CN112877720B

CN112877720B - S-doped Sn oxide catalytic electrode and preparation and application thereof

Info

Publication number: CN112877720B
Application number: CN202110145142.7A
Authority: CN
Inventors: 龙玉佩; 张轶; 马浩; 张广峰; 沈阳; 王洪君; 李方颖; 强涛; 曾林; 丛燕青; 王齐
Original assignee: Zhejiang Gongshang University
Current assignee: Zhejiang Gongshang University
Priority date: 2021-02-02
Filing date: 2021-02-02
Publication date: 2022-06-14
Anticipated expiration: 2041-02-02
Also published as: CN112877720A

Abstract

The invention discloses an S-doped Sn oxide catalytic electrode, a preparation method thereof and application thereof in reduction of carbon dioxide to produce formate and formaldehyde. The preparation method comprises the following steps: mixing S-SnO₂Uniformly dispersing nano material powder, multi-walled carbon nano tubes and a surfactant in ethylene glycol to obtain a mixed solution, soaking and absorbing a substrate electrode in the mixed solution, taking out and drying to obtain the S-SnO load₂And multiwall carbon nanotube electrodes, i.e., S-doped Sn oxide catalytic electrodes; S-SnO₂The preparation method of the nano material powder comprises the following steps: (1) adding NaOH and SnCl₄·5H₂O and Na₂S₂O₃·5H₂Mixing and grinding O in a molar ratio of 1-3: 0.05-0.15: 0.03-0.07 for 5-20 min, standing and aging for 2-4 h, and then, heating in an oven at 120-180 ℃ for 1-3 h to obtain a precursor mixture; (2) stirring and soaking the precursor mixture in deionized water for 0.5-1.5 h, then centrifugally washing and cleaning, and finally drying at 60-120 ℃ to obtain S-SnO₂A nanomaterial powder.

Description

S-doped Sn oxide catalytic electrode and preparation and application thereof

Technical Field

The invention relates to the technical field of carbon dioxide reduction, in particular to an S-doped Sn oxide catalytic electrode, a preparation method thereof and application thereof in producing formate and formaldehyde by carbon dioxide reduction.

Background

After the human beings enter the industrial era, the demand for energy is continuously increased, and the energy crisis becomes a main problem restricting the development of the human beings. At the same time, excessive use of fossil fuels leads to large amounts of CO₂The emission of gases into the atmosphere, in turn, causes serious environmental problems, namely the "greenhouse effect", the direct consequence of which is global warming. In the face of energy crisis and greenhouse effect, it is desirable to capture and store CO₂But CO₂There are many problems with storage, such as leakage concerns. Therefore, in recent years, it has become possible to treat CO₂The resource recycling of the organic acid has attracted the attention of researchers.

Formic acid and formates (HCOOH and HCOO)^-) It is a basic organic chemical raw material, can be directly used as fuel of fuel cell, also can be used as means for storing hydrogen gas and can be used as raw material for synthesizing fine chemicals. Formaldehyde is one of the most important chemicals in the world. It is used as a feedstock for over 50 industries and is currently growing at a rate of 5.4% per year worldwide due to its high demand in various industrial applications. Thus, reducing CO₂Produce formate and formaldehyde, and can solve CO₂The environmental problem brought by the method can be relieved, and the restriction development caused by energy crisis can be relieved.

However, CO ₂Is a completely oxidized and thermodynamically very stable molecule, so that a proper catalyst not only can reduce the energy consumption of the reaction process to the maximum extent, but also can assist CO₂And (4) transformation of a reduction technology. It is therefore important to develop a highly active, selective and stable catalyst to promote the reduction of carbon dioxide.

