Composite photocatalyst, preparation method and application thereof

Abstract

The application relates to the field of catalysts, in particular to a composite photocatalyst and a preparation method and application thereof, in particular to an alpha-NiS / Cd 1‑x Zn x S composite catalyst in hydrogen production by reforming lignin, the composite photocatalyst comprising mesoporous Cd 1‑x Zn x S and alpha-NiS, wherein x=0.2-0.8, the mass ratio of the alpha-NiS and mesoporous Cd 1‑x Zn x S is (1-15):100, and the pore size of the mesoporous Cd 1‑ x Zn x S is 2-10 nm. The composite photocatalyst can catalyze hydrogen production by reforming lignin, and the hydrogen production rate is fast.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and particularly to a composite photocatalyst, its preparation method, and its applications, especially an α-NiS / Cd catalyst. 1-x Zn x Application of S composite catalyst in hydrogen production from lignin reforming. Background Technology

[0002] Biomass is a renewable resource, with lignin being the most representative and abundant component. While lignin is used for incineration, its utilization rate is low and it pollutes the environment. However, its structure contains numerous functional groups, giving it the potential to produce high-value-added chemicals. Earth possesses abundant solar energy resources, and photocatalytic reforming of lignin to produce hydrogen, driven by sunlight, is a promising strategy that addresses both the energy crisis and environmental issues. Visible light accounts for approximately 45% of sunlight, while ultraviolet light accounts for 5%. Therefore, the preparation of efficient, visible-light-responsive composite photocatalytic materials is a research hotspot in the photocatalytic reforming of lignin to produce hydrogen. Summary of the Invention

[0003] The purpose of this invention is to address the lack of a catalyst capable of catalyzing the reforming of lignin to produce hydrogen, as mentioned in the background section. This invention proposes a composite photocatalyst and its preparation method, which can catalyze the reforming of lignin to produce hydrogen at a rapid rate.

[0004] The technical solution adopted by this invention to solve its technical problem is: a composite photocatalyst, wherein the composite photocatalyst comprises mesoporous Cd 1-x Zn x S and α-NiS, where x = 0.2-0.8, the α-NiS and mesoporous Cd 1-x Zn x The mass ratio of S is (1-15):100, and the mesoporous Cd 1-x Zn x The pore size of S is 2-10 nm, preferably 2-3 nm, and more preferably 2.952 nm.

[0005] Preferably, x = 0.8, and the composite photocatalyst is α-NiS / Cd. 0.2 Zn 0.8 S.

[0006] Preferably, the α-NiS and mesoporous Cd 1-x Zn x The mass ratio of S is 7:100.

[0007] A method for preparing the composite photocatalyst as described above, the method comprising the following steps:

[0008] 1) Dissolve cadmium nitrate and zinc nitrate in diethylenetriamine (DETA) aqueous solution, stir at room temperature for 30±5 min, add L-cysteine ​​and continue stirring for 30±5 min to obtain a mixed solution;

[0009] 2) Transfer the mixed solution obtained in step 1) into a polytetrafluoroethylene reactor and react at 170-190℃ for 15-18 hours. After cooling, wash with water and anhydrous ethanol sequentially, and then vacuum dry at 55-65℃ to constant weight to obtain the metal precursor, i.e., mesoporous Cd. 1-x Zn x S;

[0010] 3) Mix the metal precursor obtained in step 2) with α-NiS, add anhydrous ethanol dropwise, grind for 1-2 hours, and then dry to obtain α-NiS / Cd. 1-x Zn x S stands for composite photocatalyst.

[0011] As a preferred technical solution, the preparation method comprises the following steps:

[0012] 1) Dissolve cadmium nitrate tetrahydrate and zinc nitrate hexahydrate in diethylenetriamine aqueous solution, stir at room temperature for 30 min, add L-cysteine ​​and continue stirring for 30 min to obtain a mixed solution;

[0013] 2) The mixed solution obtained in step 1) was transferred into a polytetrafluoroethylene reactor and reacted at 180°C for 16 hours. After cooling, it was washed successively with water and anhydrous ethanol, and then vacuum dried at 60°C to constant weight to obtain the metal precursor, i.e., mesoporous Cd. 1-x Zn x S;

[0014] 3) The metal precursor obtained in step 2) was mixed with α-NiS, anhydrous ethanol was added dropwise, and the mixture was ground for 1 hour and then dried with infrared light to obtain α-NiS / Cd. 1-x Zn x S stands for composite photocatalyst.

