Preparation method and application of an electrochemically activated MXene modified BiVO4 photoelectrode

Abstract

The application discloses a preparation method and application of an electrochemically activated MXene modified BiVO4 photoelectrode, and the preparation method comprises the following steps: taking a BiVO4 photoelectrode as a working electrode, taking a solution containing layered MXene as an electrolyte, depositing MXene on the BiVO4 photoelectrode through an electrophoresis method to obtain a MXene / BiVO4 composite photoelectrode, and applying a bias voltage to the MXene / BiVO4 composite photoelectrode to activate the MXene / BiVO4 composite photoelectrode, so that the electrochemically activated MXene modified BiVO4 photoelectrode is obtained. The preparation method and application of the electrochemically activated MXene modified BiVO4 photoelectrode have excellent photoelectrocatalytic activity, and the electrochemically activated MXene modified BiVO4 photoelectrode has excellent effects on photoelectrocatalytic water splitting.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrode material technology, and particularly relates to a method for preparing and applying an electrochemically activated MXene-modified BiVO4 photoelectrode. Background Technology

[0002] With the pollution and irreversible consumption of fossil fuels, energy shortages have become a severe challenge, attracting increasing attention from human society. Photoelectrochemical water splitting (PEC) offers an attractive strategy for obtaining oxygen and hydrogen by directly converting solar energy into chemical energy, potentially addressing both energy shortages and environmental pollution. Over the past few decades, researchers have focused on developing photoelectrodes with superior performance, such as α-Fe₂O₃, Ta₃N₅, ZnO, BiVO₄, WO₃, TiO₂, and CdS. Among these, monoclinic bismuth vanadate (BiVO₄) is considered an ideal photoelectrode for PEC water splitting, attracting significant attention due to its suitable band gap, appropriate band positions, excellent visible light response, and low toxicity. However, the PEC water splitting performance of BiVO₄ is severely limited by the high recombination rate of photogenerated electron-hole pairs and the slow interface-related water oxidation process. Therefore, the actual photocurrent density of pure BiVO₄ is significantly lower than its theoretical value of 7.5 mA / cm². 2 (AM 1.5G, 100mW / cm) 2 ).

[0003] Currently, modification techniques for pristine BiVO4 mainly focus on the material's structure, including elemental doping (Angew. Chem. Int. Ed. 2024, e202416340), nanostructure manipulation (Chemical Engineering Journal 2023, 465, 142571), co-catalyst loading (ACS Appl. Nano Mater. 2024, 7, 14115-14122), and heterostructure construction, primarily targeting light absorption, charge separation, and catalytic efficiency. However, the efficiency improvement of PEC based on these methods is limited and nears a bottleneck. Many researchers are increasingly considering how to introduce external energy to significantly improve the performance of BiVO4 photoelectrodes.

[0004] As is well known, MXene composites have attracted much attention due to their metallic conductivity and high specific surface area, and also possess stronger light-harvesting and bandgap tuning capabilities. MXene (Ti3C2) is often used as a titanium source in photoanodes for photoelectrochemical water splitting to produce hydrogen (Journal of Energy Chemistry. 2023, 87, 518-539). MXene can also serve as a hole transport layer to promote carrier transport. The ability to introduce MXene compounds as an intermediate layer and apply MXene composites to BiVO4 photoelectrodes to construct a photoelectrode with a hole transport layer loaded on it, thereby achieving the ability to regulate charge separation and transfer to improve the performance of photoelectrochemical water splitting and oxidation, is of great significance for enhancing the performance of BiVO4 photoelectrodes. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a method for preparing and applying an electrochemically activated MXene-modified BiVO4 photoelectrode. The electrochemically activated MXene-modified BiVO4 photoelectrode has excellent photoelectrocatalytic activity and excellent effect on photoelectrocatalytic water splitting.

