Preparation method and application of sulfur-doped defective porous zinc oxide catalyst

Abstract

The present invention relates to a preparation method and application of a sulfur-doped defective porous zinc oxide catalyst, the preparation method comprising the following steps: S1, dissolving zinc nitrate in water-ethanol with a volume ratio of 1:1 and stirring evenly to obtain a zinc nitrate solution; S2, adding sodium hydroxide solution to the zinc nitrate solution, stirring for 30min and then filtering and washing to obtain porous zinc oxide; S3, treating the porous zinc oxide by a muffle furnace in an air atmosphere; S4, mixing the porous zinc oxide treated by step S3 with sulfur, then treating the mixture by a Plasma high-energy ball mill, and finally washing the mixture to obtain sulfur-doped defective porous zinc oxide. The invention has the beneficial effects of: the preparation process is simple to operate, low cost, the obtained sulfur-doped defective porous zinc oxide has a high current density and a high Faraday efficiency for carbon monoxide products, and can be used as a catalyst with excellent performance in carbon dioxide reduction technology.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide reduction, and in particular to a preparation method and application of a sulfur-doped defective porous zinc oxide catalyst. Background Art

[0002] Electrocatalytic carbon dioxide reduction has attracted extensive attention from researchers due to its high catalytic efficiency and easy operation. It can efficiently convert atmospheric carbon dioxide into high-value carbon-based compounds and fuels, such as carbon monoxide, methane, formic acid, methanol, ethanol, ethylene, propanol, etc., and can solve the greenhouse effect and energy shortage problems currently facing the world to a certain extent. However, electrocatalytic carbon dioxide reduction faces problems such as high thermodynamic energy, complex and diverse products, and high hydrogen production (competitive reaction) performance of catalysts. Electrocatalysts with low design and development costs, large-scale production, high catalytic activity and high selectivity can effectively solve these shortcomings.

[0003] Metal catalysts are highly active carbon dioxide electrocatalysts, among which zinc metal is abundant in the earth and cheap. When used as a carbon dioxide electrocatalyst, like gold and silver, the zinc metal surface has a low adsorption effect on the *CO intermediate product, so the product of carbon dioxide reduction under the electrocatalytic action of zinc metal is mainly carbon monoxide, which has high selectivity. However, the carbon dioxide catalytic activity of zinc metal is often limited by its low specific surface area and unstable surface structure (easily oxidized to zinc oxide). For this reason, zinc oxide, which is easier to prepare, has a diverse and controllable structure, and is stable in structure, can also be used as a carbon dioxide reduction catalyst. However, the catalytic activity and selectivity of zinc oxide for carbon monoxide products are not high, and there are certain HER side reactions. Therefore, it is necessary to regulate the structure and surface electronic environment of the oxide to improve the catalytic activity and selectivity. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a sulfur-doped defective porous zinc oxide catalyst. The preparation process is simple to operate and low in cost. The prepared sulfur-doped defective porous zinc oxide has a high current density and a high Faraday efficiency for carbon monoxide products, and can be used as a catalyst with excellent performance in carbon dioxide reduction technology.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a sulfur-doped defective porous zinc oxide catalyst comprises the following steps:

[0007] S1, dissolving zinc nitrate in water-ethanol in a volume ratio of 1:1 and stirring evenly to obtain a zinc nitrate solution;

[0008] S2, adding sodium hydroxide solution to the zinc nitrate solution, stirring for 30 minutes, filtering, washing, and drying to obtain porous zinc oxide;

[0009] S3, treating the porous zinc oxide in an air atmosphere through a muffle furnace to obtain porous zinc oxide with high cleanliness;

[0010] S4. Mix high-purity porous zinc oxide with sulfur and put the mixture into a zirconia sealed can. After the air in the can is evacuated, argon gas is filled into the can. Then, the zirconia sealed can containing the mixture is placed in a Plasma high-energy ball mill for processing. Finally, the mixture is cleaned to obtain sulfur-doped defective porous zinc oxide.

[0011] Furthermore, in step S1, the concentration of zinc nitrate is 0.8-1.2 mol / L.

[0012] Furthermore, in step S2, the concentration of the sodium hydroxide solution is 0.8-1.2 mol / L.