[0015] Preferably, the total molar amount of cadmium nitrate and zinc nitrate in step 1) is in the volume ratio of the diethylenetriamine aqueous solution to 1 mmol: (12-15) mL, wherein the preferred volume ratio of the total molar amount of cadmium nitrate and zinc nitrate to the diethylenetriamine aqueous solution is 1:12.

[0016] Preferably, the volume ratio of water to diethylenetriamine in the diethylenetriamine aqueous solution in step 1) is 1:(0.25-2.5), wherein the preferred volume ratio of water to diethylenetriamine in the diethylenetriamine aqueous solution is 1:2.5.

[0017] Preferably, the molar ratio of L-cysteine ​​to the total molar amounts of cadmium nitrate and zinc nitrate in step 1) is (1-1.5):1, and more preferably 1.2:1.

[0018] Preferably, the ratio of the metal precursor to anhydrous ethanol in step 3) is 95-100 mg / mL, and more preferably 100 mg / mL.

[0019] An application of the composite photocatalyst described in this invention in the photocatalytic reforming of lignin for hydrogen production.

[0020] As a preferred application, this specifically involves: under illumination, applying the composite photocatalyst α-NiS / Cd... 1-x Zn x S is dispersed in an alkaline lignin solution to produce hydrogen. The ratio of the composite photocatalyst to the alkaline lignin solution is 0.4-1 mg / mL, and the preferred ratio is 3:7 mg / mL. The concentration of the alkaline lignin solution is 0.1-0.3 g / L.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention employs a solvothermal method to prepare mesoporous Cd with adjustable band gap width. 1-x Zn x In the study of Cd semiconductor materials with varying amounts of α-NiS loading prepared by a grinding method using a controlled variable method, the presence of different amounts of α-NiS-loaded Cd was investigated. 0.2 Zn 0.8 S composite material, to screen for the optimal Cd loading 1-x Zn x S composite material, which can photocatalytically reform lignin under visible light irradiation, at lignin concentrations of 0.1, 0.2, and 0.3 g / L, 7%-α-NiS / Cd 0.2 Zn 0.8 The hydrogen production rates of S can reach 269.7, 317.5, and 338.6 μmol·g. -1 ·h -1 ;

[0023] 2. The preparation method of this invention is simple, and the photocatalytic water splitting hydrogen production performance is also excellent, with a maximum hydrogen production performance of 12857.1 μmol·g. -1 ·h -1 . Attached Figure Description

[0024] Figure 1 The hydrogen production rate diagrams for the metal precursors prepared in Examples 9-32 are shown, where (a) represents Examples 9-16, (b) represents Examples 17-24, and (c) represents Examples 25-32.

[0025] Figure 2 The images show the XRD patterns of different substances, where (a) is the XRD pattern of pure α-NiS and (b) is the XRD pattern of pure Cd. 0.2 Zn 0.8 S and α-NiS / Cd with different mass percentages prepared in Examples 1-6 0.2 Zn 0.8 XRD pattern of S and standard diffraction patterns of ZnS, CdS and CdZnS;

[0026] Figure 3 7% α-NiS / Cd 0.2 Zn 0.8 TEM and HRTEM images of S, (a) TEM image, (b) HRTEM image;

[0027] Figure 4 For pure Cd 0.2 Zn 0.8 S and α-NiS / Cd with different mass percentages prepared in Examples 1-6 0.2 Zn 0.8 The UV-Vis diffuse reflectance spectrum of S, where (a) is the UV-Vis diffuse reflectance spectrum and (b) is the band gap width spectrum;

[0028] Figure 5 For pure Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Fluorescence spectrum of S;

[0029] Figure 6 For Cd 0.2 Zn 0.8 S, 5% -α-NiS / Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Typical nitrogen adsorption-desorption curves and pore size distribution diagrams corresponding to S, where (a) and (b) are Cd 0.2 Zn 0.8 S, (c)(d) is 5% -α-NiS / Cd 0.2 Zn 0.8 S,(e)(f) is 7%-α-NiS / Cd 0.2 Zn 0.8 S;

