CN117568843A - Selenium-defect-enriched tin diselenide nanosheet electrocatalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a method for preparing a tin selenide nanosheet electrocatalyst rich in selenium defects: dissolving selenium dioxide and metal tin salt, adding hydrazine hydrate solution, stirring and mixing, and obtaining selenium-rich defects through hydrothermal reaction. tin diselenide nanosheet electrocatalyst. The invention also discloses the selenium-deficient tin diselenide nanosheet electrocatalyst obtained by the above preparation method and its application as a working electrode in the electrosynthesis of formic acid. The catalyst provided by the invention achieves high selectivity for HCOOH electrosynthesis in alkaline, neutral and acidic electrolytes respectively. Under corresponding pH conditions, the HCOOH bias current density reaches the industrial level, fully demonstrating its excellent performance in the entire pH range. HCOOH electrosynthetic properties.

Description

A kind of tin diselenide nanosheet electrocatalyst rich in selenium defects and preparation method thereof and application

Technical field

The invention relates to the technical field of electrocatalysts, and in particular to a tin diselenide nanosheet electrocatalyst rich in selenium defects and its preparation method and application.

Background technique

Renewable energy is used to electrically reduce carbon dioxide (CO ₂ ) into high value-added carbon-containing chemicals (such as carbon monoxide, formic acid, and methane). Among various reduction products, formic acid (HCOOH) is considered to be the most technically and economically efficient. One of the products has been widely used in practical applications. To date, several major p-block metal main group catalysts, including Sn, In, and Bi, etc., as well as a series of corresponding metal oxides (such as tin oxide and indium oxide) have been reported for the synthesis of HCOOH via electroreduction of _CO2 . Among them, metal tin-based materials are widely used in the electroreduction of CO2 to synthesize HCOOH due to their low cost and moderate adsorption energy for the * _OOCH intermediate in the electrosynthesis of HCOOH. However, currently reported metallic tin-based catalysts still face significant challenges in achieving the electrosynthesis of HCOOH at highly selective industrial-grade current densities (>200 mA cm ^-2 ).

Currently, HCOOH electrosynthesis is mostly carried out in alkaline or neutral electrolytes, so carbonate by-products are inevitably formed, resulting in reduced _CO utilization efficiency. Using acidic electrolyte is one of the effective ways to solve these problems. However, achieving sustained and efficient _CO conversion in acidic electrolytes still faces huge challenges due to the competitive hydrogen evolution side reaction and inevitable proton concentration changes during the electroreduction of _CO . Therefore, in industrial applications, it is very necessary to develop ideal catalysts that work well in the full pH range. For example, the Chinese patent document with publication number CN115584522A discloses a three-dimensional porous electrode preparation method and its application in acidic electrocatalytic CO ₂ reduction to prepare formic acid. The catalyst, polymer, and organic solvent are mixed evenly to form a composite slurry, and the paste is spread with a scraper. The shape is uniformly coated on the carbon cloth to obtain an unshaped embryo body, and finally a three-dimensional porous electrode is obtained through drying, which enables the preparation of HCOOH by electroreduction under acidic conditions with a pH of less than 3.77.

Due to the slow reaction kinetics during proton formation and transport, the formation of the *OOCH intermediate is usually the rate-determining reaction step. Therefore, accelerating the generation and transfer of protons is an effective method to increase the generation rate of *OOCH/HCOOH. The introduction of defect structures is considered to be one of the most direct and effective methods to regulate metal electronics and surface structures, and has been extensively studied in recent years. For example, the Chinese patent document No. CN116103680A discloses a bismuth oxycarbonate electrocatalyst rich in oxygen vacancies and its preparation method. The bismuth salt is dissolved in ethylene glycol and an aqueous solution, an appropriate amount of auxiliary conductive salt is added and then refrigerated to obtain an electrolyte. The galvanostatic method electrochemically deposits bismuth oxycarbonate nanosheets rich in oxygen vacancies on the working electrode. The introduction of oxygen vacancies improves the conductivity of bismuth oxycarbonate, enhances the water splitting ability of bismuth oxycarbonate and the intrinsic properties of HCOOH synthesis. active.

Although great progress has been made in the electroreduction of _CO2 to synthesize HCOOH under different electrolyte environments, the electrosynthesis of HCOOH to achieve industrial-grade current density (>200mA cm ^-2 ) in the full pH range still faces low selectivity. And other issues.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a tin diselenide nanosheet electrocatalyst rich in selenium defects. The prepared catalyst is rich in selenium defects and exhibits excellent catalytic performance for HCOOH electrosynthesis.

