A heterojunction catalyst, its preparation method and use

Abstract

The present invention relates to a heterojunction catalyst, a preparation method thereof and uses thereof. The heterojunction catalyst contains CuO and CuS; the CuO is in a porous spherical structure; the CuS is distributed on the surface of the porous spherical structure. The preparation method includes mixing a copper salt solution and an alkali solution, then adding a reducing agent to obtain a Cu₂O porous precursor, heating the Cu₂O porous precursor in air to obtain a CuO porous precursor, and mixing the CuO porous precursor and a sulfur source to obtain the heterojunction catalyst. The heterojunction catalyst provided by the present invention has a CuO / CuS heterostructure and a porous spherical structure, has a large specific surface area, and has excellent catalytic activity and reaction efficiency for catalytic ozone decomposition. The preparation method provided by the present invention is simple in operation, low in production cost, and easy to be popularized industrially.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and particularly to a heterojunction catalyst and its preparation method and uses. Background Art

[0002] Ozone is a pale blue gas with a special fishy smell. Its molecular structure is an isosceles triangle structure, with three oxygen atoms respectively occupying the three vertices of the isosceles triangle, the bond angle is 116.49°, the O - O bond is 0.128 nm. Ozone will slowly decompose at room temperature and has stronger oxidizing property than oxygen. Ozone can absorb ultraviolet rays harmful to human health and prevent them from directly irradiating the earth's surface, so that organisms on the earth's surface are not harmed by ultraviolet rays. However, at the near - earth surface, the existence of high - concentration ozone will reduce the productivity of forests and grasslands and pose a great threat to biodiversity.

[0003] At present, the main methods for decomposing ozone include activated carbon method, thermal decomposition method, plasma decomposition method, electromagnetic wave radiation decomposition method, liquid medicine decomposition method, catalytic decomposition method, pre - ozonation method and atmospheric dilution and emission method. Among them, compared with other methods, the catalytic decomposition method can meet the requirements of high decomposition rate, stability, safety and economy, and is the main research method for ozone decomposition. The catalysts for ozone decomposition mainly include supported noble metal catalysts and supported transition metal oxide catalysts. Among them, the supported noble metal catalysts are mainly loaded with noble metals such as Ag, Au, Pt, etc. Although the supported noble metal catalysts have good catalytic activity, they are expensive. The supported transition metal oxide catalysts are mainly loaded with one or two transition metal oxides such as Mn, Fe, Cu, Co, etc., which are generally metastable metal oxides or variable - valence metal oxides. The metastable oxides are in long - term contact with strongly oxidizing ozone and exposed to air, and are easily oxidized to high - valence states, thus greatly reducing the catalytic activity of the catalyst. Therefore, the stability of transition metal oxides severely restricts the development of this kind of catalyst. In addition, for ozone systems containing acidic gases such as H2S and HCl, common ozone decomposition catalysts such as manganese oxide or iron oxide are prone to poisoning, resulting in poor catalytic effects.

[0004] CN108114711B discloses a transition metal oxide catalyst for catalytic removal of ozone and its preparation method. The disclosed catalyst uses transition metal oxide MO x as the active component, where x = 0.5 - 2.5, and the transition metal M is a combination of Mn and one or more selected from Cu, Co, V, Cr, Fe, Ru, Rh, Pd, Ag, Pt, Au, Ce, La. This catalyst contains more metal elements, the preparation method is complex and the cost is high, and the obtained catalyst is not suitable for ozone systems containing acidic gases.

[0005] CN112642424A discloses a noble metal catalyst for ozone oxidation and a preparation method thereof. The catalyst uses one or more of Ru, Rh, Au, Pt or Pd as noble metals and S as a carrier. The resulting catalyst has a relatively high production cost, and its industrial application is limited.

[0006] Therefore, it is of great significance to provide an ozone decomposition catalyst with low cost and good catalytic activity. Summary of the Invention

[0007] In view of the above problems, the purpose of the present invention is to provide a heterojunction catalyst, a preparation method and a use thereof. Compared with the prior art, the heterojunction catalyst provided by the present invention is composed of CuO and CuS to form a heterojunction structure. This heterojunction structure contains a large number of defects and vacancies, and has strong activity for the catalytic decomposition of ozone. The preparation method of the heterojunction catalyst provided by the present invention is simple in operation and can be promoted industrially.

