Preparation method of zn2sn04 / zno nanomaterial and application thereof

Abstract

The application belongs to the technical fields of new energy materials and electrochemical catalysis, and provides a preparation method of Zn2SnO4 / ZnO nanomaterials to solve the problem that existing ZnO-based composite nanometer catalysts cannot effectively electrocatalyze CO2 into HCOOH; in a mixed solution of sodium hydroxide, cetyltrimethylammonium bromide and ultrapure water, anhydrous zinc acetate is added to form two-dimensional zinc oxide nanosheets as a loaded precursor, anhydrous stannous chloride is then added, and finally Zn2SnO4 octahedral modified ZnO nanosheets are formed; the Zn2SnO4 / ZnO nanomaterials prepared by the application have high catalytic activity and product selectivity when applied as catalysts in the process of electrocatalytic reduction of carbon dioxide to generate HCOOH; the preparation method is simple, raw materials are easy to obtain, and the cost is low.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials and electrochemical catalysis, and particularly relates to a preparation method of Zn2SnO4 / ZnO nanomaterial and application thereof. BACKGROUND

[0002] Energy shortage and environmental pollution are great challenges faced by human beings, and over-reliance on fossil fuels has led to a sharp rise in CO2 emissions. Converting excess greenhouse gases into fuels or high-value chemicals in a clean way has become a global focus and difficulty.

[0003] Literatures report that single-atom carriers generally have FeO x , CeO2, TiO2, Al2O3 and ZnO, and ZnO enables the doped single atom to maintain the metallic state of the metal atom, which is more conducive to the subsequent doping process and also conducive to performance improvement. Nanoscale ZnO has special properties and new uses in magnetism, light, electricity, chemistry, physics, sensitivity and the like, which cannot be compared with general zinc oxide products. ZnO itself also has the performance of electrocatalytic CO2 reduction reaction (CO2RR). The CO2RR reduction products are complex, and common ones are CO, HCOOH, CH4, C2H5OH, C2H4, etc. Multi-electron transfer process leads to C1 to C2+, although C2+ products have high industrial value, but the electro-reduction of CO2 into C2+ products still faces great challenges at the industrial level, because of low selectivity and slow reaction pathway, ultimately leading to high production cost. On the contrary, recent studies show that the production of C1 products including CO and HCOOH is more economically feasible and has great industrialization prospect. In addition, compared with CO gas, stable liquid HCOOH product is more conducive to separation and collection in the preparation and storage process.

[0004] Electrocatalytic CO2 reduction reaction provides a feasible method for renewable electric power energy to be converted into high-value fuels and chemical raw materials in the form of stored in chemical bonds. Formic acid (HCOOH) is not only a very valuable reaction raw material in organic synthesis, but also a key intermediate in Water-Gas-Shift reaction and other reactions. More importantly, formic acid can be used as a liquid hydrogen storage material to store energy. Here, carbon dioxide is considered to play a carrier role, realizing hydrogen storage in formic acid, and hydrogen can be released through formic acid degradation, while carbon dioxide as a byproduct is an ideal carbon neutralization process, realizing sustainable development and energy cycle. Formic acid is applied to pesticide, medicine and dye production, and formic acid is not only a chemical raw material, but also an energy production raw material with environmental protection properties, so it can be used as a raw material for fuel cells and automobile fuels to provide power and power for human beings, and formic acid has good market development prospect.

[0005] CN112642434A uses zinc nitrate hexahydrate as a raw material, sodium hydroxide as a precipitant, and sodium citrate as a surfactant to synthesize flower-like ZnO carriers by a solvothermal method; then uses copper sulfate pentahydrate as a raw material and hydrazine hydrate as a reducing agent to synthesize flower-like Cu2O-loaded ZnO nanomaterials with different Cu2O contents by a rapid thermal reduction method, and the faradaic efficiency of catalytic reduction of CO2 to CO can reach 86.9%. This method uses zinc nitrate hexahydrate as a zinc source, and zinc nitrate hexahydrate decomposes at high temperatures to produce nitrogen oxide gas, which is irritating and toxic; it reacts violently with sulfur, phosphorus, carbon powder, copper, metal sulfides, and organic matter, so the use of zinc nitrate hexahydrate has very high process requirements; the prepared Cu2O-loaded ZnO nanomaterials are used for catalytic reduction of CO2 to CO, and cannot be used for catalytic reduction of CO2 to HCOOH.

