Iron cobalt / carbon nitride sulfide heterojunction material, preparation method thereof and application thereof in photocatalytic hydrogen production

Abstract

The present application relates to a kind of iron cobaltate / thiocarbamide nitride heterojunction material and its preparation method and application in photocatalytic hydrogen production, the iron cobaltate / thiocarbamide nitride heterojunction material is obtained by the compounding of iron cobaltate and thiocarbamide nitride, with the flocculent morphology of folded sheet laminated into.The iron cobaltate / thiocarbamide nitride heterojunction material provided by the present application has strong light absorption capacity, high photocatalytic hydrogen production activity, and excellent cycle stability, and has good photocatalytic hydrogen production application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts containing nitrogen, and particularly relates to a cobalt iron oxide / carbon nitride sulfide heterojunction material, a preparation method thereof and application thereof in photocatalytic hydrogen production. BACKGROUND

[0002] In recent years, overexploitation of fossil energy has led to energy shortage, global climate warming, environmental deterioration and a series of problems. Global energy and environmental problems are imminent, hydrogen energy as a kind of green energy has the advantages of high energy density, cleanliness and sustainability, and the use of hydrogen energy to replace non-renewable fossil fuels can effectively solve the problems of environmental pollution and energy shortage, so the hydrogen production technology has attracted people's attention.

[0003] The existing hydrogen production methods include thermochemical method, electrochemical method, plasma method, biological method and photocatalytic method. Photocatalytic method uses the energy of light to convert water into hydrogen and oxygen under the action of photocatalyst, and the reaction is mild and has no negative impact on the environment. Photocatalytic method needs the participation of photocatalyst, and the current related research mainly focuses on oxide semiconductor photocatalytic materials. Oxide semiconductor photocatalytic materials have a wide application in the field of photocatalysis, but also have some limitations. The energy band structure of many oxide semiconductor materials determines that they can only absorb ultraviolet light or part of the wavelength range of visible light, which limits their application in visible light photocatalysis. In addition, oxide semiconductor materials usually have strong oxidizing ability, and in some photocatalytic reactions, unwanted side reactions may occur.

[0004] g-C3N4 has the advantages of stable physical and chemical properties, diverse structure, simple preparation and abundant and cheap raw materials, so it has application prospects in the field of photocatalytic decomposition of water to produce hydrogen. However, g-C3N4 has the disadvantages of low specific surface area, wide band gap (about 2.72eV), easy recombination of photo-generated electrons and holes and low conductivity, which limits its catalytic activity, so it needs to be modified. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a cobalt iron oxide / carbon nitride sulfide heterojunction material, a preparation method thereof and application thereof in photocatalytic hydrogen production, which solves the above-mentioned problems in the prior art. The cobalt iron oxide / carbon nitride sulfide heterojunction material is sensitive to visible light, has high photocatalytic hydrogen production efficiency, and the preparation method is simple, easy to operate and has good repeatability.

[0006] To solve the above technical problems, the technical scheme provided by the present application is:

[0007] A cobalt iron oxide / carbon nitride sulfide heterojunction material is provided, which is obtained by compounding cobalt iron oxide and carbon nitride sulfide, and has a flocculent morphology formed by stacking wrinkle-shaped thin sheets.

[0008] According to the above scheme, the specific surface area of the heterojunction material is 100-130 m 2 / g.

[0009] The application further provides a preparation method of the above-mentioned iron cobaltate / carbon thiocyanide heterojunction material, and the specific steps are as follows:

[0010] 1) calcining thiocyanic acid to obtain sulfur-containing carbon thiocyanide;

[0011] 2) dissolving iron nitrate, cobalt nitrate and urea in water, then adding ammonium fluoride and fully stirring and mixing, and obtaining an iron cobaltate precursor through hydrothermal reaction, and then placing the iron cobaltate precursor in an alumina crucible and transferring to a muffle furnace for calcination and grinding to obtain iron cobaltate;

[0012] 3) mixing the sulfur-containing carbon thiocyanide obtained in step 1) with the iron cobaltate obtained in step 2), fully grinding until the color is uniform, and then ultrasonic dispersing in ethanol, drying and annealing to obtain the iron cobaltate / carbon thiocyanide heterojunction material.