Patent specification publication No. CN 110052281A discloses oxygen vacancy enrichmentThe preparation process includes roasting dicyandiamide at specific temperature and time and obtaining block C₃N₄Grinding to powder, calcining at specific temperature and time to obtain g-C₃N₄Nanosheet and SnCl₂·2H₂Grinding and mixing O according to the mass ratio of 1:1, roasting at a specific temperature and time, collecting and grinding the obtained product to obtain Ov-N-SnO₂A nanoparticle; the oxygen vacancy enriched nitrogen doped tin oxide can be applied to preparing formic acid by electrocatalysis of carbon dioxide reduction.

Patent specification CN 110484930 a discloses an electrode for reducing carbon dioxide to produce formic acid, and a preparation method and application thereof, wherein the preparation method comprises the following steps: zn is added_0.5Cd_0.5Dissolving the composite material of the S solid solution and the CoP nanowire, the multi-walled carbon nanotube and the surfactant in ethylene glycol, impregnating the foamed nickel in the solution, taking out and drying to obtain the loaded Zn _0.5Cd_0.5S solid solution, CoP nano wire and multi-wall carbon nano tube.

Disclosure of Invention

Aiming at the defects in the field, the invention provides the preparation method of the S-doped Sn oxide catalytic electrode, the preparation method is simple, the prepared electrode has stable and efficient practical application effect, and CO can be reduced₂Formate and formaldehyde are produced.

A method of making an S-doped Sn oxide catalytic electrode, comprising: mixing S-SnO₂Uniformly dispersing nano material powder, multi-walled carbon nanotubes (MWNTs) and a surfactant in ethylene glycol to obtain a mixed solution, soaking and absorbing a substrate electrode in the mixed solution, taking out and drying to obtain the S-SnO load₂And a multi-walled carbon nanotube electrode, i.e., the S-doped Sn oxide catalytic electrode;

the S-SnO₂The preparation method of the nano material powder comprises the following steps:

(1) crystallizing sodium hydroxide (NaOH) and stannic chloride (SnCl) pentahydrate₄·5H₂O) and sodium thiosulfate pentahydrate (Na)₂S₂O₃·5H₂O) mixing and grindingGrinding, standing and aging, and then heating in an open mouth in a drying oven to obtain a precursor mixture;

(2) stirring and soaking the precursor mixture by deionized water, centrifugally washing the precursor mixture, and drying the precursor mixture to obtain the S-SnO₂A nanomaterial powder.

In the step (1), the molar ratio of the sodium hydroxide to the crystalline stannic chloride pentahydrate to the sodium thiosulfate pentahydrate is 1-3: 0.05-0.15: 0.03-0.07.

In the step (1), the mixing and grinding time is 5-20 min.

In the step (1), the standing and aging time is 2-4 h.

In the step (1), the open heating temperature is 120-180 ℃, and the time is 1-3 h.

In the step (2), the deionized water is stirred and soaked for 0.5-1.5 h, and the drying temperature is 60-120 ℃.

The S-SnO prepared by the special preparation method₂The nano material powder is one of the raw materials, and is further cooperated with the multi-wall carbon nano tube to be modified and fixed on the substrate electrode by an immersion method, and the obtained composite catalytic electrode has excellent performance of reducing carbon dioxide to produce formate and formaldehyde under the plasma technology.

According to the preparation method of the S-doped Sn oxide catalytic electrode, the substrate electrode can be sponge, foamed nickel, carbon paper, carbon felt or the like, and is preferably a sponge electrode. The sponge has light weight, high porosity, strong adsorbability and plasticity, and can adsorb multi-wall carbon nanotubes and nanomaterials on an electrode, and greatly improve CO synergistically when a reaction is carried out on the electrode₂The reducing effect of (3).

The S-SnO₂The mass ratio of the nano material powder to the multi-walled carbon nano tube is preferably 0.1-0.4: 1, and the obtained composite catalytic electrode has the best performance of cooperatively reducing carbon dioxide by plasma to produce formate and formaldehyde. S-SnO ₂The combination of the nano material and the multi-wall carbon nano tube can improve the electrocatalytic performance of the metal material and obtain the hybrid material capable of promoting charge transfer. S-SnO₂When the concentration of the nano material is too highThe agglomeration phenomenon can be caused, the performance of the catalyst is reduced in the catalysis process, when the concentration is too low, the catalyst is easily wrapped by the multi-wall carbon nano tube and can not be uniformly exposed on the surface of the electrode, and the catalysis performance of the electrode in the system is also reduced.

