A Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material, its preparation method and application

Abstract

The present invention discloses a Zn / Fe co-doped SnO2 ultrathin hollow prismatic nanocage superstructure composite material, its preparation method and application; the preparation method includes the following steps: preparing a zinc-iron Prussian blue nanocubic precursor, dispersing it in deionized water and standing for precipitation to obtain zinc-iron Prussian blue nanocages; dispersing them in deionized water to form suspension A, dissolving stannous salt in concentrated hydrochloric acid to form solution B, pouring solution B into A under stirring, stirring evenly and then standing for reaction at 30-180 °C for 3-24 h to obtain a tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prismatic nanocage material; annealing it at 280-550 °C for 1-5 h; this material has a unique hollow prism and a completely open cage-like cavity structure, and when it is used as a gas-sensitive material for a gas sensor, it has a very high sensitive response to hydrogen sulfide gas and good stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and particularly relates to a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material, a preparation method thereof, and an application thereof. Background Art

[0002] The problem of air quality remains a major issue in many countries. A clean air supply is crucial for our health and the environment. The human nose is a highly advanced sensing system that can distinguish hundreds of odors, but it fails when it comes to detecting absolute gas concentrations or odorless gases. Therefore, there is an urgent need to support or replace the human nose for the detection of toxic and harmful gases. Although a large number of gas detection systems are currently used in process control and laboratory analysis, high-performance gas sensors with high sensitivity, high selectivity, and fast response speed are still needed to improve the gas detection level.

[0003] Metal oxide gas sensors have the advantages of low cost, easy fabrication, small size, and simple measurement electronic devices, and are widely used in portable gas detection systems. However, the performance of such sensors is significantly affected by the morphology and structure of the sensing material, resulting in great obstacles to achieving high-sensitivity performance for gas sensors based on bulk materials or dense films. Nanomaterial gas sensors are an important development direction for improving gas sensing sensitivity, selectivity, and response speed.

[0004] Metal oxide semiconductors have been widely studied for H2S sensors due to their advantages of compatibility with microelectronic devices, simple fabrication, economy, low operating cost, high response, and short response / recovery time. Sensitive materials for H2S detection reported in the current literature include ZnO, SnO2, WO3, TiO2, CuO, Fe2O3, In2O3, and NiO, etc. Among these materials, SnO2 nanostructure-based H2S sensors have shown excellent performance so far. As a broad-spectrum semiconductor, compared with other semiconductor gas-sensitive materials, SnO2 has the advantages of simple preparation, short response and recovery times, and high sensitivity.

[0005] So far, many SnO2 materials with different structures have been prepared for the detection of toxic and harmful gases. Among various gas sensors, metal oxide semiconductor gas sensors have received particular attention. Metal oxide semiconductor gas sensors detect gases by the change in resistance when the gas comes into contact with the surface of the sensing material. Compared with other gas sensors, they have the advantages of low cost, long lifespan, high stability, and wide measurement range. SnO2 is an n-type wide-bandgap semiconductor (Eg = 3.6 eV at 300 K), with the advantages of high gas sensitivity, high chemical stability, and low cost. As is well known, the gas-sensing performance of SnO2 depends on its morphology. In addition, the loading of metals or metal oxides (such as Ag, Pt, Pd, CuO, NiO, etc.) can improve the gas sensitivity. Hollow porous SnO2 with unique structural features has received considerable attention in many applications such as gas sensors. The porous structure can effectively increase the specific surface area and porosity of the material; the large specific surface area can provide sufficient active sites and improve the gas adsorption capacity on the material surface, and the large porosity helps to accelerate the diffusion of target gas molecules in the material, which are all beneficial to the improvement of the gas-sensing performance of the material. In addition, increasing the complexity of nanomaterials in terms of structure and composition is also an effective way to enhance the chemical performance of gas-sensing materials.

