A carbon-coated tungsten-molybdenum alloy, a composite photocatalyst, its preparation method and application

Abstract

This invention provides a carbon-coated tungsten-molybdenum alloy, a composite photocatalyst, its preparation method, and its application, belonging to the field of materials preparation technology. The carbon-coated tungsten-molybdenum alloy provided by this invention includes a tungsten-molybdenum alloy core and a carbon layer coating the surface of the tungsten-molybdenum alloy core and chemically bonded to it. By introducing a specific amount of carbon atoms that form chemical bonds with the alloy onto the surface of the molybdenum-tungsten alloy, it is possible to fine-tune the large number of unpaired single electrons present in the orbitals of the tungsten-molybdenum alloy, thereby balancing the pairing of H atoms between the metal atoms. + The adsorption energy is increased, thereby improving the catalytic efficiency of photocatalytic hydrogen production. Therefore, the carbon-coated tungsten-molybdenum alloy provided by this invention is expected to become an ideal material to replace precious metal co-catalysts.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology, specifically relating to a carbon-coated tungsten-molybdenum alloy, a composite photocatalyst, its preparation method, and its application. Background Technology

[0002] Developing clean and environmentally friendly renewable energy sources can help alleviate problems such as air pollution, water pollution, and global warming. Solar energy has the advantages of being renewable, having abundant energy storage, and being inexpensive. Hydrogen is clean, non-toxic, and has high energy density, making it the best alternative to fossil fuels. Therefore, solar photocatalytic hydrogen production is one of the most promising solutions to environmental pollution and the development of sustainable clean energy.

[0003] Since Fujishima et al. demonstrated the photoelectrochemical splitting of water to produce hydrogen (H2) and oxygen (O2) using TiO2 under light irradiation in 1972, semiconductor photocatalytic water splitting for H2 production has developed rapidly. However, due to the ease with which photogenerated charge carriers recombine in current photocatalysts, coupled with the high overpotential of the surface hydrogen evolution reaction, the photocatalytic hydrogen evolution activity of current semiconductor photocatalysts is not yet ideal. Research has found that modification with highly efficient co-catalysts can effectively improve the stability of photocatalysts, the separation efficiency of photogenerated charges, and the surface hydrogen evolution reaction rate, representing an effective method to enhance the activity of semiconductor photocatalytic hydrogen evolution reactions.

[0004] Precious metal phosphorus (Pt) is an ideal cocatalyst for photocatalytic hydrogen production systems, but its high price and limited reserves severely restrict its widespread application. Non-precious metals are abundant in the Earth's crust, making the development of efficient non-precious metal cocatalysts that can replace Pt of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon-coated tungsten-molybdenum alloy, a composite photocatalyst, its preparation method, and its application, so as to overcome the problem that the use of co-catalysts is limited due to the high price and limited reserves of precious metals.

[0006] In the process of realizing this invention, it was discovered that because tungsten and molybdenum atoms have extremely similar atomic radii and identical crystal structures, tungsten-molybdenum alloys can achieve atomic-level contact, thereby enabling more effective control over the d orbitals of molybdenum atoms and higher conductivity. This allows tungsten-molybdenum alloys to be used as co-catalysts in photocatalytic hydrogen production. However, after alloying tungsten and molybdenum, a large number of unpaired electrons exist in the orbitals, leading to H... + The strong adsorption of tungsten molybdenum is not conducive to the subsequent catalytic reaction, which in turn limits the use of tungsten molybdenum alloys in the field of photocatalytic hydrogen production.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a carbon-coated tungsten-molybdenum alloy, the carbon-coated tungsten-molybdenum alloy comprising an alloy core and a carbon layer coating the outer surface of the alloy core, the alloy core comprising a tungsten-molybdenum alloy, and the carbon layer being connected to the tungsten-molybdenum alloy by chemical bonds; wherein...

[0009] In the tungsten-molybdenum alloy, the molar ratio of tungsten to molybdenum is (3-9):1;

[0010] The mass ratio of the alloy core to the carbon layer is (97.5–93.5):(2.5–6.5).