[0013] Furthermore, in step S2, the volume ratio of the zinc nitrate solution to the sodium hydroxide solution is 10:1.

[0014] Furthermore, in step S3, the porous zinc oxide is treated in a muffle furnace at a temperature of 300 to 400° C. for 0.5 to 1.5 h.

[0015] Furthermore, in step S4, the treatment is performed by a plasma high energy ball mill at a power of 180 to 220 W for 1.5 to 2.5 hours.

[0016] Furthermore, in the mixture of porous zinc oxide and sulfur, the mass of the porous zinc oxide is 1 g, and the mass of the sulfur is 200 mg.

[0017] Furthermore, in step S4, during cleaning, an appropriate amount of carbon disulfide is added to the mixture to dissolve excess sulfur.

[0018] Furthermore, in step S2, the mixed solution of the zinc nitrate solution and the sodium hydroxide solution is filtered 3 to 5 times, and washed with deionized water 3 to 5 times.

[0019] Based on the above preparation method, the present invention also provides an application of a sulfur-doped defective porous zinc oxide catalyst prepared by the above preparation method in carbon dioxide reduction.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention achieves the regulation of the catalyst surface structure and electronic environment through the introduction of atomic doping and defect structures, thereby creating a sub-environment that breaks the equilibrium and creates a more active catalytic site, thereby reducing the energy barrier required for carbon dioxide activation.

[0022] 2. The sulfur-doped defective porous zinc oxide catalyst prepared by the preparation method of the present invention has a high current density and a high Faraday efficiency for carbon monoxide products, has a high catalytic activity and good stability, and can be used as an excellent catalyst in carbon dioxide reduction.

[0023] 3. The preparation method of the present invention has a simple process, does not require high-temperature annealing, has a high yield, has abundant and inexpensive raw materials, has a low manufacturing cost, and can be developed and utilized on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a scanning electron microscope image of ZnO in the present invention;

[0025] Figure 2 This is a high-magnification scanning electron microscope image of ZnO in the present invention;

[0026] Figure 3 is a scanning electron microscope image of ZnO-Vo in the present invention;

[0027] Figure 4 It is a transmission electron microscope image of ZnO-Vo in the present invention;

[0028] Figure 5 is a scanning electron microscope image of ZnO-Vo-S in the present invention;

[0029] Figure 6 is a transmission electron microscope image of ZnO-Vo-S in the present invention;

[0030] Figure 7 This is a high-resolution transmission electron microscopy image of ZnO-Vo-S in the present invention;

[0031] Figure 8 XRD spectra of ZnO-Vo-S, ZnO-Vo and ZnO in the present invention;

[0032] Fig. 9 It is a comparison diagram of the linear scanning curves of ZnO-Vo-S, ZnO-Vo and ZnO in the present invention;

[0033] Fig.10 This is a comparison diagram of the carbon dioxide reduction current density of ZnO-Vo-S, ZnO-Vo and ZnO under different voltage conditions in the present invention;

[0034] Fig.11This is a comparison chart of the Faraday efficiency of ZnO-Vo-S, ZnO-Vo and ZnO in the present invention for catalytic production of CO by carbon dioxide reduction under different voltage conditions. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0036] Embodiment 1:

[0037] A method for preparing a sulfur-doped defective porous zinc oxide catalyst comprises the following steps:

[0038] S1. Dissolve zinc nitrate in water-ethanol at a volume ratio of 1:1 and stir evenly to obtain a zinc nitrate solution. Preferably, the concentration of the prepared zinc nitrate is 0.8-1.2 mol / L.

[0039] S2. Add sodium hydroxide solution to the zinc nitrate solution, stir for 30 minutes, filter and wash to obtain porous zinc oxide (ZnO).

[0040] In the specific operation, a sodium hydroxide solution with a concentration of 0.8 to 1.2 mol / L is added, wherein the volume ratio of the zinc nitrate solution to the sodium hydroxide solution is 10:1, and the following reaction is produced after mixing:

[0041] Zn(NO3)2+2NaOH=Zn(OH)2↓+2NaNO3, Zn(OH)2→ZnO+H2O,

[0042] After the reaction, the porous zinc oxide is obtained by suction filtering 3 to 5 times, washing with deionized water 3 to 5 times, and drying.

