A kind of photo-electrocatalytic photoanode nanomaterial and its preparation method

Abstract

The present invention discloses a photo-electrocatalytic photoanode nanomaterial and a preparation method thereof, belonging to the synthesis technical field of photo-electrocatalytic nanomaterials. The photo-electrocatalyst has good catalytic activity and stability; moreover, the preparation process is simple to operate, the reaction conditions are mild, and the target materials used are wide in source and low in price. In the present invention, Bi source and V source target materials are used for segmented sputtering by a magnetron sputtering instrument, with argon as the sputtering atmosphere. First, the Bi source is sputtered, and then the V source is sputtered. Bi and V are deposited on FTO conductive glass under a certain pressure, heat-treated at a certain temperature, and then soaked with KOH to remove the excess vanadium oxide. After washing with water and drying, the target product is obtained. The obtained photo-electrocatalyst is a BiVO4 photoanode, which exhibits high photocurrent activity under simulated sunlight irradiation after being loaded with NiFeO x as an oxygen evolution co-catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of the synthesis of photoelectrocatalytic nanomaterials, and particularly relates to a photoelectrocatalytic photoanode nanomaterial and a preparation method thereof. Background Art

[0002] With the extensive use of fossil fuels, the global energy crisis has become increasingly severe. Therefore, it is crucial to accelerate the construction of a clean, low-carbon, safe and efficient energy system. Hydrogen energy is a secondary energy source with the advantages of wide sources, high combustion calorific value, cleanliness and no pollution, and is an ideal clean energy. At present, the industrial hydrogen production technologies mainly include fossil fuel hydrogen production, industrial by-product hydrogen production and electrolytic water hydrogen production. Although fossil fuel hydrogen production has a relatively low cost, it is not conducive to environmental protection. Industrial by-product hydrogen production is restricted by the original products, and there is an upper limit to hydrogen production capacity. Although electrolytic water hydrogen production is environmentally friendly and pollution-free, its cost is relatively high, accounting for only about 5% of industrial hydrogen production. How to produce hydrogen efficiently, environmentally friendly and at low cost has become the key issue to promote the development of hydrogen energy.

[0003] Photoelectrocatalytic water splitting is a technology that uses carriers generated by the photoelectric effect of semiconductors to decompose water into hydrogen and oxygen, which can directly convert solar energy into hydrogen energy and provides a reliable strategy for the development of future hydrogen energy strategies. The photoelectrocatalytic water splitting process includes hydrogen evolution reaction and oxygen evolution reaction. Compared with the hydrogen evolution reaction, the oxygen evolution reaction has a lower photo-conversion efficiency of the photoanode due to its slow water oxidation kinetics and complex four-electron transfer process. Therefore, the development of efficient, stable and low-cost photoanodes has become the key to current research. BiVO4 has a band gap of 2.4 eV, with a long carrier lifetime, stable properties and wide sources. Due to its excellent properties, it is considered to be one of the most promising PEC water splitting photoanodes. However, poor electron transport performance and fast recombination of photo-generated carriers still limit the large-scale development and application of BiVO4.

[0004] There are many methods for studying the preparation of BiVO4, such as hydrothermal method, spin coating method and electrodeposition method, etc. Among them, the BiVO4 photoanode prepared by electrodeposition method published by Kim et al. in "Science" in 2014 showed high photoelectrocatalytic performance. However, the disadvantage of preparing BiVO4 by chemical method is that the thickness is difficult to control, and it is only limited to small-scale preparation, which is not suitable for the industrial development of BiVO4 photoanodes. As a kind of physical vapor deposition method, magnetron sputtering method has the remarkable advantages of fast deposition speed, batch production, uniform and pure products, and flexible control of film thickness, etc., and is more convenient for realizing large-scale PEC applications. Many studies have shown that dense BiVO4 films can be prepared by co-deposition magnetron sputtering method, but the atomic synthesis ratio is difficult to control and more impurity phases are likely to be generated. Summary of the Invention

