Electrocatalyst based on spiral carrier modified Cu monatomic as well as preparation method and application of electrocatalyst

Abstract

The invention provides an electrocatalyst based on spiral carrier modified Cu monatomic and a preparation method and application thereof, and belongs to the technical field of monatomic catalytic material preparation. Chiral small molecules are used as an element structure, morphology isomerization of a composite catalyst carrier precursor is achieved, and the composite catalyst has typical spiral characteristics and has the structural potential of regulating and controlling an electrochemical microenvironment in an electro-catalysis carbon dioxide reduction reaction; by utilizing electrostatic adsorption, a metal salt is combined with a carrier precursor with an organic property, regulation and optimization of the Cu monatomic loading capacity in the spiral carrier modified Cu monatomic electrocatalyst are realized, and the preparation technology is simple and universal and is easy for industrial production; by customizing a spiral carrier for a Cu single atom, changing an electronic structure of the Cu atom and inducing electrons of a Cu atom site to be converted into a high-spin state from a low-spin state, the adsorption energy of the catalyst to a key intermediate is reduced, the activity of the catalyst in electrocatalytic carbon dioxide reduction reaction is improved, and the yield of formic acid is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-atom catalytic material preparation, and specifically relates to an electrocatalyst based on a spiral carrier modified Cu single atom, and a preparation method and application thereof. Background Art

[0002] Electrocatalytic CO2 reduction reaction (ECO2RR) technology is considered a key guarantee for solving the current greenhouse effect and energy shortage problems. Researchers are committed to developing relevant catalysts to assist ECO2RR research in converting CO2 into carbon-based chemicals or fuels with high energy density and high economic value. However, current ECO2RR catalysts still have problems such as low catalytic activity, low product selectivity, and insufficient long-cycle performance.

[0003] Electrocatalyst materials play a decisive role in the ECO2RR reaction. A good catalyst needs to quickly enrich reactants, suppress the competition of the competitive hydrogen evolution side reaction (HER), improve product selectivity, and take into account working conditions including reaction activity and stability. At present, precious metal materials, non-metallic materials and metal-organic framework materials have been widely used in the ECO2RR reaction. However, due to the uncertainty of the active sites in the study of general scales such as micrometers and sub-nanometer catalyst materials, it is difficult to reflect the real proton-coupled electron transfer mechanism in the ECO2RR process, and it is also difficult to take into account the advantages of catalytic performance and cost. Single-atom-based catalysts have excellent performance in ECO2RR research due to their unique electronic structure, theoretically the highest atomic utilization efficiency and stable catalytic performance, and have great potential for industrial application. However, due to the lack of effective carrier construction methods, the metal Cu single-atom-based catalyst has insufficient regulation of its own catalytic activity, and the Faradaic selectivity for electrocatalytic CO2 reduction to produce formic acid is not high.

[0004] Therefore, the design and preparation of functional carriers for the metal Cu single atom active sites in order to regulate their electronic structure and improve the adsorption relationship between the active center and the formic acid precursor intermediate still requires in-depth research. Problems such as the low activity of existing Cu-based single atom catalysts in the electrocatalytic production of formic acid from CO2 and poor product selectivity also need to be urgently addressed. Summary of the invention

[0005] The present invention is based on the above background technology and aims to provide an electrocatalyst based on a spiral carrier modified Cu single atom and a preparation method and application thereof.

[0006] The invention provides a preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom, which has the following characteristics and comprises the following steps: S10, mixing an ethanol dispersion of a single one of D-glutamic acid or L-glutamic acid with an aqueous dispersion of pyrrole to obtain a mixed solution; S20, adding ammonium persulfate into the mixed solution for stirring reaction, and separating to obtain spiral polypyrrole; S30, dispersing the spiral polypyrrole in methanol, adding copper acetate tetrahydrate thereto, heating after ultrasonication for reaction, separating and drying to obtain a catalyst precursor; S40, annealing, pickling, washing and drying the catalyst precursor to obtain Cu SAs / HCNT, i.e., an electrocatalyst based on a spiral carrier modified Cu single atom, wherein the content of Cu single atom in the electrocatalyst based on a spiral carrier modified Cu single atom is adjusted by adjusting the feeding amount of copper acetate tetrahydrate in step S30.

[0007] In the preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein, step S10 includes the following sub-steps: S11, dispersing the pyrrole monomer in water, mixing to obtain a first dispersion; S12, ultrasonically dispersing a single type of D-glutamic acid or L-glutamic acid in ethanol to obtain a second dispersion; S13, under low temperature stirring conditions, adding the second dispersion into the first dispersion and stirring for a certain period of time to obtain a mixed solution.

