CN112899710A

CN112899710A - For electrocatalytic reduction of CO2Preparation method of catalyst for preparing formic acid

Info

Publication number: CN112899710A
Application number: CN202110116776.XA
Authority: CN
Inventors: 刘立成; 张欣欣; 陈志鹏
Original assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Current assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Priority date: 2021-01-28
Filing date: 2021-01-28
Publication date: 2021-06-04
Anticipated expiration: 2041-01-28
Also published as: CN112899710B

Abstract

The invention discloses a preparation method of a catalyst for preparing formic acid by electrocatalytic reduction of carbon dioxide and the catalyst obtained by the preparation method. The preparation method comprises the following steps: 1) reacting ZnCl₂、SnCl₄·5H₂Mixing the solution of O with NaOH solution to obtain ZnSn (OH)₆Precipitating a precursor; 2) mixing ZnSn (OH)₆Carrying out hydro-thermal treatment on the precursor; 3) mixing ethylenediaminetetraacetic acid, thioacetamide and ZnSn (OH)₆Carrying out hydrothermal reaction on the intermediate; 4) SnS obtained in the step 3)₂The powder sample was dispersed In a dispersion containing In (NO)₃)₃·4.5H₂And stirring the mixture in an ethanol solution of O to obtain a final product. The preparation method according to the invention uses a two-step stepwise thinning method to make micron-sized ZnSn (OH)₆Cubic precursor is first converted to thickNano-sized ZnSn (OH) sheet with a degree of-200 nm₆Reconverting the intermediate into two-dimensional ultrathin (2-3 nm) SnS₂Nanosheets, while utilizing In (NO)₃)₃Mild oxidation and doping of EtOH to give the final catalyst product, which is used for the electrocatalytic reduction of CO₂Excellent selectivity of formic acid product is shown: high FE_HCOOFaradaic efficiency, and a wider interval of high active potential.

Description

For electrocatalytic reduction of CO2Preparation method of catalyst for preparing formic acid

Technical Field

The invention relates to a technology for converting carbon dioxide by electrocatalytic reduction, In particular to a preparation method of a catalyst for preparing formic acid by electrocatalytic reduction of carbon dioxide, and In obtained by the preparation method³⁺-O-ultra-thin-SnS₂A catalyst.

Background

At present, environmental problems caused by excessive emission of the greenhouse gas carbon dioxide have become one of the focuses of world concerns. Carbon dioxide storage and conversion technology is one of the important measures to alleviate this problem. In which the electrocatalytic reduction reaction (CO) of carbon dioxide₂R' R ") has attracted considerable attention from researchers because of the mild reaction conditions, i.e., the reaction can be carried out at normal temperature and pressure. It is worth pointing out that CO₂Main product (C) of R₁(single carbon atom product): formic acid, carbon monoxide, methane; c₂₊(product of two or more carbon atoms): ethylene, ethanol, acetone, etc.), and even by-products (H)₂) The fuel is chemical fuel with added value, and can relieve the problem of energy shortage to a certain extent. It can thus be seen that the electrocatalytic reduction of CO was studied₂The technology has important significance. The design and preparation of the high-efficiency durable electrocatalyst are the key points of the technology for electrocatalytic reduction of carbon dioxide and are also important points of research. Among them, excellent selectivity to a target product, high active current density, wide active potential range and long-term stability are important indexes for evaluating a catalyst. However, there are few catalysts satisfying the above evaluation conditions at the same time. Although some catalysts have good selectivity for the target product, they are limited by narrow active potential regions or low current densities, among other factors. Such as the Li project group (J.Mater.chem.A., 2019,7, 1267-₂Hollow SnO prepared by oxidation treatment of nanosheet₂Nanosheets, albeit exhibiting excellent formic acid selectivity (FE)_HCOOMaximum 83% at-0.9V vs. RHE, corresponding to j_HCOO-16 mA cm^-2) But is limited to a narrow active potential interval. When the potential rises to-1.0V or falls to-0.8V vs. RHE, the corresponding FE_HCOOOnly about 70% remains. This application is sentTwo catalysts (3D SnO) prepared before Ming₂-NCs and SnO₂NFs) are subjected to abundant nano-and microporous structure modification (nanoscales, 2019,11, 18715-18722). However, the active sites cannot be completely exposed, limited by the micron-scale bulk structure, ultimately resulting in less than outstanding catalytic performance. Highest FE_HCOO72.6% and 82.1%, respectively, the corresponding current densities being only 9.4 and 10.3mA cm, respectively^-2. Most disappointingly, the potential interval for high activity is narrow, e.g.in the range of-0.9 to-1.2V vs. RHE, FE_HCOO-above 70% and FE when the potential drops to-0.8V_HCOO-as low as 45%.