In the preparation method of the S-doped Sn oxide catalytic electrode, the surfactant has no special requirement, and the surfactant commonly used in the field, such as sodium dodecyl benzene sulfonate and the like, can be used. The addition amount can be controlled according to the requirement of the dispersion degree.

The invention also provides the S-doped Sn oxide catalytic electrode prepared by the preparation method of the S-doped Sn oxide catalytic electrode.

As a general inventive concept, the invention also provides an application of the S-doped Sn oxide catalytic electrode in the reduction of carbon dioxide to produce formate and formaldehyde. The S-doped Sn oxide catalytic electrode is preferably used as a plasma discharge electrode for the plasma synergistic reduction of carbon dioxide to produce formate and formaldehyde.

In a preferred embodiment, the application is that carbonate solution is used as electrolyte, the S-doped Sn oxide catalytic electrode is used as an electrode, the electrode is arranged in the electrolyte, the dielectric baffle is horizontally arranged above the electrolyte, the area between the electrode and the dielectric baffle is a discharge area, and the CO is catalytically reduced by adopting dielectric barrier discharge plasma ₂Producing formate and formaldehyde.

Preferably, the distance between the dielectric baffle and the surface of the electrolyte is 2-8 mm. The dielectric baffle plate has a high energy loss due to a high distance from the surface of the electrolyte, and cannot stably discharge due to a low distance.

Preferably, the dielectric barrier discharge adopts 20-40V pulse voltage and 1-10 kHz pulse frequency. If the voltage is too high, the electrode is easy to damage, and the stability of the electrode material is influenced, and if the voltage is too low, continuous and stable discharge cannot be realized. The pulse frequency has the same influence law as the voltage. Within the above preferred range, the electrode has better catalytic reduction of CO in the system₂The effect of (1).

Compared with the prior art, the invention has the main advantages that:

(1) S-SnO of the present invention₂The nano material is prepared by doping S to change the local structure of the catalyst and generate external defects, S and SnO₂The interaction synergistically increases the reactivity and conductivity of the material, thereby increasing the activity of reducing carbon dioxide.

(2) S-SnO using the present invention₂The composite catalytic electrode is used for reducing carbon dioxide, and the rates of generating formate and formaldehyde can respectively reach 160.44 mu mol.h^-1And 2.03. mu. mol. h^-1。

(3) The invention is simple and easy to operate, the raw materials do not contain any noble metal, and the reserves of all elements in the nature are rich, thereby being beneficial to popularization and application.

(4) Compared with undoped SnO₂The stability of the S-doped Sn oxide catalytic electrode prepared by the invention and the selectivity of reducing carbon dioxide to produce formate and formaldehyde are obviously improved.

Drawings

FIG. 1 shows S-SnO₂Scanning Electron Microscope (SEM) photograph of/MWNTs/sponge electrode;

FIG. 2 is SnO₂MWNTs/sponge electrode and S-SnO₂Linear cyclic voltammogram of/MWNTs/sponge electrode;

fig. 3 is a graph of the yields of formate (a) and formaldehyde (b) under the action of dielectric barrier discharge plasma of two electrode materials of an application example.

Detailed Description

The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.

Examples

1、S-SnO₂The preparation method of the nano material comprises the following steps:

1) adding 0.2mol of NaOH and 0.01mol of SnCl₄·5H₂O and 0.005mol of Na₂S₂O₃·5H₂Grinding for 10min, standing, aging for 3 hr, and transferring into ovenHeating the mixture for 1h at 150 ℃ in an open way to obtain a precursor mixture.