[0008] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a heterojunction catalyst, and the heterojunction catalyst contains CuO and CuS; the CuO is in a porous spherical structure; the CuS is distributed on the surface of the porous spherical structure.

[0010] The heterojunction catalyst provided by the present invention is composed of CuO and CuS to form a porous spherical heterojunction structure. On the one hand, since CuS is a p-type semiconductor and CuO is an n-type semiconductor, there is a subgrain boundary region at the junction of the two crystals. The crystal structure in this region is relatively disordered and has abundant defects and vacancies. These defects and vacancies are the active centers of the catalytic reaction, which can attract the oxygen atoms of the reactants to approach the vacancies and then a catalytic reaction occurs, having good catalytic activity. On the other hand, the porous spherical structure of the heterojunction catalyst has a more excellent specific surface area compared with the flake structure, which can increase the probability of contact with the reactants and has a higher reaction efficiency. Moreover, the porous spherical structure can selectively adsorb small molecules by adjusting the pore size, preventing macromolecules from entering the interior, achieving the effect of selecting specific products. Compared with the CuO or CuS catalyst with a single structure, the heterojunction catalyst provided by the present invention not only has a large specific surface area, but also has abundant defects and vacancies, and has more advantages in catalytic effect.

[0011] Preferably, the molar ratio of CuO to CuS in the heterojunction catalyst is (0.2-4):1. For example, it can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1 or 4:1. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable. Preferably, it is (0.5-4):1.

[0012] The present invention preferably controls the molar ratio of CuO to CuS in the heterojunction catalyst within a specific range, which can save costs while constructing a good heterojunction structure.

[0013] Preferably, the particle size of the heterojunction catalyst is 100-300nm. For example, it can be 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm or 300nm. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0014] Preferably, the specific surface area of the heterojunction catalyst is 10-50m 2 / g. For example, it can be 10m 2 / g, 20m 2 / g, 30m 2 / g, 32m 2 / g, 34m 2 / g, 36m 2 / g, 38m 2 / g, 40m 2 / g, 42m 2 / g, 44m 2 / g, 46m 2 / g, 48m 2 / g or 50m 2 / g. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Preferably, the total pore volume of the heterojunction catalyst is 0.1-0.4cm 3 / g. For example, it can be 0.1cm 3 / g, 0.2cm 3 / g, 0.22cm 3 / g, 0.24cm 3 / g, 0.26cm 3 / g, 0.28cm 3 / g, 0.3cm 3 / g, 0.32cm3 / g, 0.34 cm 3 / g, 0.36 cm 3 / g, 0.38 cm 3 / g or 0.4 cm 3 / g, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] In a second aspect, the present invention provides a method for preparing a heterojunction catalyst as described in the first aspect of the present invention, characterized in that the preparation method comprises the following steps:

[0017] (1) Mix a copper salt solution and an alkali solution, and then add a reducing agent to react to obtain a Cu2O porous precursor;

[0018] (2) Heat the Cu2O porous precursor obtained in step (1) in air to obtain a CuO porous precursor;

[0019] (3) Mix the CuO porous precursor obtained in step (2) and a sulfur source to obtain the heterojunction catalyst.

[0020] The method for preparing the heterojunction catalyst provided by the present invention first prepares a porous spherical Cu2O porous precursor by reacting a copper salt under the conditions of an alkali solution and a reducing agent, then oxidizes the Cu2O porous precursor in air to obtain a CuO porous precursor, and then mixes the CuO porous precursor and a sulfur source. Due to the difference in solubility, CuO will be converted into more insoluble CuS to obtain a CuO / CuS heterostructure. The preparation method provided by the present invention is simple to operate and has low production costs, and the obtained heterojunction catalyst has excellent catalytic activity.

[0021] Preferably, the copper salt in the copper salt solution in step (1) includes any one or a combination of at least two of copper sulfate, copper chloride, copper acetate or copper nitrate. Typical but non-limiting combinations include the combination of copper sulfate and copper chloride, the combination of copper chloride and copper acetate, or the combination of copper chloride, copper acetate and copper nitrate.

[0022] Preferably, the alkali solution includes a sodium hydroxide solution and / or a potassium hydroxide solution.