[0011] In one optional embodiment, the carbon-coated tungsten-molybdenum alloy has a particle size of 20–30 nm.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned carbon-coated tungsten-molybdenum alloy, comprising the following steps:

[0013] S1. Zinc acetate dihydrate, phosphomolybdic acid, phosphotungstic acid and methanol are mixed to obtain solution A; wherein the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is 100:(3~9):1;

[0014] S2. Disperse dimethylimidazole in methanol to obtain solution B; wherein the molar ratio of zinc acetate dihydrate to dimethylimidazole is 1:(9-12).

[0015] S3. Mix the A solution with the B solution, separate the solid, wash and dry it to obtain the precursor;

[0016] S4. The precursor is calcined in an inert atmosphere; wherein the calcination conditions include: a heating rate of 4-7°C / min, a calcination temperature of 750-850°C, and a calcination time of 2-4 hours.

[0017] In one alternative implementation, in step S4, the inert atmosphere includes at least one of nitrogen, helium, and argon.

[0018] In an optional embodiment, in step S3, when mixing solution A and solution B, the mixture is stirred for 24–36 hours; the drying method includes vacuum drying at a temperature of 50–75°C for 8–16 hours; and the washing includes washing with methanol and ethanol sequentially.

[0019] Thirdly, the present invention provides the application of the above-mentioned carbon-coated tungsten-molybdenum alloy in the preparation of a cocatalyst for photocatalytic hydrogen production.

[0020] Fourthly, the present invention provides a composite photocatalyst, the composite photocatalyst comprising a co-catalyst and a photocatalyst, wherein the co-catalyst comprises the above-mentioned carbon-coated tungsten-molybdenum alloy.

[0021] In one optional embodiment, the mass ratio of the photocatalyst to the cocatalyst is 1:(0.05 to 0.2).

[0022] In one alternative embodiment, the photocatalyst comprises Zn. 0.5 Cd 0.5 S photocatalyst and / or CdS photocatalyst.

[0023] Fifthly, the present invention provides a method for preparing the above-mentioned composite photocatalyst, comprising the following steps:

[0024] The photocatalyst was dispersed in deionized water, the co-catalyst was added, the mixture was stirred, the solid was separated, washed, and dried; wherein...

[0025] The stirring time is 12–16 h, the drying temperature is 70–105 ℃, and the drying time is 2–4 h.

[0026] In a sixth aspect, the present invention provides the application of the above-mentioned carbon-coated tungsten-molybdenum alloy or composite photocatalyst in photocatalytic hydrogen production.

[0027] The technical solution of this invention has the following advantages:

[0028] (1) The carbon-coated tungsten-molybdenum alloy provided by the present invention includes a tungsten-molybdenum alloy core and a carbon layer coating the surface of the tungsten-molybdenum alloy core. By introducing a specific amount of carbon atoms that form chemical bonds with the alloy onto the surface of the tungsten-molybdenum alloy, it is possible to fine-tune the large number of unpaired single electrons present in the orbitals of the tungsten-molybdenum alloy, thereby balancing the pairing of metal atoms with H. + The adsorption energy is increased, thereby improving the catalytic efficiency of photocatalytic hydrogen production. Therefore, the carbon-coated tungsten-molybdenum alloy provided by this invention is expected to become an ideal material to replace precious metal co-catalysts.

[0029] (2) The method for preparing carbon-coated tungsten-molybdenum alloy provided by the present invention first prepares the structure of the organic-coated tungsten-molybdenum alloy precursor through a one-step reaction method, and then calcines it under an inert atmosphere. During the calcination process, the organic matter carbonizes and reduces the tungsten-molybdenum alloy precursor to tungsten-molybdenum alloy, thus obtaining the carbon-coated tungsten-molybdenum alloy. This method can prepare carbon-coated tungsten-molybdenum alloy simply and efficiently.

[0030] (3) The composite photocatalyst provided by this invention, by using a carbon-coated tungsten-molybdenum alloy as a cocatalyst and modifying the photocatalyst, can effectively improve the separation efficiency of photogenerated charges and the surface hydrogen evolution reaction rate of the photocatalyst, thereby improving the activity of semiconductor photocatalytic hydrogen evolution reaction. Therefore, the carbon-coated tungsten-molybdenum alloy cocatalyst provided in this application is expected to replace precious metal cocatalysts, greatly reducing the cost of photocatalysts. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 The image shows the XRD pattern of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of this invention.

