Cu-doped MnMoO4 photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a Cu-doped MnMoO4 photocatalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: grinding copper sulfate pentahydrate into a MnMoO4 precursor, and changing the molar ratio of a copper source to obtain the MnMoO4-x% Cu composite material with different molar ratios, which can be applied to the field of hydrogen evolution by photocatalytic decomposition of water. Compared with an existing photocatalyst, the Cu-doped MnMoO4 photocatalyst has the advantages that the controllability is good when the Cu-doped MnMoO4 is used as a catalyst, the separation efficiency of current carriers is further improved, and the Cu-doped MnMoO4 photocatalyst is relatively high in hydrogen yield and relatively good in stability when being applied to photocatalytic water decomposition. The method is green and environment-friendly, simple, convenient to operate and low in material preparation cost, conforms to the green and environment-friendly concept advocated at present, and has a wide application market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and specifically relates to a Cu-doped MnMoO4 photocatalyst and a preparation method and application thereof. Background Art

[0002] In recent years, the problems of energy shortage and environmental damage have seriously restricted the sustainable development of society, and the development of efficient and green hydrogen resources has become the focus of most researchers. Hydrogen is becoming increasingly popular as an environmentally friendly, sustainable and renewable energy source because it has the potential to alleviate the energy shortage caused by the abuse of fossil fuels. To date, many methods for generating hydrogen energy have been established, including high-temperature decomposition of water and electrocatalytic water splitting. In particular, photocatalytic water splitting to produce hydrogen is easy to operate and widely used, and is a potential environmental protection technology, but it is not easy to achieve efficient hydrogen production. Therefore, a key issue in high-performance photocatalytic water splitting to produce hydrogen is to explore photocatalysts that can effectively achieve charge separation.

[0003] MnMoO4 has attracted extensive attention and application due to its significant advantages of simple synthesis, environmental friendliness, good stability and suitable band structure. However, the photocatalytic efficiency of pure MnMoO4 photocatalysts is usually limited, mainly due to its significantly lower efficiency in sunlight development and a large amount of recombination of photogenerated charges. Therefore, people have designed a variety of modification techniques to improve the photocatalytic efficiency of MnMoO4 photocatalytic hydrogen production, but there has been no relevant report on Cu-doped MnMoO4 as a photocatalyst for hydrogen evolution. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a Cu-doped MnMoO4 photocatalyst and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A Cu-doped MnMoO4 photocatalyst, wherein the doping amount of Cu is 1-3% of MnMoO4 in terms of molar percentage.

[0007] The above-mentioned method for preparing a Cu-doped MnMoO4 photocatalyst includes the following steps: adding (NH4)2MoO4 and MnSO4·H2O into a mortar and grinding to form a uniform precursor powder; adding CuSO4·5H2O to the precursor powder, continuing to grind it evenly, transferring it to a high-temperature muffle furnace for calcination reaction, and cooling it to room temperature after the reaction is completed to obtain a Cu-doped MnMoO4 photocatalyst.

[0008] Preferably, in the above preparation method, the molar ratio is (NH4)2MoO4:MnSO4·H2O=1:5.

[0009] Preferably, in the above preparation method, the calcination reaction conditions are: reacting at 600° C. for 3 h at a heating rate of 5° C. / min.

[0010] The invention provides an application of a Cu-doped MnMoO4 photocatalyst in photocatalytic water decomposition to produce hydrogen under visible light irradiation.

[0011] Preferably, the above application method is as follows: the Cu-doped MnMoO4 photocatalyst is uniformly dispersed in a mixed solution of deionized water, triethanolamine (TEOA) and chloroplatinic acid, argon gas is continuously introduced at a constant flow rate, and irradiated under visible light conditions.

[0012] Preferably, the concentration of the triethanolamine is 7.2 mmol / mL; the concentration of the chloroplatinic acid is 0.75 wt %.

[0013] Preferably, according to the solid-liquid ratio, Cu-doped MnMoO4: deionized water: triethanolamine: chloroplatinic acid = 20 mg: 18 mL: 3 mL: 20 μL.

[0014] The beneficial effects of the present invention are:

[0015] 1. The present invention uses a hydrothermal method to prepare a Cu-doped MnMoO4 photocatalyst. After Cu doping modification, impurity energy levels are generated in the original energy band structure, which reduces the electron transition barrier, can effectively reduce the recombination of photogenerated electrons and holes, and improve the separation efficiency of carriers, thereby significantly improving the visible light response of the catalyst and enhancing the photocatalytic activity.