In summary, the preparation of a robust catalyst with high target product selectivity, high active current density, and wide active potential range is the key of research.

Disclosure of Invention

In view of the problems of the prior art, according to one aspect of the present invention, it is an object of the present invention to provide a method for preparing a catalyst for preparing formic acid by electrocatalytic reduction of carbon dioxide, the method comprising the steps of:

step 1) reacting ZnCl₂、SnCl₄·5H₂Mixing O in deionized water according to the molar ratio of 1:1 to mark as a solution A, fully dissolving NaOH in the deionized water to mark as a solution B, and dropwise adding the solution B into the solution A under magnetic stirring; while stirring, a white precipitate formed, giving micron-sized cubic ZnSn (OH)₆Precursor, wherein ZnCl is in A solution₂And SnCl₄·5H₂The concentration of O is 10mmol/L to 40mmol/L respectively, the concentration of NaOH in the solution B is 200mmol/L to 450mmol/L, ZnCl₂And SnCl₄·5H₂The ratio of the total molar amount of O to the molar amount of NaOH is 1:6 to 1: 10;

step 2) synthesizing ZnSn (OH) in the step 1)₆Transferring and packaging the original solution of the precursor in a stainless steel reaction kettle with a polytetrafluoroethylene lining, placing the stainless steel reaction kettle in an oven for hydrothermal reaction at the reaction temperature of 180-240 ℃ for 10-30 h, and performing centrifugal separation after the reaction to obtain a sample of ZnSn (OH)₆An intermediate;

step 3) adding ethylene diamine tetraacetic acid and thioacetamide into deionized water in sequence, stirring at room temperature for 0.5-1 h to fully mix uniformly, and then adding ZnSn (OH) prepared in step 2)₆Performing ultrasonic dispersion on the intermediate, transferring the intermediate into a polytetrafluoroethylene lining, putting the intermediate into a stainless steel reaction kettle, performing hydrothermal reaction, standing the intermediate after the reaction is finished, and then centrifuging, washing and drying the intermediate to obtain yellow SnS₂Sample of powder in which ZnSn (OH)₆The molar ratio of the ethylene diamine tetraacetic acid to the thioacetamide is 0.1-0.3:0.6-1.0: 1.5-2.1; based on 1 mole of ZnSn (OH)₆The volume of the deionized water is 80-160L; the hydrothermal reaction temperature is 100-180 ℃, and the reaction time is 3-10 h;

step 4) SnS obtained in the step 3)₂The powder sample was dispersed In a dispersion containing In (NO)₃)₃·4.5H₂In ethanol solution of O, magnetically stirring In water bath at 40-80 deg.C for 18-36h to obtain surface layer indium doped and partially oxidized sample, and recording as In³⁺-O-ultra-thin-SnS₂Wherein SnS₂Powder sample and In (NO)₃)₃·4.5H₂O mass ratio is preferably 1:1 to 1:8, In (NO)₃)₃·4.5H₂The concentration of the O/ethanol solution is preferably 8 to 15mmol L^-1。

Preferably, ZnCl is contained in the solution A in the step 1)₂And SnCl₄·5H₂The concentration of O is respectively 25mmol/L, the concentration of NaOH in the solution B is 375mmol/L, ZnCl₂And SnCl₄·5H₂The ratio of the total molar amount of O to the molar amount of NaOH was 1: 7.5.

Preferably, in the hydrothermal reaction in the step 2), the reaction temperature is preferably 220 ℃, and the reaction time is preferably 20 h.

Preferably, ZnSn (OH) in step 3)₆The preferred molar ratio of ethylene diamine tetraacetic acid to thioacetamide is 0.3:0.8: 1.8; based on 1 mole of ZnSn (OH)₆The volume of the deionized water is 120L; the hydrothermal reaction temperature is preferably 150 ℃ and the reaction time is preferably 6 h.