[0008] In the preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein, in step S11, the volume concentration of pyrrole in the first dispersion is 0.2% to 0.5%, and the mixing condition is stirring in an ice-water bath for more than 10 minutes; in step S12, the concentration of D-glutamic acid or L-glutamic acid in the second dispersion is 1.2 mg / mL to 2.4 mg / mL, and the mixing condition is stirring at room temperature for more than 15 minutes; in step S13, the feed volume ratio of the first dispersion to the second dispersion is 2:1.

[0009] In the preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein, step S20 includes the following sub-steps: S21, adding ammonium persulfate into the mixed solution and stirring the reaction to obtain a spiral polypyrrole dispersion; S22, centrifuging, washing, vacuum drying and grinding the spiral polypyrrole dispersion to obtain the spiral polypyrrole.

[0010] In the preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein the molar ratio of pyrrole in step S10, D-glutamic acid or L-glutamic acid in step S21, and ammonium persulfate in step S21 is 1:1:(1~2), the stirring time is 15 minutes, and the stirring rate is 800rpm~2000rpm.

[0011] In the preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein, in step S30, the mass ratio of spiral polypyrrole to copper acetate tetrahydrate is 40:(9-36), the ultrasonic time is 30min-60min, the heating reaction method is stirring for 20h-24h under 40℃-60℃ water bath conditions, the separation method is centrifugal separation, and the drying method is freeze-drying.

[0012] In the preparation method of an electrocatalyst based on a spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein, in step S40, the annealing treatment method is: in a tube furnace, under an inert atmosphere, heating to 800°C~850°C at a heating rate of 2°C / min~5°C / min and annealing for 2h~3h, the pickling method is: dispersed in sulfuric acid (aq) for pickling, the liquid used for washing is deionized water, and the drying method is freeze-drying.

[0013] In the preparation method of the electrocatalyst based on the spiral carrier modified Cu single atom provided by the present invention, it can also have the following characteristics: wherein the concentration of sulfuric acid (aq) is 1.0 mol / L to 1.2 mol / L.

[0014] The present invention also provides an electrocatalyst based on a spiral carrier modified Cu single atom, which has the following characteristics: it is prepared by any of the aforementioned methods for preparing an electrocatalyst based on a spiral carrier modified Cu single atom, wherein the electrocatalyst based on a spiral carrier modified Cu single atom is a nanofiber with a spiral structure characteristic, whose diameter is 70nm to 100nm and whose length is 1μm to 2μm, and the Cu single atom loading of the electrocatalyst based on a spiral carrier modified Cu single atom is 1.12wt% to 3.79wt%.

[0015] The present invention also provides an application of an electrocatalyst based on a spiral carrier modified Cu single atom in the electrocatalytic production of formic acid from CO2, wherein, when the feed mass ratio of spiral polypyrrole to copper acetate tetrahydrate in step S30 is 5:18, the electrocatalyst based on a spiral carrier modified Cu single atom maintains a formic acid product selectivity greater than 80% (-1.05V, E vs. RHE), and the stable operation time is greater than 30 hours.

[0016] Functions and Effects of the Invention

[0017] The present invention utilizes chiral small molecules as metastructures and successfully realizes the morphological isomerization of the composite catalyst carrier precursor, so that the composite catalyst has typical helical characteristics and has the structural potential to regulate the electrochemical microenvironment in the ECO2RR reaction.

[0018] The present invention utilizes the general strategy of electrostatic adsorption to successfully combine metal salts with organic carrier precursors, and realizes the regulation and optimization of the Cu single atom loading in Cu SAs / HCNT. The relevant preparation technology is simple and universal, and is convenient for industrial production practice.