[0006] The present invention proposes a method for preparing an electrochemically activated MXene-modified BiVO4 photoelectrode, comprising the following steps:

[0007] S1. Using a BiVO4 photoelectrode as the working electrode and a solution containing MXene as the electrolyte, MXene is deposited on the BiVO4 photoelectrode by electrophoresis to obtain an MXene / BiVO4 composite photoelectrode.

[0008] S2. Apply a bias voltage to the MXene / BiVO4 composite photoelectrode to activate it, thereby obtaining the electrochemically activated MXene-modified BiVO4 photoelectrode.

[0009] Preferably, in step S1, the MXene is MXene Ti3C2.

[0010] Preferably, in step S1, in addition to using the BiVO4 photoelectrode as the working electrode, a saturated Ag / AgCl electrode is used as the reference electrode, and a Pt sheet is used as the counter electrode.

[0011] Preferably, in step S1, the deposition voltage of the electrophoresis method is 2-5V and the deposition time is 120-1200s.

[0012] Preferably, in step S2, the bias voltage is 0.5-0.8V and the activation time is at least 1000s.

[0013] Preferably, in step S1, the BiVO4 photoelectrode is a BiVO4 / FTO composite photoelectrode.

[0014] Preferably, the BiVO4 / FTO composite photoelectrode is prepared by the following method:

[0015] Using an FTO substrate as the working electrode and a solution containing potassium iodide, bismuth nitrate, and p-benzoquinone as the electrolyte, BiOI was deposited on the FTO substrate by electrochemical deposition to obtain a BiOI / FTO composite photoelectrode.

[0016] The solution of dimethyl sulfoxide containing vanadium acetylacetonate is then drop-coated onto the BiOI / FTO composite photoelectrode, and after calcination, the BiVO4 / FTO composite photoelectrode is obtained.

[0017] Preferably, the deposition voltage of the electrophoresis method is -(0.1-0.2)V, the deposition time is 150-250s, and the calcination temperature is 430-470℃, and the time is 1-3h.

[0018] The present invention also proposes an electrochemically activated MXene-modified BiVO4 photoelectrode, which is prepared by the above-mentioned preparation method.

[0019] This invention also proposes an application of the above-mentioned electrochemically activated MXene-modified BiVO4 photoelectrode in photoelectrocatalytic water splitting.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) This invention provides a method for preparing an electrochemically activated MXene-modified BiVO4 photoelectrode. Using a BiVO4 photoelectrode prepared by electrochemical deposition and calcination as the electrode substrate, MXene is then deposited onto the BiVO4 photoelectrode by electrophoresis, thus achieving a method to increase the photocurrent density of BiVO4. This preparation method is simple to operate and low in cost. First, a BiVO4 photoelectrode is obtained by electrodeposition. Then, utilizing the conductivity of the MXene solution, a bias voltage is applied to activate the MXene, which is then tightly adsorbed onto the BiVO4, resulting in an electrochemically activated MXene-modified BiVO4 photoelectrode.

[0022] (2) The electrochemically activated MXene-modified BiVO4 photoelectrode prepared in this invention not only improves the performance of BiVO4 photoelectrode, but also the electrochemically activated MXene can serve as a hole transport layer to promote carrier transport, reduce the recombination rate of electrons and holes in BiVO4, and prolong the electron-hole lifetime; at the same time, the deposition of MXene on BiVO4 ensures the stability of BiVO4.

[0023] (3) The electrochemically activated MXene-modified BiVO4 photoelectrode prepared by this invention for photoelectrocatalytic water splitting has potential value in the field of PEC water splitting. It is committed to deepening interface engineering research to improve the photoelectric performance of BiVO4 and provides a new idea for the conversion of solar energy into clean, renewable and sustainable energy. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation process of the electrochemically activated MXene-modified BiVO4 photoelectrode described in this invention;

[0025] Figure 2 The images shown are scanning electron microscope (SEM) images of the BiVO4 photoelectrode described in Comparative Example 1 and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3 of the present invention. Figure (ab) is an SEM image of the BiVO4 photoelectrode described in Comparative Example 1, and Figure (cd) is an SEM image of the MXene / BiVO4 composite photoelectrode described in Comparative Example 3.