Preferably, in step 4), the ultra-thin SnS₂Sample and In (NO)₃)₃·4.5H₂The O mass ratio is preferably 1:5, In (NO)₃)₃·4.5H₂The concentration of the O/ethanol solution is preferably 13.4mmol L^-1The temperature of the water bath is preferably 60 ℃, and the treatment time is preferably 25 h.

According to another aspect of the present invention, it is another object of the present invention to provide an In³⁺-O-ultra-thin-SnS₂A catalyst obtained according to the above preparation method.

According to another aspect of the present invention, it is another object of the present invention to provide a composition containing said In³⁺-O-ultra-thin-SnS₂A working electrode of a catalyst.

According to another aspect of the present invention, it is another object of the present invention to provide a method for preparing the working electrode, the method comprising: in to be according to the invention³⁺-O-ultra-thin-SnS₂And mixing the catalyst material with isopropanol and a Nafion solution, performing ultrasonic dispersion to obtain a mixed solution, uniformly coating the mixed solution on carbon cloth, and drying to form the working electrode.

Preferably, In the method for preparing the working electrode³⁺-O-ultra-thin-SnS₂The ratio of the catalyst material to the isopropanol and Nafion solution was 6mg:0.35mL:0.07 mL.

Preferably, the Nafion solution is a 5 wt% Nafion solution of perfluorosulfonic acid resin.

According to another aspect of the present invention, it is another object of the present invention to provide a method for preparing formic acid from carbon dioxide through an electrocatalytic reduction reaction, which is performed using the working electrode according to the present invention.

Advantageous effects

According to the preparation method, a two-step stepwise thinning method is utilized to make micron-sized (1-2 mu m) ZnSn (OH)₆Cubic precursor is firstly converted into flower-shaped ZnSn (OH) with the thickness of nano-sheet of 200nm₆The precursor is converted into two-dimensional ultrathin (2-3 nm) SnS₂Nanosheets, and ultrathin-SnS₂Showing a very large geometric total current densityDegree; in ultra-thin-SnS₂In (NO) is used on the basis of the ultra-thin structure of (2)₃)₃Mild oxidation and doping of-EtOH ultimately yields highly efficient In³⁺-O-ultra-thin-SnS₂Catalyst for the electrocatalytic reduction of CO₂Excellent selectivity of formic acid product is shown: high FE_HCOOFaraday efficiency (FE at-1.2V vs. RHE)_HCOO-(max)88.6%), and a wide high-activity potential range (-0.8 to-1.4V vs. FE: FE_HCOO->70％)。

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a micron-sized (1-2 μm) cubic ZnSn (OH) prepared in step 1) of example 1 of the present invention₆Scanning electron microscopy of the precursor.

FIG. 2 is a micron-sized (1-2 μm) cubic ZnSn (OH) prepared in step 1) of example 1 of the present invention₆X-ray diffraction pattern of the precursor.

FIG. 3 is flower-like ZnSn (OH) having a lamella thickness of 200nm prepared in step 2) of example 1 of the present invention₆Scanning electron microscopy of the intermediate.

FIG. 4 shows 2-3 nm thick ultrathin SnS prepared in step 3) of example 1 of the present invention₂Transmission electron microscopy of nanoplatelets.

FIG. 5 shows that the ultra-thin-SnS with a thickness of 2-3 nm prepared in step 3) of example 1 of the present invention₂X-ray diffraction pattern of the nanoplatelets.

FIG. 6 is the ultra-thin-SnS prepared in step 3) of example 1 of the present invention₂Atomic force microscopy of nanoplatelets.

FIG. 7 is the ultra-thin-SnS prepared in step 3) of example 1 of the present invention₂Nanosheet catalystAgents for electrocatalytic reduction of carbon dioxide performance diagrams (HCOO)^-、CO、H₂Faradaic efficiency plot of the product).

FIG. 8 shows In prepared In step 4) of example 1 of the present invention³⁺-O-ultra-thin-SnS₂Transmission electron microscopy of nanoplatelets.

FIG. 9 shows In prepared In step 4) of example 1 of the present invention³⁺-O-ultra-thin-SnS₂X-ray diffraction pattern of the nanoplatelets.

FIG. 10 is an ultra-thin-SnS prepared in steps 3) and 4) of example 1 of the present invention₂And In³⁺-O-ultra-thin-SnS₂X-ray photoelectron spectroscopy of the nanoplatelets.