[0019] The present invention customizes a helical carrier for Cu single atoms, which changes the electronic structure of the Cu active site compared to a non-helical carrier, induces the electrons at the Cu atomic site to change from a low-spin state to a high-spin state, significantly reduces the adsorption free energy of the catalyst Cu SAs / HCNT for key intermediates, improves its ECO2RR reaction activity, and increases the formic acid yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flowchart of a method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom in an embodiment of the present invention;

[0021] Figure 2 is a diagram of the preparation strategy of helical polypyrrole in an embodiment of the present invention;

[0022] Figure 3 The SEM images of the helical polypyrrole obtained in the preparation process S22 of the catalyst 2 in the embodiment of the present invention and the non-helical polypyrrole fiber carrier obtained in the preparation process S22 of the comparative sample are compared;

[0023] Figure 4 It is a comparison of SEM images of catalyst 2 (electrocatalyst based on helical support modified Cu single atom) in the embodiment of the present invention and a comparative sample (electrocatalyst based on non-helical support modified Cu single atom);

[0024] Figure 5 TEM images of catalyst 2 and a comparative sample in the embodiment of the present invention are compared;

[0025] Figure 6 TEM images of catalyst 1 and catalyst 3 in the embodiment of the present invention;

[0026] Figure 7 is an AC-TEM image of catalyst 2 in an embodiment of the present invention;

[0027] Figure 8is the X-ray photoelectron spectrum of catalyst 2 in the embodiment of the present invention, including N1s high resolution and O1s high resolution spectra;

[0028] Fig. 9 The linear sweep voltammogram (LSV) of catalyst 1, catalyst 2 and catalyst 3 in the test example of the present invention, wherein the electrochemical operating conditions are 0.1M KHCO3 electrolyte under a fixed cell, the scanning window is 0V to -1.65V (E vs. RHE), and the scanning speed is 50mV / s; Fig.10 is a Faraday efficiency diagram of the ECO2RR reaction products of catalyst 1, catalyst 2 and catalyst 3 in the test example of the present invention;

[0029] Fig.11 This is a long cycle stability test of catalyst 2 in the test example of the present invention. DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following examples and drawings specifically illustrate an electrocatalyst based on a spiral carrier modified Cu single atom and its preparation method and application of the present invention.

[0031] <Example>

[0032] Figure 1 It is a flowchart of a method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom in an embodiment of the present invention; Figure 2 Schematic diagram of the preparation strategy of helical polypyrrole in the embodiment of the present invention.

[0033] like Figure 1 and 2 As shown, this embodiment provides a method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom, comprising the following steps:

[0034] S10, mixing an ethanol dispersion of either D-glutamic acid or L-glutamic acid with an aqueous dispersion of pyrrole to obtain a mixed solution, specifically comprising the following sub-steps:

[0035] S11, dispersing 0.498 mL of pyrrole monomer in 120 mL of deionized water, stirring in an ice-water bath for more than 10 min to obtain a first dispersion;

[0036] S12, dispersing 1.05 g of D-glutamic acid or L-glutamic acid in 60 mL of ethanol by ultrasonication, and stirring at room temperature for more than 15 min to obtain a second dispersion;

[0037] S13, in an ice water bath and under magnetic stirring at 1000 rpm, the second dispersion liquid is added into the first dispersion liquid at once and stirred for 15 minutes to obtain a mixed liquid.

[0038] S20, adding ammonium persulfate into the mixed solution and stirring for reaction, and separating and obtaining helical polypyrrole, specifically comprising the following sub-steps:

[0039] S21, adding 1.8 g of ammonium persulfate into the mixed solution and stirring the mixture for 1.5 h to obtain a helical polypyrrole dispersion;

[0040] S22, the helical polypyrrole dispersion is centrifuged, washed (to remove excess reactants and by-product small molecules), vacuum dried and ground to obtain black helical polypyrrole.

[0041] S30, weigh 200 mg of helical polypyrrole, disperse it in methanol, add 45 mg to 180 mg of copper acetate tetrahydrate, ultrasonicate for 30 min, stir for 24 h in a 40° C. water bath, centrifuge and freeze-dry to obtain a catalyst precursor.

[0042] S40, the catalyst precursor is heated to 800°C at a heating rate of 5°C / min in an argon atmosphere in a tube furnace and annealed for 2h, then dispersed in a 1M sulfuric acid solution for acid washing, then washed with deionized water, and finally dried to obtain Cu SAs / HCNT, that is, an electrocatalyst based on a spiral carrier modified Cu single atom.

[0043] This embodiment also provides an electrocatalyst based on a spiral carrier modified Cu single atom, which is prepared by the preparation method of the electrocatalyst based on a spiral carrier modified Cu single atom in this embodiment.

[0044] In this example, three electrocatalysts based on spiral carrier modified Cu single atoms (Cu SAs / HCNT) were prepared, which were respectively named catalyst 1, catalyst 2 and catalyst 3.