[0016] 2. The Cu-doped MnMoO4 photocatalyst prepared by the present invention has a larger specific surface area and a more effective photogenerated electron and hole separation ability, as well as a stronger photocatalytic reduction ability, participates in the catalytic reaction, and is an effective way to improve the visible light catalytic activity.

[0017] 3. The Cu-doped MnMoO4 photocatalyst prepared by the present invention has good photocatalytic hydrogen evolution performance, and the method is simple, convenient, low-cost, mild in conditions, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 These are the X-ray diffraction patterns of the MnMoO4, MnMoO4-1%Cu, MnMoO4-2%Cu and MnMoO4-3%Cu photocatalysts prepared in Example 1.

[0019] Figure 2 This is a photocurrent-time curve of the MnMoO4, MnMoO4-1%Cu, MnMoO4-2%Cu and MnMoO4-3%Cu photocatalysts prepared in Example 1.

[0020] Figure 3 This is a comparison chart of the activity of MnMoO4, MnMoO4-1%Cu, MnMoO4-2%Cu and MnMoO4-3%Cu photocatalysts prepared in Example 1 for decomposing water and evolving hydrogen. DETAILED DESCRIPTION

[0021] Example 1 Cu-doped MnMoO4 photocatalyst (I) Preparation of MnMoO4

[0022] 1mmol (NH4)2MoO4 and 5mmol MnSO4·H2O were put into a mortar, mixed evenly to form a precursor powder, and then put into a porcelain boat and reacted at 600℃ in a high-temperature muffle furnace at a heating rate of 5℃ / min for 3h, and naturally cooled to room temperature to obtain MnMoO4.

[0023] (II) Preparation of MnMoO4 photocatalyst with 1% Cu doping

[0024] Put 1mmol (NH4)2MoO4 and 5mmol MnSO4·H2O into a mortar, mix them evenly to form a precursor powder, then add 0.01mmol CuSO4·5H2O, mix them evenly and continue grinding for 30min. After being fully ground, transfer them to a porcelain boat and react at 600℃ in a high-temperature muffle furnace at a heating rate of 5℃ / min for 3h. After the reaction, naturally cool to room temperature to obtain a MnMoO4 photocatalyst with a Cu doping amount of 1%, marked as MnMoO4-1%Cu.

[0025] (III) Preparation of MnMoO4 photocatalyst with 2% Cu doping

[0026] Put 1mmol (NH4)2MoO4 and 5mmol MnSO4·H2O into a mortar, mix them evenly to form a precursor powder, then add 0.02mmol CuSO4·5H2O, mix them evenly and continue grinding for 30 minutes. After being fully ground, transfer them to a porcelain boat and react at 600℃ in a high-temperature muffle furnace at a heating rate of 5℃ / min for 3h. After the reaction, naturally cool to room temperature to obtain a MnMoO4 photocatalyst with a Cu doping amount of 1%, marked as MnMoO4-2%Cu.

[0027] (IV) Preparation of MnMoO4 photocatalyst with 3% Cu doping

[0028] Put 1mmol (NH4)2MoO4 and 5mmol MnSO4·H2O into a mortar, mix them evenly to form a precursor powder, then add 0.03mmol CuSO4·5H2O, mix them evenly and continue grinding for 30min. After being fully ground, transfer them to a porcelain boat and react at 600℃ in a high-temperature muffle furnace at a heating rate of 5℃ / min for 3h. After the reaction, naturally cool to room temperature to obtain a MnMoO4 photocatalyst with a Cu doping amount of 3%, marked as MnMoO4-3%Cu.

[0029] (V) Testing

[0030] Figure 1 These are the X-ray diffraction patterns of the MnMoO4, MnMoO4-1%Cu, MnMoO4-2%Cu and MnMoO4-3%Cu photocatalysts prepared in Example 1. Figure 1 In the 5 significant characteristic diffraction peaks at 2θ=12.9°, 22.7°, 25.7°, 27.7° and 37.7°, they correspond to the (100), (021), (220), (-311) and (040) crystal planes of MnMoO4, respectively (standard card PDF#72-0285). Figure 1 No characteristic peaks of other impurities were observed, which indicates that the original structure of MnMoO4 is still retained after Cu doping MnMoO4.