[0006] Therefore, by regulating the composition, size and morphology of ZnO-based composite nanocatalysts, the preparation of formic acid by electrocatalytic reduction of carbon dioxide is realized, and the activity and selectivity in the catalytic process are improved, which has great research prospects and practical significance. SUMMARY

[0007] In view of the above problems that existing ZnO-based composite nanocatalysts cannot effectively electrocatalyze CO2 to HCOOH, the application provides a preparation method of Zn2SnO4 / ZnO nanomaterials, in which anhydrous zinc acetate is added to a mixed solution of sodium hydroxide, cetyltrimethylammonium bromide and ultrapure water to form two-dimensional zinc oxide nanosheets as a precursor for loading, then anhydrous stannous chloride is added, and finally Zn2SnO4 octahedral modified ZnO nanosheets are formed. The Zn2SnO4 / ZnO nanomaterials prepared by the application have high catalytic activity and product selectivity in the process of electrocatalytic reduction of carbon dioxide to generate HCOOH.

[0008] In order to achieve the above application purposes, the application provides the following technical solutions:

[0009] A preparation method of Zn2SnO4 / ZnO nanomaterials, comprising the following steps:

[0010] (1) Weigh sodium hydroxide and cetyltrimethylammonium bromide, add them to ultrapure water, and stir vigorously until the two mixtures are dissolved and ultrasonic is performed;

[0011] (2) Weigh zinc acetate and dissolve it in ultrapure water, and add the zinc acetate solution dropwise to the solution after ultrasonic in step (1) and stir uniformly;

[0012] (3) Add stannous chloride to the mixture in step (2) and stir uniformly, and perform hydrothermal reaction at a temperature of 110-170℃;

[0013] (4) After the reaction is completed, centrifugation, washing, drying, to obtain the Zn2SnO4 octahedral modified ZnO nanosheet;

[0014] The molar ratio of the sodium hydroxide, cetyltrimethylammonium bromide, zinc acetate and stannous chloride is (50-85):(20-30):(6-9):1.

[0015] As preferred, the molar ratio of the sodium hydroxide, cetyltrimethylammonium bromide, zinc acetate and stannous chloride is (60-75):(23-27):(7-8):1; more preferably 68:25:7.5:1.

[0016] As preferred, in the step (1), the ultrasonic time is 10-50 minutes, and the temperature is normal temperature. As preferred, the ultrasonic frequency is 20-40 kHz.

[0017] As preferred, in the step (2), the zinc acetate solution is added dropwise within 10-30 minutes.

[0018] As preferred, in the step (2), the stirring time after the zinc acetate solution is added dropwise is 10-60 minutes.

[0019] As preferred, in the step (3), the stirring time after the stannous chloride is added is 2-6 h.

[0020] As preferred, in the step (3), the hydrothermal reaction temperature is 120-160℃, more preferably 130-150℃.

[0021] As preferred, in the step (4), the centrifugal washing is carried out at 6000-9000 rpm, the precipitate after centrifugation is washed with ultrapure water first and then with ethanol, and the precipitate is vacuum dried at 50-70℃ for 2-6 h.

[0022] As preferred, in the step (1), the mass of the sodium hydroxide and cetyltrimethylammonium bromide is 0.24 g and 0.73 g respectively, which are dissolved in 40 mL of ultrapure water;

[0023] As preferred, in the step (2), anhydrous zinc acetate is used, the mass of which is 0.11 g, which is dissolved in 2 mL of ultrapure water, and the zinc acetate solution is added dropwise within 30 minutes, and the stirring time is 30 min;

[0024] As preferred, in the step (3), anhydrous stannous chloride is used, the amount of which is 13 mg, the stirring time is 4 h, the hydrothermal reaction temperature is 150℃, and the reaction time is 16 h;

[0025] As preferred, in the step (4), the centrifugal washing is carried out at 8000 rpm for 5 minutes, the washing with water and alcohol is carried out twice respectively, the precipitate after centrifugation is vacuum dried at 60℃, and the drying time is 4 h.

[0026] The application also provides application of the Zn2SnO4 / ZnO nanomaterial as described above as a catalyst in electrocatalytic reduction of carbon dioxide.

[0027] As preferred, the Zn2SnO4 / ZnO nanomaterial is used for electrocatalytic reduction of carbon dioxide to prepare formic acid.

[0028] The Zn2SnO4 / ZnO nanomaterial is prepared by using sodium hydroxide, cetyltrimethylammonium bromide and anhydrous zinc acetate as raw materials and by adopting a hydrothermal method. Different sizes of the Zn2SnO4 / ZnO nanomaterial can be obtained by adjusting the ultrasonic time in step (1) and the stirring time in steps (2) and (3). The obtained Zn2SnO4 / ZnO nanomaterial can have excellent catalytic activity and selectivity in reduction of carbon dioxide by adjusting the concentration of surface oxygen vacancies and the size of the nanomaterial, and the nanomaterial has high selectivity to HCOOH as a catalyst for electrocatalytic reduction of carbon dioxide.