[0043] S3. Treat the porous zinc oxide in an air atmosphere using a muffle furnace.

[0044] During the specific treatment, the porous zinc oxide is treated in a muffle furnace at a temperature of 300 to 400° C. for 0.5 to 1.5 hours to finally obtain porous zinc oxide (ZnO) with high purity.

[0045] like Figure 1 , 2 As shown, through scanning electron microscopy observation, it can be seen that the morphology of porous zinc oxide (ZnO) presents a three-dimensional flower-like structure, which is self-assembled by pieces of zinc oxide flakes, is relatively evenly dispersed, and the particle size is greater than 2 microns.

[0046] S4. Mix high-purity porous zinc oxide with sulfur and put the mixture into a zirconia sealed can. After the air in the can is evacuated, argon gas is filled into the can. Then, the zirconia sealed can containing the mixture is placed in a plasma high-energy ball mill for processing. Finally, the mixture is cleaned to obtain sulfur-doped defective porous zinc oxide (ZnO-Vo-S).

[0047] In the specific operation, 1g of porous zinc oxide and 200mg of sulfur are mixed, and argon gas is filled to maintain an inert atmosphere in the zirconia sealed can to effectively prevent the influence of air, so that the ions generated after ionization will not chemically react with the substrate. The mixture is processed by a Plasma high-energy ball mill at a power of 180 to 220 W for 1.5 to 2.5 hours. During the processing, the material molecules in the mixture are easily converted into atomic states and excited states for recombination, which greatly improves the ball milling efficiency. After the treatment, an appropriate amount of carbon disulfide is added to the mixture for cleaning to dissolve excess sulfur in the mixture.

[0048] The sulfur-doped defective porous zinc oxide (ZnO-Vo-S) prepared by the above preparation method was used as a carbon dioxide reduction catalyst, and an electrochemical workstation was used to carry out a carbon dioxide reduction test.

[0049] Based on the above preparation method, the present invention also provides an application of a sulfur-doped defective porous zinc oxide catalyst prepared by the above preparation method in carbon dioxide reduction.

[0050] Embodiment 2:

[0051] Based on the preparation method in Example 1, this embodiment provides a method for preparing porous zinc oxide, which specifically includes the following steps:

[0052] S1. Dissolve zinc nitrate in water-ethanol at a volume ratio of 1:1 and stir evenly to prepare 1 L of zinc nitrate solution with a concentration of 1 mol / L.

[0053] S2. Add 100 ml of 1 mol / L sodium hydroxide solution to the zinc nitrate solution. Zinc oxide is generated in the solution. Stir for 30 min. After the reaction, filter 3 to 5 times, wash with deionized water 3 to 5 times, and dry to obtain porous zinc oxide.

[0054] S3. In air, porous zinc oxide is treated in a muffle furnace at a temperature of 300 to 400° C. for 0.5 to 1.5 hours to obtain porous zinc oxide (ZnO) with high purity.

[0055] The porous zinc oxide (ZnO) finally prepared was used as a carbon dioxide reduction catalyst, and an electrochemical workstation was used to test the carbon dioxide reduction. The current density at a fixed voltage and the Faraday efficiency of carbon dioxide reduction catalysis to produce CO at different voltages were tested. The specific test results are as follows: Fig.10 , 11 shown.

[0056] Embodiment three:

[0057] Based on the preparation method of Example 1, this embodiment provides a method for preparing defective porous zinc oxide (ZnO-Vo), which specifically includes the following steps:

[0058] S1. Dissolve zinc nitrate in water-ethanol at a volume ratio of 1:1 and stir evenly to prepare 1 L of zinc nitrate solution with a concentration of 1 mol / L.

[0059] S2. Add 100 ml of 1 mol / L sodium hydroxide solution to the zinc nitrate solution. Zinc oxide is generated in the solution. Stir for 30 min. After the reaction, filter 3 to 5 times, wash with deionized water 3 to 5 times, and dry to obtain porous zinc oxide.

[0060] S3. In air, porous zinc oxide is treated at 350° C. in a muffle furnace for 0.5 to 1.5 h to obtain porous zinc oxide (ZnO) with high purity.