[0030] Figure 7 α-NiS / Cd with different mass percentages prepared in Examples 1-6 0.2 Zn 0.8 Photocatalytic hydrogen production rate diagram of S;

[0031] Figure 8 7% α-NiS / Cd 0.2 Zn 0.8 Photocatalytic cycle stability diagram of S;

[0032] Figure 9 7% α-NiS / Cd 0.2 Zn 0.8 S-photocatalytic reforming of hydrogen production rates of alkaline lignin at different concentrations;

[0033] Figure 10 For Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Comparison of transient photocurrents of S;

[0034] Figure 11 For Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Electrochemical impedance spectroscopy of S. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] The present invention will now be further illustrated with specific examples. The following embodiments are only for explaining the present invention and do not constitute a limitation thereof. The test samples and test procedures used in the following embodiments include the following (if the specific experimental conditions are not specified in the embodiments, they are usually performed according to conventional conditions or the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following embodiments can be obtained commercially unless otherwise specified).

[0038] The reagents used in this invention are sourced from Sinopharm Group and Aladdin Reagent Co., Ltd.

[0039] Example 1

[0040] A method for preparing a composite photocatalyst, comprising the following steps:

[0041] 1) Dissolve 1 mmol cadmium nitrate tetrahydrate and 4 mmol zinc nitrate hexahydrate in diethylenetriamine aqueous solution, stir at room temperature for 30 min, then slowly add 6 mmol L-cysteine ​​and continue stirring for 30 min to obtain a mixed solution;

[0042] The aqueous solution of diethylenetriamine is 60 mL, in which the volume ratio of water to diethylenetriamine is 1:2.5.

[0043] 2) The above mixed solution was transferred to a 100 mL polytetrafluoroethylene reactor and reacted at 180 °C for 16 h. After cooling, the sample was washed with distilled water and anhydrous ethanol, respectively. The washed sample was then placed in a vacuum drying oven and dried at 60 °C to constant weight to obtain mesoporous Cd. 0.2 Zn 0.8 S;

[0044] 3) Add 100mg of mesoporous Cd 0.2 Zn 0.8 S and 1 mg of α-NiS powder were placed in a mortar, 1 mL of anhydrous ethanol was added dropwise, and after grinding for one hour, the composite photocatalyst was rapidly dried in an infrared drying oven, denoted as 1%-α-NiS / Cd. 0.2 Zn 0.8 S.

[0045] Example 2

[0046] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that in step 3), the amount of α-NiS powder added is 3 mg, and the resulting composite photocatalyst is denoted as 3%-α-NiS / Cd. 0.2 Zn 0.8 S.

[0047] Example 3

[0048] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that in step 3), the amount of α-NiS powder added is 5 mg, and the resulting composite photocatalyst is denoted as 5%-α-NiS / Cd. 0.2 Zn 0.8 S.

[0049] Example 4

[0050] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that in step 3), the amount of α-NiS powder added is 7 mg, and the resulting composite photocatalyst is denoted as 7%-α-NiS / Cd. 0.2 Zn 0.8S.

[0051] Example 5

[0052] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that in step 3), the amount of α-NiS powder added is 10 mg, and the resulting composite photocatalyst is denoted as 10%-α-NiS / Cd. 0.2 Zn 0.8 S.

[0053] Example 6

[0054] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that in step 3), the amount of α-NiS powder added is 15 mg, and the resulting composite photocatalyst is denoted as 15%-α-NiS / Cd. 0.2 Zn 0.8 S.

[0055] Example 7

[0056] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that the volume ratio of water to diethylenetriamine in step 1) is 1:1.

[0057] Example 8

[0058] A method for preparing a composite photocatalyst, the steps of which are similar to those in Example 1, except that the volume ratio of water to diethylenetriamine in step 1) is 4:1.