2) And stirring and soaking the obtained precursor mixture in deionized water for 1h, centrifugally cleaning the obtained sample for 3 times by using the deionized water, and finally drying at 100 ℃ to obtain yellow sample powder.

2、S-SnO₂The preparation method of the/MWNTs/sponge electrode comprises the following steps:

I) preparing a stock solution: weighing 0.4g of multi-walled carbon nanotube, 4g of sodium dodecylbenzenesulfonate and 0.1g of the above S-SnO₂The nano material is uniformly dispersed in 100mL of glycol, stirred for 1h and subjected to ultrasonic treatment for 1h for later use.

II) soaking and absorbing. 1, soaking and sucking: 4mL of the stock solution was pipetted onto a sponge and then removed for drying at 90 ℃ for 10 h. Soaking and sucking for 2 and 3 times: soaking 3mL of multi-walled carbon nanotube stock solution on a sponge, taking out and drying at 90 ℃ for 10h to obtain S-SnO₂MWNTs/sponge electrode, size of sponge: 70 mm. times.1.5 mm. times.0.5 mm. The SEM photograph is shown in FIG. 1.

Comparative example

SnO was prepared by the same method as in example₂MWNTs/sponge electrode, with the difference that S-SnO is introduced₂Replacement by undoped SnO₂. Wherein, the non-doped SnO₂The preparation method comprises the following steps: 7g of SnCl₄·5H₂O was dissolved in distilled water to form a clear solution. Aqueous ammonia was added dropwise to the solution under magnetic stirring until pH 9. The precipitate formed was washed several times with deionized water by centrifugation and then dried overnight at 60 ℃. Calcining the obtained powder in a muffle furnace at 550 ℃ for 4h at a heating rate of 5 ℃/min, and then cooling to room temperature at a rate of 5 ℃/min to obtain yellow SnO ₂And (3) powder.

For exploring the electrocatalytic properties of the prepared catalyst, S-SnO₂MWNTs/sponge electrode and SnO₂MWNTs/sponge electrodes in CO respectively₂And N₂LSV detection was performed in saturated electrolyte solution. The experimental conditions were: an electrode (1cm multiplied by 1cm) is pasted on FTO conductive glass through conductive adhesive to be used as a working electrode, a platinum plate (2cm multiplied by 2cm) is used as a counter electrode, a saturated Ag/AgCl electrode is used as a reference electrode, and an electrolyte solution is 0.1mol/L KHCO₃The scanning speed is 20mV/s, and the scanning range is-0.1 to-2.1V. As can be seen from FIG. 2, the two electrodes are at CO₂Current density in saturated solution compared to that in N₂A significant increase in saturated solution, indicating CO₂Reduction occurs. Furthermore, S-SnO₂The current density of the/MWNTs/sponge electrode is larger, and the peak potential of the/MWNTs/sponge electrode is shifted positively, which indicates that the/MWNTs/sponge electrode has CO₂The reduction effect is better.

From the analysis results, the S-SnO prepared by the invention₂the/MWNTs/sponge electrode has excellent catalytic carbon dioxide reduction activity.

Application example

The application example adopts plasma to catalyze and reduce CO₂Is formate and formaldehyde with 0.1mol/L KHCO₃As an electrolyte by using CO₂Vigorous bubbling of 0.1mol/L KOH for at least 20min, and confirmed a pH of 6.8 before use.

Mixing 0.1mol/L KHCO₃The electrolyte was transferred to a cylindrical quartz cell, and the electrode material of the example or comparative example was added, and the electrode material absorbed water and sunk into the electrolyte.