[0061] S4. Take 1 g of the porous zinc oxide (ZnO) treated in step S3 and put it into a zirconia sealed can. After the air in the can is evacuated, argon gas is filled into the can. The can is put into a plasma high-energy ball mill and treated at a power of 180-220 W for 1.5 to 2.5 h to finally obtain defective porous zinc oxide (ZnO-Vo).

[0062] like Figure 3 As shown, through scanning electron microscopy observation, it can be seen that the morphology of defective porous zinc oxide (ZnO-Vo) presents a three-dimensional flower-like structure, which is self-assembled by pieces of zinc oxide flakes and is dispersed relatively evenly.

[0063] like Figure 4 As shown, through transmission electron microscopy observation, it can be seen that there are many mesoporous structures inside the defective porous zinc oxide (ZnO-Vo). These mesoporous structures are beneficial to the storage of electrolyte and the release of catalytic reaction products, which is beneficial to improving the catalytic activity of the material.

[0064] The prepared defective porous zinc oxide (ZnO-Vo) was used as a carbon dioxide reduction catalyst, and an electrochemical workstation was used to test the carbon dioxide reduction. The current density at a fixed voltage and the Faraday efficiency of carbon dioxide reduction catalysis to produce CO at different voltages were tested. The specific test results are as follows: Fig.10 , 11 shown.

[0065] Embodiment 4:

[0066] Based on the preparation method of Example 1, this embodiment provides a preparation method of a sulfur-doped defective porous zinc oxide catalyst (ZnO-Vo-S), which specifically includes the following steps:

[0067] S1. Dissolve zinc nitrate in water-ethanol at a volume ratio of 1:1 and stir evenly to prepare 1 L of zinc nitrate solution with a concentration of 1 mol / L.

[0068] S2. Add 100 ml of 1 mol / L sodium hydroxide solution to the zinc nitrate solution. Zinc oxide is generated in the solution. Stir for 30 min. After the reaction, filter 3 to 5 times, wash with deionized water 3 to 5 times, and dry to obtain porous zinc oxide.

[0069] S3. In air, porous zinc oxide is treated at 350° C. in a muffle furnace for 0.5 to 1.5 h to obtain porous zinc oxide (ZnO) with high purity.

[0070] S4. Take 1 g of the porous zinc oxide (ZnO) treated in step S3 and mix it with 200 mg of sulfur and put the mixture into a zirconia sealed can. After the air in the can is evacuated, argon gas is filled into the can. Then, the can is put into a plasma high-energy ball mill and treated at a power of 180-220 W for 1.5 to 2.5 h to finally obtain sulfur-doped defective porous zinc oxide (ZnO-Vo-S).

[0071] like Figure 5 As shown, through scanning electron microscopy observation, it can be seen that the morphology of sulfur-doped defective porous zinc oxide (ZnO-Vo-S) presents a three-dimensional flower-like structure, which is self-assembled by pieces of zinc oxide flakes and is dispersed relatively evenly.

[0072] like Figure 6 As shown, through transmission electron microscopy observation, it can be seen that the interior of the sulfur-doped defective porous zinc oxide (ZnO-Vo-S) is also a mesoporous morphology, which is beneficial to the storage of the electrolyte and the release of the catalytic reaction products.

[0073] like Figure 7As shown, through high-resolution transmission electron microscopy observation, it can be seen that the sulfur-doped defective porous zinc oxide (ZnO-Vo-S) has obvious lattice fringes (the lattice fringes spacing is 0.26nm, attributed to the (002) crystal plane of zinc oxide).

[0074] The prepared sulfur-doped defective porous zinc oxide (ZnO-Vo-S) was used as a carbon dioxide reduction catalyst and was tested for carbon dioxide reduction using an electrochemical workstation. The current density at a fixed voltage and the Faraday efficiency of carbon dioxide reduction catalysis to produce CO at different voltages were tested. The specific test results are shown in the figure. Fig.10 , 11 shown.

[0075] XRD analysis was performed on the three products ZnO-Vo-S, ZnO-Vo and ZnO, and the XRD spectra were compared as shown in the figure. It can be seen that the main diffraction peaks correspond to the (010), (002), (011), (012), (110), (013), (112) and (021) crystal planes in zinc oxide, and no impurities or other zinc compounds appeared during the process of introducing defect structure and sulfur doping in zinc oxide.

