CN109675545B

CN109675545B - SnO with multilayer structurexCatalyst, method for the production and use thereof

Info

Publication number: CN109675545B
Application number: CN201811590954.7A
Authority: CN
Inventors: 张延荣; 潘鸿辉
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2018-12-20
Filing date: 2018-12-20
Publication date: 2020-06-02
Anticipated expiration: 2038-12-20
Also published as: CN109675545A

Abstract

The invention belongs to the field of electrocatalytic materials, and particularly relates to SnO with a multilayer structure_xCatalyst, process for its preparation and use. It fully combines with CO₂The characteristics and requirements of the electrocatalyst are specific to SnO_xRedesigning the preparation process of the catalyst to correspondingly obtain SnO with a multilayer structure prepared by a hydrothermal method through combined action of hydrolysis and coordination_xCatalyst capable of reacting CO₂Selective reduction to HCOO^‑The catalyst is applied to electrocatalytic reduction of CO in aqueous solution₂The catalyst is converted into formate, has excellent catalytic activity, and has good stability and durability, thereby solving the problem that the existing tin oxide catalyst is used for electrocatalytic reduction of CO₂The time efficiency and the stability are not high enough.

Description

SnO with multilayer structurexCatalyst, method for the production and use thereof

Technical Field

The invention belongs to the field of electrocatalytic materials, and particularly relates to a catalyst with multiple functionsSnO of layer structure_xCatalyst, process for its preparation and use.

Background

CO₂As the most dominant greenhouse gas, the contribution rate to the greenhouse effect is about 56%; meanwhile, countries in the world are generally faced with the serious problem of shortage of energy and basic chemical raw materials, and CO₂As a potential carbon resource, the carbon resource is a hot spot for competitive research, development and utilization at home and abroad at present. From CO₂Starting from the raw materials, the raw materials can be directly reduced to synthesize useful chemical products such as methane, methanol, formaldehyde, formic acid, urea, low-carbon hydrocarbons, vinegar carbonate, polymers and the like. Development of CO₂By utilizing the technology, not only can the stone resources such as petroleum, natural gas, coal and the like be saved, but also the harm is changed into treasure, the environmental pollution is reduced, and the economic benefit and the environmental benefit are obvious.

In CO₂In the reduction aspect, three systems are commonly used at present, namely a photocatalytic system, an electrocatalytic system and a photoelectric catalytic system. Because the photoproduction electrons and the holes are easy to be combined, the CO is reduced₂Over-high potential of (A), insufficient stability of the material itself, etc., leading to photocatalytic reduction of CO₂The yield and the light utilization efficiency are very low. The electrocatalytic reaction system is simple, the condition is easy to regulate and control, and the reduction product is easier to separate and recycle. Although the two technologies are coupled by photoelectrocatalysis, the difficulty of matching the two systems is high, the conditions are difficult to control, and the practicability is poor. So that the electrocatalytic technology is more suitable for CO₂And (4) practical application of reduction.

The key is the preparation of the catalyst material. Generally, it is prepared from rare noble metals such as Au, Ag and Pt and heavy metal substances such as Cu and Pb. However, rare metals are expensive, and heavy metals are harmful to human bodies and organisms; on the other hand, the preparation process of the catalyst is complicated and complicated, and is not suitable for large-scale preparation and practicality; moreover, the catalyst has poor stability, and the catalytic performance of the catalyst is greatly reduced and even the catalytic activity of the catalyst is lost after the catalyst is used for a long time or for multiple times. Therefore, the design is cheap, the stability is good, and the carbon dioxide is CO resistant₂The electrocatalytic material with high enrichment efficiency and high selectivity is used for reducing and converting CO₂Has leading edge property.

Tin oxide is a metal inorganic oxide rich in earth crust. Because of good chemical stability, thermal stability and high hydrogen evolution overpotential, the catalyst can activate CO₂And the existing particle structure catalyst with extremely high selectivity has poor stability although the activity is not poor. The main goal of electrocatalysis technology is to prepare cheap, efficient and stable electrocatalysts. Synthesis of SnO_xThe raw materials are cheap, the sources are rich, the method is simple, and the requirement of low price is met. However, the requirements in terms of efficiency and stability are far from being met.

Disclosure of Invention

In response to the above-identified deficiencies in the art or needs for improvement, the present invention provides a SnO having a multilayer structure_xCatalyst, method for its preparation and use, which combines CO well₂The characteristics and requirements of the electrocatalyst are specific to SnO_xRedesigning the preparation process of the catalyst to correspondingly obtain SnO with a multilayer structure prepared by a hydrothermal method through combined action of hydrolysis and coordination_xCatalyst capable of reacting CO₂Selective reduction to HCOO^-The catalyst is applied to electrocatalytic reduction of CO in aqueous solution₂The catalyst is converted into formate, has excellent catalytic activity, and has good stability and durability, thereby solving the problem that the existing tin oxide catalyst is used for electrocatalytic reduction of CO₂The time efficiency and the stability are not high enough.

To achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a SnOx catalyst having a multilayer structure, comprising the steps of:

carrying out hydrothermal reaction on a mixed solution of a divalent metal tin salt, an organic solvent, water and an amino ligand to obtain a sample, washing to remove impurities, and drying to obtain SnO with a multilayer structure_xA catalyst, wherein x is 1-2; wherein:

the organic solvent is used for dissolving the divalent metal tin salt, and the molecular structure composition of the organic solvent does not contain oxygen element;

the water is used for hydrolyzing the divalent metallic tin salt dissolved in the organic solvent and carrying out coordination reaction with the amine-based ligand.

Preferably, the volume ratio of the organic solvent to the water to the amino ligand in the mixed solution is 20:4.25: 0.75-20: 0.75:4.25, and the concentration of the divalent tin metal salt in the mixed solution is 1 g/L-5 g/L.

Preferably, the divalent metallic tin salt is SnCl₂·2H₂O、Sn(NO₃)₂·20H₂O or SnSO₄。

Preferably, the organic solvent is N-dimethylformamide.

Preferably, the hydrothermal reaction temperature is 150-220 ℃, and the hydrothermal reaction time is 1-6 hours.

Preferably, the hydrothermal reaction temperature is 180-200 ℃, and the hydrothermal reaction time is 2-4 hours.

Preferably, the obtained sample is washed by a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and is dried in vacuum at 40-80 ℃ for more than 8 hours to obtain SnO with a multilayer structure_xA catalyst.

Preferably, the vacuum drying temperature is 50-70 ℃, and the vacuum drying time is 10-12 hours.

In accordance with another aspect of the present invention, there is provided a multilayer SnO_xThe catalyst is prepared according to the preparation method.

According to another aspect of the present invention, there is provided said SnO having a multilayer structure_xApplication of catalyst in electrocatalytic selective reduction of CO in aqueous solution₂Converted to formate.

Preferably, the SnO having a multilayer structure_xCatalyst in CO₂Saturated 0.1 mol/L-0.5 mol/LNaHCO₃Applying a potential of-1.2V to-2.0V (vs. SCE) in the electrolyte solution to selectively reduce CO₂Converted to formate.

Preferably, NaHCO is present in said electrolyte solution₃The concentration of (B) is 0.1mol/L to 0.3 mol/L.

Preferably, the applied potential is between-1.4V and-1.9V (vs. SCE), which represents the potential applied relative to a saturated calomel electrode.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) the invention obtains a SnOx catalyst with a multilayer structure by a hydrothermal method through combined action of hydrolysis and coordination, and the catalyst can convert CO₂Selective reduction to HCOO^-The catalyst is applied to electrocatalytic reduction of CO in aqueous solution₂Converted to formate.

(2) The invention successfully prepares the multilayer SnO with simple preparation process, rich raw material resources and low price_xA catalyst, provides an electrocatalytic selective reduction of CO₂Conversion to formate. The catalyst shows higher electrocatalyst activity and selectivity, which indicates that the catalyst is suitable for practical production and application;

(3) the multilayer SnO prepared by the invention_xThe catalyst is an inorganic oxide, has stable property, no metal dissolution, safety and no toxicity, so the catalyst can be widely used, and simultaneously, a compact oxidation film is formed on the surface of the catalyst and is very stable at normal temperature.

(4) SnO of the present invention having a multilayer Structure_xThe catalyst not only improves the catalytic activity, but also greatly improves the stability and the durability. When the catalyst is actually applied, no metal ions are dissolved out in the electrocatalytic reduction process, and the repeated utilization rate of the catalyst is extremely high, so the catalyst has excellent durability.