[0006] With the development of materials science and nanotechnology, more and more complex superstructure nanomaterials have been prepared by people and have achieved ideal chemical properties. For example: Fu et al. combined the Marangoni effect to convert ZIF-67 nanocubes into ZIF-L open nanocages, providing a new perspective for the preparation of complex nanostructures; Lou's team prepared Cu-substituted Mn-PBAs double-shell nanoboxes using tannic acid etching and cation exchange processes and applied them to zinc ion batteries. The unique hollow nanostructure can not only provide abundant active sites and a large specific surface area but also adapt to the large structural changes during the ion insertion / extraction process, thus improving the battery capacity and cycle stability; Zheng et al. controllably prepared SnO2 triple-shell hollow boxes with a definite cubic shape using a multi-step deposition strategy. Compared with the reference single-shell and double-shell SnO2 nanoboxes, the gas-sensing response performance of the SnO2 triple-shell hollow boxes was significantly improved, and the response / recovery time was shortened.

[0007] Even though the above work has greatly expanded the complexity of nanomaterials, however, traditional double-shell / multi-shell structures are mostly closed structures, which are not conducive to the diffusion and transmission of target reactants. During the chemical reaction (especially the surface reaction) process, the probability of the inner shell layer coming into contact with the target reactants is limited, which is not conducive to the full utilization of active sites. Due to the difficulties in design and preparation, there have been no reports on hollow prism nanocage superstructures with more complex open structures. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material, a preparation method thereof, and an application thereof. This material has a unique hollow prism and a completely open cage-like cavity structure. The gas-sensing test results show that the sensor based on the SnO2 hollow prism nanocage has a relatively low operating temperature, fast response / recovery time, good reversibility and long-term stability, and significantly better selectivity for H2S than other reducing gases.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A preparation method of a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material, characterized in that the preparation method comprises the following steps:

[0011] (1) Prepare zinc-iron Prussian blue nanocubic precursors, disperse them in deionized water and let them stand for aging to obtain zinc-iron Prussian blue nanocages;

[0012] (2) Disperse the zinc-iron Prussian blue nanocages in deionized water to form suspension A, dissolve stannous salts in concentrated hydrochloric acid to form solution B, pour solution B into A under stirring, stir evenly, and let it stand and react at 30-180 °C for 3-24 h to obtain tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage materials;

[0013] (3) Anneal the tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage materials at 280-550 °C for 1-5 h to obtain a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material.

[0014] In step (1), the preparation method of the zinc-iron Prussian blue nanocubic precursors is: dissolve zinc salts in dilute hydrochloric acid, add an aqueous solution of potassium ferrocyanide thereto, stir until the solution becomes a yellow suspension, and let it stand and age at 10-95 °C for 2-36 h, followed by filtration, washing, and drying.

[0015] Furthermore, the zinc salts are one or more of zinc chloride, zinc sulfate, zinc acetate, and zinc nitrate; the molar ratio of potassium ferrocyanide to zinc salts is 1:1.

[0016] The concentration of the aqueous solution of potassium ferrocyanide is 0.1-2.0 mol / L; the concentration of the zinc salts in dilute hydrochloric acid is 0.1-2.0 mol / L; the concentration of the dilute hydrochloric acid is 0.1-1.2 mol / L.

[0017] The conditions for the standing aging are preferably standing aging at 60-80 °C for 12-24 h.

[0018] In step (1), the standing aging time is 1-5 days.

[0019] In step (2), the stannous salt is one or both of stannous chloride and stannous sulfate.

[0020] In step (2), the mass ratio of zinc-iron Prussian blue nanocages to the stannous salt is 1:0.3 - 1.5.

[0021] In step (2), the concentration of zinc-iron Prussian blue nanocages in deionized water is 0.4 - 20 mg / mL.

[0022] In step (2), the concentration of the stannous salt in concentrated hydrochloric acid is 3.0 - 15.0 mg / mL; the concentration of the concentrated hydrochloric acid is 10 - 12 mol / L.