[0059] Examples 9-32

[0060] A mesoporous Cd 1-x Zn x The preparation method of S is similar to that in Example 1, except that the amount of raw materials added is different, as shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] Application Example 1

[0065] The mesoporous Cd prepared in Examples 9-32 1-x Zn x S was subjected to photocatalytic hydrogen production testing. The testing steps are as follows: 30 mg of the synthesized sample (the sample is the mesoporous Cd prepared in Examples 9-32) was weighed. 1-x Zn xSolution A was obtained by dissolving S in a beaker containing 40 mL of ultrapure water; solution B was obtained by dissolving sacrificial agent (5.8830 g NaS·9H2O, 2.2050 g Na2SO3) in a beaker containing 30 mL of ultrapure water and sonicating for 15 minutes. Solutions A and B were then poured into sealed glass reactors with high-transparency quartz lids and connected to a photocatalytic water splitting hydrogen production testing device. A xenon lamp (HXF300, 300W) with a filter (λ≥400 nm) was used as the light source (simulating sunlight) to drive the photocatalytic water splitting experiment. The reaction system was kept under stirring and controlled at 15°C using a cooling circulating water system. Simultaneously, a vacuum pump was used to vent dissolved air from the reaction device and the aqueous solution. Hydrogen gas was quantitatively collected from the hydrogen evolution device every 30 minutes and detected by gas chromatography. This test was used to screen different transition metal precursors, namely mesoporous Cd. 1-x Zn x The effects of sulfur ratio, solvent volume, and sulfur source ratio on hydrogen production performance.

[0066] like Figure 1 As shown, based on the hydrogen production rate, it can be seen that when the molar ratio of cadmium nitrate tetrahydrate to zinc nitrate hexahydrate is 1:4, the volume ratio of water to diethylenetriamine in the diethylenetriamine aqueous solution is 1:2.5, and the molar ratio of L-cysteine ​​to the total molar amount of cadmium nitrate tetrahydrate and zinc nitrate hexahydrate is 1.2:1, mesoporous Cd 0.2 Zn 0.8 S exhibits the best hydrogen production performance, with a value of 6200.4 μmol·g. -1 ·h -1 .

[0067] Characterization of the composite photocatalysts prepared in the above embodiments:

[0068] XRD pattern: The crystal structure of the sample was characterized using X-ray powder diffraction (XRD, Bruker D8), such as... Figure 2 As shown, Figure 2 (a) is the XRD pattern of pure α-NiS, indexed to the α-NiS crystal form based on the diffraction peaks (PDF Card: 02-1280). Figure 2 (b) is pure Cd 0.2 Zn 0.8 S and α-NiS / Cd with different mass percentages prepared in Examples 1-6 0.2 Zn 0.8 XRD pattern of S and standard diffraction patterns of ZnS, CdS, and CdZnS. Compared to the standard diffraction peaks of ZnS, CdS... 0.2 Zn 0.8 The diffraction peaks of S shift to lower angles, indicating that the sample is not ZnS (PDF Card: 79-2204). Compared to the standard diffraction peaks of CdS, CdS...0.2 Zn 0.8 The diffraction peak of S shifts to a higher angle towards α-NiS, indicating that the sample is not CdS (PDF Card: 75-1505), suggesting the formation of Cd. 0.2 Zn 0.8 S solid solution. α-NiS supported on Cd 0.2 Zn 0.8 After S surface, Cd 0.2 Zn 0.8 The diffraction peak of S did not shift, and the (100) diffraction peak of α-NiS appeared at 30.5℃, indicating that α-NiS successfully reacted with Cd. 0.2 Zn 0.8 S composites formed α-NiS / Cd 0.2 Zn 0.8 S composite material, and the loading of α-NiS does not affect Cd 0.2 Zn 0.8 Crystal structure of S.

[0069] TEM images: The morphology and microstructure of the material were observed using a high-resolution transmission electron microscope (HRTEM, Thermo Scientific Talos F200X). For example... Figure 3 As shown, Figure 3 (a) is 7%-α-NiS / Cd 0.2 Zn 0.8 TEM image of S composite material, showing Cd 0.2 Zn 0.8 S is an irregular sphere. Figure 3 (b) is 7% α-NiS / Cd 0.2 Zn 0.8 The HRTEM image of S shows lattice fringes at 0.33 nm and 0.28 nm, respectively, attributed to Cd. 0.2 Zn 0.8 The (002) and (100) crystal planes of S and α-NiS further confirm the α-NiS / Cd 0.2 Zn 0.8 Successful synthesis of S composite material.