[0033] Figure 2 The above are XPS spectra of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of the present invention; wherein, (a) is a high-resolution XPS spectrum of W, and (b) is a high-resolution XPS spectrum of Mo.

[0034] Figure 3 The image shows the SEM image of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of this invention.

[0035] Figure 4 The TEM image of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of this invention;

[0036] Figure 5 The HRTEM image and elemental distribution diagram of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of this invention are shown below.

[0037] Figure 6 The X-ray absorption spectrum of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of the present invention is shown below. Among them, (a) is the normalized intensity curve of the energy dispersive X-ray spectrum of W7Mo1 / C, molybdenum foil and MoC, (b) is the spectrum after Fourier transform processing, and (c) is the two-dimensional distribution of small-angle X-ray scattering of molybdenum foil and W7Mo1 / C.

[0038] Figure 7 The AC impedance spectra of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of the present invention and the carbon-coated tungsten prepared in Comparative Example 7 are shown.

[0039] Figure 8 Linear scanning voltammetric spectra of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 of this invention and the carbon-coated tungsten prepared in Comparative Example 7. Detailed Implementation

[0040] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0041] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0042] Example 1

[0043] Carbon-coated tungsten-molybdenum alloy was prepared using the following method:

[0044] (1) Weigh 2.2g of zinc acetate dihydrate (Zn(COOCH3)2·2H2O, about 0.01mol) and 0.184g of phosphomolybdic acid (H5PMo). 12 O 41 (approximately 0.0001 mol) and 2.02 g phosphotungstic acid (H3PW) 12 O 40 (Approximately 0.0007 mol) was dispersed in 180 ml of methanol, sonicated for 30 min, and stirred for 30 min to obtain solution A; wherein the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid was approximately 100:7:1;

[0045] (2) Weigh 9.85g of dimethylimidazole (C4H6N2, about 0.12mol), disperse it in 180 ml of methanol, stir for 30 min to obtain solution B; wherein the molar ratio of zinc acetate dihydrate to dimethylimidazole is 1:12;

[0046] (3) Solution A was rapidly added dropwise to solution B, stirred at room temperature (25 °C) for 24 h, filtered, washed with methanol and ethanol respectively, and dried under vacuum at 60 °C for 8 h to obtain carbon-coated tungsten-molybdenum alloy precursor;

[0047] (4) The carbon-coated tungsten-molybdenum alloy precursor prepared in step (3) is placed in a tube furnace and heated to 850 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined for 2 h to obtain carbon-coated tungsten-molybdenum alloy (W7Mo1 / C).

[0048] The carbon-coated tungsten-molybdenum alloy prepared in this embodiment includes a tungsten-molybdenum alloy core and a carbon layer coating the outer surface of the tungsten-molybdenum alloy core. The molar ratio of tungsten to molybdenum is 7:1, and the mass ratio of the tungsten-molybdenum alloy core to the carbon layer is 96.8:3.2.

[0049] Figure 1 This is the XRD pattern of the carbon-coated tungsten-molybdenum alloy prepared in this embodiment. Figure 1As shown, the XRD diffraction peaks of the carbon-coated tungsten-molybdenum alloy correspond to the Mo standard card (JCPDS No. 42-1120) and the W standard card (JCPDS No. 04-0806), indicating that the carbon-coated tungsten-molybdenum alloy was successfully synthesized in this embodiment.

[0050] Figure 2 The images show the high-resolution XPS spectra of W and Mo in the carbon-coated tungsten-molybdenum alloy prepared in this embodiment. (a) is the high-resolution XPS spectrum of W, where the peaks at 31.3 eV and 33.4 eV represent W with a valence of 0, and the peaks at 31.8 eV and 34.1 eV represent W with a valence of +4, indicating W-C bonded W. (b) is the high-resolution XPS spectrum of Mo, where the peak at 228.3 eV represents Mo with a valence of 0, the peaks at 231.3 eV and 228.6 eV represent Mo with a valence of +4, and the peaks at 235.2 eV and 232.3 eV represent Mo with a valence of +6. As can be seen, W and Mo in the carbon-coated tungsten-molybdenum alloy sample prepared in this embodiment mainly exist in elemental form, with a small amount also present in oxidized forms.