[0023] In step (3), the annealing conditions are preferably 320 - 400 °C for 2 - 3 h.

[0024] In step (3), the heating rate to the specified annealing temperature is 1 - 6 °C / min, preferably 1 - 2 °C / min.

[0025] The present invention also provides a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material prepared by the above preparation method.

[0026] The present invention also provides the application of the Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material in a gas sensor. When used as a gas-sensitive material of the gas sensor, it has a high sensitive response to hydrogen sulfide gas and good stability.

[0027] In the preparation method disclosed by the present invention, zinc-iron Prussian blue nanocubes which are easy to prepare are used as a precursor, zinc-iron Prussian blue nanocages are obtained through aging, a tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage material is obtained through coating, and a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material is obtained after high-temperature calcination.

[0028] Some chemical reaction formulas involved in the reaction process are shown as follows:

[0029] 3Zn 2+ +3[Fe(CN)6] 3- →Zn3[Fe(CN)6]2 (1)

[0030] 21Sn 2+ +20H2O+16Cl - →Sn 21 Cl 16 (OH) 14 O6+26H + (2)

[0031] Sn 21 Cl 16 (OH) 14 O6 + 11O2 → 21SnO2 + 14HCl + Cl2 (3)

[0032] The preparation method of the Zn / Fe co-doped SnO2 ultrathin hollow-edged nanocage superstructure composite material provided by the present invention is simple. Using the Zn-Fe Prussian blue open nanocage as a hard template, under the condition of no additional surfactant or protective agent involved, combined with the annealing process, the controllable preparation of the Zn / Fe co-doped SnO2 ultrathin hollow-edged nanocage superstructure composite material is realized for the first time. The combination of the nanoscale cavity and the chemical function of the porous ultrathin shell layer makes the Zn / Fe co-doped SnO2 ultrathin hollow-edged nanocage superstructure composite material have the characteristics of uniform pore size, extremely large specific surface area, sufficient active sites, and small crystal size.

[0033] The sensor device prepared based on this material has high sensitivity and good anti-interference performance. The gas-sensing mechanism research shows that during the H2S gas sensing response process of the Zn / Fe co-doped SnO2 hollow-edged nanocage, both the chemisorbed oxygen on the material surface and the material itself react with H2S. The synergistic effect of the surface adsorbed oxygen and the formation of metastable sulfide at the particle interface makes the material show excellent gas-sensing performance to H2S. Description of the Drawings

[0034] Figure 1 SEM image of the Zn / Fe co-doped SnO2 ultrathin hollow-edged nanocage superstructure composite material prepared in Example 1;

[0035] Figure 2 SEM image of the Zn / Fe co-doped SnO2 ultrathin hollow-edged nanocage superstructure composite material prepared in Example 2;

[0036] Figure 3 SEM image of the zinc-iron Prussian blue nanocubic precursor prepared in Example 3;

[0037] Figure 4 XRD pattern of the zinc-iron Prussian blue nanocubic precursor prepared in Example 3;

[0038] Figure 5 SEM image of the zinc-iron Prussian blue nanocage prepared in Example 3;

[0039] Figure 6 SEM image of the tin-coated zinc-iron Prussian blue nanocage ultrathin hollow-edged nanocage superstructure prepared in Example 3;

[0040] Figure 7 SEM image of the Zn / Fe co-doped SnO2 ultrathin hollow-edged nanocage superstructure composite material prepared in Example 3;

[0041] Figure 8 XRD pattern of the Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material prepared in Example 3;

[0042] Figure 9 EDS pattern of the Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material prepared in Example 3;

[0043] Figure 10 BET pattern of the Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material prepared in Example 3;

[0044] Figure 11 SEM image of the Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material prepared in Example 4;

[0045] Figure 12 SEM image of the Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material prepared in Example 5;

[0046] Figure 13 Response sensitivity of the Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material prepared in Example 3 to 10 ppm H₂S and 100 ppm different kinds of VOCs (including ethanol, isopropanol, acetone, benzene, toluene, n-butanol, methanol, ammonia, etc.) at a working temperature of 130 °C. Detailed implementation manners

[0047] The present invention will be described in detail below in conjunction with the embodiments.

