Preparation method of octahedral structure SnO2@SnS2 catalyst for electro-reduction of CO2

Abstract

The application discloses a preparation method of an octahedral structure SnO2@SnS2 CO2 electro-reduction catalyst, which comprises the following steps: dissolving SnCl4.5H2O and polyvinylpyrrolidone K30 in a mixed solution, wherein the mixed solution comprises hydrochloric acid and an ethanol aqueous solution, and then transferring the mixed solution to a reaction kettle for heating reaction; after the reaction is completed, centrifugal separation, cleaning and drying are performed to obtain an octahedral structure SnO2 with exposed {221} crystal faces; dissolving the octahedral structure SnO2 in anhydrous ethanol to obtain a solution A, dissolving thioacetamide in a formic acid aqueous solution to obtain a solution B, and then mixing the solution A and the solution B and transferring the mixture to a reaction kettle for heating reaction; after the reaction is completed, centrifugal separation, cleaning and drying are performed to obtain an octahedral structure SnO2@SnS2. According to the method, SnS2 material in a sheet shape can be epitaxially grown on the basis of retaining the octahedral morphology of SnO2, and the advantages of each component can be maximized, so that the electro-catalytic performance of the SnO2@SnS2 is improved.

Description

Technical Field

[0001] This invention relates to the field of catalytic nanomaterial preparation technology, specifically to a method for preparing an octahedral SnO2@SnS2 electroreduction CO2 catalyst. Background Technology

[0002] Among catalysts for CO2 reduction, SnO2 possesses advantages such as non-toxicity, abundant reserves, and high catalytic activity. SnO2 materials exhibit high selectivity for the product HCOOH and are considered a promising catalyst for the electroreduction of CO2 to HCOOH. However, issues such as high overpotential and low current density still need to be addressed, hindering the further development of SnO2. Therefore, modification of SnO2 to improve its electrocatalytic performance has attracted increasing attention. Constructing heterojunctions by combining nanosheets with other nanomaterials to prepare composite materials can maximize the advantages of each component. Growing ultrathin nanosheets on high surface area support materials not only provides more edge sites and active sites but also allows for the use of highly conductive materials as supports, ensuring rapid electron transfer between external circuits and electrodes.

[0003] Using SnO2 with an exposed {221} octahedral morphology as a precursor, SnS2 nanosheets were further grown via hydrothermal sulfidation to construct a SnO2 / SnS2 heterostructure. Since SnO2 has a conduction band bottom of 3.5 eV and a valence band top of 0 eV, while SnS2 has a conduction band bottom of 2.1 eV and a valence band top of -0.06 eV, the band structure exhibits good band matching, allowing electrons to easily transition from the SnS2 conduction band to the SnO2 conduction band. This SnS2 / SnO2 heterostructure is expected to possess exposed highly active surfaces and become a highly efficient interfacial charge transfer system. In particular, the 2D self-assembled nanosheets with exposed active surfaces can provide sufficient contact areas and active sites with the electrolyte, accelerating the electrocatalytic reduction of CO2. Similarly, the strong electron interactions near the SnS2 / SnO2 catalyst heterostructure interface significantly reduce electron transfer resistance, potentially further improving its electrocatalytic CO2 reduction performance. However, designing and preparing an electroreduction catalyst for CO2 by SnO2 coated with sheet-like SnS2 remains a huge challenge.

[0004] Currently, most methods for preparing SnO2@SnS2 catalysts either synthesize the SnO2 / SnS2 composite material in a single step or reduce a portion of SnO2 to SnS2 through oxygen reduction after synthesizing pure SnS2 to obtain the SnO2 / SnS2 composite material. However, the materials synthesized by the above methods have relatively uniform morphologies, with some exhibiting only lamellar structures and others only exhibiting blocky structures. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an octahedral SnO2@SnS2 electroreduction CO2 catalyst. This method can epitaxially grow sheet-like SnS2 material while retaining the octahedral morphology of the precursor SnO2, thereby maximizing the advantages of each component and improving the electrocatalytic performance of the prepared sheet-like SnS2-coated SnO2 composite material SnO2@SnS2.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing an octahedral SnO2@SnS2 electroreduction CO2 catalyst, comprising the following steps:

[0007] S1: SnCl4·5H2O and polyvinylpyrrolidone K30 are dissolved in a mixed solution, which includes hydrochloric acid and an aqueous ethanol solution. The solution is then transferred to a reaction vessel and heated for a period of time. After the reaction is completed, the product is collected by centrifugation, washed, and dried to obtain an octahedral SnO2 structure with exposed {221} crystal planes.

[0008] S2: Dissolve the octahedral SnO2 synthesized in step S1 in anhydrous ethanol to obtain solution A, and dissolve thioacetamide in formic acid aqueous solution to obtain solution B. Then, mix solution A and solution B and transfer them to a reaction vessel and heat them for a period of time. After the reaction is completed, collect the product by centrifugation, wash and dry it to obtain the SnO2 composite catalyst coated with sheet-like SnS2, namely SnO2@SnS2 with octahedral structure supported on nanosheets.