[0051] Figure 3 These are SEM images of W and Mo in the carbon-coated tungsten-molybdenum alloy prepared in this embodiment. Figure 4 This is a TEM image of the carbon-coated tungsten-molybdenum alloy sample prepared in this embodiment. Figure 3 and Figure 4 It can be seen that the carbon-coated tungsten-molybdenum alloy prepared in this embodiment consists of nanoparticles with a diameter of 20-30 nm.

[0052] Figure 5 The figures show the HRTEM image and elemental plane distribution of the carbon-coated tungsten-molybdenum alloy prepared in this embodiment. The figures clearly show the 110 crystal plane structure of the tungsten-molybdenum alloy, with carbon atoms uniformly distributed on the material surface to form a coating structure.

[0053] Figure 6The X-ray absorption spectra of the carbon-coated tungsten-molybdenum alloy prepared in this embodiment are shown. (a) shows the normalized intensity curves of the energy-dispersive X-ray spectra of W7Mo1 / C, molybdenum foil, and MoC. It can be seen that the molybdenum K-energy edge spectrum of W7Mo1 / C exhibits a positive shift compared to the spectrum of the molybdenum foil, indicating that the presence of carbon in the W7Mo1 / C alloy leads to an increase in valence states. (b) shows the spectrum after Fourier transform processing, where the main peak at approximately 2.4 Å represents the Mo–Mo bond in W7Mo1 / C. (c) shows the two-dimensional distribution of small-angle X-ray scattering (SAXS) of the molybdenum foil and W7Mo1 / C. It can be seen that the intensity of the molybdenum-carbon bond can be detected in W7Mo1 / C, indicating that carbon can form chemical bonds with molybdenum in the WMo alloy. Since tungsten and molybdenum have very similar properties, tungsten in the WMo alloy can also combine with carbon to form chemical bonds.

[0054] Example 2

[0055] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1, except that in step (1) of this example, phosphotungstic acid (H3PW) was used. 12 O 40 The amount used is 0.866g, which means that the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is about 100:3:1.

[0056] In the carbon-coated tungsten-molybdenum alloy prepared in this embodiment, the molar ratio of tungsten to molybdenum is 3:1, and the mass ratio of the tungsten-molybdenum alloy core to the carbon layer is 93.5:6.5.

[0057] Example 3

[0058] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1, except that in step (1) of this example, phosphotungstic acid (H3PW) was used. 12 O 40 The amount used is 2.60g, which means that the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is about 100:9:1.

[0059] In the carbon-coated tungsten-molybdenum alloy prepared in this embodiment, the molar ratio of tungsten to molybdenum is 9:1, and the mass ratio of the tungsten-molybdenum alloy core to the carbon layer is 97.5:2.5.

[0060] Example 4

[0061] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1, except that in step (1) of this example, phosphotungstic acid (H3PW) was used. 12 O 40The amount of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid used in step (2) is 1.44g, that is, the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is about 100:5:1; the amount of dimethylimidazole (C4H6N2) used in step (2) is 8.21g, that is, the molar ratio of zinc acetate dihydrate and dimethylimidazole is 1:10.

[0062] In the carbon-coated tungsten-molybdenum alloy prepared in this embodiment, the mass ratio of the tungsten-molybdenum alloy core to the carbon layer is 95.5:4.5.

[0063] Example 5

[0064] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1, except that in step (1) of this example, phosphotungstic acid (H3PW) was used. 12 O 40 The amount of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid used in step (2) is 2.02g, that is, the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is about 100:7:1; the amount of dimethylimidazole (C4H6N2) used in step (2) is 7.39g, that is, the molar ratio of zinc acetate dihydrate and dimethylimidazole is 1:9.