[0048] The reaction vessels used in step (2) of each embodiment are all beakers, and the mouths of the beakers are covered with plastic wrap during heating.

[0049] Example 1

[0050] A preparation method of a Zn / Fe co-doped SnO₂ ultrathin hollow prism nanocage superstructure composite material, comprising the following steps:

[0051] (1) Potassium ferrocyanide is dissolved in deionized water to prepare 1000 mL of a 2M potassium ferrocyanide solution; zinc chloride is dissolved in 0.1M dilute hydrochloric acid to prepare 1000 mL of a 2M zinc chloride solution; the potassium ferrocyanide solution is added to the zinc chloride solution under magnetic stirring at a speed of 150 rpm, and then stirring is continued at room temperature for 50 min to obtain a mixed suspension, which is allowed to stand for 2 h at 99° C. to obtain a yellow precipitate, which is filtered, washed, and dried at 100° C. for 6 h to obtain a zinc iron Prussian blue nanocube precursor; the obtained zinc iron Prussian blue nanocubes are allowed to stand for 5 days in deionized water, and then fully washed with anhydrous ethanol and dried to obtain a zinc iron Prussian blue nanocage.

[0052] (2) 0.2 g of zinc iron Prussian blue nanocages were dispersed in 500 mL of deionized water to form suspension A, 0.06 g of stannous chloride was dissolved in 20 mL of 10 M concentrated hydrochloric acid to form solution B, solution B was poured into solution A under stirring, and after continuous stirring for 10 min, the solution was transferred into a 99°C oven and kept warm for 3 h. The supernatant was then discarded, and the blue precipitate was thoroughly washed and dried with deionized water and ethanol to obtain a tin-coated zinc iron Prussian blue nanocage ultra-thin hollow ridge nanocage superstructure.

[0053] (3) The obtained tin-coated zinc-iron Prussian blue nanocage ultra-thin hollow rib nanocage sample was transferred to a muffle furnace, heated to 550°C at a heating rate of 6°C / min and annealed for 1 h to obtain a Zn / Fe co-doped SnO2 ultra-thin hollow rib nanocage superstructure composite material. The SEM image is shown in Figure 1 shown.

[0054] Example 2

[0055] A method for preparing a Zn / Fe co-doped SnO2 ultra-thin hollow rib nanocage superstructure composite material comprises the following steps:

[0056] (1) Potassium ferrocyanide is dissolved in deionized water to prepare 1000 mL of a 1M potassium ferrocyanide solution; zinc chloride is dissolved in 0.5M dilute hydrochloric acid to prepare 1000 mL of a 1M zinc chloride solution; the potassium ferrocyanide solution is added to the zinc chloride solution under magnetic stirring at a speed of 130 rpm, and then stirring is continued at room temperature for 40 min to obtain a mixed suspension, which is allowed to stand for 4 h at 90° C. to obtain a yellow precipitate, which is filtered, washed, and dried at 90° C. for 8 h to obtain a zinc iron Prussian blue nanocube precursor; the obtained zinc iron Prussian blue nanocubes are allowed to stand for 4 days in deionized water, and then fully washed with anhydrous ethanol and dried to obtain a zinc iron Prussian blue nanocage.

[0057] (2) Disperse 0.2 g of zinc-iron Prussian blue nanocages in 300 mL of deionized water to form suspension A. Dissolve 0.14 g of stannous chloride in 20 mL of concentrated hydrochloric acid with a concentration of 11 M to form solution B. Pour solution B into A under stirring, continue stirring for 20 min, and then transfer it to an oven at 90 °C for heat preservation for 6 h. Then pour out the supernatant, and wash and dry the blue precipitate with deionized water and ethanol to obtain a tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage superstructure.