[0029] The Zn2SnO4 / ZnO material provided by the application is in a sheet shape, has high conductivity and specific surface area, and effectively reduces the overpotential of CO2RR. The results show that the CO2RR process of the Zn2SnO4 / ZnO material is a 2-electron catalytic mechanism, which is a relatively ideal CO2RR reaction process.

[0030] Advantages:

[0031] (1) The sheet-shaped ZnO-based catalyst with controllable size is prepared by the hydrothermal method, has high catalytic activity and product selectivity in the process of electrocatalytic reduction of carbon dioxide, and has good stability.

[0032] (2) The electrocatalytic reduction of CO2 to prepare HCOOH is realized.

[0033] (3) The preparation method uses water as a solvent, has simple process, raw materials are easy to obtain, cost is low, market prospect is wide, and is conducive to large-scale development and utilization. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 XRD pattern of the Zn2SnO4 / ZnO nanomaterial prepared in Example 1;

[0035] Figure 2 Ar, CO2 atmosphere LSV curve of the Zn2SnO4 / ZnO nanomaterial prepared in Example 1;

[0036] Figure 3 Stability test of the Zn2SnO4 / ZnO nanomaterial prepared in Example 1 under different voltages in a CO2 atmosphere;

[0037] Figure 4SEM image of Zn2SnO4 / ZnO nanomaterial prepared in Example 1;

[0038] Figure 5 Impedance of Zn2SnO4 / ZnO nanomaterial prepared in Example 1. DETAILED DESCRIPTION

[0039] The application will be further described in connection with specific embodiments.

[0040] Example 1

[0041] (1) 0.24 g of sodium hydroxide and 0.73 g of cetyltrimethylammonium bromide were weighed and dissolved in 40 mL of ultrapure water, and the two mixtures were stirred until they were basically dissolved;

[0042] (2) The mixed solution of step (1) was subjected to ultrasonic treatment for 10-20 minutes;

[0043] (3) 0.11 g of anhydrous zinc acetate was dissolved in 2 mL of ultrapure water;

[0044] (4) The dissolved solution of step (3) was added dropwise to the ultrasonically treated solution of step (2);

[0045] (5) The solution after dropwise addition of step (4) was stirred for 0.5 h;

[0046] (6) 13 mg of anhydrous stannous chloride was added to the stirred solution of step (5), and stirred for 4 h;

[0047] (7) The stirred solution of step (6) was placed in a 50 mL polytetrafluoroethylene-lined stainless steel reaction kettle, and high-temperature reaction was carried out at 150°C for 16 h. After natural cooling to room temperature, a solid-liquid mixture was obtained;

[0048] (8) The solid-liquid mixture after reaction in step (7) was centrifuged at 8000 rpm for 5 minutes, and washed with water and alcohol twice;

[0049] (9) The precipitate after centrifugation in step (10) was vacuum dried at 60°C for 4 h, and the Zn2SnO4 / ZnO nanomaterial was obtained.

[0050] Example 2

[0051] (1) 0.235 g of sodium hydroxide and 0.725 g of cetyltrimethylammonium bromide were weighed and dissolved in 40 mL of ultrapure water, and the two mixtures were stirred until they were basically dissolved;

[0052] (2) The mixed solution of step (1) was subjected to ultrasonic treatment for 10-20 minutes;

[0053] (3) Dissolve 0.105 g of anhydrous zinc acetate in 2 mL of ultrapure water;

[0054] (4) Add the solution dissolved in step (3) dropwise to the solution sonicated in step (2);

[0055] (5) Stir the solution after adding it in step (4) for 1 hour;

[0056] (6) Add 13.5 mg of anhydrous stannous chloride to the solution stirred in step (5) and stir for 4 h;

[0057] (7) Place the solution stirred in step (6) into a 50 mL stainless steel reactor lined with polytetrafluoroethylene, react at 130 °C for 16 h, and then cool naturally to room temperature to obtain a solid-liquid mixture.

[0058] (8) Wash the solid-liquid mixture after the reaction in step (7) by centrifugation at 9000 rpm for 5 minutes, and wash it twice with water and twice with alcohol.

[0059] (9) The precipitate after centrifugation in step (10) is dried under vacuum at 60°C for 2 hours to obtain Zn2SnO4 / ZnO nanomaterials.

[0060] 1. Morphology of ZnO nanomaterials

[0061] like Figure 4 As shown, the morphology of the main sample can be clearly seen under an electron microscope as ultrathin nanosheets with a size of about 20 nm, which is conducive to the exposure of active sites.

[0062] 2. Electrochemical testing

[0063] The test used a standard three-electrode system and was conducted on an electrochemical workstation (CHI760E). Nickel foam was used as the counter electrode, Ag / AgCl electrode was used as the reference electrode, and the flow electrolysis cell was separated by a Nafion 117 proton exchange membrane.