[0070] UV-Vis Diffuse Reflectance Spectroscopy: The light absorption capacity of the samples was measured using UV-Vis DRS (Shimadzu UV-2550). UV-Vis DRS was used to compare the light absorption capacity of a series of α-NiS / Cd samples with different α-NiS loadings in the examples. 0.2 Zn 0.8 The optical properties of S composite materials were studied, such as... Figure 4 As shown, Figure 4 (a) is pure Cd 0.2Zn 0.8 S and α-NiS / Cd with different mass percentages prepared in Examples 1-6 0.2 Zn 0.8 UV-Vis diffuse reflectance spectrum of S, pure Cd 0.2 Zn 0.8 The absorption edge of S appears at 504 nm, similar to that of pure Cd. 0.2 Zn 0.8 Compared to S, α-NiS / Cd 0.2 Zn 0.8 The visible light absorption intensity of S increases with increasing α-NiS loading, 7%-α-NiS / Cd 0.5 Zn 0.5 The absorption edge of S redshifts to 518 nm, indicating that α-NiS reacts with Cd. 0.2 Zn 0.8 A heterojunction is formed between S and S, effectively improving the separation efficiency of photogenerated carriers. Pure Cd 0.2 Zn 0.8 S and series α-NiS / Cd 0.2 Zn 0.8 S corresponds to the band gap width (E) g This can be calculated using the formula ahv = A(hv - Eg). n / 2 Confirmed. Band gap width as follows: Figure 4 As shown in (b), pure Cd can be seen. 0.2 Zn 0.8 S, 7%-α-NiS / Cd 0.2 Zn 0.8 S, 15% -α-NiS / Cd 0.2 Zn 0.8 The band gaps of S are 2.52 eV, 2.50 eV, and 2.47 eV, respectively. After introducing black α-NiS, the α-NiS / Cd ratio... 0.2 Zn 0.8 The light absorption capacity of the S composite material is effectively enhanced, which is beneficial to improving photocatalytic performance.

[0071] Fluorescence spectra: The fluorescence spectra (PL) of the samples were obtained using a Hitachi F-4700 fluorescence spectrophotometer. Figure 5 As shown, this is pure Cd. 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 The fluorescence spectrum of S, with an excitation wavelength of 374 nm, for pure Cd 0.2 Zn 0.8 S exhibits a strong emission peak at approximately 532 nm, attributed to band-band photoluminescence. Furthermore, we observed that at the same excitation wavelength, 7%-α-NiS / Cd...0.2 Zn 0.8 The fluorescence emission intensity of the S composite material decreases due to the formation of heterojunction, which helps reduce the recombination of photogenerated carriers and thus improves the photocatalytic activity of the material.

[0072] Specific surface area analysis: Cd 0.2 Zn 0.8 S, 5% -α-NiS / Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Typical nitrogen adsorption-desorption curves corresponding to S, such as Figure 6 As shown. By Figure 6 (a)(c)(e) can be seen, Cd 0.2 Zn 0.8 S, 5% -α-NiS / Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 The specific surface area of ​​S decreases sequentially, reaching 72.356 m². 2 / g、62.366m 2 / g and 57.06m 2 / g. From Figure 6 (b)(d)(f) It can be seen that Cd 0.2 Zn 0.8 S, 5% -α-NiS / Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 The pore sizes of S are 9.533 nm, 4.201 nm and 2.952 nm, respectively, proving that it is a mesoporous material.

[0073] Application Example 2

[0074] The composite photocatalysts prepared in Examples 1-6 were subjected to photocatalytic hydrogen production tests. The test steps were as follows: 30 mg of the synthesized sample (the composite photocatalysts prepared in Examples 1-6) was weighed and dissolved in a beaker containing 40 mL of ultrapure water to obtain solution A; sacrificial agents (5.8830 g NaS·9H2O, 2.2050 g Na2SO3) were dissolved in a beaker containing 30 mL of ultrapure water and sonicated for 15 minutes to obtain solution B. Solutions A and B were poured into sealed glass reactors with high-transparency quartz lids, and the glass reactors were connected to the photocatalytic water splitting hydrogen production test equipment. A xenon lamp (HXF300, 300W) with a filter (λ≥400 nm) was used as the light source to drive the photocatalytic water splitting experiment. The reaction system was kept under stirring and controlled at 15°C using a cooling circulating water system. At the same time, the air dissolved in the reaction device and aqueous solution was purged using a vacuum pump. Hydrogen gas was quantitatively collected from the hydrogen evolution device every 30 minutes and detected by gas chromatography.