[0058] (3) Transfer the obtained tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage sample to a muffle furnace, heat it to 420 °C at a heating rate of 4 °C / min and anneal for 2 h to obtain a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material. Its SEM image is as Figure 2 shown.

[0059] Example 3

[0060] A preparation method of a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material includes the following steps:

[0061] (1) Dissolve potassium ferricyanide in deionized water to prepare a 1000 mL, 0.1 M potassium ferricyanide solution; dissolve zinc chloride in dilute hydrochloric acid with a concentration of 0.7 M to prepare a 1000 mL, 0.1 M zinc chloride solution; under magnetic stirring at a rotation speed of 120 r / min, add the above potassium ferricyanide solution to the zinc chloride solution, and then continue stirring at room temperature for 30 min to obtain a mixed suspension. Let it stand and age at 80 °C for 12 h to obtain a yellow precipitate. Filter and wash the yellow precipitate, and dry it at 80 °C for 8 h to obtain a zinc-iron Prussian blue nanocube precursor; its SEM image is as Figure 3 shown. It can be seen from the figure that it is a uniform cubic block; its XRD pattern is as Figure 4 shown. The diffraction pattern proves that the prepared zinc-iron Prussian blue has strong peaks and high purity. Let the obtained zinc-iron Prussian blue nanocubes stand and age in deionized water for 3 days, and then wash and dry them thoroughly with absolute ethanol. The obtained product is zinc-iron Prussian blue nanocages. Its SEM image is as Figure 5 shown. It can be seen from the figure that it is a nanocage structure.

[0062] (2) Disperse 0.2 g of zinc-iron Prussian blue nanocages in 100 mL of deionized water to form suspension A. Dissolve 0.35 g of stannous sulfate in 20 mL of concentrated hydrochloric acid with a concentration of 11 M to form solution B. Pour solution B into A under stirring, continue for 30 min, and then transfer it to an oven at 80 °C for heat preservation for 8 h. Then pour out the supernatant, and wash and dry the blue precipitate with deionized water and ethanol to obtain a tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage superstructure. Its SEM image is as Figure 6as shown

[0063] (3) Transfer the obtained tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage sample to a muffle furnace, heat it to 350 °C at a heating rate of 1 °C / min and anneal for 2 h to obtain a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material. Its SEM image is as shown in Figure 7 as shown, and its XRD is as shown in Figure 8 as shown. It can be found that all diffraction peaks are consistent with the Fe4[Fe(CN)6]3 (JCPDS No. 01-0239) card, and there are no other impurity peaks; the Sn element exists in an amorphous state on the surface of the zinc-iron Prussian blue nanocage. The remaining Prussian blue and its analogues shown in the XRD test results provide effective physical support for the attachment of amorphous Sn elements. The EDS image of the product is as shown in Figure 9 as shown, indicating that the product contains zinc, iron, tin and oxygen elements, and the silicon element comes from the silicon substrate. The BET image of the product is as shown in Figure 10 as shown, its specific surface area is 520.19 m 2 g -1 , and the average pore diameter is 2.37 nm, indicating that it is a porous material with a relatively large specific surface area.

[0064] Example 4

[0065] A preparation method of a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material, comprising the following steps:

[0066] (1) Dissolve potassium ferricyanide in deionized water to prepare a 1000 mL, 0.5 M potassium ferricyanide solution; dissolve zinc chloride in dilute hydrochloric acid with a concentration of 0.9 M to prepare a 1000 mL, 0.5 M zinc chloride solution; under magnetic stirring at a rotation speed of 80 r / min, add the above potassium ferricyanide solution to the zinc chloride solution, and then continue to stir at room temperature for 20 min to obtain a mixed suspension. Let it stand and age at 60 °C for 30 h to obtain a yellow precipitate. Filter and wash the yellow precipitate, and dry it at 60 °C for 20 h to obtain a zinc-iron Prussian blue nanocube precursor; let the obtained zinc-iron Prussian blue nanocubes stand and age in deionized water for 2 days, then wash them thoroughly with absolute ethanol and dry them to obtain the product, which is the zinc-iron Prussian blue nanocage.