Drawings

FIG. 1 is a multilayer SnO_xScanning electron micrographs of the catalyst;

FIG. 2 is a multilayer SnO_xX-ray diffraction pattern of the catalyst;

FIG. 3(a) is a multilayer SnO_xLinear sweep voltammogram, FIG. 3(b) is a multilayer SnO_xThe catalysts react for 4 hours at-1.4V to-2.0V (vs. SCE) respectively to produce the Faraday efficiency of formate;

FIG. 4(a) is a multilayer SnO_xThe catalyst was reacted at-1.8V (vs. SCE) for 40 hoursCurrent density profile, FIG. 4(b) is a multilayer SnO_xFaradaic efficiency of the catalyst to formate when reacting at-1.8V (vs. SCE) for 40 hours;

FIG. 5 is a multilayer SnO_xThe catalyst reacts for 4 hours at-1.8V (vs. SCE) to carry out repeatability test;

FIGS. 6(a) and (b) are SnO having a granular structure_xScanning electron micrograph (c).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides SnO with a multilayer structure_xThe preparation method of the catalyst comprises the following steps:

carrying out hydrothermal reaction on a mixed solution of a divalent metal tin salt, an organic solvent, water and an amino ligand to obtain a sample, washing to remove impurities, and drying to obtain SnO with a multilayer structure_xA catalyst, wherein x is 1-2; i.e., it is a mixture of tin monoxide and tin dioxide, wherein,

the organic solvent is used for dissolving the divalent metal tin salt, and the molecular structure composition of the organic solvent does not contain oxygen element; it has been found that when the organic solvent is replaced by an oxygen-containing organic solvent, or water, the resulting product is tin dioxide, rather than a mixture of tin monoxide and tin dioxide.

The water is used for hydrolyzing the divalent metallic tin salt dissolved in the organic solvent to generate Sn (OH)₂And further form [ Sn (OH)₄]^2-Amines capable of coordinating the OH group^-Ligand, reducing surface activation energy, forming specific layered structure.

The control of the raw materials in the preparation process of the invention in a proper range is important for obtaining the SnOx with the layered structure, the volume ratio of the organic solvent, the water and the amine ligand in the mixed solution is 20:4.25: 0.75-20: 0.75:4.25 in some embodiments, and the concentration of the divalent metal tin salt in the mixed solution is 1 g/L-5 g/L.

In some embodiments, the divalent metallic tin salt is SnCl₂·2H₂O、Sn(NO₃)₂·20H₂O or SnSO₄Preferably SnCl₂·2H₂O。

In some embodiments, the organic solvent is N-dimethylformamide.

In some embodiments, the hydrothermal reaction temperature is 150 ℃ to 220 ℃, preferably 180 ℃ to 200 ℃, and the hydrothermal reaction time is 1 hour to 6 hours, preferably 2 hours to 4 hours.

In a preferred embodiment, SnCl is added₂·2H₂Adding O into the N-N-dimethylformamide mixed solution, fully stirring and uniformly mixing, then adding the mixture into the mixed solution according to the volume ratio of water to N-butylamine of 0.1-4.25, fully stirring and uniformly mixing, and carrying out hydrothermal reaction in a high-pressure reaction kettle at the temperature of 150-220 ℃ for 1-6 hours. The prepared sample is washed by a mixed solution of cyclohexane and ethanol to remove impurities, the cyclohexane is used for washing away nonpolar impurities, the ethanol is used for washing away polar impurities, and the mixed solution of cyclohexane and ethanol with equal volume is preferably adopted to be dried for more than 8 hours under vacuum at the temperature of 40-80 ℃, so that multilayer SnO can be obtained_xA catalyst.

In some preferred embodiments, the vacuum drying temperature is 50 ℃ to 70 ℃, and the vacuum drying time is 10 hours to 12 hours.

Multilayer SnO prepared by the invention_xCatalyst for electrocatalytic selective reduction of CO in aqueous solution₂Converted to formate.

In particular applications, in some embodiments, the multilayer SnOx catalyst is applied to CO₂Saturated 0.1 mol/L-0.5 mol/L NaHCO₃Applying a potential of-1.2V to-2.0V (vs. SCE) in the electrolyte solution to selectively reduce CO₂Converted to formate. Preferably NaHCO in said electrolyte solution₃The concentration of (A) is 0.1mol/L to 0.3mol/L. The applied potential is-1.4V to-1.9V (vs. SCE), and the electrocatalytic performance is better.

In addition to the generation of CO during the above-mentioned electrocatalytic reduction process₂Reduction to formate also accompanied by other side reactions such as hydrogen evolution produces H₂CO, and the like, and the SnO with a laminated structure prepared by the method_xCatalyst for electrocatalytic reduction of CO₂In the process, it catalyzes CO₂The Faraday efficiency of reducing the metal into formate is up to 67.66 percent, which shows that the multilayer SnO_xCatalyst pair CO₂The reduction has high selectivity and high catalytic activity, and the hydrogen evolution reaction is inhibited to a high degree.