[0023] Preferably, the pH of the alkali solution is 12 - 14, for example, it can be 12, 12.2, 12.4, 12.6, 12.8, 13, 13.2, 13.4, 13.6, 13.8 or 14, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable, and preferably it is 13.

[0024] Preferably, the molar ratio of hydroxide in the alkali solution to copper ions in the copper salt solution is (2 - 2.5):1. For example, it can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5:1. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] In the present invention, after the copper salt solution and the alkali solution are mixed and a blue flocculent precipitate appears, a reducing agent is added. The present invention preferably controls the molar ratio of hydroxide in the alkali solution to copper ions in the copper salt solution within a specific range, which can better synthesize Cu(OH)₂ and then better react with the reducing agent to obtain the Cu₂O porous precursor.

[0026] Preferably, the reducing agent includes ascorbic acid.

[0027] The present invention preferably uses ascorbic acid as the reducing agent, which can preferably obtain the reduction product Cu₂O porous precursor, and it is inexpensive and safe to use.

[0028] Preferably, the molar ratio of the reducing agent to copper ions in the copper salt solution is (0.6 - 1.5):1. For example, it can be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, or 1.5:1. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable, and preferably 1:1.

[0029] The present invention preferably controls the molar ratio of the reducing agent to copper ions in the copper salt solution within a specific range, which can make the Cu₂O porous precursor have a larger specific surface area and better catalytic effect.

[0030] Preferably, the temperature of the mixing in step (1) is 25 - 30°C. For example, it can be 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the time of the mixing in step (1) is 0.5 - 1.5 h. For example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, or 1.5 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable, and preferably 1 h.

[0032] Preferably, the reaction time in step (1) is 3 - 5 min. For example, it can be 3 min, 3.5 min, 4 min, 4.5 min, or 5 min. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] In the present invention, after the reaction described in step (2) is completed, through solid-liquid separation, and then the solid is washed with deionized water and ethanol and dried, the obtained Cu₂O porous precursor is obtained. The method of solid-liquid separation is not particularly limited. For example, it can be filtration or centrifugation.

[0034] Preferably, the heating temperature in step (2) is 300 - 400 °C. For example, it can be 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C or 400 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable. Preferably, it is 350 °C.

[0035] The present invention preferably controls the heating temperature within a specific range, which can more completely convert the Cu₂O porous precursor into the CuO porous precursor, ensure that the CuO porous precursor has a good morphology and a large specific surface area, and enable the catalyst to have high catalytic activity.

[0036] Preferably, the heating time in step (2) is 1 - 2 h. For example, it can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0037] Preferably, the molar ratio of Cu element in the CuO porous precursor in step (3) to S element in the sulfur source is (1.2 - 5):1. For example, it can be 1.2:1, 1.5:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1 or 4:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable. Preferably, it is (1.5 - 5):1.

[0038] The present invention preferably controls the molar ratio of Cu element in the CuO porous precursor to S element in the sulfur source within a specific range, which can better prepare the heterojunction structure and save production costs.

[0039] Preferably, the sulfur source includes any one or at least two combinations of sodium sulfide, potassium sulfide, ammonium sulfide or hydrogen sulfide. Among them, typical but non-limiting combinations include the combination of sodium sulfide and potassium sulfide, the combination of potassium sulfide and ammonium sulfide, or the combination of potassium sulfide, ammonium sulfide and hydrogen sulfide.

[0040] Preferably, the mixing temperature in step (3) is 25 - 30 °C. For example, it can be 25 °C, 26 °C, 27 °C, 28 °C, 29 °C or 30 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0041] Preferably, the mixing time in step (3) is 20 - 40 min, for example, it can be 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min or 40 min, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable, and preferably it is 30 min.

[0042] In the present invention, after the mixing in step (3) is completed, through solid-liquid separation, and then the solid is washed with deionized water and ethanol and dried, the obtained heterojunction catalyst. The method of solid-liquid separation has no special limitation, for example, it can be filtration or centrifugation.