[0013] According to the above scheme, the purity of the thiocyanic acid in step 1) is ≥95wt%.

[0014] According to the above scheme, the calcination process condition in step 1) is as follows: under an inert atmosphere, the temperature is raised to 500-600℃ at a rate of 5-20℃ / min, and the temperature is kept for 1-4h.

[0015] According to the above scheme, the molar ratio of the iron nitrate, cobalt nitrate, urea and ammonium fluoride in step 2) is iron nitrate: cobalt nitrate: urea: ammonium fluoride = 1: 1-3: 10-20: 5-10, and the concentration of urea in water is 0.1-0.5mol / L. The urea can decompose to produce ammonia, adjust the pH value of the solution, promote the generation of crystals, and the ammonium fluoride can also adjust the pH value and adjust the morphology of the product, and promote the formation of spinel structure substances.

[0016] According to the above scheme, the temperature of the hydrothermal reaction in step 2) is 100-150℃, and the time of the hydrothermal reaction is 10-15h.

[0017] According to the above scheme, the calcination process condition in step 2) is as follows: under an air atmosphere, the temperature is raised to 300-500℃ at a rate of 1-5℃ / min, and the temperature is kept for 1-3h.

[0018] According to the above scheme, the mass ratio of the iron cobaltate to the sulfur-containing carbon thiocyanide in step 3) is 0.025-0.1: 1.

[0019] According to the above scheme, the mass-volume ratio of the sulfur-containing carbon thiocyanide to ethanol in step 3) is 0.01-0.1g / mL.

[0020] According to the above scheme, the process conditions of the annealing treatment in step 3) are as follows: under an inert atmosphere, the temperature is raised to 500-600 DEG C at a temperature raising rate of 5-10 DEG C / min, and the temperature is kept for 1-3 h.

[0021] The application also includes the application of the above-mentioned iron cobaltate / thiocarbonsulfide heterojunction material as a photocatalyst in the photocatalytic production of hydrogen, and the specific use method is as follows: under visible light irradiation, the iron cobaltate / thiocarbonsulfide heterojunction material is placed in water, and the water is reduced to hydrogen in the presence of a sacrificial agent (such as triethanolamine).

[0022] In the application, the iron cobaltate and the sulfur-containing carbonsulfide are fully ground and then added into ethanol, and then the iron cobaltate / thiocarbonsulfide heterojunction material is obtained through ultrasonic dispersion, drying and annealing treatment. During the annealing treatment in the tube furnace, the inert gas has a certain stripping effect on the sulfur-containing carbonsulfide, so that the material is thinned and dispersed, which facilitates the intercalation of the iron cobaltate to form a heterojunction. The obtained heterojunction material has a reduced recombination rate of photo-generated electron-hole pairs and enhanced photocatalytic effect. Test results show that the iron cobaltate / thiocarbonsulfide heterojunction material has excellent photocatalytic hydrogen production performance.

[0023] The application has the following beneficial effects: 1. The iron cobaltate / thiocarbonsulfide heterojunction material provided by the application has strong light absorption capacity, high photocatalytic hydrogen production activity and excellent cycle stability, and has good application prospects in photocatalytic hydrogen production. 2. The preparation method of the application is safe, low in cost and suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The visible light photocatalytic hydrogen production effect comparison chart of the SCN, SCN-D samples prepared for Comparative Example 1 and the samples prepared in Examples 1-4 is shown in FIG. 1.

[0025] Figure 2 The TEM chart of the material prepared in Example 2 is shown in FIG. 2.

[0026] Figure 3 The XRD charts of the SCN-D sample prepared in Comparative Example 1, the iron cobaltate prepared in Example 1 and the samples prepared in Examples 1-4 are shown in FIG. 3.

[0027] Figure 4 The photocurrent test charts of the SCN-D sample prepared in Comparative Example 1 and the samples prepared in Examples 1-4 are shown in FIG. 4.