[0005] The present invention provides a method for preparing a photo-electrocatalytic photoanode nanomaterial by using a segmented magnetron sputtering technique, which is convenient for controlling the proportion of atomic synthesis, and the permeability between elements is beneficial to preparing BiVO4 with higher purity. The obtained BiVO4 has good catalytic activity and stability; moreover, the preparation process is simple, the reaction conditions are mild, and the target materials used are widely sourced and inexpensive.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A method for preparing a photo-electrocatalytic photoanode nanomaterial, comprising the following steps:

[0008] (1) Place the prepared substrate into a magnetron sputtering instrument, install a Bi source target, introduce argon to control the pressure at 1 - 5 Pa, and sputter the Bi source target at a power of 5 - 10 W for 0.5 - 2 hours;

[0009] (2) Install a V source target, introduce argon to control the pressure at 1 - 5 Pa, and sputter the V source target at a power of 200 - 370 W for 0.5 - 2 hours;

[0010] (3) Subsequently, switch the sputtering sequence back to the Bi source target for sputtering, and repeat steps (1) and (2) for 5 - 20 cycles;

[0011] (4) Keep the sample obtained in step (3) at 400 - 800 °C for 2 - 10 hours;

[0012] (5) Immerse the sample after high-temperature heat treatment in step (4) in KOH for 10 - 40 minutes to remove excess vanadium oxide, and obtain a BiVO4 thin film after washing and drying;

[0013] (6) Place the BiVO4 thin film synthesized in step (4) into a potassium borate solution with a molar ratio of FeSO4·7H2O to NiSO4·6H2O of 10:1, and perform photo-electrodeposition for 5 - 20 minutes to prepare BiVO4 / NiFeO x photoanode.

[0014] In the above steps, the Bi source target described in step (1) is one or more of a metal Bi target and a Bi2O3 target, and the V source target described in step (2) is one or more of a metal V target and a V2O5 target; the thickness of the BiVO4 thin film obtained in step (4) is 200 - 500 nanometers.

[0015] The photo-electrocatalytic photoanode nanomaterial prepared by the above method is a BiVO4 photoanode prepared by segmented magnetron sputtering and loaded with NiFeO x as an oxygen evolution co-catalyst. The segmented sputtering is to first sputter with the Bi source and then with the V source. The NiFeO xThe loading amount is 1.0 wt%.

[0016] Beneficial effects: The present invention provides a photo-electrocatalytic photoanode nanomaterial and a preparation method thereof. The photo-electrocatalyst is a BiVO4 photoanode, which is more conducive to controlling the atomic composition ratio compared with co-deposited magnetron sputtered BiVO4. The BiVO4 / NiFeO x photoanode prepared by the present invention exhibits high photocurrent activity under simulated sunlight irradiation and has good catalytic activity and stability in the photo-electrocatalytic reaction. Moreover, the preparation process of the present invention is simple in operation, mild in reaction conditions, and the target materials used are wide in source and low in price. Description of the drawings

[0017] Figure 1 is the XRD pattern of the BiVO4 material prepared in Example 1 of the present invention;

[0018] Figure 2 is the scanning electron microscope image of BiVO4 prepared in Example 1 of the present invention;

[0019] Figure 3 is the linear sweep voltammogram of BiVO4 and BiVO4 / NiFeO x prepared in Example 2 of the present invention under simulated sunlight irradiation and the comparison diagram with BiVO4 prepared by co-deposited magnetron sputtering. Detailed implementation manners

[0020] The present invention will be described in detail below with reference to the drawings and specific embodiments:

[0021] Example 1

[0022] A preparation method of a photo-electrocatalytic photoanode nanomaterial, comprising the following steps:

[0023] First, clean the FTO conductive glass with a plasma cleaner, and after cleaning, put it into a magnetron sputtering instrument. First, install the metal Bi target, evacuate to a pressure of 5×10 -3 Pa, then introduce argon to control the flow rate to 50 sccm, keep the baffle closed, pre-sputter the metal Bi target for 10 minutes with a DC power supply of 9 W, then change the argon flow rate to control the pressure in the instrument to 4 Pa, open the baffle, and sputter the metal Bi target for 1 hour with a DC power supply of 9 W; then install the metal V target, evacuate to a pressure of 5×10 -3Pa, then introduce argon gas to control the flow rate at 50 sccm, keep the baffle closed, pre-sputter the metal V target with a DC power supply of 200 W for 10 minutes, then change the argon gas flow rate to control the pressure inside the instrument at 4 Pa, open the baffle, and sputter the metal V target with a DC power supply of 200 W for 1 hour; subsequently, switch the target to the Bi source, and sputter the metal Bi target and the metal V target repeatedly for 10 times; after sputtering, calcine at 450 °C in air for 2 hours, then soak in 1 M KOH solution for 15 minutes, wash and dry to obtain the BiVO4 film. Put the BiVO4 film into a potassium borate solution with a molar ratio of FeSO4·7H2O to NiSO4·6H2O of 10:1, and perform photoelectrodeposition for 10 minutes to obtain BiVO4 / NiFeO x photoanode.

[0024] The XRD pattern of the BiVO4 photo-electrocatalytic photoanode is as Figure 1 shown, and its crystal form is the monoclinic scheelite type of BiVO4 and has a very high purity.

[0025] The scanning electron microscope image is as Figure 2 shown, and the thickness of the prepared BiVO4 photoanode film is 200 - 500 nanometers.

[0026] Example 2

[0027] A preparation method of a photo-electrocatalytic photoanode nanomaterial, comprising the following steps:

[0028] First, clean the FTO conductive glass with a plasma cleaner. After cleaning, put it into a magnetron sputtering instrument. First, install the Bi2O3 target, evacuate to a pressure of 3×10 -3 Pa, then introduce argon gas to control the flow rate at 50 sccm, keep the baffle closed, pre-sputter the Bi2O3 target with an RF power supply of 7 W for 15 minutes, then change the argon gas flow rate to control the pressure inside the instrument at 5 Pa, open the baffle, and sputter the Bi2O3 target with an RF power supply of 7 W for 1.5 hours; then install the V target, evacuate to a pressure of 5×10 -3 Pa, then introduce argon gas to control the flow rate at 50 sccm, keep the baffle closed, pre-sputter the metal V target with a DC power supply of 235 W for 10 minutes, then change the argon gas flow rate to control the pressure inside the instrument at 4 Pa, open the baffle, and sputter the metal V target with a DC power supply of 235 W for 1.5 hours; subsequently, switch the target to the Bi source, and sputter repeatedly for 4 times. After sputtering, calcine at 500 °C in air for 2 hours, then soak in 1 M KOH solution for 20 minutes, wash and dry to obtain the BiVO4 film; put the BiVO4 film into a potassium borate solution with a molar ratio of FeSO4·7H2O to NiSO4·6H2O of 10:1, and perform photoelectrodeposition for 10 minutes to obtain BiVO4 / NiFeO x photoanode.

[0029] The obtained BiVO4 and BiVO4 / NiFeO x nano-catalyst materials were used for photoelectrocatalytic performance testing. For comparison, co-deposited magnetron sputtered BiVO4 was also prepared with reference to relevant literature (Phy. Chem, 2015, Chemically induced porosity on BiVO4 films produced by double magnetron sputtering to enhance the photo-electrochemical response). The test was carried out using a three-electrode electrochemical cell structure, with the prepared photoanode as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The area of the photoanode film was 1 cm 2 , under AM1.5G illumination. As Figure 3 shown, at 1.23 V vs. the reversible hydrogen electrode, the photocurrent density of BiVO4 prepared by the co-deposition method was 1.3 mA / cm 2 , while the photocurrent density of BiVO4 prepared by segmented magnetron sputtering was 2 mA / cm 2 , and after loading NiFeO x cocatalyst, it was increased to 4.2 mA / cm 2 , and the photoelectrocatalytic performance was improved by 2.1 times. The BiVO4 prepared by the segmented method is more convenient to control the atomic synthesis ratio compared to the co-deposition method, and it is easier to obtain high-purity monoclinic scheelite phase BiVO4. At the same time, in the multi-period magnetron sputtering, each element has sufficient time to penetrate each other, resulting in a higher crystallinity of the film, a denser microstructure, and smaller grain sizes. Therefore, the film has excellent corrosion resistance and strong charge transport ability, and better performance.