[0043] As a preferred technical solution of the second aspect of the present invention, the preparation method includes the following steps:

[0044] (1) Mix a copper salt solution and an alkali solution with a pH of 12 - 14 at 25 - 30 °C. The molar amount of hydroxide ions in the alkali solution is in a ratio of (2 - 2.5):1 to the molar amount of copper ions in the copper salt solution. The mixing time is 0.5 - 1.5 h, and then a reducing agent is added for reaction for 3 - 5 min. The molar ratio of the reducing agent to the copper ions in the copper salt solution is (0.6 - 1.5):1 to obtain a Cu2O porous precursor. The copper salt in the copper salt solution includes any one or at least two combinations of copper sulfate, copper chloride, copper acetate or copper nitrate. The alkali solution includes sodium hydroxide solution and / or potassium hydroxide solution. The reducing agent includes ascorbic acid;

[0045] (2) Heat the Cu2O porous precursor obtained in step (1) in air at 300 - 400 °C for 1 - 2 h to obtain a CuO porous precursor;

[0046] (3) Mix the CuO porous precursor obtained in step (2) and a sulfur source at 25 - 30 °C. The mixing time is 20 - 40 min. The molar amount of Cu element in the CuO porous precursor is in a ratio of (1.2 - 5):1 to the S element in the sulfur source. The sulfur source includes any one or at least two combinations of sodium sulfide, potassium sulfide, ammonium sulfide or hydrogen sulfide to obtain the heterojunction catalyst.

[0047] In the third aspect, the present invention provides a use of the heterojunction catalyst as described in the first aspect of the present invention, and the heterojunction catalyst is used for catalyzing ozone decomposition.

[0048] The heterojunction catalyst provided by the present invention has abundant defects and vacancies, making the surrounding copper atoms carry more positive charges, which can attract reactants to the defects or vacancies for catalytic decomposition reactions. The heterojunction catalyst provided by the present invention has a porous spherical structure with a large specific surface area, which can increase the contact area with reactants and has significant advantages in the catalytic decomposition of ozone gas, with higher reaction efficiency.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The heterojunction catalyst provided by the present invention has a CuO / CuS heterostructure and a porous spherical structure, and has excellent catalytic activity for catalytic ozone decomposition. Under relatively optimal conditions, the catalytic conversion rate of ozone can reach more than 90%, and it has a large catalytic specific surface area, which can reach more than 23.338 m 2 / g, with higher reaction efficiency, and can selectively adsorb small molecules, preventing macromolecules from entering the interior, achieving the effect of selecting specific products.

[0051] (2) The heterojunction catalyst provided by the present invention still has excellent catalytic effects on ozone systems containing acidic gases such as H2S and HCl, and can avoid catalyst poisoning under acidic gases.

[0052] (3) The preparation method of the heterojunction catalyst provided by the present invention is simple in operation, low in production cost, and easy to promote industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is the SEM photograph of the heterojunction catalyst described in Example 1 of the present invention;

[0054] Figure 2 is the TEM photograph of the heterojunction catalyst described in Example 1 of the present invention;

[0055] Figure 3 is the ultra-high resolution photograph of the heterojunction catalyst described in Example 1 of the present invention;

[0056] Figure 4 is the SEM photograph of the catalyst described in Comparative Example 2 of the present invention;

[0057] Figure 5 is the XRD pattern of the catalysts described in Examples 1-2 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0058] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0059] Example 1

[0060] This embodiment provides a method for preparing a heterojunction catalyst, and the preparation method includes the following steps:

[0061] (1) Take 2.5 g of copper sulfate pentahydrate and dissolve it in 150 mL of deionized water. Then, at 25 °C, mix the copper sulfate solution and the NaOH solution with a pH of 13. The molar amount of hydroxide ions in the NaOH solution is in a ratio of 2:1 to the molar amount of copper ions in the copper sulfate solution. The mixing time is 1 h. After blue flocculent precipitate appears, add ascorbic acid and react for 4 min. The molar ratio of ascorbic acid to copper ions in the copper sulfate solution is 1:1. Then, centrifuge, and wash and dry the obtained solid successively with deionized water and ethanol to obtain a Cu2O porous precursor;

[0062] (2) Heat the Cu2O porous precursor obtained in step (1) in air at 350 °C for 2 h to obtain a CuO porous precursor;

[0063] (3) Take 0.8 g of the CuO porous precursor obtained in step (2) and dissolve it in 200 mL of deionized water. Then, at 25 °C, mix the CuO porous precursor and a 0.5 mol / L sodium sulfide solution. The mixing time is 30 min. The molar amount of Cu element in the CuO porous precursor is in a ratio of 2:1 to the molar amount of S element in the sodium sulfide solution. Then, centrifuge, and wash and dry the obtained solid successively with deionized water and ethanol to obtain the heterojunction catalyst.