[0026] Figure 3 The graph shows the change in photocurrent density of the electrochemically activated MXene-modified BiVO4 photoelectrode as a function of activation time.

[0027] Figure 4 The LSV diagrams are of the MXene / BiVO4 composite photoelectrodes described in Comparative Examples 2-4 of this invention.

[0028] Figure 5 The LSV diagrams are of the electrochemically activated MXene-modified BiVO4 photoelectrode described in Examples 1-3 of this invention, the BiVO4 photoelectrode described in Multiple Example 1, and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3.

[0029] Figure 6 The images show the ABPE diagrams of the electrochemically activated MXene-modified BiVO4 photoelectrode described in Examples 1-3 of this invention, the BiVO4 photoelectrode described in Multiple Example 1, and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3.

[0030] Figure 7 Figure 1 shows the XPS spectra of the electrochemically activated MXene-modified BiVO4 photoelectrode of Example 1 and the MXene / BiVO4 composite photoelectrode of Comparative Example 3. Figure 1(a) shows the Ti 2p XPS spectra of the electrochemically activated MXene-modified BiVO4 photoelectrode of Example 1, and Figure 2(b) shows the C1s XPS spectra of the MXene / BiVO4 composite photoelectrode of Comparative Example 3. Detailed Implementation

[0031] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0032] Example 1

[0033] Reference Figure 1 This embodiment proposes a method for preparing an electrochemically activated MXene-modified BiVO4 photoelectrode, comprising the following steps:

[0034] (1) Weigh 3.32g of potassium iodide and add it to 50mL of deionized water. Then, under the action of magnetic stirring, let it dissolve completely. Then, slowly add a small amount of 1M dilute nitric acid to the solution to maintain the final pH between 1.60 and 1.65. Weigh 0.970g of bismuth nitrate pentahydrate and add it to the above solution to obtain an orange-red solution. Continue to weigh 0.498g of p-benzoquinone and add it to the orange-red solution to form the desired precipitate.

[0035] (2) Using the above-mentioned deposition solution as the electrolyte, the FTO substrate as the working electrode, the saturated Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode, electrochemical deposition was performed in this three-electrode system. The deposition potential was -0.144V and the deposition time was 200s. A BiOI film was deposited on the FTO substrate. After washing the surface with a large amount of distilled water, a BiOI / FTO composite electrode was obtained. 0.265g of vanadium acetylacetone oxide was weighed and added to 5mL of dimethyl sulfoxide. After sonication for 15min, it was dissolved to form a dimethyl sulfoxide solution containing vanadium acetylacetone oxide. 100μL of the dimethyl sulfoxide solution containing vanadium acetylacetone oxide was drop-coated onto the above-mentioned BiOI / FTO composite electrode. The obtained sample was then placed in a muffle furnace and heated at 450℃ for 2h. After removing it, the surface residual impurities were removed with 1M sodium hydroxide solution and dried at room temperature to obtain a BiVO4 / FTO composite electrode, which is the BiVO4 photoelectrode.

[0036] (3) After sonicating 2.5 mL of MXene Ti3C2 solution for 10 min, add 47.5 mL of deionized water, and sonicate for another 20 min until completely dispersed to obtain a solution containing MXene with a concentration of 0.05 mg / mL.

[0037] (4) Using the above-mentioned MXene-containing solution as the electrolyte, the BiVO4 photoelectrode as the working electrode, the saturated Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode, electrochemical deposition was performed in the three-electrode system. The deposition voltage was 3V and the deposition time was 600s. MXene was deposited on the BiVO4 photoelectrode. After washing the surface with deionized water to remove residual electrolyte, it was dried in a vacuum oven at 60°C for 12h to obtain the MXene / BiVO4 composite photoelectrode.