The following are examples:

example 1

50mg of SnCl₂·2H₂Adding O into 20ml of N-N-dimethylformamide mixed solution, fully stirring and uniformly mixing, and then mixing the mixture with a total volume of 5ml and a volume ratio of 1: 1, mixing the water and the n-butylamine solution, adding the mixture into the mixed solution, fully stirring and uniformly mixing, and carrying out hydrothermal reaction in a high-pressure reaction kettle for 3 hours at the temperature of 200 ℃. Washing the prepared sample with a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and drying the sample in vacuum for 12 hours at the temperature of 60 ℃ to obtain multilayer SnO_xA catalyst.

According to the analysis of the results carried out on the catalysts prepared in the examples:

(1) multilayer SnO_xScanning electron microscope image of catalyst

As can be seen from FIG. 1, the prepared catalyst has a multilayer structure, which indicates that the applied hydrolytic coordination hydrothermal synthesis method successfully prepares SnO with a multilayer structure_xA catalyst.

(2) X-ray diffraction spectrum of multilayer SnOx catalyst

As shown in fig. 2, the X-ray diffraction pattern of the catalyst showed that peaks appearing at 18.3 °,29.9 °,33.3 °, 37.2 °,47.8 °,50.8 °,57.4 °,62.5 °,79.2 ° correspond to (001), (101), (110), (002), (200), (112), (211), (103), (004) crystal planes of SnO. Peaks appearing at 22.6 °,33.8 °,51.8 ° correspond to SnO₂The (110), (101), (211) crystal planes of (1). These results surface multilayer catalysts in mixed crystal phaseSnO_xAnd x is between 1 and 2.

(3) Electrochemical performance testing of multilayer SnOx catalyst

The multilayer SnOx catalyst is made into a working electrode, a platinum sheet is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode. NaHCO with electrolyte volume of 60mL and concentration of 0.1mol/L₃And (3) solution. Before the experiment, CO is introduced into the electrolyte solution₂Gas is used for 30min, electrochemical test is carried out by using an electrochemical workstation after saturated equilibrium is reached, and generated HCOO is detected by using ion chromatography^-And (4) concentration.

As shown in FIG. 3(a), by respectively saturating N₂And CO₂The electrolyte solution of (a) is subjected to a linear scanning test, the scanning range is-0.4V to-2.0V (vs. SCE), and the scanning speed is 20mV^-1. The results show that saturated CO was introduced₂Is far larger than the current of the saturated N₂Indicating multilayer SnO_xCatalyst pair CO₂The reduction has very good catalytic activity; as shown in FIG. 3(b), a multilayer SnO_xCatalyst in CO₂Saturated 0.1mol/L NaHCO₃Electrolyte solution is applied with a potential of-1.4V to-1.9V (vs. SCE) for 4 hours to perform selective CO reaction₂Reduced to formate. Wherein when the applied potential is-1.8V (vs. SCE), the voltage is applied to CO₂The Faraday efficiency of reducing formate to 67.66% shows that multilayer SnO_xCatalyst pair CO₂The reduction has high selectivity and high catalytic activity.

(4) Multilayer SnO_xCatalyst stability;

as shown in FIG. 4(a), multilayer SnO_xCatalyst in CO₂Saturated 0.1mol/L NaHCO₃Electrolyte solution, applied with a potential of-1.8V (vs. SCE) for 40 hours for selective CO₂Reduced and converted into formate, and the current density is maintained at-1.5 mA/cm²～-2.0mA/cm²And substantially no attenuation. For selective CO, as shown in FIG. 4(b)₂The Faraday efficiency of the reduction and conversion into formate maintains about 67 percent. These results show that multilayer SnO_xCatalyst pair CO₂The reduction has excellent stability.

(5) Multilayer SnO_xCatalyst durability;

as shown in fig. 5, multilayer SnO_xCatalyst in CO₂Saturated 0.1mol/L NaHCO₃Electrolyte solution, applied potential of-1.8V (vs. SCE), for 4 hours of reaction, selective CO₂Reductive conversion to formate for 5 replicates, CO₂The faradaic efficiency of the reductive conversion to formate remained around 67%, indicating that the multilayer SnOx catalyst pair possessed superior durability.

From the above analysis, it can be seen that the multilayer SnO prepared by the method of this example_xElectrocatalytic reduction of CO by catalyst in aqueous solution₂The conversion into formate has strong catalytic activity and selectivity, and the catalyst has excellent stability and durability and is more beneficial to practical application.

Example 2

50mg of SnCl₂·2H₂Adding O into 20ml of N-N-dimethylformamide mixed solution, fully stirring and uniformly mixing, and then mixing the mixture with a total volume of 5ml and a volume ratio of 4: 1, mixing the water and the n-butylamine solution, adding the mixture into the mixed solution, fully stirring and uniformly mixing, and carrying out hydrothermal reaction in a high-pressure reaction kettle for 3 hours at the temperature of 200 ℃. Washing the prepared sample with a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and drying the sample in vacuum for 12 hours at the temperature of 60 ℃ to obtain multilayer SnO_xA catalyst.