[0045] The preparation processes of catalyst 1, catalyst 2 and catalyst 3 are generally similar, the only difference being that the feeding amount of copper acetate tetrahydrate in step S30 of the preparation process is 45 mg, 90 mg and 180 mg respectively. The Cu loading in the above three catalysts is 1.12 wt%, 2.01 wt% and 3.79 wt% respectively.

[0046] In this embodiment, a non-helical Cu single atom electrocatalyst (Cu SAs / NHCNT) was also prepared, which was recorded as a comparative sample. The preparation process and parameters of the comparative sample were generally similar to those of the preparation process of catalyst 1, with the only difference being that the raw material used in step S12 of the preparation process was the racemic form of glutamic acid (DL-glutamic acid).

[0047] Figure 3The SEM images of the helical polypyrrole obtained in the preparation process S22 of the catalyst 2 in the embodiment of the present invention and the non-helical polypyrrole fiber carrier obtained in the preparation process S22 of the comparative sample are compared.

[0048] like Figure 3 As shown in the figure, the helical polypyrrole carrier has obvious helical twisting features and a relatively rough surface. In comparison, the non-helical polypyrrole, although similar to the helical polypyrrole in fiber length and diameter, does not show any twisting features and has a relatively smooth surface.

[0049] Figure 4 It is a comparison of SEM images of catalyst 2 (electrocatalyst based on helical support modified Cu single atom) in the embodiment of the present invention and a comparative sample (electrocatalyst based on non-helical support modified Cu single atom); Figure 5 TEM images of catalyst 2 and a comparative sample in the embodiment of the present invention are compared.

[0050] like Figure 4 and 5 As shown, catalyst 2 is a nanofiber with helical structural characteristics, with a diameter of 70nm-100nm and a length of 1μm-2μm, and consistent with the precursor carrier, catalyst 2 has obvious helical twisting characteristics, and the carbonized carrier structure shows obvious pitch. The control sample is consistent with its precursor template non-helical polypyrrole fiber, no pitch or twisting characteristics are observed, and the surface is relatively smooth.

[0051] Figure 6 TEM images of catalyst 1 and catalyst 3 in Examples of the present invention.

[0052] like Figure 6 As shown, the helical polypyrrole template showed good compatibility with Cu single atoms, and the morphology of the composite catalysts under different loading amounts did not show obvious changes. Even in catalyst 3 with the highest Cu loading amount, no Cu metal-related particles or aggregation of Cu species were observed, which indicates that Cu single atoms were well dispersed on the helical support according to the above strategy.

[0053] Figure 7 is an AC-TEM image of catalyst 2 in an example of the present invention.

[0054] like Figure 7 As shown, the atomic image of the Cu species of Catalyst 2 (electrocatalyst based on spiral support modified Cu single atom) of this embodiment is clearly discernible.

[0055] Figure 8 It is the X-ray photoelectron spectrum of catalyst 2 in the embodiment of the present invention, including N1s high resolution and O1s high resolution spectra.

[0056] like Figure 8As shown, the chemical structure of catalyst 2 was analyzed by X-ray photoelectron spectroscopy. From the presence of Cu-N peak in N1s high resolution spectrum and Cu-O peak in O1s high resolution spectrum, the Cu single atom in the catalyst was co-coordinated with N and O.

[0057] <Test example>

[0058] This test example conducts corresponding electrochemical performance tests on catalyst 1, catalyst 2 and catalyst 3 in the embodiment, and provides an application of an electrocatalyst based on a spiral carrier modified Cu single atom in the electrocatalytic production of formic acid from CO2.

[0059] First, catalyst 1, catalyst 2, and catalyst 3 were placed in a fixed cell for electrochemical performance testing.

[0060] Fig. 9 The linear sweep voltammogram (LSV) of catalyst 1, catalyst 2 and catalyst 3 in the test example of the present invention, wherein the electrochemical operating conditions are 0.1M KHCO3 electrolyte under a fixed cell, the scanning window is 0V to -1.65V (E vs. RHE), and the scanning speed is 50mV / s; Fig.10 3 is a Faraday efficiency diagram of the ECO2RR reaction products of catalyst 1, catalyst 2 and catalyst 3 in the test example of the present invention.

[0061] like Fig. 9 and 10 As shown, catalyst 2 (Cu loading is 2.01 wt%) has the highest Faradaic efficiency for electrocatalytic reduction of CO2 to produce formic acid at -1.05 V (E vs. RHE).

[0062] Fig.11 This is a long cycle stability test of catalyst 2 in the test example of the present invention.