In order to achieve the above objects, the technical solution adopted by the present invention is:

A method for preparing a selenium-deficient tin diselenide nanosheet electrocatalyst. The preparation method includes the following steps: dissolving selenium dioxide and metal tin salt, adding hydrazine hydrate solution, stirring and mixing, and obtaining through hydrothermal reaction Selenium-rich tin diselenide nanosheet electrocatalysts.

The preparation principle of the selenium-deficient tin diselenide nanosheet electrocatalyst provided by the invention is: adding the reducing reagent hydrazine hydrate to a uniformly dispersed mixed solution of selenium dioxide and metal tin salts, and the strongly reducing hydrazine hydrate molecules convert the solution into Sn ²⁺ and Se ⁴⁺ are reduced to atoms, and the highly reactive Sn atoms and Se atoms combine to form tin diselenide molecules, accompanied by the formation of selenium defects. Among them, the introduction of selenium defects causes more electrons to be transferred from Se sites to Sn sites, effectively accelerating the dissociation of water molecules, increasing the proton transfer rate, and thereby accelerating the efficient conversion of CO ₂ at the tin active site.

The metal tin salt is a soluble salt. Preferably, the metal tin salt is stannous chloride dihydrate.

The molar ratio of selenium dioxide and metal tin salt is 1.5-2.5:1. The present invention prepares tin diselenide nanosheets rich in selenium defects of different purity by changing the dosage of selenium dioxide. When the molar concentration of selenium dioxide is too low, the purity of the obtained tin diselenide will be reduced, and there will be the presence of heterogeneous tin. The performance of the electroreduction of CO ₂ to synthesize HCOOH will not be significantly improved; when selenium dioxide When the molar concentration is too high, selenium impurity phases will appear, significantly reducing the performance of HCOOH electrosynthesis.

Further, selenium dioxide and metal tin salt are dissolved in water. In the obtained mixed solution, the mass concentration of selenium dioxide is 7.4-22.2g L ^-1 and the mass concentration of tin salt is 15.0g L ^-1 . Preferably, the mass concentration of selenium dioxide is 14.8g L ^-1 .

Among them, selenium dioxide and metal tin salt are dissolved in a certain amount of aqueous solution, the reaction temperature is room temperature, and the stirring time is 10 to 20 minutes. Preferably, the stirring time is 20 minutes.

Further, in the mixed solution after adding hydrazine hydrate, the mass concentration of hydrazine hydrate was 54.8g L ^-1 .

Wherein, after the mixed solution of selenium dioxide and metal tin salt is added to the hydrazine hydrate solution, the reaction temperature is normal temperature, and the stirring time is 3 to 8 minutes. Excessive stirring time will affect the uneven morphology of tin diselenide and the formation of selenium defects, thereby affecting the performance of the electrocatalyst. Preferably, the stirring time is 3 minutes.

The hydrothermal reaction temperature is 160-200°C. By changing the hydrothermal reaction temperature, tin diselenide nanosheets with different contents of selenium defects were prepared. When the hydrothermal reaction temperature is too low, it is difficult to form tin diselenide nanosheets rich in selenium defects; when the hydrothermal reaction temperature is too high, the tin diselenide nanosheets are prone to crystal phase transformation at high temperatures, resulting in The performance of electroreduction of _CO2 to prepare HCOOH is reduced.

Preferably, the molar ratio of selenium dioxide and metal tin salt is 1.5-2:1, and the hydrothermal reaction temperature is 180-200°C. By limiting the above molar ratio and reaction temperature, the purity and content of selenium defects in the prepared tin diselenide nanosheets are more conducive to improving the selectivity of electroreduction of CO ₂ to prepare HCOOH.

The invention also provides a selenium-deficient tin diselenide nanosheet electrocatalyst obtained according to the above preparation method.

Abundant selenium defects in the catalyst exist in tin diselenide nanosheets, and the atomic ratio of selenium to tin in the tin diselenide nanosheet electrocatalyst is 1.8 to 2.0:1.

The present invention also provides an application of the above-mentioned tin diselenide nanosheet electrocatalyst rich in selenium defects as a working electrode in the electrosynthesis of formic acid.

Further, the selenium-deficient tin diselenide nanosheet electrocatalyst is used as a working electrode in the electrosynthesis of formic acid at industrial-grade current density in the full pH range.

The selenium-deficient tin diselenide nanosheet electrocatalyst provided by the present invention achieves high selectivity performance under industrial current density (>200mAcm ^-2 ). Among them, the highest selectivities of HCOOH in alkaline, neutral and acidic electrolytes are 94.1%, 81.7% and 78.1% respectively. The peak bias current density of HCOOH is 800, 568 and 495mA cm ^-2 respectively. Its electrocatalytic performance Far better than commercial tin diselenide catalysts.