[0065] In the carbon-coated tungsten-molybdenum alloy prepared in this embodiment, the mass ratio of the tungsten-molybdenum alloy core to the carbon layer is 96.8:3.2.

[0066] Example 6

[0067] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1. The difference is that in step (4) of this example, the heating rate during calcination is 4℃ / min, the calcination temperature is 800℃, and the calcination time is 3h.

[0068] Example 7

[0069] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1. The difference is that in step (4) of this example, the heating rate during calcination is 7℃ / min, the calcination temperature is 750℃, and the calcination time is 4h.

[0070] Comparative Example 1

[0071] Carbon-coated tungsten-molybdenum alloys were prepared according to the method in Example 1, except that in step (1) of this comparative example, phosphotungstic acid (H3PW) was used. 12 O 40 The amount used is 0.577g, that is, the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is about 100:2:1.

[0072] In the carbon-coated tungsten-molybdenum alloy prepared in this comparative example, the molar ratio of tungsten to molybdenum is 2:1.

[0073] Comparative Example 2

[0074] Carbon-coated tungsten-molybdenum alloys were prepared according to the method in Example 1, except that in step (1) of this comparative example, phosphotungstic acid (H3PW) was used. 12 O 40 The amount used is 2.89g, which means that the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is about 100:10:1.

[0075] In the carbon-coated tungsten-molybdenum alloy prepared in this comparative example, the molar ratio of tungsten to molybdenum is 10:1.

[0076] Comparative Example 3

[0077] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1. The difference is that the amount of dimethylimidazole (C4H6N2) used in step (2) of this comparative example is 6.57g, that is, the molar ratio of zinc acetate dihydrate to dimethylimidazole is 1:8.

[0078] In the carbon-coated tungsten-molybdenum alloy prepared in this comparative example, the mass ratio of the tungsten-molybdenum alloy core to the carbon layer was 97.9:2.1.

[0079] Comparative Example 4

[0080] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1. The difference is that the amount of dimethylimidazole (C4H6N2) used in step (2) of this comparative example is 10.7g, that is, the molar ratio of zinc acetate dihydrate to dimethylimidazole is 1:13.

[0081] In the carbon-coated tungsten-molybdenum alloy prepared in this comparative example, the mass ratio of the tungsten-molybdenum alloy core to the carbon layer was 92.6:7.4.

[0082] Comparative Example 5

[0083] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1. The difference is that in step (4) of this comparative example, the heating rate during calcination was 3℃ / min, the calcination temperature was 700℃, and the calcination time was 5h.

[0084] Comparative Example 6

[0085] The carbon-coated tungsten-molybdenum alloy was prepared according to the method of Example 1. The difference is that in step (4) of this comparative example, the heating rate during calcination was 8℃ / min, the calcination temperature was 900℃, and the calcination time was 1h.

[0086] Comparative Example 7

[0087] Carbon-coated tungsten was prepared according to the method of Example 1, except that phosphomolybdic acid (H5PMo) was not added in step (1) of this comparative example. 12 O 41That is, the molar ratio of zinc acetate dihydrate to phosphotungstic acid is approximately 100:7, resulting in the sample W / C ratio.

[0088] Figure 7 The AC impedance spectra are those of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 and the carbon-coated tungsten alloy prepared in Comparative Example 7. Figure 7 It is known that carbon-coated tungsten-molybdenum alloys can significantly reduce the impedance of materials and thus improve conductivity compared to carbon-coated tungsten metal, thereby enabling electrons to transfer to the surface of the tungsten-molybdenum alloy more quickly to participate in the hydrogen evolution reaction.

[0089] Figure 8 Linear scanning voltammetric spectra of the carbon-coated tungsten-molybdenum alloy prepared in Example 1 and the carbon-coated tungsten alloy prepared in Comparative Example 7. Figure 8 It can be seen that, under the same current density, carbon-coated tungsten-molybdenum alloy has a smaller hydrogen evolution overpotential than carbon-coated tungsten sample, which is beneficial to the hydrogen evolution reaction.