[0038] (5) The above Mxene / BiVO4 composite photoelectrode was activated by applying a bias voltage of 0.6V for 3000s to obtain the electrochemically activated MXene-modified BiVO4 photoelectrode, denoted as MXene / BVO-3000s.

[0039] Example 2

[0040] This embodiment proposes a method for preparing an electrochemically activated MXene-modified BiVO4 photoelectrode, specifically referring to Example 1, except that the activation time in step (5) is 6000s, denoted as MXene / BVO-6000s.

[0041] Example 3

[0042] This embodiment proposes a method for preparing an electrochemically activated MXene-modified BiVO4 photoelectrode, specifically referring to Example 1, except that the activation time in step (5) is 8000s, denoted as MXene / BVO-8000s.

[0043] Comparative Example 1

[0044] This comparative example presents a method for preparing a BiVO4 photoelectrode, comprising the following steps:

[0045] (1) Weigh 3.32g of potassium iodide and add it to 50mL of deionized water. Then, under the action of magnetic stirring, let it dissolve completely. Then, slowly add a small amount of 1M dilute nitric acid to the solution to maintain the final pH between 1.60 and 1.65. Weigh 0.970g of bismuth nitrate pentahydrate and add it to the above solution to obtain an orange-red solution. Continue to weigh 0.498g of p-benzoquinone and add it to the orange-red solution to form the desired precipitate.

[0046] (2) Using the above-mentioned deposition solution as the electrolyte, the FTO substrate as the working electrode, the saturated Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode, electrochemical deposition was performed in this three-electrode system. The deposition potential was -0.144V and the deposition time was 200s. A BiOI film was deposited on the FTO substrate. After washing the surface with a large amount of distilled water, a BiOI / FTO composite electrode was obtained. 0.265g of vanadium acetylacetone oxide was weighed and added to 5mL of dimethyl sulfoxide. After sonication for 15min, it was dissolved to form a dimethyl sulfoxide solution containing vanadium acetylacetone oxide. 100μL of this dimethyl sulfoxide solution containing vanadium acetylacetone oxide was drop-coated onto the above-mentioned BiOI / FTO composite electrode. The obtained sample was then placed in a muffle furnace and heated at 450℃ for 2h. After removal, the surface residual impurities were removed with 1M sodium hydroxide solution and dried at room temperature to obtain a BiVO4 / FTO composite electrode, which is the BiVO4 photoelectrode, denoted as BVO.

[0047] Comparative Example 2

[0048] This comparative example presents a method for preparing an MXene / BiVO4 composite photoelectrode, specifically referring to Example 1. The difference is that the deposition voltage in step (4) is 2V, and step (5) is omitted, resulting in an MXene / BiVO4 composite photoelectrode, denoted as MXene / BiVO4-2V.

[0049] Comparative Example 3

[0050] This comparative example presents a method for preparing an MXene / BiVO4 composite photoelectrode, specifically referring to Example 1, except that step (5) is omitted, resulting in an MXene / BiVO4 composite photoelectrode, denoted as MXene / BiVO4-3V or MXene / BVO.

[0051] Comparative Example 4

[0052] This comparative example presents a method for preparing an MXene / BiVO4 composite photoelectrode, specifically referring to Example 1. The difference is that the deposition voltage in step (4) is 4V, and step (5) is omitted, resulting in an MXene / BiVO4 composite photoelectrode, denoted as MXene / BiVO4-4V.

[0053] The BiVO4 photoelectrode described in Comparative Example 1 and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3 were characterized using scanning electron microscopy. The results are as follows: Figure 2 As shown.