[0075] like Figure 7 As shown, 7%-α-NiS / Cd 0.2 Zn 0.8 S has the fastest hydrogen production rate, at 12857.1 μmol·g. -1 ·h -1 , with Cd 0.2 Zn 0.8 Compared to S, the hydrogen production performance of the composite material loaded with α-NiS is improved, but excessively high loading amounts, such as 15% α-NiS / Cd, can hinder this process. 0.2 Zn 0.8 The hydrogen production performance of S actually decreased, which may be due to the masking effect of α-NiS. The loading of α-NiS reduces Cd. 0.2 Zn 0.8 S light absorption.

[0076] In addition, 7%-α-NiS / Cd was tested every 3 hours. 0.2 Zn 0.8 The photocatalytic cycle stability of S composite materials, such as Figure 8 As shown, after five cycles of testing, the composite material 7%-α-NiS / Cd 0.2 Zn 0.8 The photocatalytic hydrogen production activity of 7%-α-NiS / Cd did not decrease significantly, indicating that the photocatalytic hydrogen production activity of 7%-α-NiS / Cd was not significantly reduced. 0.2 Zn 0.8 S exhibits good photocatalytic stability and resistance to photocorrosion.

[0077] Application Example 3

[0078] Photocatalytic reforming of lignin for hydrogen production was tested using the following method: 30 mg of sample (7% α-NiS / Cd) was prepared. 0.2 Zn 0.8S) Disperse the hydrogen into 70 mL glass reactors containing 0.1, 0.2, and 0.3 g / L alkaline lignin solutions, and perform the same procedures as in Application Example 1. Collect hydrogen gas every hour and detect it by gas chromatography. Quantify the hydrogen production using a standard curve.

[0079] like Figure 9 It can be seen that when the lignin concentration is 1.0, 0.2, and 0.3 g / L, the 7% α-NiS / Cd 0.2 Zn 0.8 The hydrogen production rate of S was 269.7 μmol·g. -1 ·h -1 317.5 μmol·g -1 ·h -1 and 338.6 μmol·g -1 ·h -1 No hydrogen was detected in the control group without lignin, indicating that the presence of lignin is a necessary condition for hydrogen production through photocatalytic reforming.

[0080] Photoelectrochemical performance testing

[0081] A three-electrode system was constructed using the electrode containing the sample as the working electrode, the Ag / AgCl standard electrode as the reference electrode, the Pt electrode as the counter electrode, and 0.100M Na2SO4 solution as the electrolyte. The photoelectrochemical performance of the sample was tested using an electrochemical workstation (CHI-660E, Shanghai Chenhua). The performance of the 7%-α-NiS / Cd electrode was evaluated. 0.2 Zn 0.8 S-composite photocatalyst for photogenerated carrier separation and transfer efficiency detection.

[0082] like Figure 10 As shown, this is Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Comparison of transient photocurrents of S. 7%-α-NiS / Cd 0.2 Zn 0.8 S composites exhibit better performance than pure Cd. 0.2 Zn 0.8 The higher photocurrent in S indicates that the loaded α-NiS can accelerate the separation and transfer of electrons.

[0083] like Figure 11 As shown, this is Cd 0.2 Zn 0.8 S and 7%-α-NiS / Cd 0.2 Zn 0.8 Electrochemical impedance spectroscopy of S, 7%-α-NiS / Cd 0.2 Zn 0.8 The radius of curvature of S is smaller than that of pure Cd.0.2 Zn 0.8 S further demonstrates that the introduction of α-NiS reduces the charge transfer resistance.