SnO prepared by applying the conditions_xAlso has a multilayer structure, and the performances are basically similar, and the Faraday efficiency is up to more than 60%.

Example 3

50mg of SnCl₂·2H₂Adding O into 20ml of N-N-dimethylformamide mixed solution, fully and uniformly stirring, then mixing water with the total volume of 5ml and the volume ratio of 1:4 with N-butylamine solution, adding into the mixed solution, fully and uniformly stirring, and carrying out hydrothermal reaction in a high-pressure reaction kettle at the temperature of 200 ℃ for 3 hours. Washing the prepared sample with a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and drying the sample in vacuum for 12 hours at the temperature of 60 ℃ to obtain multilayer SnO_xA catalyst.

Comparative example 1

50mg of SnCl₂·2H₂And adding O into 20ml of N-N-dimethylformamide mixed solution, fully and uniformly stirring, then adding 5ml of water into the mixed solution, fully and uniformly stirring, and carrying out hydrothermal reaction in a high-pressure reaction kettle at the temperature of 200 ℃ for 3 hours. Washing the prepared sample with a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and drying the sample in vacuum for 12 hours at the temperature of 60 ℃ to obtain multilayer SnO_xA catalyst.

As can be seen from fig. 6(a), a multilayer structure cannot be constructed without adding a complexing agent, and only a particle structure is formed, indicating that the complexing action plays a key role in the formation of the multilayer structure.

Comparative example 2

50mg of SnCl₂·2H₂And O is added into 20ml of N-N-dimethylformamide mixed solution to be fully stirred and uniformly mixed, then 5ml of N-butylamine is mixed and added into the mixed solution to be fully stirred and uniformly mixed, and the mixture is subjected to hydrothermal reaction for 3 hours in a high-pressure reaction kettle at the temperature of 200 ℃. Washing the prepared sample with a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and drying the sample in vacuum for 12 hours at the temperature of 60 ℃ to obtain multilayer SnO_xA catalyst.

As can be seen from fig. 6(b), the multilayer structure cannot be constructed without adding water, and only the granular structure is formed, indicating that hydrolysis plays a key role in the formation of the multilayer structure.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. SnO with multilayer structure_xThe preparation method of the catalyst is characterized by comprising the following steps:

carrying out hydrothermal reaction on a mixed solution of a divalent metal tin salt, an organic solvent, water and an amino ligand to obtain a sample, washing to remove impurities, and drying to obtain SnO with a multilayer structure_xA catalyst, wherein x is 1-2; wherein: the volume ratio of the organic solvent to the water to the amino ligand in the mixed solution is 20:4.25: 0.75-20: 0.75: 4.25; the hydrothermal reaction temperature is 150-220 ℃;

the organic solvent is used for dissolving the divalent metal tin salt, and the molecular structure composition of the organic solvent does not contain oxygen element; the organic solvent is N-N-dimethylformamide;

2. The method according to claim 1, wherein the concentration of the divalent metallic tin salt in the mixed solution is 1g/L to 5 g/L.

3. The method of claim 1, wherein the divalent tin metal salt is SnCl₂·2H₂O、Sn(NO₃)₂·20H₂O or SnSO₄。

4. The method according to claim 1, wherein the hydrothermal reaction temperature is 180 ℃ to 200 ℃ and the hydrothermal reaction time is 1 hour to 6 hours.

5. The preparation method according to claim 1, wherein the obtained sample is washed with a mixed solution of cyclohexane and ethanol in an equal volume ratio to remove impurities, and is dried under vacuum at 40-80 ℃ for more than 8 hours to obtain multilayer SnO_xA catalyst.

6. SnO with multilayer structure_xThe catalyst is characterized by being prepared according to the preparation method of any one of claims 1 to 5.

7. SnO having multilayer structure according to claim 6_xThe application of the catalyst is characterized in that the catalyst is applied to electrocatalytic selective reduction of CO in aqueous solution₂Converted to formate.

8. The use according to claim 7, wherein said SnO having a multilayer structure_xCatalyst in CO₂Saturated 0.1 mol/L-0.5 mol/L NaHCO₃In the electrolyte solution, the applied potential of the saturated calomel electrode is-1.2V to-2.0V, and CO is selectively reduced₂Converted to formate.

9. The use according to claim 8, wherein the applied potential is between-1.4V and-1.9V relative to the saturated calomel electrode.