[0090] Comparative Example 8

[0091] 0.096 g of analytical grade molybdenum powder and 1.287 g of tungsten powder were weighed and dissolved in 100 mL of 28% ammonia water. The mixture was slowly neutralized with hydrochloric acid, resulting in the precipitation of needle-like crystals. The precipitated WO3 and MoO3 were mixed and calcined in air at 800 °C. The mixed powder was then reduced in hydrogen at 1000 °C to prepare W7Mo1 alloy powder.

[0092] Experimental Example 1

[0093] 1. Preparation of carbon-coated tungsten-molybdenum alloy modified Zn 0.5 Cd 0.5 S photocatalyst

[0094] (1) Weigh 0.1999 g of cadmium acetate dihydrate (C4H) 10 CdO6) and 0.1647g zinc acetate dihydrate (C4H) 10 ZnO6 was dispersed in 12.5 mL of water, and the pH was adjusted to 7.3 with a 0.2 mol / L sodium hydroxide solution. While stirring, 7.5 mL of a 0.3 mol / L sodium sulfide nonahydrate (Na2S·9H2O) solution was added, and stirring continued for 20 min until completely dissolved. The solution was then transferred to a polytetrafluoroethylene hydrothermal reactor and placed in an oven at 160℃ for 4 h. After the reaction, the solution was washed with distilled water to obtain a yellow precipitate of Zn. 0.5 Cd 0.5 S is denoted as ZCS.

[0095] (2) Weigh 0.095 g Zn 0.5 Cd 0.5S was dispersed in 30 mL of deionized water, and 0.005 g of carbon-coated tungsten-molybdenum alloy nanoparticles prepared in Example 1 were added. The mixture was stirred at room temperature (25 °C) for 12 h, washed three times with deionized water, and dried at 80 °C for 6 h to obtain 5% W7Mo1 / C-ZCS-1.

[0096] (3) Following the same method as in step (2), carbon-coated tungsten-molybdenum alloy nanoparticles, carbon-coated tungsten, tungsten-molybdenum alloy and metal Pt nanoparticles prepared in Examples 2-7 and Comparative Examples 1-8 were used in sequence to prepare 5% WMo / C-ZCS-2, 5% WMo / C-ZCS-3, 5% WMo / C-ZCS-4, 5% WMo / C-ZCS-5, 5% WMo / C-ZCS-6, 5% WMo / C-ZCS-7, 5% WMo / C-ZCS-D1, 5% WMo / C-ZCS-D2, 5% WMo / C-ZCS-D3, 5% WMo / C-ZCS-D4, 5% WMo / C-ZCS-D5, 5% WMo / C-ZCS-D6, 5% W / C-ZCS, 5% WMo-ZCS and 5% Pt-ZCS.

[0097] (4) Adjust Zn using the same method as in step (2). 0.5 Cd 0.5 The amount of S used was determined by preparing carbon-coated tungsten-molybdenum alloy nanoparticles as described in Example 1, and then sequentially preparing 10% W7Mo1 / C-ZCS, 15% W7Mo1 / C-ZCS, and 20% W7Mo1 / C-ZCS.

[0098] 2. Hydrogen production performance test

[0099] Take 15 mg of the W7Mo1 / C nanoparticles prepared in Example 1 and 15 mg of each of the above-prepared photocatalysts or composite photocatalysts, disperse them in 30 ml of lactic acid aqueous solution, place them in a quartz reactor, keep the reaction temperature constant at 15 °C, use a xenon lamp as the light source for unilateral irradiation (300 W, Perfect Light, with a 400 nm cutoff filter), use Ar as the carrier gas, analyze the hydrogen production performance every 1 h using a gas chromatograph, calculate the hydrogen production rate, and the results are shown in Table 1.