[0028] Figure 5 The continuous 24h photocatalytic hydrogen production cycle stability test chart of the material prepared in Example 2 is shown in FIG. 5.

[0029] Figure 6 The nitrogen isothermal adsorption and desorption curve charts of the materials prepared in Comparative Example 1 and Example 2 are shown in FIG. 6.

[0030] Figure 7 The pore size distribution of the material prepared in Comparative Example 1 and Example 2. DETAILED DESCRIPTION

[0031] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings.

[0032] Comparative Example 1

[0033] A thiocarbodiimide material, the specific preparation method is as follows:

[0034] 1) 2 g of thiocyanic acid (purity 95 wt%) was laid flat in a porcelain boat and placed in a constant temperature zone of a tube furnace for calcination, the calcination process conditions were as follows: under inert atmosphere, the temperature was raised to 550°C at a rate of 10°C / min, and the temperature was kept for 2 h, and then the sample was naturally cooled to room temperature and ground into powder to obtain a sulfur-containing carbon nitride (denoted as SCN);

[0035] 2) 0.2 g of SCN was weighed and placed in a tube furnace for annealing treatment, the annealing treatment process conditions were as follows: under inert atmosphere, the temperature was raised to 550°C at a rate of 10°C / min, and the temperature was kept for 1 h, and then the sample was naturally cooled to room temperature and ground into powder to obtain a blank control sample of thiocarbodiimide (denoted as SCN-D).

[0036] Example 1

[0037] An iron cobalt oxide / thiocarbodiimide heterojunction material, the specific preparation method is as follows:

[0038] 1) SCN was prepared by the same method as in Comparative Example 1 for standby;

[0039] 2) 1 mmol of iron nitrate, 2 mmol of cobalt nitrate and 15 mmol of urea were dissolved in 60 mL of water, 6 mmol of ammonium fluoride was added, and the mixture was stirred thoroughly and then transferred to a stainless steel reaction kettle, which was placed in a blast drying oven at a temperature of 120°C for hydrothermal reaction, the reaction time was 12 h, and then the sample was naturally cooled and washed and dried to obtain an iron cobalt oxide precursor, and then the iron cobalt oxide precursor was placed in an alumina crucible and transferred to a muffle furnace, which was heated to 400°C at a rate of 2°C / min under air atmosphere, and the temperature was kept for 2 h, and then the sample was naturally cooled to room temperature and ground into powder to obtain iron cobalt oxide.

[0040] 3) 0.005 g of the iron cobaltate obtained in step 2) was mixed with 0.2 g of the SCN obtained in step 1), and after being ground for 30 min, it was transferred into a beaker containing 10 mL of ethanol and ultrasonically dispersed for 10 min, and then it was dried in a blast drying oven at 60 °C for 8 h, and finally it was placed in a porcelain boat and annealed in a tube furnace, with the annealing process conditions being: under an inert atmosphere, the temperature was raised to 550 °C at a rate of 10 °C / min, and the temperature was maintained for 1 h, to obtain an iron cobaltate / carbon thiocyanide heterojunction material, and the obtained product was recorded as SCN / 2.5%-FeCo2O4.

[0041] Example 2

[0042] An iron cobaltate / carbon thiocyanide heterojunction material was prepared by a method similar to that of Example 1, except that the amount of iron cobaltate in step 3) was 0.01 g, and the obtained product was recorded as SCN / 5%-FeCo2O4.

[0043] Example 3

[0044] An iron cobaltate / carbon thiocyanide heterojunction material was prepared by a method similar to that of Example 1, except that the amount of iron cobaltate in step 3) was 0.015 g, and the obtained product was recorded as SCN / 7.5%-FeCo2O4.

[0045] Example 4

[0046] An iron cobaltate / carbon thiocyanide heterojunction material was prepared by a method similar to that of Example 1, except that the amount of iron cobaltate in step 3) was 0.02 g, and the obtained product was recorded as SCN / 10%-FeCo2O4.