FIG. 11 shows In prepared In step 4) of example 1 In test example 1 of the present invention³⁺-O-ultra-thin-SnS₂Nano-sheet catalyst for electrocatalytic reduction of carbon dioxide performance diagram (HCOO)^-、CO、H₂Faradaic efficiency plot of the product).

Detailed Description

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description herein is of preferred examples for the purpose of illustration only and is not intended to limit the scope of the present invention, so it will be understood that other equivalent implementations and modifications may be made without departing from the spirit and scope of the present invention.

ZnCl is used in the preparation process according to the invention₂As one of the reaction raw materials, in ZnCl₂In the presence of ZnSn (OH) which can form cubic blocks in coordination₆And controlling subsequent Sn⁴⁺The release rate. Under the complexation of ethylenediamine tetraacetic acid, Zn²⁺Is removed while allowing Sn to exist⁴⁺Is exposed to ensure the presence of S in thioacetamide^2-And (4) coordinating to finally form the ultrathin nanosheet. If it is notWithout ZnCl addition₂It is difficult to control the morphology of the particles and form SnS in the shape of ultrathin nanosheets₂。

The following examples are given by way of illustration of embodiments of the invention and are not to be construed as limiting the invention, and it will be understood by those skilled in the art that modifications may be made without departing from the spirit and scope of the invention. Unless otherwise specified, reagents and equipment used in the following examples are commercially available products.

Example 1

1) 1mmol of ZnCl₂And 1mmol of SnCl₄·5H₂Fully dissolving O in 40mL of deionized water to obtain a marked solution A, fully dissolving 15mmol of NaOH in 40mL of deionized water to obtain a marked solution B, and dropwise adding the solution B into the solution A under magnetic stirring; white precipitate is formed during stirring, and the formed white precipitate is micron-sized cubic ZnSn (OH)₆A precursor;

2) preparation of ZnSn (OH) as described above₆Packaging the original solution of the precursor in a 100mL stainless steel reaction kettle with a polytetrafluoroethylene lining, placing the stainless steel reaction kettle in a 220 ℃ oven for hydrothermal reaction for 20h, and marking a sample obtained after the reaction as ZnSn (OH)₆An intermediate;

3) 0.3mmol of ZnSn (OH)₆Ultrasonically dispersing the intermediate into 35mL of deionized water containing 0.8mmol of ethylenediamine tetraacetic acid and 1.8mmol of thioacetamide, and fully stirring; then transferring the solution to a 100mL polytetrafluoroethylene lining, putting the stainless steel lining into a stainless steel reaction kettle, screwing the stainless steel reaction kettle, putting the stainless steel reaction kettle into a drying oven at 150 ℃ for hydrothermal reaction for 6 hours, and centrifuging, washing and drying the solution after standing after the reaction is finished to obtain yellow ultrathin SnS₂A powder sample;

4) weighing the 50mg ultrathin SnS₂Dispersing the powder sample In 50mL ethanol solution containing 250mg indium nitrate, and magnetically stirring In a water bath kettle at 60 ℃ for 24h to obtain an indium-doped and partially oxidized sample, which is marked as In³⁺-O-ultra-thin-SnS₂。

Test example 1

In to be according to example 1³⁺-O-ultra-thin-SnS₂Mixing a catalyst material with isopropanol and a Nafion solution, performing ultrasonic dispersion to obtain a mixed solution, uniformly coating the mixed solution on carbon cloth, and drying to form a working electrode, wherein In³⁺-O-ultra-thin-SnS₂The ratio of the catalyst material to the isopropanol and Nafion solution was 6mg:0.35mL:0.07 mL. The Nafion solution is 5 wt% Nafion solution of perfluorinated sulfonic acid resin.