[0100] Table 1. Hydrogen production rates of various materials in Experiment Example 1

[0101] Material <![CDATA[Hydrogen production rate, mmol˙g -1 ˙h -1 > <![CDATA[W7Mo1 / C]]> 0 ZCS 2.1 <![CDATA[5% W7Mo1 / C-ZCS-1]]> 23.99 <![CDATA[10% W7Mo1 / C-ZCS]]> 29.45 <![CDATA[15% W7Mo1 / C-ZCS]]> 33.27 <![CDATA[20% W7Mo1 / C-ZCS]]> 28.00 5% WMo / C-ZCS-2 20.38 5% WMo / C-ZCS-3 21.09 5% WMo / C-ZCS-4 22.56 5% WMo / C-ZCS-5 23.22 5% WMo / C-ZCS-6 23.05 5% WMo / C-ZCS-7 22.43 5% WMo / C-ZCS-D1 16.55 5% WMo / C-ZCS-D2 15.23 5% WMo / C-ZCS-D3 17.52 5% WMo / C-ZCS-D4 16.70 5% WMo / C-ZCS-D5 14.95 5% WMo / C-ZCS-D6 13.77 5% W / C-ZCS 6.24 5% WMo -ZCS 1.92 5% Pt-ZCS 19.23

[0102] Experiment Example 2

[0103] 1. Preparation of CdS photocatalyst modified with carbon-coated tungsten-molybdenum alloy

[0104] (1) Weigh 0.1999 g of cadmium acetate dihydrate (C4H) 10 CdO6) and 0.1647g zinc acetate dihydrate (C4H) 10 ZnO6 was dispersed in 12.5 mL of water, and the pH was adjusted to 7.3 with a 0.2 mol / L sodium hydroxide solution. While stirring, 3.75 mL of a 0.3 mol / L sodium sulfide nonahydrate (Na2S·9H2O) solution was added, and stirring was continued for 20 min until it was completely dissolved. The solution was then transferred to a polytetrafluoroethylene hydrothermal reactor and placed in an oven at 160 °C for 4 h. After the reaction was completed, the mixture was washed with distilled water to obtain a yellow precipitate CdS, denoted as CS.

[0105] (2) Weigh 0.095 g of CdS and disperse it in 30 mL of deionized water. Add 0.005 g of carbon-coated tungsten-molybdenum alloy nanoparticles prepared in Example 1. Stir at room temperature (25 °C) for 12 h, wash three times with deionized water, and dry at 80 °C for 6 h to obtain 5% W7Mo1 / C-CS-1.

[0106] (3) Following the same method as in step (2), carbon-coated tungsten-molybdenum alloy nanoparticles, carbon-coated tungsten, tungsten-molybdenum alloy and metal Pt nanoparticles prepared in Examples 2-7 and Comparative Examples 1-8 were used in sequence to prepare 5% WMo / C-CS-2, 5% WMo / C-CS-3, 5% WMo / C-CS-4, 5% WMo / C-CS-5, 5% WMo / C-CS-6, 5% WMo / C-CS-7, 5% WMo / C-CS-D1, 5% WMo / C-CS-D2, 5% WMo / C-CS-D3, 5% WMo / C-CS-D4, 5% WMo / C-CS-D5, 5% WMo / C-CS-D6, 5% W / C-CS, 5% WMo-CS and 5% Pt-CS.

[0107] (4) Following the same method as in step (2), adjust the amount of CdS and use the carbon-coated tungsten-molybdenum alloy nanoparticles prepared in Example 1 to prepare 10% W7Mo1 / C-CS, 15% W7Mo1 / C-CS and 20% W7Mo1 / C-CS in sequence.

[0108] 2. Hydrogen production performance test

[0109] Take 15 mg of the W7Mo1 / C nanoparticles prepared in Example 1 and 15 mg of each of the above-prepared photocatalysts or composite photocatalysts, disperse them in 30 ml of lactic acid aqueous solution, place them in a quartz reactor, keep the reaction temperature constant at 15 °C, use a xenon lamp as the light source for unilateral irradiation (300 W, Perfect Light, with a 400 nm cutoff filter), use Ar as the carrier gas, analyze the hydrogen production performance every 1 h using a gas chromatograph, calculate the hydrogen production rate, and the results are shown in Table 2.