[0031] Example 2 Application of Cu-doped MnMoO4 photocatalyst in catalytic decomposition of water and hydrogen evolution under light

[0032] The method is as follows: at room temperature and pressure, 18 mL of deionized water, 3 mL of TEOA solution with a concentration of 7.2 mmol / mL, and 20 μL of 0.75 wt% chloroplatinic acid aqueous solution are added to a container, and 20 mg of MnMoO4, MnMoO4-1% Cu, MnMoO4-2% Cu, and MnMoO4-3% Cu photocatalysts prepared in Example 1 are added respectively, and ultrasonic treatment is performed for 10 min to obtain a dispersed solution. Argon gas is introduced into the container at a rate of 40 mL / min for 30 min, and the container is sealed. Under visible light irradiation conditions, 1000 μL of gas in the container is taken with a micro syringe every 30 min, and the sample gas components are detected by gas chromatography separation technology to determine the concentration of hydrogen evolution.

[0033] Figure 2 The photocurrent-time curves of MnMoO4, MnMoO4-1%Cu, MnMoO4-2%Cu and MnMoO4-3%Cu photocatalysts prepared in Example 1. The results show that the photocurrent intensity of MnMoO4-2%Cu is about 1.84μA·cm -2 , is pure MnMoO4 (0.65μA·cm -2) is 2.83 times of that of the semiconductor. This indicates that doping with Cu improves the separation efficiency of photogenerated carriers in the semiconductor, thereby improving the photoelectrochemical performance of the semiconductor.

[0034] Figure 3 This is a comparison chart of the activity of MnMoO4, MnMoO4-1%Cu and MnMoO4-2%Cu photocatalysts prepared in Example 1 for decomposing water and releasing hydrogen. Figure 3 It can be seen that after 2.5h of light reaction, the maximum hydrogen production of MnMoO4 reached 279μmol·g -1 ·h -1 The maximum H2 production of MnMoO4-1%Cu is 410μmol·g -1 ·h -1 The maximum H2 production of MnMoO4-2%Cu is 690μmol·g -1 ·h -1 The maximum H2 production of MnMoO4-3%Cu is 589μmol·g -1 ·h -1 The catalytic hydrogen production performance of Cu-doped MnMoO4 photocatalyst is greatly improved compared with pure MnMoO4. This shows that after Cu doping MnMoO4, the photogenerated electron transfer ability is stronger, and the electron holes have stronger redox ability.

Claims

1. A Cu-doped MnMoO4 photocatalyst, characterized in that: In terms of molar percentage, the doping amount of Cu is 1-3% of MnMoO4.

2. The method for preparing a Cu-doped MnMoO4 photocatalyst according to claim 1, characterized in that: The method comprises the following steps: adding (NH4)2MoO4 and MnSO4·H2O into a mortar and grinding to form a uniform precursor powder; adding CuSO4·5H2O into the precursor powder, continuing to grind the powder evenly, transferring the powder into a high-temperature muffle furnace for calcination reaction, and cooling the mixture to room temperature after the reaction is completed to obtain a Cu-doped MnMoO4 photocatalyst.

3. The preparation method according to claim 2, characterized in that: In molar ratio, (NH4)2MoO4:MnSO4·H2O=1:

5.

4. The preparation method according to claim 2, characterized in that: The calcination reaction conditions are: reacting at 600° C. for 3 h at a rate of 5° C. / min.

5. Use of the Cu-doped MnMoO4 photocatalyst according to claim 1 in catalytic decomposition of water to produce hydrogen under visible light irradiation.

6. The use according to claim 5, characterized in that: The method is as follows: the Cu-doped MnMoO4 photocatalyst is uniformly dispersed in a mixed solution of deionized water, triethanolamine and chloroplatinic acid, argon gas is continuously introduced at a constant flow rate, and irradiated under visible light conditions.

7. The use according to claim 6, characterized in that: The concentration of the triethanolamine is 7.2 mmol / mL; the concentration of the chloroplatinic acid is 0.75 wt %.

8. The use according to claim 7, characterized in that: According to the solid-liquid ratio, Cu-doped MnMoO4: deionized water: triethanolamine: chloroplatinic acid = 20 mg: 18 mL: 3 mL: 15 μL.

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