[0067] (2) Take 0.2 g of zinc - iron prussian blue nanocages and disperse them in 50 mL of deionized water to form suspension A. Take 0.35 g of stannous chloride and 0.1 g of stannous sulfate and dissolve them in 20 mL of concentrated hydrochloric acid with a concentration of 12 M to form solution B. Pour solution B into A under stirring. After continuously stirring for 20 min, transfer it into an oven at 70 °C and keep it warm for 12 h. Then pour out the supernatant, and wash the blue precipitate thoroughly with deionized water and ethanol and dry it to obtain a tin - coated zinc - iron prussian blue nanocage ultrathin hollow prism nanocage superstructure.

[0068] (3) Transfer the obtained tin - coated zinc - iron prussian blue nanocage ultrathin hollow prism nanocage sample to a muffle furnace, heat it to 300 °C at a heating rate of 3 °C / min and anneal for 3 h to obtain a Zn / Fe co - doped SnO2 ultrathin hollow prism nanocage superstructure composite material. Its SEM image is as Figure 11 shown.

[0069] Example 5

[0070] A preparation method of a Zn / Fe co - doped SnO2 ultrathin hollow prism nanocage superstructure composite material includes the following steps:

[0071] (1) Dissolve potassium ferricyanide in deionized water to prepare 1000 mL of 0.3 M potassium ferricyanide solution; dissolve zinc chloride in dilute hydrochloric acid with a concentration of 1.2 M to prepare 1000 mL of 0.3 M zinc chloride solution; under magnetic stirring at a rotation speed of 50 r / min, add the above potassium ferricyanide solution to the zinc chloride solution, then continue to stir at room temperature for 10 min to obtain a mixed suspension, let it stand and age at 30 °C for 48 h to obtain a yellow precipitate. Filter and wash the yellow precipitate, and dry it at 30 °C for 24 h to obtain a zinc - iron prussian blue nanocubic precursor. Let the obtained zinc - iron prussian blue nanocubes stand and age in deionized water for 1 day, then wash them thoroughly with absolute ethanol and dry them. The obtained product is the zinc - iron prussian blue nanocage.

[0072] (2) Take 0.2 g of zinc - iron prussian blue nanocages and disperse them in 10 mL of deionized water to form suspension A. Take 0.6 g of stannous sulfate and dissolve it in 20 mL of concentrated hydrochloric acid with a concentration of 12.0 M to form solution B. Pour solution B into A under stirring. After continuously stirring for 50 min, transfer it into an oven at 60 °C and keep it warm for 24 h. Then pour out the supernatant, and wash the blue precipitate thoroughly with deionized water and ethanol and dry it to obtain a tin - coated zinc - iron prussian blue nanocage ultrathin hollow prism nanocage superstructure.

[0073] (3) Transfer the obtained tin - coated zinc - iron prussian blue nanocage ultrathin hollow prism nanocage sample to a muffle furnace, heat it to 280 °C at a heating rate of 2 °C / min and anneal for 5 h to obtain a Zn / Fe co - doped SnO2 ultrathin hollow prism nanocage superstructure composite material. Its SEM image is asFigure 12 as shown

[0074] Application Example 1

[0075] Application of Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material in gas sensors