[0054] Figure 2 The images shown are scanning electron microscope (SEM) images of the BiVO4 photoelectrode described in Comparative Example 1 and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3 of the present invention, with reference to... Figure 2It can be seen that the BiVO4 photoelectrode described in Comparative Example 1 exhibits a worm-like structure, while in the MXene / BiVO4 composite photoelectrode described in Comparative Example 3, MXene appears as a sheet and is accumulated on BiVO4, indicating that MXene is deposited on the surface of BiVO4.

[0055] The photoelectrode described in the embodiments or comparative examples uses a standard optical power of 100mW / cm². 2 The water splitting performance of PEC was studied under simulated sunlight using AM 1.5G. In a standard three-electrode system, the electrolyte solution was a potassium borate buffer solution with a pH of 9. The test was conducted using linear sweep voltammetry (LSV), and the results are as follows: Figure 3-5 As shown.

[0056] Figure 3 This is a curve showing the change in photocurrent density of the electrochemically activated MXene-modified BiVO4 photoelectrode as a function of activation time, as described in this invention. Figure 3 It can be seen that as the activation time increases, up to 8000s, the photocurrent density of the electrochemically activated MXene-modified BiVO4 photoelectrode tends to level off.

[0057] Figure 4 The LSV diagrams of the MXene / BiVO4 composite photoelectrodes described in Comparative Examples 2-4 of this invention are shown below. Figure 4 It can be seen that, compared with the electrochemically activated MXene-modified BiVO4 photoelectrodes described in Examples 1-3, the performance of the unactivated MXene / BiVO4 composite photoelectrodes in Comparative Examples 2-4 is not different with the increase of the bias voltage applied for MXene deposition. This indicates that the bias voltage of MXene deposition has no effect on the performance of the electrochemically activated MXene / BiVO4 composite photoelectrodes. Therefore, the bias voltage range for MXene deposition can be set to 2-5V.

[0058] Figure 5 The LSV diagrams of the electrochemically activated MXene-modified BiVO4 photoelectrode described in Examples 1-3 of this invention, the BiVO4 photoelectrode described in Multiple Example 1, and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3 are shown below. Figure 5 It can be seen that, compared with the electrochemically activated MXene-modified BiVO4 photoelectrode described in Examples 1-3, the unactivated MXene / BiVO4 composite photoelectrode in Comparative Example 3 has similar performance to the BiVO4 photoelectrode described in Comparative Example 1, with a photocurrent density of approximately 1.72 mA / cm². 2 Furthermore, with increasing activation time, the performance of the MXene-modified BiVO4 photoelectrode significantly improved. After 8000 s of activation, the photocurrent density of MXene / BiVO4-8000 s reached 3.9 mA / cm².2 .

[0059] Figure 6 The ABPE images are of the electrochemically activated MXene-modified BiVO4 photoelectrode described in Examples 1-3 of this invention, the BiVO4 photoelectrode described in Multiple Example 1, and the MXene / BiVO4 composite photoelectrode described in Comparative Example 3, with reference to... Figure 6 It can be seen that ABPE increases significantly with increasing activation time.

[0060] Figure 5 and Figure 6 The results show that with the introduction of MXene, carrier recombination is suppressed by applying a bias voltage to activate MXene, while BiVO4 hole migration is accelerated, and the longer the activation time, the higher the carrier transport rate.