[0047] Photocatalytic hydrogen production performance test: 20 mg of the SCN-D sample prepared in Comparative Example 1 and the samples prepared in Examples 1-4 were added to 5 portions of aqueous solution (each portion of aqueous solution was 100 mL, containing 10 wt% triethanolamine, and 0.33 mL of H2PtCl4 solution with a concentration of 4 mg / mL was added, and H2PtCl4 acted as a cocatalyst in the photocatalytic system), and after ultrasonic dispersion for 30 min, the light test was carried out in a light reactor (Labsolar-6A, with a 300 W xenon lamp inserted into a 420 nm cut-off filter as the light source), and the test was carried out for a total of 4 h. The visible light photocatalytic hydrogen production effect comparison chart of the SCN-D sample prepared in Comparative Example 1 and the samples prepared in Examples 1-4 is shown in FIG. 1, and it can be seen that the sample of Example 2 has the highest photocatalytic hydrogen production rate, and the hydrogen production rate is Figure 1 6303.5 μmol / g / h, which is nearly 2 times that of Comparative Example 1.

[0048]

[0049] Figure 2 ​The TEM image of the sample obtained in Example 2 shows that the iron cobalt oxide / carbon thionitride heterojunction material has a flocculent morphology formed by stacked wrinkled sheets, which is beneficial to photocatalytic hydrogen production.

[0050] Figure 3 XRD patterns of the SCN-D sample prepared in Comparative Example 1, the iron cobalt oxide prepared in Example 1, and the samples prepared in Examples 1-4. Figure 3 It can be seen that there are two main peaks in the XRD patterns of the comparative examples and the samples of Examples 1-4. The peak at approximately 13° corresponds to the (100) plane, representing the intralayer stacking of the material unit rings. The other peak at approximately 27.1° corresponds to the interlayer stacking of the conjugated aromatic units, which belongs to the (002) plane. Comparing the positions and intensities of the corresponding peaks, the peak intensity of the corresponding (002) plane of the sample of Comparative Example 1 is the highest, while the peak intensity of the material prepared in Example 2 is significantly reduced, indicating that the crystallinity of the formed iron cobalt oxide / carbon thionitride heterojunction material is reduced, the arrangement is disordered, and the material is thinner. The XRD pattern of iron cobalt oxide shows the characteristic peaks of the spinel structure, proving that iron cobalt oxide has a spinel structure.

[0051] Photocurrent testing: The SCN-D sample prepared in Comparative Example 1 and the samples prepared in Examples 1-4 were each prepared as 1.0 g / L aqueous dispersions. 6 μL of each aqueous dispersion was drop-coated onto the surface of a glassy carbon electrode (3 mm in diameter). Using a Chenhua electrochemical workstation, under illumination conditions >420 nm, xenon lamps and baffles were used to simulate both illuminated and unilluminated conditions. The glassy carbon electrode was placed in a 0.5 mol / L Na₂SO₄ solution, and the electrode was irradiated with a xenon lamp to simulate an illuminated environment. After irradiation for 50 s, the xenon lamp was covered with a baffle to simulate a dark environment for photocurrent testing for 50 s. This process was repeated for a total of 400 s. Photocurrent reflects the photocatalytic performance of the material. Higher photocurrent promotes the separation of photogenerated carriers, resulting in better photocatalytic effects. The photocurrent test results for the SCN-D sample prepared in Comparative Example 1 and the samples prepared in Examples 1-4 are shown in the figure below. Figure 4 As shown, the test results indicate that the sample in Comparative Example 1 has the lowest photocurrent, while the sample in Example 2 has the best photocurrent response.