[0076] Disperse the Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material prepared in Example 3 in absolute ethanol, and then evenly coat it on a ceramic tube with electrodes to make a gas sensor. Dry it at 50 °C for 2 h, and then heat-treat it at 200 °C for 2 h. Then, put a small nickel-chromium alloy coil into the tube as a heater to provide the working temperature for the sensor. Age the sensor at 300 °C for 48 h, and then test different volatile organic gases at the working temperature. The specific test operation steps are as follows: Use a syringe to inject a certain amount of organic vapor into the sensor test chamber. Wait for about 2 minutes. After the sensor output response value is stable, then introduce dry air into the test chamber. The sensor output response gradually recovers again. Use an electrochemical workstation and a computer to test and record the output response values of the sensor in dry air and when there is a target gas. The gas response sensitivity of the sensor is defined as S = R a / R g (reducing gas), R a is the resistance of the sensor in dry air, and R g is the resistance of the sensor in the test gas.

[0077] The performance test research shows that the prepared Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material has good sensitive responses to common toxic and harmful organic gases in the air, such as Figure 13 as shown. It can be seen from the figure that the Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material prepared by this method shows good selectivity to hydrogen sulfide compared with different types of VOCs (including ethanol, isopropanol, acetone, benzene, toluene, n-butanol, methanol, and ammonia, etc.). Therefore, it is appropriate to select the Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material as the sensitive material for H2S gas.

[0078] The above detailed description of a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material and its preparation method and application with reference to the embodiments is illustrative rather than restrictive. Several embodiments can be listed according to the defined scope. Therefore, changes and modifications within the overall concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A preparation method of a Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite material, characterized in that, The preparation method includes the following steps: (1) Prepare zinc-iron Prussian blue nanocubic precursors, disperse them in deionized water and let them stand for aging to obtain zinc-iron Prussian blue nanocages; (2) Disperse the zinc-iron Prussian blue nanocages in deionized water to form suspension A, dissolve stannous salts in concentrated hydrochloric acid to form solution B, pour solution B into A under stirring, after stirring evenly, let it stand and react at 30-180 °C for 3-24 h to obtain tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage materials; (3) Anneal the tin-coated zinc-iron Prussian blue nanocage ultrathin hollow prism nanocage materials at 280-550 °C for 1-5 h to obtain Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite materials.

2. The preparation method according to claim 1, characterized in that, In step (1), the preparation method of the zinc-iron Prussian blue nanocubic precursors is as follows: dissolve zinc salts in dilute hydrochloric acid, add an aqueous solution of potassium ferrocyanide thereto, stir until the solution becomes a yellow suspension, let it stand and age at 10-95 °C for 2-36 h, and then filter, wash and dry.

3. The preparation method according to claim 2, characterized in that, The zinc salts are one or more of zinc chloride, zinc sulfate, zinc acetate and zinc nitrate; the molar ratio of potassium ferrocyanide to zinc salts is 1:

1.

4. The preparation method according to claim 2, characterized in that, The concentration of the aqueous solution of potassium ferrocyanide is 0.1-2.0 mol / L; the concentration of the zinc salts in dilute hydrochloric acid is 0.1-2.0 mol / L; the concentration of the dilute hydrochloric acid is 0.1-1.2 mol / L.

5. The preparation method according to claim 1, characterized in that, In step (2), the stannous salts are one or two of stannous chloride and stannous sulfate.

6. The preparation method according to claim 1, wherein In step (2), the mass ratio of zinc-iron Prussian blue nanocages to stannous salts is 1:0.3-1.

5.

7. The preparation method according to claim 1, characterized in that, In step (2), the concentration of zinc-iron Prussian blue nanocages in deionized water is 0.4-20 mg / mL.

8. The preparation method according to claim 1, wherein In step (2), the concentration of stannous salts in concentrated hydrochloric acid is 3.0-15.0 mg / mL; the concentration of the concentrated hydrochloric acid is 10-12 mol / L.

9. Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite materials prepared by the preparation method according to any one of claims 1-8.

10. Application of the Zn / Fe co-doped SnO2 ultrathin hollow prism nanocage superstructure composite materials according to claim 9 in gas sensors.

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