[0110] Table 2 Hydrogen production rates of various materials in Experiment Example 2

[0111] Material <![CDATA[Hydrogen production rate, mmol˙g -1 ˙h -1 > <![CDATA[W7Mo1 / C]]> 0 CS 1.52 <![CDATA[5% W7Mo1 / C-CS-1]]> 16.56 <![CDATA[10% W7Mo1 / C-CS]]> 20.91 <![CDATA[15% W7Mo1 / C-CS]]> 22.87 <![CDATA[20% W7Mo1 / C-CS]]> 19.88 5% WMo / C-CS-2 14.60 5% WMo / C-CS-3 14.93 5% WMo / C-CS-4 15.47 5% WMo / C-CS-5 16.08 5% WMo / C-CS-6 15.71 5% WMo / C-CS-7 15.96 5% WMo / C-CS-D1 11.92 5% WMo / C-CS-D2 10.51 5% WMo / C-CS-D3 12.96 5% WMo / C-CS-D4 11.86 5% WMo / C-CS-D5 10.47 5% WMo / C-CS-D6 9.54 5% W / C-CS 4.33 5% WMo-CS 1.38 5% Pt-CS 13.52

[0112] As shown in Tables 1 and 2, the introduction of carbon-coated tungsten-molybdenum alloy can significantly improve the hydrogen evolution efficiency of ZCS and CdS. Furthermore, the carbon-coated tungsten-molybdenum alloy exhibits superior co-catalytic performance compared to metallic Pt, while its cost is far lower.

[0113] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. The application of carbon-coated tungsten-molybdenum alloy in the preparation of a cocatalyst for photocatalytic hydrogen production, wherein the carbon-coated tungsten-molybdenum alloy comprises an alloy core and a carbon layer coating the outer surface of the alloy core, the alloy core comprising a tungsten-molybdenum alloy, and the carbon layer being chemically bonded to the tungsten-molybdenum alloy; wherein, In the tungsten-molybdenum alloy, the molar ratio of tungsten to molybdenum is (3-9):1; The mass ratio of the alloy core to the carbon layer is (97.5–93.5):(2.5–6.5).

2. Use according to claim 1, characterized in that, The particle size of the carbon-coated tungsten-molybdenum alloy is 20–30 nm.

3. Use according to claim 1 or 2, characterized in that, The preparation method of the carbon-coated tungsten-molybdenum alloy includes the following steps: S1. Zinc acetate dihydrate, phosphomolybdic acid, phosphotungstic acid and methanol are mixed to obtain solution A; wherein the molar ratio of zinc acetate dihydrate, phosphotungstic acid and phosphomolybdic acid is 100:(3~9):1; S2. Disperse dimethylimidazole in methanol to obtain solution B; wherein the molar ratio of zinc acetate dihydrate to dimethylimidazole is 1:(9-12). S3. Mix the A solution with the B solution, separate the solid, wash and dry it to obtain the precursor; S4. The precursor is calcined in an inert atmosphere; wherein the calcination conditions include: a heating rate of 4-7°C / min, a calcination temperature of 750-850°C, and a calcination time of 2-4 hours.

4. Use according to claim 3, characterized in that, In step S4, the inert atmosphere includes at least one of nitrogen, helium, and argon.

5. A composite photocatalyst, characterized by The composite photocatalyst includes a co-catalyst and a photocatalyst. The co-catalyst comprises a carbon-coated tungsten-molybdenum alloy, which includes an alloy core and a carbon layer coating the outer surface of the alloy core. The alloy core comprises a tungsten-molybdenum alloy, and the carbon layer is chemically bonded to the tungsten-molybdenum alloy. In the tungsten-molybdenum alloy, the molar ratio of tungsten to molybdenum is (3-9):1; The mass ratio of the alloy core to the carbon layer is (97.5–93.5):(2.5–6.5). The mass ratio of the photocatalyst to the cocatalyst is 1:(0.05~0.2). The photocatalyst comprises Zn 0.5 Cd 0.5 S photocatalyst and / or a CdS photocatalyst.

6. The method for preparing the composite photocatalyst according to claim 5, characterized by, Includes the following steps: The photocatalyst was dispersed in deionized water, the co-catalyst was added, the mixture was stirred, the solid was separated, washed, and dried; wherein... The stirring time is 12–16 h, the drying temperature is 70–105 ℃, and the drying time is 2–4 h.

7. The application of the composite photocatalyst according to claim 5 in photocatalytic hydrogen production.

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