[0009] Preferably, in step S1, the heating temperature is 200°C and the reaction time is 12 hours.

[0010] Preferably, in step S1, the concentration of the hydrochloric acid is 12M, and the volume ratio between the hydrochloric acid and the aqueous ethanol solution is 1:12; the aqueous ethanol solution is prepared by mixing water and anhydrous ethanol in a volume ratio of 1:1.

[0011] Preferably, in step S2, the volume ratio between solution A and solution B is 1:1; the concentration of solution A is 2.5 g / L; and the concentration of solution B is 450 g / L.

[0012] Preferably, in step S2, the heating temperature is 150°C and the reaction time is 12 hours.

[0013] Preferably, in step S2, the formic acid in the aqueous formic acid solution has a volume percentage of 5 vol%.

[0014] This invention allows for the epitaxial growth of sheet-like SnS2 materials while preserving the octahedral morphology of the precursor SnO2(221). By combining nanosheets with other nanomaterials to prepare composite materials, the advantages of each component can be maximized. Growing ultrathin nanosheets on high surface area support materials can provide more edge sites and active sites, and the use of highly conductive materials as supports ensures rapid electron transfer between external circuits and electrodes, thereby improving the electrocatalytic performance of the material.

[0015] This invention synthesizes octahedral SnO2 with exposed {221} faces using a simple hydrothermal method. Then, using octahedral SnO2 as a precursor, a SnO2 composite material SnO2(221)@SnS2 coated with sheet-like SnS2 is finally obtained through a simple hydrothermal sulfidation method. The prepared electrocatalyst SnO2(221)@SnS2 exhibits higher electrocatalytic activity than pure SnO2(221) and SnS2. The addition of HCl solution in this invention can inhibit the electrocatalytic activity of SnO2 to a certain extent. 4+ The hydrolysis of ions and the slowing down of SnO2 nanocrystal growth provide an opportunity for the growth of SnO2 nanocrystals through Cl. - Opportunities for specific adsorption of ions to dynamically control the shape of SnO2 nanocrystals; surfactant PVP (polyvinylpyrrolidone K30) plays a key role in dispersing SnO2 particles. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope (SEM) image (ab) of the octahedral SnO2 structure prepared in the embodiments of the present invention;

[0017] Figure 2 This is the X-ray powder diffraction (XRD) pattern of the octahedral SnO2 structure prepared in the embodiments of the present invention;

[0018] Figure 3 This is an elemental distribution diagram (df) of the octahedral SnO2 structure prepared in the embodiments of the present invention, where d is a scanning electron microscope image of a single octahedral SnO2 structure, e is the elemental distribution diagram of Sn, and f is the elemental distribution diagram of O.

[0019] Figure 4 Crystal structure diagram (ab) of octahedral SnO2 prepared in the embodiments of the present invention, where a is a scanning electron microscope image of the synthesized octahedral SnO2 and b is the crystal structure of the simulated octahedral SnO2.

[0020] Figure 5 This is a scanning electron microscope (SEM) image of SnO2@SnS2 with octahedral structure supported nanosheets prepared in the embodiments of the present invention.

[0021] Figure 6This is the X-ray powder diffraction (XRD) pattern of SnO2@SnS2 with octahedral structure supported on nanosheets prepared in the embodiments of the present invention.

[0022] Figure 7 These are transmission electron microscopy (TEM) images (c), crystal structure diagram (d), and transmission electron microscopy (TEM) image (e) of SnO2@SnS2 with octahedral structure supported nanosheets prepared in the embodiments of the present invention.

[0023] Figure 8 The image shows the elemental distribution of SnO2@SnS2 with octahedral structure supported on nanosheets prepared in the embodiments of the present invention (fi), where f is a scanning electron microscope image of a single SnO2@SnS2, g is the elemental distribution of Sn, h is the elemental distribution of O, and i is the elemental distribution of S.

[0024] Figure 9 The figures show the Faradaic efficiencies of SnO2@SnS2(a), SnO2(b), and SnS2(c) in a 0.1 mol / L KHCO3 electrolyte for the electrocatalytic reduction of CO2 products. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Unless otherwise specified, the raw materials and reagents used in the following examples are all from commercially available stores.

[0027] Example

[0028] A method for preparing an octahedral SnO2@SnS2 electroreduction CO2 catalyst includes the following steps:

[0029] S1: Synthetic SnO2 precursor with octahedral structure;

[0030] SnCl4·5H2O (3.15 g, 1 mmol) and PVPK30 (0.315 g) were dissolved in a mixed solution containing 12 M HCl (0.5 mL), H2O (3 mL), and EtOH (3 mL). After mixing thoroughly, the solution was transferred to a polytetrafluoroethylene high-pressure reactor and reacted at 200 °C for 12 h. The product was then collected by centrifugation, washed several times with ethanol, and dried overnight at 60 °C to obtain an octahedral SnO2 structure with exposed {221} crystal faces.