[0030] Example 3

[0031] A preparation method of a photoelectrocatalytic photoanode nano-material, comprising the following steps:

[0032] First, clean the FTO conductive glass with a plasma cleaner. After cleaning, place it in a magnetron sputtering instrument. First, install the metal Bi target, evacuate to a pressure of 5×10 -3 Pa, then introduce argon to control the flow rate at 50 sccm, keep the baffle closed, pre-sputter the metal Bi target with a DC power of 8 W for 10 minutes, and then change the argon flow rate to control the pressure in the instrument at 4 Pa, open the baffle, and sputter the metal Bi target with a DC power of 8 W for 1.5 hours; then install the V2O5 target, evacuate to a pressure of 4×10 -3Pa, and then introduce argon with a flow rate of 50 sccm, keep the baffle closed, pre-sputter the V2O5 target with a radio frequency power of 220 W for 15 minutes, then change the argon flow rate to control the pressure in the instrument to 3 Pa, open the baffle, and sputter the V2O5 target with a radio frequency power of 220 W for 1 hour; after sputtering, calcine in air at 450 °C for 3 hours, then soak in 1 M KOH solution for 15 minutes, wash and dry to obtain a BiVO4 photoanode. Place the BiVO4 thin film in a potassium borate solution with a molar ratio of FeSO4·7H2O to NiSO4·6H2O of 10:1, and perform photodeposition for 10 minutes to obtain BiVO4 / NiFeO x photoanode.

[0033] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a photo-electrocatalytic photoanode nanomaterial, characterized in that, It includes the following steps: (1) Put the prepared substrate into a magnetron sputtering instrument, install the Bi source target, control the pressure at 1 - 5 Pa, and sputter the Bi source target at a power of 5 - 10 W for 0.5 - 2 hours; (2) Install the V source target, control the pressure at 1 - 5 Pa, and sputter the V source target at a power of 200 - 370 W for 0.5 - 2 hours; (3) Using the segmented magnetron sputtering technique, repeat steps (1) and (2) for 5 - 20 cycles to complete sputtering, and perform high - temperature heat treatment on the sample; (4) Treat the sample after the high - temperature heat treatment in step (3) to remove the excess vanadium oxide, wash and dry it to obtain the BiVO4 thin film; (5) Place the BiVO4 thin film obtained in step (4) into a potassium borate solution mixed with FeSO4·7H2O and NiSO4·6H2O, and perform photoelectrodeposition for 5 - 20 minutes to prepare the BiVO4 / NiFeO x photoanode nanomaterial.

2. The preparation method of the photo-electrocatalytic photoanode nanomaterial according to claim 1, characterized in that, The Bi source target is one or more of a metal Bi target and a Bi2O3 target.

3. The preparation method of the photocatalytic photoanode nanomaterial according to claim 1, characterized in that The V source target is one or more of a metal V target and a V2O5 target.

4. The preparation method of the photo-electrocatalytic photoanode nanomaterial according to claim 1, characterized in that, The temperature of the high - temperature heat treatment in step (3) is 400 - 800 °C, and the time is 2 - 10 hours.

5. The preparation method of the photo-electrocatalytic photoanode nanomaterial according to claim 1, characterized in that, The thickness of the BiVO4 thin film obtained in step (4) is 200 - 500 nanometers.

6. The preparation method of the photo-electrocatalytic photoanode nanomaterial according to claim 1, characterized in that, The molar ratio of FeSO4·7H2O and NiSO4·6H2O in step (5) is 10:

1.

7. The photocatalytic photoanode nanomaterial prepared by the method according to any one of claims 1-6, characterized in that, The photoanode nanomaterial is BiVO4 photoanode loaded with NiFeO x as an oxygen evolution cocatalyst, and the loading amount of the NiFeO x is 1.0 wt%.

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