the two reach the maximum value instantaneously, and once the light source is turned off, the photocurrent value drops rapidly to a position close to 0, indicating that the ITO glass grown with CdS nanorod arrays and the Nb2C nanosheet / CdS nanorod composite photoanode of the present invention both have good light response and photosensitivity.

[0045] from Figure 5 It can also be seen that the photocurrent of ITO glass with CdS nanorod arrays decreases significantly with the increase of illumination time. The reason is that the S 2- It is easily oxidized by photogenerated holes, resulting in photocorrosion and poor stability. In contrast, the attenuation of the Nb2C nanosheet / CdS nanorod composite photoanode is not obvious, indicating that the composite of Nb2C nanosheets can inhibit S to a certain extent. 2- The oxidation condition of the CdS material can be improved, which can improve the photocorrosion problem of the CdS material and improve the photocurrent stability of the composite photoanode.

[0046] Functions and Effects of the Embodiments

[0047] As described above, according to the photocorrosion-resistant nanorod array photoanode provided in this embodiment, a Nb2C nanosheet / CdS nanorod composite photoanode is prepared by using a CdS nanorod array and a few-layer Nb2C nanosheet layer, wherein the CdS is in the shape of a vertical hexagonal nanorod. After being compounded with the two-dimensional Nb2C nanosheet, a "one-dimensional + two-dimensional" interface design is constructed, which can inhibit the photocorrosion phenomenon of the CdS material, improve the transmission path of the photogenerated charge, and optimize the catalytic performance of the photoelectrode.

[0048] In addition, since the few-layer Nb2C nanosheet is obtained by ultrasonically peeling off multiple layers of Nb2C nanosheet under N2 conditions, it has an ultra-thin structure and can be more easily covered on the CdS nanorods, so that the two can effectively form a composite, and the composite operation process is simple and easy to implement.

[0049] The above embodiments are preferred examples of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing a photocorrosion-resistant nanorod array photoanode, characterized in that: The steps include: Step S1, preparing indium tin oxide conductive glass with CdS nanorod arrays grown thereon; Step S2, preparing a few-layer Nb2C nanosheet; Step S3, using the indium tin oxide conductive glass on which the CdS nanorod array is grown and the few-layer Nb2C nanosheet layer to prepare a Nb2C nanosheet / CdS nanorod composite photoanode as the photocorrosion-resistant nanorod array photoanode, Wherein, step S3 includes: Step S3-1, ultrasonically dispersing the few-layer Nb2C nanosheets in ethanol to form a few-layer Nb2C nanosheet dispersion; Step S3-2: drop a predetermined amount of the Nb2C nanosheet dispersion onto the indium tin oxide conductive glass on which the CdS nanorod array is grown, and dry the film naturally to obtain the Nb2C nanosheet / CdS nanorod composite photoanode.

2. The method for preparing the photocorrosion-resistant nanorod array photoanode according to claim 1, wherein: in, Step S1 includes the following steps: Step S1-1, cleaning the ITO conductive glass, testing the conductive surface, and drying the conductive surface upward for later use; Step S1-2, dissolving cadmium nitrate tetrahydrate, thiourea, and reduced glutathione in ultrapure water, and mixing them uniformly by ultrasonication to obtain a precursor solution; Step S1-3, the conductive surface of the indium tin oxide conductive glass is placed downwardly and tilted against the polytetrafluoroethylene-lined side wall of a stainless steel autoclave, and then the precursor liquid is poured into the autoclave and subjected to a hydrothermal reaction in an oven. After cooling to room temperature, the precursor liquid is taken out, cleaned, and dried to obtain the indium tin oxide conductive glass on which the CdS nanorod array is grown.

3. The method for preparing the photocorrosion-resistant nanorod array photoanode according to claim 2, wherein: in, The cleaning process in step S1-1 is as follows: placing the ITO conductive glass in acetone, anhydrous ethanol and ultrapure water in sequence for ultrasonic cleaning, each ultrasonic cleaning lasting 30 minutes.

4. The method for preparing the photocorrosion-resistant nanorod array photoanode according to claim 2, wherein: in, In the precursor solution of step S1-2, the concentration of cadmium nitrate tetrahydrate is 1 mM, the concentration of thiourea is 3 mM, and the concentration of glutathione is 0.6 mM.

5. The method for preparing the photocorrosion-resistant nanorod array photoanode according to claim 2, wherein: in, The hydrothermal reaction conditions of step S1-3 are 200° C. and the reaction duration is 3.5 h.

6. The method for preparing the photocorrosion-resistant nanorod array photoanode according to claim 1, Its characteristics are: Wherein, step S2 includes: Step S2-1, uniformly mixing Nb2AlC and NaBF4 in an HCl solution, transferring the resulting solution to a polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction to obtain a suspension after reaction; Step S2-2, filtering, washing, and drying the suspension obtained in step S2-1 to obtain a multilayer Nb2C nanosheet; Step S2-3, adding the multilayer Nb2C nanosheets into ultrapure water with N2 gas continuously flowing therein to perform ultrasonic exfoliation; Step S2-4, centrifuging, filtering, and drying the solution after the ultrasonic stripping in step S2-3 to obtain the few-layer Nb2C nanosheet.

7. The method for preparing the photocorrosion-resistant nanorod array photoanode according to claim 6, wherein: in, The hydrothermal reaction temperature in step S2-1 is 180°C and the duration is 24 hours; The duration of ultrasonic peeling in step S2-3 is 1 h.

8. A photo-corrosion resistant nanorod array photoanode, characterized in that: The Nb2C nanosheet / CdS nanorod composite photoanode is prepared by the preparation method according to any one of claims 1 to 7.

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