The plasma catalytic reduction process is carried out in a reaction chamber, the reaction chamber is a stainless steel box body, and the shell of the box body is grounded. A Dielectric Barrier Discharge (DBD) reactor is arranged in the reaction chamber and comprises an upper polar plate and a lower polar plate. The bottom surface of the upper polar plate is fixed with a quartz medium baffle plate, and the upper polar plate is connected with an experimental power supply through a high-voltage wire. The cylindrical quartz cell is used as a reaction container and is arranged on the lower polar plate, 100mL of electrolyte is contained, and the distance between the quartz medium baffle and the surface of the electrolyte solution is 2 mm. The voltage regulator regulates the discharge pulse voltage of the experimental power supply, controls the pulse voltage to be 30V and controls the pulse frequency to be 10 kHz.

One sample was taken at 20min and the amount of formate produced was determined by Saimer ion chromatograph with a Dionex IonPac AG23 (4X 250mm) column and guard column. And detecting the formaldehyde content by adopting an acetylacetone spectrophotometry.

The S-SnO of examples were used respectively₂MWNTs/sponge electrode and SnO of comparative example₂Reduction of CO by MWNTs/sponge electrode under action of dielectric barrier discharge plasma₂Producing formate and formazanThe aldehyde, formate and formaldehyde yields vs. time are shown in figure 3. As can be seen in the figure, S-SnO ₂The amount of formate and formaldehyde produced by the/MWNTs/sponge electrode is obviously superior to that of SnO₂MWNTs/sponge electrodes, since sulfur doping changes the local structure of the catalyst and creates external defects, S and SnO₂The interaction synergistically improves the conductivity and activity of the electrode, thereby improving the catalytic conversion efficiency of the reaction.

Furthermore, it should be understood that various changes or modifications can be made by those skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention defined by the appended claims.

Claims

1. A preparation method of an S-doped Sn oxide catalytic electrode is characterized by comprising the following steps: mixing S-SnO₂Uniformly dispersing nano material powder, multi-walled carbon nano tubes and a surfactant in ethylene glycol to obtain a mixed solution, soaking and sucking a substrate electrode in the mixed solution, taking out and drying to obtain the S-SnO loaded material₂And a multi-walled carbon nanotube electrode, i.e., the S-doped Sn oxide catalytic electrode;

(1) adding NaOH and SnCl₄·5H₂O and Na₂S₂O₃·5H₂Mixing and grinding O in a molar ratio of 1-3: 0.05-0.15: 0.03-0.07 for 5-20 min, standing and aging for 2-4 h, and then heating in an oven at 120-180 ℃ for 1-3 h in an open manner to obtain a precursor mixture;

(2) Stirring and soaking the precursor mixture for 0.5-1.5 h by using deionized water, then centrifugally washing the precursor mixture, and finally drying the precursor mixture at the temperature of 60-120 ℃ to obtain the S-SnO₂A nanomaterial powder.

2. The method of claim 1, wherein the substrate electrode is a sponge, a nickel foam, a carbon paper, or a carbon felt.

3. The method of claim 1The preparation method of the S-doped Sn oxide catalytic electrode is characterized in that the S-SnO₂The mass ratio of the nano material powder to the multi-walled carbon nano tube is 0.1-0.4: 1.

4. The S-doped Sn oxide catalytic electrode prepared by the preparation method of the S-doped Sn oxide catalytic electrode according to any one of claims 1 to 3.

5. Use of the S-doped Sn oxide catalytic electrode of claim 4 in the reduction of carbon dioxide to formate and formaldehyde.

6. The use of claim 5, wherein the carbonate solution is used as electrolyte, the S-doped Sn oxide catalytic electrode is used as electrode, the electrode is placed in the electrolyte, the dielectric baffle is horizontally placed above the electrolyte, the area between the electrode and the dielectric baffle is a discharge area, and the CO is catalytically reduced by using dielectric barrier discharge plasma ₂Producing formate and formaldehyde.

7. The use according to claim 6, wherein the distance between the dielectric barrier and the surface of the electrolyte is 2-8 mm.

8. The use of claim 6, wherein the dielectric barrier discharge uses a pulse voltage of 20-40V and a pulse frequency of 1-10 kHz.