[0052] Cobalt iron oxide / carbon nitride sulfide heterojunction material prepared in Example 2 was tested for its cyclic stability in photocatalytic hydrogen production: 20 mg of the sample prepared in Example 2 was added to 100 mL of an aqueous solution (containing 10 wt% triethanolamine and 0.33 mL of a H2PtCl4 solution with a concentration of 4 mg / mL), and after ultrasonic dispersion for 30 min, the sample was subjected to cyclic hydrogen production stability testing in a photoreactor (Labsolar-6A, light source: 300 W xenon lamp with a 420 nm cut-off filter) with 4 h of stopping every 4 h, for a total of 6 cycles of 24 h. The results of the continuous 24 h cyclic stability test of the cobalt iron oxide / carbon nitride sulfide heterojunction material prepared in Example 2 are shown in FIG. 2, indicating that the cobalt iron oxide / carbon nitride sulfide heterojunction material has good cyclic stability. Figure 5

[0053] Figure 6 The nitrogen adsorption / desorption isotherm graphs of the samples prepared in Comparative Example 1 and Example 2 are shown in FIG. 3, Figure 7 and the pore size distribution graphs of the samples prepared in Comparative Example 1 and Example 2 are shown in FIG. 4. Figure 6 As can be seen from the typical N2 adsorption / desorption isotherm, the material has a mesoporous structure, and the specific surface area of the sample prepared in Example 2 is larger, reaching 117.4480 m 2 / g. Figure 7 As can be seen from the pore size distribution graphs, the pore sizes of the two samples are about 2-10 nm, indicating that the pores in the material are mesopores. It can also be seen that the pore volume of Example 2 is significantly increased, and the increase in specific surface area and pore volume helps to expose the photocatalytically active surface sites, thereby improving the photocatalytic hydrogen production activity.​

Claims

1. The application of an iron cobalt oxide / carbon thionitride heterojunction material as a photocatalyst in photocatalytic hydrogen production, characterized in that, The specific method of use is as follows: Under visible light irradiation, place the iron cobalt oxide / carbon thionitride heterojunction material in water, and reduce the water to hydrogen in the presence of a sacrificial agent; The iron cobalt oxide / carbon thionitride heterojunction material is obtained by compositing iron cobalt oxide and carbon thionitride, and has a flocculent morphology formed by stacked wrinkled flakes. The specific steps of its preparation method are as follows: 1) Calcining trithiocyanate yields sulfur-containing carbon nitride; 2) Dissolve ferric nitrate, cobalt nitrate and urea in water, then add ammonium fluoride and stir thoroughly. After hydrothermal reaction, ferric cobalt oxide precursor is obtained. Then, the ferric cobalt oxide precursor is placed in an alumina crucible, transferred to a muffle furnace for calcination and grinding to obtain ferric cobalt oxide. 3) Mix the sulfur-containing carbon nitride obtained in step 1) with the iron cobalt oxide obtained in step 2), grind thoroughly until the color is uniform, then ultrasonically disperse in ethanol, dry and anneal to obtain iron cobalt oxide / carbon thionitride heterojunction material.

2. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, The specific surface area of ​​the heterojunction material is 100-130 m². 2 / g.

3. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, Step 1) The calcination process conditions are as follows: under an inert atmosphere, the temperature is increased to 500-600℃ at a rate of 5-20℃ / min, and held for 1-4 hours.

4. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, Step 2) The molar ratio of ferric nitrate, cobalt nitrate, urea and ammonium fluoride is ferric nitrate:cobalt nitrate:urea:ammonium fluoride = 1:1-3:10-20:5-10, wherein the concentration of urea in water is 0.1-0.5 mol / L.

5. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, Step 2) The hydrothermal reaction temperature is 100-150℃, and the hydrothermal reaction time is 10-15h.

6. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, Step 2) The calcination process conditions are as follows: under an air atmosphere, heat to 300-500℃ at a heating rate of 1-5℃ / min, and hold for 1-3 hours.

7. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, In step 3), the mass ratio of iron cobalt oxide to sulfur-containing carbon nitride is 0.025-0.1:1; and in step 3), the mass-volume ratio of sulfur-containing carbon nitride to ethanol is 0.01-0.1 g / mL.

8. The application of the iron cobalt oxide / carbon thionitride heterojunction material according to claim 1 as a photocatalyst for photocatalytic hydrogen production, characterized in that, Step 3) The annealing process conditions are as follows: under an inert atmosphere, heat to 500-600℃ at a heating rate of 5-10℃ / min, and hold for 1-3 hours.

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