[0064] This embodiment also provides a heterojunction catalyst obtained by the above preparation method. The heterojunction catalyst contains CuO and CuS; the CuO is in a porous spherical structure; the CuS is distributed on the surface of the porous spherical structure; the molar ratio of CuO to CuS in the heterojunction catalyst is 1:1; through BET characterization, the particle size of the heterojunction catalyst is 100 - 200 nm; the specific surface area is 38.728 m 2 / g; the total pore volume is 0.271213 cm 3 / g.

[0065] The obtained heterojunction catalyst of this embodiment is tested by SEM and TEM. The SEM photograph of the obtained heterojunction catalyst is as Figure 1 shown. It can be seen from Figure 1 that sheet-like or thorn-like CuS grows on the surface of the heterojunction catalyst. The TEM photograph of the obtained heterojunction catalyst is as Figure 2 shown. It can be seen from Figure 2 that the heterojunction catalyst is formed by the accumulation of tiny grains to form a porous spherical structure, having micropores and mesopores. The ultra-high resolution photograph of the heterojunction interface of the obtained heterojunction catalyst is as Figure 3 shown. It can be seen fromFigure 3 It can be seen that acicular or flaky CuS crystals are in-situ grown between CuO crystals, and a region without obvious lattice fringes, namely the CuO-CuS sub-boundary region, is formed at the junction of the two.

[0066] Example 2

[0067] This example provides a preparation method of a heterojunction catalyst, and the preparation method includes the following steps:

[0068] (1) Dissolve 1.345 g of copper chloride in 150 mL of deionized water, then mix the copper chloride solution and the NaOH solution with a pH of 14 at 26 °C. The molar ratio of hydroxide ions in the NaOH solution to copper ions in the copper chloride solution is 2:1, and the mixing time is 1.5 h. After blue flocculent precipitate appears, add ascorbic acid and react for 3 min. The molar ratio of ascorbic acid to copper ions in the copper chloride solution is 1.1:1, then centrifuge. The obtained solid is washed with deionized water and ethanol in sequence and dried to obtain a Cu2O porous precursor;

[0069] (2) Heat the Cu2O porous precursor obtained in step (1) in air at 300 °C for 1.5 h to obtain a CuO porous precursor;

[0070] (3) Take 0.8 g of the CuO porous precursor obtained in step (2) and dissolve it in 200 mL of deionized water, then mix the CuO porous precursor and a 0.2 mol / L sodium sulfide solution at 26 °C. The mixing time is 20 min. The molar ratio of Cu element in the CuO porous precursor to S element in the sodium sulfide solution is 5:1, then centrifuge. The obtained solid is washed with deionized water and ethanol in sequence and dried to obtain the heterojunction catalyst.

[0071] This example also provides a heterojunction catalyst obtained by the above preparation method. The heterojunction catalyst contains CuO and CuS; the CuO is in a porous spherical structure; the CuS is distributed on the surface of the porous spherical structure; the molar ratio of CuO to CuS in the heterojunction catalyst is 4:1; through BET characterization, the particle size of the heterojunction catalyst is 200 - 300 nm; the specific surface area is 23.883 m 2 / g; the total pore volume is 0.160981 cm 3 / g.

[0072] Example 3

[0073] This example provides a preparation method of a heterojunction catalyst, and the preparation method includes the following steps:

[0074] (1) Dissolve 2.5 g of copper sulfate pentahydrate in 150 mL of deionized water. Then, mix the copper sulfate solution and the KOH solution with a pH of 12 at 28 °C. The molar ratio of hydroxide ions in the KOH solution to copper ions in the copper sulfate solution is 2.5:1. The mixing time is 0.5 h. After blue flocculent precipitate appears, add ascorbic acid and react for 5 min. The molar ratio of ascorbic acid to copper ions in the copper sulfate solution is 0.6:1. Then, centrifuge, and wash and dry the obtained solid with deionized water and ethanol successively to obtain the Cu₂O porous precursor;