Electrocatalytic reduction of CO₂The reaction was carried out in a two-compartment H-type electrolytic cell. The electrolytic cell consists of a cathode reaction chamber and an anode reaction chamber, and the two chambers are separated by a Nafion 117 type proton exchange membrane. The activity of the catalyst is evaluated by adopting a three-electrode system and a constant potential electrolysis method, and a CHI660E type electrochemical workstation is externally connected with three electrodes. The working electrode prepared above and an Ag/AgCl electrode filled with saturated KCl are fixed by a platinum sheet electrode clamp and are placed in a cathode chamber as reference electrodes, and a Pt sheet (1 multiplied by 1cm) electrode is placed in an anode chamber as a reference electrode. The cathode chamber and the anode chamber are respectively filled with 25mL of 0.5M KHCO₃As an electrolyte. Continuously introducing high-purity CO into the cathode working chamber before the start of the electrocatalysis reaction₂(99.999%) gas for 30min to remove oxygen from the cell and saturate the electrolyte with CO₂. Continuously and constantly introducing CO in the electrocatalytic reaction process₂The flow rate was 30 mL/min. Electrocatalytic reduction of CO on the working electrode of the cathode compartment₂And (4) reacting, wherein the counter electrode in the anode chamber generates an electrolytic reaction of water. And (3) electrolyzing for 30min at each potential, sampling and analyzing a liquid product, and automatically feeding and analyzing the gas product once every 10 min. FIG. 11 shows In prepared In step 4) of example 1 In test example 1 of the present invention³⁺-O-ultra-thin-SnS₂Nano-sheet catalyst for electrocatalytic reduction of carbon dioxide performance diagram (HCOO)^-、CO、H₂Faradaic efficiency plot of the product).

Claims

1. A method for preparing a catalyst for preparing formic acid by electrocatalytic reduction of carbon dioxide, the method comprising the steps of:

step 1) reacting ZnCl₂、SnCl₄·5H₂Mixing O according to the molar ratio of 1:1Marking solution A in deionized water, fully dissolving NaOH in the deionized water to mark solution B, and dropwise adding solution B into solution A under magnetic stirring; while stirring, a white precipitate formed, giving micron-sized cubic ZnSn (OH)₆Precursor, wherein ZnCl is in A solution₂And SnCl₄·5H₂The concentration of O is 10mmol/L to 40mmol/L respectively, the concentration of NaOH in the solution B is 200mmol/L to 450mmol/L, ZnCl₂And SnCl₄·5H₂The ratio of the total molar amount of O to the molar amount of NaOH is 1:6 to 1: 10;

2. The method according to claim 1, wherein the solution A in step 1) contains ZnCl₂And SnCl₄·5H₂The concentration of O is respectively 25mmol/L, the concentration of NaOH in the solution B is 375mmol/L, ZnCl₂And SnCl₄·5H₂The ratio of the total molar amount of O to the molar amount of NaOH was 1: 7.5.

3. The preparation method according to claim 1, wherein in the hydrothermal reaction in step 2), the reaction temperature is preferably 220 ℃ and the reaction time is preferably 20 h.

4. The process according to claim 1, wherein ZnSn (OH) in the step 3)₆The preferred molar ratio of ethylene diamine tetraacetic acid to thioacetamide is 0.3:0.8: 1.8; based on 1 mole of ZnSn (OH)₆The volume of the deionized water is 120L; the hydrothermal reaction temperature is preferably 150 ℃ and the reaction time is preferably 6 h.

5. The method according to claim 1, wherein in step 4), the SnS is ultra-thin₂Sample and In (NO)₃)₃·4.5H₂The O mass ratio is preferably 1:5, In (NO)₃)₃·4.5H₂The concentration of the O/ethanol solution is preferably 13.4mmol L^-1The temperature of the water bath is preferably 60 ℃, and the treatment time is preferably 25 h.

6. In³⁺-O-ultra-thin-SnS₂Catalyst obtained according to the preparation process of any one of claims 1 to 5.

7. A composition comprising In according to claim 6³⁺-O-ultra-thin-SnS₂A working electrode of a catalyst.

8. The method of making the working electrode of claim 7, comprising: will be in accordance with claim 1In any one of (1) to (5)³⁺-O-ultra-thin-SnS₂Mixing a catalyst material with isopropanol and a Nafion solution, performing ultrasonic dispersion to obtain a mixed solution, uniformly coating the mixed solution on carbon cloth, and drying to form the working electrode;

preferably, In the method for preparing the working electrode³⁺-O-ultra-thin-SnS₂The proportion of the catalyst material to the isopropanol and Nafion solution is 6mg to 0.35mL to 0.07 mL;

9. A method for producing formic acid from carbon dioxide via an electrocatalytic reduction reaction, which is carried out using the working electrode according to claim 7 or 8.