[0061] Figure 7 XPS spectra of the electrochemically activated MXene-modified BiVO4 photoelectrode of Example 1 and the MXene / BiVO4 composite photoelectrode of Comparative Example 3 are shown. The activated version corresponds to the electrochemically activated MXene-modified BiVO4 photoelectrode of Example 1, while the pre-activated version corresponds to the MXene / BiVO4 composite photoelectrode of Comparative Example 3. The chemical structure of MXene (Ti3C2) can be determined through analysis of Ti and C elements. (Refer to...) Figure 7 (a) It can be seen that in the Ti 2p spectrum of the MXene / BiVO4 composite photoelectrode before activation, in Ti 2p... 3 / 2 In the middle, Ti-C, Ti 2+ Ti 3+ The binding energies with Ti-O are 454.68, 455.28, 456.48, and 458.68 eV, respectively, in Ti 2p 1 / 2 In the middle, Ti-C, Ti 2+ Ti 3+ The binding energies with Ti-O were 460.48, 460.78, 461.88, and 464.58 eV, respectively, with satellite peaks. The binding energy was 465.88 eV, consistent with previous XPS studies. The activated MXene-modified BiVO4 photoelectrode differed significantly from the unactivated MXene / BiVO4 composite photoelectrode, with Ti 2p... 3 / 2 and Ti 2p 1 / 2 Ti-C, Ti 2+ Ti 3+ The peaks all disappeared, and only the Ti-O peak and satellite peak were observed, suggesting the presence of Ti-C and Ti. 2+ Ti 3+ Transformation into Ti-O X This indicates the formation of new substances; refer to Figure 7(b) It can be seen that in the C1s spectrum of the MXene / BiVO4 composite photoelectrode before activation, the C1s spectrum is divided into four peaks centered at 281.65, 284.8, 286.45, and 288.35 eV, corresponding to C-Ti, CC, and CH, respectively. x The disappearance of the C-Ti peaks after activation of CO and COO also proves that the material composition of the activated MXene-modified BiVO4 photoelectrode has undergone new changes.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an electrochemically activated MXene-modified BiVO4 photoelectrode, characterized in that, Includes the following steps: S1. Using a BiVO4 photoelectrode as the working electrode and a solution containing MXene as the electrolyte, MXene is deposited on the BiVO4 photoelectrode by electrophoresis to obtain an MXene / BiVO4 composite photoelectrode. S2. Apply a bias voltage to the MXene / BiVO4 composite photoelectrode to activate it, thereby obtaining the electrochemically activated MXene-modified BiVO4 photoelectrode; In step S1, the deposition voltage of the electrophoresis method is 2-5 V, and the deposition time is 120-1200 s; In step S2, the bias voltage is 0.5-0.8 V and the activation time is at least 1000 s.

2. The method for preparing the electrochemically activated MXene-modified BiVO4 photoelectrode according to claim 1, characterized in that, In step S1, the MXene is MXene Ti3C2.

3. The method for preparing the electrochemically activated MXene-modified BiVO4 photoelectrode according to claim 1 or 2, characterized in that, In step S1, in addition to using the BiVO4 photoelectrode as the working electrode, a saturated Ag / AgCl electrode is used as the reference electrode, and a Pt sheet is used as the counter electrode.

4. The method for preparing the electrochemically activated MXene-modified BiVO4 photoelectrode according to claim 1 or 2, characterized in that, In step S1, the BiVO4 photoelectrode is a BiVO4 / FTO composite photoelectrode.

5. The method for preparing the electrochemically activated MXene-modified BiVO4 photoelectrode according to claim 4, characterized in that, The BiVO4 / FTO composite photoelectrode was prepared by the following method: Using an FTO substrate as the working electrode and a solution containing potassium iodide, bismuth nitrate, and p-benzoquinone as the electrolyte, BiOI was deposited on the FTO substrate by electrodeposition to obtain a BiOI / FTO composite photoelectrode. The solution of dimethyl sulfoxide containing vanadium acetylacetonate is then drop-coated onto the BiOI / FTO composite photoelectrode, and after calcination, the BiVO4 / FTO composite photoelectrode is obtained.

6. The method for preparing the electrochemically activated MXene-modified BiVO4 photoelectrode according to claim 5, characterized in that, The electrochemical deposition method has a deposition voltage of -(0.1-0.2)V and a deposition time of 150-250 s; the calcination temperature is 430-470 ℃ and the time is 1-3 h.

7. An electrochemically activated MXene-modified BiVO4 photoelectrode, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

8. The application of the electrochemically activated MXene-modified BiVO4 photoelectrode of claim 7 in photoelectrocatalytic water splitting.

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