[0075] (2) Heat the Cu₂O porous precursor obtained in step (1) in air at 400 °C for 1 h to obtain the CuO porous precursor;

[0076] (3) Take 0.8 g of the CuO porous precursor obtained in step (2) and dissolve it in 200 mL of deionized water. Then, mix the CuO porous precursor and 0.5 mol / L potassium sulfide solution at 27 °C. The mixing time is 40 min. The molar ratio of Cu element in the CuO porous precursor to S element in the potassium sulfide solution is 1.5:1. Then, centrifuge, and wash and dry the obtained solid with deionized water and ethanol successively to obtain the heterojunction catalyst.

[0077] This example also provides a heterojunction catalyst obtained by the above preparation method. The heterojunction catalyst contains CuO and CuS; the CuO is in a porous spherical structure; the CuS is distributed on the surface of the porous spherical structure; the molar ratio of CuO to CuS in the heterojunction catalyst is 0.5:1; through BET characterization, the particle size of the heterojunction catalyst is 100 - 200 nm; the specific surface area is 31.997 m 2 / g; the total pore volume is 0.182698 cm 3 / g.

[0078] Example 4

[0079] This example provides a preparation method of a heterojunction catalyst. The difference compared with Example 1 is only that the heating temperature in step (2) is 200 °C.

[0080] Example 5

[0081] This example provides a preparation method of a heterojunction catalyst. The difference compared with Example 1 is only that the heating temperature in step (2) is 500 °C.

[0082] Example 6

[0083] This example provides a method for preparing a heterojunction catalyst. The difference compared with Example 1 is only that in step (3), the amount of the CuO porous precursor is kept unchanged, and the concentration of the sodium sulfide solution is adjusted so that the molar ratio of the Cu element in the CuO porous precursor to the S element in the sodium sulfide solution is 1.2:1. The molar ratio of CuO to CuS in the heterojunction catalyst obtained in this example is 0.2:1.

[0084] Example 7

[0085] This example provides a method for preparing a heterojunction catalyst. The difference compared with Example 1 is only that in step (3), the amount of the CuO porous precursor is kept unchanged, and the concentration of the sodium sulfide solution is adjusted so that the molar ratio of the Cu element in the CuO porous precursor to the S element in the sodium sulfide solution is 6:1. The molar ratio of CuO to CuS in the heterojunction catalyst obtained in this example is 5:1.

[0086] Comparative Example 1

[0087] This comparative example provides a method for preparing a catalyst. The difference compared with Example 1 is only that in step (3), the amount of the CuO porous precursor is kept unchanged, and the concentration of the sodium sulfide solution is adjusted so that the molar ratio of the Cu element in the CuO porous precursor to the S element in the sodium sulfide solution is 1:1. The catalyst obtained in this comparative example is a CuS catalyst.

[0088] Comparative Example 2

[0089] This comparative example provides a method for preparing a catalyst. The difference compared with Example 1 is only that step (3) is removed. The catalyst obtained in this comparative example is a CuO catalyst. The SEM photograph of the catalyst obtained in this comparative example is as Figure 4 shown. It can be seen from Figure 4 that the CuO is a spherical structure composed of grain accumulation and contains fine pores.

[0090] Comparative Example 3

[0091] This comparative example provides a method for preparing a catalyst. The difference compared with Example 1 is only that steps (2) and (3) are removed. The catalyst obtained in this comparative example is a Cu2O catalyst.

[0092] The catalysts in Examples 1 - 2 and Comparative Example 2 were subjected to XRD tests, and the results are as Figure 5 shown. It can be seen from Figure 5 that the catalysts in Examples 1 - 2 all showed the characteristic peaks of Cu2O and CuS, while the catalyst in Comparative Example 2 only showed the characteristic peak of CuO. Thus, it can be seen that the preparation method provided by the present invention can obtain a Cu2O / CuS heterojunction structure.

[0093] The BET test was carried out on the catalysts described in Examples 1-7 and Comparative Examples 1-3, and the specific surface areas obtained are shown in Table 1.