[0084] In summary, this invention uses optimized Cd 0.2 Zn 0.8 α-NiS / Cd was prepared using S as a support via a grinding method. 0.2 Zn 0.8 S photocatalyst; the morphology, structure and optical properties of the prepared samples were analyzed by XRD, TEM, HRTEM, UV-Vis diffuse reflectance spectroscopy, fluorescence spectroscopy and nitrogen adsorption. When α-NiS and mesoporous Cd are supported... 1-x Zn x When the mass ratio of S is 7:100, the sample 7%-α-NiS / Cd 0.2 Zn 0.8 S exhibited the best visible light photocatalytic water splitting and hydrogen evolution performance, with a hydrogen production rate of 12857.1 μmol·g. -1 ·h -1 And the sample 7%-α-NiS / Cd 0.2 Zn 0.8 S is further applied to the photocatalytic reforming of lignin for hydrogen production. When the lignin concentration is 0.1–0.3 g / L, the 7% α-NiS / Cd ratio is [value missing]. 0.2 Zn 0.8 The hydrogen production rate of S was 269.7 μmol·g. -1 ·h -1 317.5 μmol·g -1 ·h -1 and 338.6 μmol·g -1 ·h -1 This composite photocatalyst is suitable for photocatalytic reforming of lignin to produce hydrogen.

[0085] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0086] The present invention provides a detailed description of a composite photocatalyst, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of the invention. These examples are merely illustrative and are intended to aid in understanding the method and core concepts of the invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A composite photocatalyst, characterized in that: The composite photocatalyst includes mesoporous Cd. 1-x Zn x S and α-NiS, where x=0.8, the α-NiS and mesoporous Cd 1-x Zn x The mass ratio of S to S is (1-10):100, and the mesoporous Cd 1-x Zn x The aperture of S is 2-10 nm; The preparation method of the composite photocatalyst includes the following steps: 1) Dissolve cadmium nitrate and zinc nitrate in diethylenetriamine aqueous solution, stir at room temperature for 30±5 min, add L-cysteine ​​and continue stirring for 30±5 min to obtain a mixed solution; 2) Transfer the mixed solution obtained in step 1) into a polytetrafluoroethylene reactor and react at 170-190℃ for 15-18 hours. After cooling, wash with water and anhydrous ethanol sequentially, and then vacuum dry at 55-65℃ to constant weight to obtain the metal precursor, i.e., mesoporous Cd. 1-x Zn x S; 3) Mix the metal precursor obtained in step 2) with α-NiS, add anhydrous ethanol dropwise, grind for 1-2 hours, and then dry to obtain α-NiS / Cd. 1-x Zn x S stands for composite photocatalyst; The volume ratio of water to diethylenetriamine in the aqueous solution is 1:2.5; The molar ratio of L-cysteine ​​to the total moles of cadmium nitrate and zinc nitrate is (1.2-1.5):

1.

2. The composite photocatalyst according to claim 1, characterized in that: The α-NiS and mesoporous Cd 1-x Zn x The mass ratio of S is 7:

100.

3. A method for preparing the composite photocatalyst as described in claim 1, characterized in that: The preparation method includes the following steps: 1) Dissolve cadmium nitrate and zinc nitrate in diethylenetriamine aqueous solution, stir at room temperature for 30±5 min, add L-cysteine ​​and continue stirring for 30±5 min to obtain a mixed solution; 2) Transfer the mixed solution obtained in step 1) into a polytetrafluoroethylene reactor and react at 170-190℃ for 15-18 hours. After cooling, wash with water and anhydrous ethanol sequentially, and then vacuum dry at 55-65℃ to constant weight to obtain the metal precursor, i.e., mesoporous Cd. 1-x Zn x S; 3) Mix the metal precursor obtained in step 2) with α-NiS, add anhydrous ethanol dropwise, grind for 1-2 hours, and then dry to obtain α-NiS / Cd. 1-x Zn x S stands for composite photocatalyst.

4. The preparation method according to claim 3, characterized in that: The total molar amount of cadmium nitrate and zinc nitrate mentioned in step 1) is in the volume ratio of 1 mmol to (12-15) mL of diethylenetriamine aqueous solution.

5. The preparation method according to claim 3, characterized in that: The ratio of the metal precursor to anhydrous ethanol used in step 3) is 95-100 mg / mL.

6. The application of the composite photocatalyst as described in claim 1 in the photocatalytic reforming of lignin for hydrogen production.

7. The application according to claim 6, characterized in that: Under illumination, the composite photocatalyst α-NiS / Cd 1-x Zn x S is dispersed in an alkaline lignin solution to produce hydrogen. The ratio of the composite photocatalyst to the alkaline lignin solution is 0.4-1.0 mg / mL, and the concentration of the alkaline lignin solution is 0.1-0.3 g / L.

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