[0031] Figures 1-4 These are the SEM, XRD, elemental distribution map, and crystal structure diagram of the sample prepared in step S1 of this embodiment. Figure 1 As can be seen, the octahedral SnO2 synthesized in this embodiment has a uniform morphology and good bonding. Figure 4The crystal structure diagram shows that the synthesized octahedral SnO2 is an octahedral SnO2 with exposed {221} crystal planes. From... Figure 2 As can be seen, the X-ray powder diffraction peak positions of the synthesized SnO2 match those of SnO2, proving that SnO2 was successfully synthesized in this embodiment. From... Figure 3 As can be seen from the above, the octahedral SnO2 synthesized in this embodiment is composed of two elements, Sn and O, and the elements are evenly distributed.

[0032] S2: Synthesis of SnO2@SnS2 electroreduction CO2 catalyst with octahedral structure supported nanosheets;

[0033] The SnO2 (5 mg) prepared in step S1 was dissolved in EtOH (2 mL) to obtain solution A, and thioacetamide (0.9 g) was dissolved in 5 vol% HCOOH (2 mL) to obtain solution B. Then, solutions A and B were mixed evenly and transferred to a polytetrafluoroethylene high-pressure reactor. The reaction was carried out at 150 °C for 12 h. The product was then collected by centrifugation, washed several times with ethanol, and dried overnight at 60 °C to obtain the SnO2@SnS2 electroreduction CO2 catalyst.

[0034] Figures 5-8 These are the SEM, XRD, TEM, crystal structure diagram, and elemental distribution diagram of the sample prepared in step S2 of this embodiment. Figure 5 and Figure 7 As can be seen from c, the SnO2@SnS2 morphology of the octahedral structure supported nanosheets synthesized in this embodiment is uniform, and sheet-like SnS2 structures are uniformly grown on the outside of the octahedral SnO2. Figure 7 Crystal structure diagram of d and Figure 7 The transmission electron microscopy (TEM) image of a single SnO2@SnS2 nanosheet synthesized in this embodiment shows that the octahedral structured supported nanosheet SnO2@SnS2 is an epitaxially grown sheet-like SnS2 morphology with exposed {221} crystal planes. From Figure 6 As can be seen, the X-ray powder diffraction peak positions of SnO2@SnS2 match those of SnO2 and SnS2, proving that this embodiment successfully synthesized the SnO2@SnS2 material. From... Figure 8 As can be seen from the above, the SnO2@SnS2 octahedral structure supported nanosheets synthesized in this embodiment are composed of three elements: Sn, O, and S, and the elements are evenly distributed.

[0035] Figure 9 This is a Faraday efficiency graph showing the electrocatalytic reduction of CO2 products by SnO2@SnS2 (a), SnO2 (b), and SnS2 (c) in a 0.1 mol / L KHCO3 electrolyte. Figure 9As can be seen, the electrocatalyst SnO2@SnS2 exhibits higher electrocatalytic activity than SnO2 and SnS2.

Claims

1. A preparation method of an octahedral structure SnO2@SnS2 electric reduction CO2 catalyst, characterized in that, The method comprises the following steps: S1: SnCl4·5H2O and polyvinylpyrrolidone K30 are dissolved in a mixed solution comprising hydrochloric acid and an ethanol aqueous solution, and then transferred to a reaction kettle for heating reaction for a period of time; after the reaction is completed, the product is collected by centrifugation, and then washed and dried to obtain SnO2 with an octahedral structure and exposed {221} crystal faces; S2: the SnO2 with an octahedral structure synthesized in step S1 is dissolved in anhydrous ethanol to obtain solution A, and thioacetamide is dissolved in an aqueous formic acid solution to obtain solution B; then solution A and solution B are mixed and transferred to a reaction kettle for heating reaction for a period of time; after the reaction is completed, the product is collected by centrifugation, washed and dried to obtain a SnO2 composite catalyst coated with SnS2 in a sheet shape, i.e., SnO2@SnS2 with an octahedral structure loaded with nanosheets; the volume ratio between solution A and solution B is 1:1; the concentration of solution A is 2.5 g / L; and the concentration of solution B is 450 g / L.

2. The preparation method of the octahedral Sn02@SnS2 catalyst for electro-reduction of CO2 according to claim 1, characterized in that, In step S1, the heating temperature is 200°C, and the reaction time is 12 h.

3. The preparation method of the octahedral Sn02@SnS2 catalyst for electro-reduction of CO2 according to claim 1 or 2, characterized in that, In step S1, the concentration of the hydrochloric acid is 12M, and the volume ratio between the hydrochloric acid and the ethanol aqueous solution is 1:12; the ethanol aqueous solution is prepared from water and anhydrous ethanol in a volume ratio of 1:

1.

4. The preparation method of the octahedral Sn02@SnS2 catalyst for electro-reduction of CO2 according to claim 1 or 2, characterized in that, In step S2, the heating temperature is 150°C, and the reaction time is 12 h.

5. The preparation method of the octahedral Sn02@SnS2 catalyst for electro-reduction of CO2 according to claim 1 or 2, characterized in that, In step S2, in the aqueous formic acid solution, the volume percentage of formic acid is 5vol%. In step S2, in the aqueous formic acid solution, the volume percentage of formic acid is 5vol%.

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