[0094] The catalytic ozone decomposition test was carried out on the catalysts described in Examples 1-7 and Comparative Examples 1-3. The test conditions were as follows: pure oxygen was introduced into the ozone generation reactor to generate ozone, and then the generated ozone was mixed with air. The concentration of ozone was adjusted to 50 ppm by adjusting the power of the generator to obtain a simulated gas. The mass space velocity of the simulated gas relative to the catalyst was 960000 cm 3 ·g -1 ·h -1 ⁻¹. The decomposition test of the simulated gas was carried out with 50 mg of the catalyst, and the concentration of ozone in the reaction system was detected in real time using an ozone monitor. The conversion rate of ozone at 60 min of reaction time was measured, and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] It can be seen from Table 1 as follows:

[0099] (1) It can be seen from the data of Examples 1-6 that the heterojunction catalyst provided by the present invention has a large specific surface area and high catalytic activity. Under optimal conditions, the catalytic specific surface area can reach more than 23.338 m 2 ² / g, and the catalytic conversion rate of ozone can reach more than 90%.

[0100] (2) By comprehensively comparing the data of Example 1 and Examples 4-5, it can be seen that the heating temperature in Example 1 was 350 °C. Compared with the heating temperatures in Examples 4-5, which were 200 °C and 500 °C respectively, the specific surface area in Example 1 was 38.728 m 2 ² / g, and the conversion rate was 96.0%. In the heterojunction catalyst of Example 4, most of the Cu₂O was not completely oxidized. Although both Cu₂O and CuO can form heterojunctions with CuS, Cu₂O is relatively unstable and is oxidized and inactivated during the catalytic decomposition of ozone. In the heterojunction catalyst of Example 5, ultrafine particle sintering and micropore blockage occurred, resulting in a decrease in the specific surface area. Therefore, the conversion rate and specific surface area in Examples 4 and 5 were less than those in Example 1. This shows that the present invention preferably controls the heating temperature within a specific range to obtain a heterojunction catalyst with a large specific surface area and high catalytic activity.

[0101] (3) By comprehensively comparing the data of Example 1 and Examples 6-7, it can be seen that the molar ratio of CuO to CuS in Example 1 is 1:1. Compared with 0.2:1 and 5:1 in Examples 6 and 7 respectively, the specific surface area and conversion rate of Example 7 are lower than those of Example 1. Although the conversion rate of Example 6 is higher than that of Example 1, Example 6 requires more sulfur source and has a relatively high production cost. This indicates that the present invention preferably controls the molar ratio of CuO to CuS in the heterojunction catalyst within a specific range, which can enable the catalyst to have a large specific surface area and high catalytic activity while controlling the production cost.

[0102] (4) By comprehensively comparing the data of Example 1 and Comparative Examples 1-3, it can be seen that the catalyst in Comparative Example 1 is a CuS catalyst, the catalyst in Comparative Example 2 is a CuO catalyst, and the catalyst in Comparative Example 3 is a Cu2O catalyst. The specific surface area and catalytic conversion rate of the heterojunction catalyst in Example 1 are higher than those in Comparative Examples 1-3. This indicates that the fully sulfided CuS catalyst loses its porous structure and its catalytic performance deteriorates. The pure CuO catalyst does not have the function of catalyzing ozone decomposition. Although the Cu2O catalyst has a certain catalytic effect, its performance is unstable and it is prone to deactivation. The heterojunction catalyst provided by the present invention has a large specific surface area, good catalytic effect, and high stability.

[0103] In summary, the heterojunction catalyst provided by the present invention has a large specific surface area and good catalytic effect, and can be used for catalyzing ozone decomposition.

[0104] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A preparation method of a heterojunction catalyst, characterized in that, The preparation method comprises the following steps: (1) Mix a copper salt solution and an alkali solution, and then add a reducing agent for reaction to obtain a Cu2O porous precursor; (2) Heat the Cu2O porous precursor obtained in step (1) in air to obtain a CuO porous precursor; (3) Mix the CuO porous precursor obtained in step (2) and a sulfur source to obtain the heterojunction catalyst; The heterojunction catalyst contains CuO and CuS; The CuO is in a porous spherical structure; The CuS is distributed on the surface of the porous spherical structure.

2. The preparation method according to claim 1, characterized in that, The molar ratio of CuO to CuS in the heterojunction catalyst is (0.2 - 4):

1.