[0076] Linear scanning of the above three products ZnO-Vo-S, ZnO-Vo, and ZnO yields the following results: Fig. 9 The linear curve scanning diagram shown in the figure shows that the current density of ZnO-Vo-S is greater than that of ZnO-Vo and ZnO, and the current density of ZnO-Vo-S can reach up to -22 mA cm -2 .

[0077] like Fig.10 As shown in the figure, the three products of ZnO-Vo-S, ZnO-Vo, and ZnO were tested for carbon dioxide reduction at fixed voltages (-0.6, -0.7, -0.8, -0.9, -1.0, -1.1, and -1.2 V vs. RHE). It can be seen that the current density of sulfur-doped defective porous zinc oxide (ZnO-Vo-S) is as high as 18 mA cm -2 .

[0078] like Fig.11 As shown in the graph, at each voltage, the Faraday efficiency of ZnO-Vo-S for carbon monoxide products is higher than that of ZnO-Vo and ZnO, and with the introduction of defect structure and the doping of sulfur atoms, the Faraday efficiency of carbon monoxide products gradually increases. Among them, the Faraday efficiency of sulfur-doped defective porous zinc oxide (ZnO-Vo-S) for carbon monoxide products is as high as 90% at -1.1 V.

[0079] Through testing, it can be seen that the sulfur-doped defective porous zinc oxide (ZnO-Vo-S) prepared by the preparation method of the present invention has a high current density and a high Faraday efficiency for carbon monoxide products, and thus has a high catalytic activity and good stability, and can be used as a reducing agent with excellent performance in the reduction of carbon dioxide. The preparation method of the present invention has a simple process, does not require high-temperature annealing, has a high yield, has abundant and inexpensive reserves of raw materials for preparation, has a low manufacturing cost, and can be developed and utilized on a large scale.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sulfur-doped defective porous zinc oxide catalyst, characterized in that: The following steps are involved: S1, dissolving zinc nitrate in water-ethanol in a volume ratio of 1:1 and stirring evenly to obtain a zinc nitrate solution; S2, adding sodium hydroxide solution to the zinc nitrate solution, stirring for 30 minutes, filtering, washing, and drying to obtain porous zinc oxide; S3, treating the porous zinc oxide in an air atmosphere through a muffle furnace to obtain porous zinc oxide with high cleanliness; S4. Mix 1 g of high-purity porous zinc oxide with 200 mg of sulfur and put the mixture into a zirconia sealed can. After the air in the can is evacuated, argon gas is filled into the can. Then, the zirconia sealed can containing the mixture is processed by a plasma high-energy ball mill at a power of 180 to 220 W for 1.5 to 2.5 hours. Finally, the mixture is cleaned to obtain sulfur-doped defective porous zinc oxide.

2. The method for preparing the sulfur-doped defective porous zinc oxide catalyst according to claim 1, characterized in that: In step S1, the concentration of zinc nitrate is 0.8-1.2 mol / L.

3. The method for preparing the sulfur-doped defective porous zinc oxide catalyst according to claim 1, characterized in that: In step S2, the concentration of the sodium hydroxide solution is 0.8-1.2 mol / L.

4. The method for preparing the sulfur-doped defective porous zinc oxide catalyst according to claim 1, characterized in that: In step S2, the volume ratio of the zinc nitrate solution to the sodium hydroxide solution is 10:

1.

5. The method for preparing the sulfur-doped defective porous zinc oxide catalyst according to claim 1, characterized in that: In step S3, the porous zinc oxide is treated in a muffle furnace at a temperature of 300 to 400° C. for 0.5 to 1.5 hours.

6. The method for preparing the sulfur-doped defective porous zinc oxide catalyst according to claim 1, characterized in that: In step S4, during cleaning, an appropriate amount of carbon disulfide is added to the mixture to dissolve excess sulfur.

7. The method for preparing the sulfur-doped defective porous zinc oxide catalyst according to claim 1, characterized in that: In step S2, the mixed solution of the zinc nitrate solution and the sodium hydroxide solution is filtered 3 to 5 times, and washed with deionized water 3 to 5 times.

8. Use of a sulfur-doped defective porous zinc oxide catalyst prepared by the preparation method according to any one of claims 1 to 7 in carbon dioxide reduction.

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