[0064] Add 30 mL of 0.5 M KHCO3 electrolyte to each of the two electrolysis chambers of the electrolytic cell. Before the test, pass carbon dioxide gas through the system for one hour to saturate it with carbon dioxide.

[0065] Weigh 1 mg of catalyst and add it to 400 μL of ethanol and 10 μL of Nafion. Disperse the mixture by ultrasonication for half an hour. Then, uniformly drop the ultrasonically dispersed ink onto 1 cm * 3 cm carbon paper as the working electrode. After natural drying, place the electrode into a flow electrolytic cell for electrochemical testing.

[0066] In the carbon dioxide reduction test, the flow rate of 20.0 sccm CO2 gas was continuously introduced into the reaction system, the gas products were detected and analyzed by gas chromatography, the cathode electrolyte was collected, liquid nuclear magnetic analysis was carried out, and the Faraday efficiency of the corresponding product was calculated, and the main products were H2, CO and HCOOH.

[0067] The working electrode was tested at-1.0V, -1.1V, -1.2V, -1.3V, -1.4V, -1.5V (vs. RHE) for 30 minutes. The Zn2SnO4 / ZnO nanosheet prepared in the example was characterized by X-ray diffraction (XRD), Figure 1 The XRD pattern of the catalyst (the curve in the figure is actually continuous, and is designed in the style of dash-dot line in order to distinguish different curves) has diffraction peaks corresponding to Zn2SnO4 (JCPDS No. 24-1470) and ZnO (JCPDS No. 65-3411).

[0068] Figure 2 The time-current curve of the catalyst Zn2SnO4 / ZnO in Ar and CO2 atmosphere is shown in the figure, from which it can be seen that the current density of the catalyst Zn2SnO4 / ZnO is 205.9 mA cm-2 at-2.0V vs. RHE, and has high activity of carbon dioxide reduction. -2

[0069] The stability test of the catalyst Zn2SnO4 / ZnO in 0.5M KHCO3 at-1.3V vs. RHE was carried out by introducing CO2, Figure 3 The time-current curve and the Faraday efficiency-time curve of the test results are shown in the figure, the Faraday efficiency of HCOOH is 85.0% (±5%), the Faraday efficiency of CO is 12.5% (±5%), the hydrogen evolution performance is poor, and can be maintained for about 12h, and the current curve remains stable, indicating that the catalyst has good electrochemical stability.

[0070] Figure 5 The impedance test of the catalyst Zn2SnO4 / ZnO is shown in the figure, and the impedance of Zn2SnO4 / ZnO is the smallest, which has good conductivity, good intrinsic activity and reaction kinetics.

[0071] The above-described examples only describe the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements of the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.​

Claims

1. An application of Zn₂SnO₄ / ZnO nanomaterials in electrocatalytic carbon dioxide reduction, characterized in that, The Zn2SnO4 / ZnO nanomaterials are used as catalysts for the electrocatalytic reduction of carbon dioxide to prepare formic acid; The preparation method of the Zn2SnO4 / ZnO nanomaterial includes the following steps: (1) Weigh out sodium hydroxide and hexadecyltrimethylammonium bromide, add them to ultrapure water, stir vigorously until the two mixtures dissolve, and sonicate for 10-50 minutes; (2) Weigh out zinc acetate and dissolve it in ultrapure water. Add the zinc acetate solution dropwise to the solution after sonication in step (1). After the zinc acetate solution is added, stir for 10-60 minutes until it is evenly mixed. (3) Add stannous chloride to the mixture in step (2), stir for 2-6 hours until homogeneous, and carry out hydrothermal reaction at a temperature of 110-170℃. (4) After the reaction was completed, the sample was centrifuged, washed and dried to obtain Zn2SnO4 octahedral modified ZnO nanosheets. The molar ratio of sodium hydroxide, hexadecyltrimethylammonium bromide, zinc acetate and stannous chloride is (50-85): (20-30): (6-9):

1.

2. The application according to claim 1, characterized in that, The molar ratio of sodium hydroxide, hexadecyltrimethylammonium bromide, zinc acetate and stannous chloride is (60-75):(23-27):(7-8):

1.

3. The application according to claim 1, characterized in that, In step (1), the temperature is room temperature.

4. The application according to claim 1, characterized in that, In step (1), the ultrasonic frequency is 20-40 kHz.

5. The application according to claim 1, characterized in that, In step (2), the zinc acetate solution is added dropwise over 10-30 minutes.

6. The application according to claim 1, characterized in that, The hydrothermal reaction temperature in step (3) is 120-160℃.

7. The application according to claim 1, characterized in that, In step (4), the precipitate is centrifuged and washed at 6000-9000 rpm, first with ultrapure water and then with ethanol. The precipitate after centrifugation is then vacuum dried at 50-70℃ for 2-6 hours.

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