3. The preparation method according to claim 1, characterized in that, The molar ratio of CuO to CuS in the heterojunction catalyst is (0.5 - 4):

1.

4. The preparation method according to claim 1, characterized in that, The particle size of the heterojunction catalyst is 100 - 300 nm.

5. The preparation method according to claim 1, wherein The specific surface area of the heterojunction catalyst is 10-50 m 2 / g.

6. The preparation method according to claim 1, wherein The total pore volume of the heterojunction catalyst is 0.1-0.4 cm 3 / g.

7. The preparation method according to claim 1, characterized in that The copper salt in the copper salt solution in step (1) includes any one or a combination of at least two of copper sulfate, copper chloride, copper acetate, or copper nitrate.

8. The preparation method according to claim 1, wherein The alkali solution includes a sodium hydroxide solution and / or a potassium hydroxide solution.

9. The preparation method according to claim 1, characterized in that, The pH of the alkali solution is 12 - 14.

10. The preparation method according to claim 1, characterized in that, The molar ratio of hydroxide ions in the alkali solution to copper ions in the copper salt solution is (2 - 2.5):

1.

11. The preparation method according to claim 1, characterized in that, The reducing agent includes ascorbic acid.

12. The preparation method according to claim 1, characterized in that, The molar ratio of the reducing agent to copper ions in the copper salt solution is (0.6 - 1.5):

1.

13. According to the preparation method described in claim 1, wherein, The temperature of the mixing in step (1) is 25 - 30 °C.

14. The preparation method according to claim 1, characterized in that, The time of the mixing in step (1) is 0.5 - 1.5 h.

15. The preparation method according to claim 1, wherein, The time of the reaction in step (1) is 3 - 5 min.

16. The preparation method according to claim 1, characterized in that, The temperature of the heating in step (2) is 300 - 400 °C.

17. The preparation method according to claim 1, characterized in that, The time of the heating in step (2) is 1 - 2 h.

18. The preparation method according to claim 1, characterized in that, The molar ratio of the Cu element in the CuO porous precursor to the S element in the sulfur source in step (3) is (1.2 - 5):

1.

19. The preparation method according to claim 1, characterized in that, The molar ratio of the Cu element in the CuO porous precursor to the S element in the sulfur source in step (3) is (1.5 - 5):

1.

20. The preparation method according to claim 1, characterized in that, The sulfur source includes any one or a combination of at least two of sodium sulfide, potassium sulfide, ammonium sulfide, or hydrogen sulfide.

21. The preparation method according to claim 1, characterized in that, The temperature of the mixing in step (3) is 25 - 30 °C.

22. The preparation method according to claim 1, wherein, The time of the mixing in step (3) is 20 - 40 min.

23. The preparation method according to claim 1, characterized in that, The preparation method comprises the following steps: (1) Mix a copper salt solution and an alkali solution with a pH of 12 - 14 at 25 - 30 °C, the molar ratio of hydroxide ions in the alkali solution to copper ions in the copper salt solution is (2 - 2.5):1, the time of the mixing is 0.5 - 1.5 h, then add a reducing agent for reaction for 3 - 5 min, the molar ratio of the reducing agent to copper ions in the copper salt solution is (0.6 - 1.5):1, to obtain a Cu2O porous precursor, the copper salt in the copper salt solution includes any one or a combination of at least two of copper sulfate, copper chloride, copper acetate, or copper nitrate, the alkali solution includes a sodium hydroxide solution and / or a potassium hydroxide solution, and the reducing agent includes ascorbic acid; (2) Heat the Cu2O porous precursor obtained in step (1) in air at 300 - 400 °C for 1 - 2 h to obtain a CuO porous precursor; (3) Mix the CuO porous precursor obtained in step (2) and the sulfur source at 25 - 30 °C. The mixing time is 20 - 40 min, and the molar ratio of Cu element in the CuO porous precursor to S element in the sulfur source is (1.2 - 5):

1. The sulfur source includes any one or a combination of at least two of sodium sulfide, potassium sulfide, ammonium sulfide, or hydrogen sulfide to obtain the heterojunction catalyst.

24. Use of a heterojunction catalyst prepared by the preparation method according to any one of claims 1 - 23, wherein the heterojunction catalyst is used for catalyzing ozone decomposition.

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