The selenium-deficient tin diselenide nanosheet electrocatalyst provided by the present invention can effectively improve its adsorption and dissociation ability of water molecules, accelerate proton transfer and the formation rate of intermediates, thereby further improving its electrocatalytic activity, and It is of great significance to prepare HCOOH under industrial conditions.

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

(1) The selenium-deficient tin diselenide nanosheet electrocatalyst provided by the present invention achieves highly selective catalytic conversion of CO ₂ into HCOOH and has a wide operable pH window (2.0-14.0). The electrosynthesis of HCOOH at industrial-grade current densities under different pH environments was achieved, providing the possibility for further industrial large-scale applications.

(2) The tin diselenide nanosheet electrocatalyst rich in selenium defects provided by the present invention effectively adjusts the electronic structure of tin diselenide by introducing selenium defects, making the electron density around the tin site richer and effectively accelerating Water molecules dissociate more protons, thereby accelerating the formation of the intermediate *COOH, and ultimately accelerating the HCOOH synthesis process.

Description of the drawings

Figure 1 is a scanning electron microscope SEM image of the catalyst prepared in Example 1;

Figure 2 is an X-ray diffraction XRD pattern of the catalyst prepared in Example 1;

Figure 3 is an electron paramagnetic resonance EPR pattern of the catalyst prepared in Example 1 and Examples 2-3;

Figure 4 shows the Faradaic efficiency of the catalyst prepared in Example 1 for the electroreduction of CO ₂ to prepare HCOOH in application examples.

Figure 5 shows the Faradaic efficiency of the catalysts prepared in Example 1 and Examples 2-3 in the electroreduction of CO ₂ to prepare HCOOH in application examples.

Figure 6 shows the Faradaic efficiency of the catalyst prepared in Example 1 and Examples 4-5 in the application example of electroreduction of CO ₂ to prepare HCOOH in an environment of pH = 14.0.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with examples. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention. Modifications or equivalent substitutions made by those skilled in the art on the basis of understanding the technical solutions of the present invention, without departing from the spirit and scope of the technical solutions of the present invention, shall be covered by the protection scope of the present invention. The raw materials used in the following specific embodiments were all purchased from the market.

Example 1

(1) Weigh 443.8 mg selenium dioxide solid particles and 451.3 mg stannous chloride dihydrate solid particles, dissolve them in 30 mL deionized water solution, stir at room temperature for 20 minutes, and set aside;

(2) Add 2 mL of 85wt.% hydrazine hydrate solution to the solution prepared in step (1), and stir for 5 minutes; transfer the obtained mixed solution to a 50 mL hydrothermal kettle, and conduct a hydrothermal reaction at 180°C for 24 hours;

(3) Centrifuge the primary product obtained in step (2), wash it more than three times with water and ethanol, and finally dry it in a vacuum oven at 60°C for 12 hours to obtain a tin diselenide nanosheet catalyst rich in selenium defects.

The microscopic morphology of the prepared catalyst was observed through scanning electron microscopy (SEM). The SEM results are shown in Figure 1. It can be seen that the morphological structure of the tin diselenide catalyst rich in selenium defects is a hexagonal lamellar structure, and the lamellar thickness is about is 50nm. The X-ray diffraction XRD pattern of the selenium-deficient tin diselenide prepared in this embodiment is shown in Figure 2. The characteristic peaks of the crystal phase of tin diselenide can be seen, and the electron paramagnetic resonance EPR pattern is shown in Figure 3. , the existence of selenium defects can be clearly seen, indicating the successful preparation of tin diselenide nanosheet electrocatalysts rich in selenium defects.

Example 2

According to the preparation process of Example 1, the hydrothermal reaction temperature in step (2) was changed to 160°C to obtain the catalyst of Example 2.

Example 3

According to the preparation process of Example 1, the hydrothermal reaction temperature in step (2) was changed to 200°C to obtain the catalyst of Example 3.

Example 4

According to the preparation process of Example 1, the mass of the selenium dioxide solid particles in step (1) was changed to 332.8 mg to obtain the catalyst of Example 4.

Example 5

According to the preparation process of Example 1, the mass of the selenium dioxide solid particles in step (1) was changed to 554.7 mg to obtain the catalyst of Example 5.

Application Example HCOOH electrosynthesis at industrial-grade current density in the full pH range

First, 10 mg of the catalyst prepared above was dispersed in 1000 μL of ethanol/Nafion dispersion with a volume ratio of 9:1, and then 100 μL of the dispersion was sprayed onto a 0.5* ^0.5cm2 gas diffusion electrode. After natural drying, It is placed as a working electrode in a three-electrode flow cell measurement device, which consists of two compartments separated by an anion exchange membrane. _Among them, 1.0M KOH solution is used as the alkaline electrolyte, 1.0M _KHCO3 solution is used as the neutral electrolyte, _{and 0.5MK2SO4} and _H2SO4 mixed solution is used as the acidic electrolyte. The counter electrode for alkaline and neutral electrolytes is nickel foam, the counter electrode for acidic electrolyte is platinum sheet, and the reference electrode is silver/silver chloride electrode.

Cyclic voltammetry (CV) activation: Shanghai Chenhua CHI 760E electrochemical workstation is used, using the CV program, the test range is 0 ~ -1.4V vs. RHE, the scanning speed is 50mV s ^-1 , and the electrode reaches stability after 40 cycles of scanning. state.

Linear sweep voltammetry (LSV) test: After CV activation, switch the program to the LSV program, the test range is 0~-1.4Vvs.RHE, and the sweep speed is 5mV s ^-1 .

Faraday efficiency (FE) test: Switch the program to a galvanostatic voltage-time test. During the galvanostatic test, use gas chromatography to measure the gas phase product concentration and calculate the FE of the product. Gas chromatography (GC, Fuli 9790II) was used for online quantification, and ^{a 1} H nuclear magnetic resonance instrument was used to analyze the FE of the liquid product, and the internal standard method was used, that is, dimethyl sulfoxide was used as the standard.

The results are shown in Figure 4. The selenium-deficient tin diselenide nanosheet electrocatalyst prepared in Example 1 exhibits excellent HCOOH electrosynthesis performance in the entire pH range, in alkaline, neutral and acidic electrolytes. The selectivities of HCOOH were 94.1%, 81.7% and 78.1% respectively, and the corresponding HCOOH partial current densities of 800, 568 and 495mA cm ^-2 reached the industrial level.

The HCOOH Faradaic efficiencies of the electrocatalysts prepared in Example 1 and Examples 2-3 were compared under different pH environments of voltage -0.8V vs. RHE. The results are shown in Figure 5. The selenium-rich electrocatalyst prepared in Example 1 The HCOOH electrosynthesis performance of the defective tin diselenide nanosheet electrocatalyst in the full pH range is far better than that of Example 2 and Example 3.

The HCOOH electrosynthesis performance of the electrocatalysts prepared in Example 1 and Examples 4-5 was compared in an environment of pH=14.0. The results are shown in Figure 6. The tin diselenide nanoparticles rich in selenium defects prepared in Example 1 The HCOOH electrosynthesis selectivity of the sheet electrocatalyst is much higher than that of Example 4 and Example 5.

Claims (8)

1. The preparation method of the tin diselenide nanosheet electrocatalyst rich in selenium defects is characterized by comprising the following steps of: and dissolving selenium dioxide and metallic tin salt, adding hydrazine hydrate solution, stirring and mixing, and performing hydrothermal reaction to obtain the selenium-enriched tin diselenide nanosheet electrocatalyst.

2. The method for preparing the selenium-defect-enriched tin diselenide nanosheet electrocatalyst according to claim 1, wherein the molar ratio of selenium dioxide to metallic tin salt is 1.5-2.5:1.

3. The method for preparing the selenium-defect-enriched tin diselenide nanosheet electrocatalyst according to claim 1, wherein the hydrothermal reaction temperature is 160-200 ℃.

4. The method for preparing the selenium-defect-enriched tin diselenide nanosheet electrocatalyst according to claim 1, wherein the molar ratio of selenium dioxide to metallic tin salt is 1.5-2:1, and the hydrothermal reaction temperature is 180-200 ℃.

5. A tin nanosheet electrocatalyst enriched in selenium defects obtainable by the process according to any one of claims 1 to 4.

6. The selenium-defect-enriched tin diselenide nanosheet electrocatalyst according to claim 5, wherein the atomic ratio of selenium to tin in the tin diselenide nanosheet electrocatalyst is from 1.8 to 2.0:1.

7. Use of the selenium-enriched defective tin diselenide nanosheet electrocatalyst according to claim 5 or 6 as a working electrode in the electrosynthesis of formic acid.

8. The use of the selenium-rich and defective tin diselenide nanosheet electrocatalyst according to claim 7, wherein the selenium-rich and defective tin diselenide nanosheet electrocatalyst is used as a working electrode for formic acid electrosynthesis at industrial grade current densities in the full pH range.