[0063] like Fig.11 As shown, Catalyst 2 is the optimal sample, which can maintain a high level of formic acid product selectivity greater than 80% (-1.05 V, E vs. RHE) at a large current and a stable operation time of more than 30 h.

[0064] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing an electrocatalyst based on a helical carrier modified Cu single atom, characterized in that: The following steps are involved: S10, mixing an ethanol dispersion of D-glutamic acid or L-glutamic acid with an aqueous dispersion of pyrrole to obtain a mixed solution; S20, adding ammonium persulfate into the mixed solution and stirring for reaction, and separating and obtaining helical polypyrrole; S30, dispersing the helical polypyrrole in methanol, adding copper acetate tetrahydrate thereto, performing ultrasonication and then heating for reaction, separating and drying to obtain a catalyst precursor; S40, annealing, pickling, washing and drying the catalyst precursor to obtain Cu SAs / HCNT, i.e., an electrocatalyst based on a spiral carrier modified Cu single atom, The content of Cu single atoms in the electrocatalyst based on spiral carrier-modified Cu single atoms is adjusted by adjusting the feeding amount of copper acetate tetrahydrate in step S30.

2. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 1, characterized in that: in, Step S10 includes the following sub-steps: S11, dispersing pyrrole monomer in water, and mixing to obtain a first dispersion; S12, dispersing D-glutamic acid or L-glutamic acid alone in ethanol by ultrasonication to obtain a second dispersion; S13, under low temperature stirring conditions, adding the second dispersion liquid into the first dispersion liquid and stirring for a certain period of time to obtain the mixed liquid.

3. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 2, characterized in that: in, In step S11, the volume concentration of pyrrole in the first dispersion is 0.2% to 0.5%, and the mixing condition is stirring in an ice-water bath for more than 10 minutes. In step S12, the concentration of D-glutamic acid or L-glutamic acid in the second dispersion is 1.2 mg / mL to 2.4 mg / mL, and the mixing condition is stirring at room temperature for more than 15 minutes. In step S13, the volume ratio of the first dispersion liquid to the second dispersion liquid is 2:

1.

4. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 1, characterized in that: in, Step S20 includes the following sub-steps: S21, adding ammonium persulfate into the mixed solution and stirring to react to obtain a helical polypyrrole dispersion; S22, centrifuging, washing, vacuum drying and grinding the helical polypyrrole dispersion to obtain the helical polypyrrole.

5. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 4, characterized in that: in, The molar ratio of pyrrole in step S10, D-glutamic acid or L-glutamic acid in step S10, and ammonium persulfate in step S21 is 1:1:(1-2), The stirring time is 15 minutes, and the stirring speed is 800 rpm to 2000 rpm.

6. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 1, characterized in that: in, In step S30, the mass ratio of the spiral polypyrrole to copper acetate tetrahydrate is 40:(9-36), Ultrasound duration is 30 to 60 minutes. The heating reaction is carried out by stirring in a water bath at 40°C to 60°C for 20h to 24h. The separation method is centrifugal separation. The drying method is freeze drying.

7. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 1, characterized in that: in, In step S40, the annealing treatment method is: in a tube furnace, in an inert atmosphere, heating to 800°C to 850°C at a heating rate of 2°C / min to 5°C / min for annealing for 2h to 3h, The pickling method is: disperse in sulfuric acid (aq) for pickling, The liquid used for washing is deionized water. The drying method is freeze drying.

8. The method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to claim 7, characterized in that: in, The concentration of sulfuric acid (aq) is 1.0 mol / L to 1.2 mol / L.

9. An electrocatalyst based on a helical carrier modified Cu single atom, characterized in that: The electrocatalyst is prepared by the method for preparing an electrocatalyst based on a spiral carrier modified Cu single atom according to any one of claims 1 to 8, The electrocatalyst based on the helical carrier modified Cu single atom is a nanofiber with helical structural characteristics, with a diameter of 70nm to 100nm and a length of 1μm to 2μm. The Cu single atom loading amount of the electrocatalyst based on the spiral carrier modified Cu single atom is 1.12 wt % to 3.79 wt %.

10. Use of the electrocatalyst based on helical carrier modified Cu single atom as claimed in claim 9 in electrocatalytic CO2 production of formic acid, in, When the mass ratio of the spiral polypyrrole to copper acetate tetrahydrate in step S30 is 5:18, the electrocatalyst based on spiral carrier modified Cu single atom maintains formic acid product selectivity greater than 80% (-1.05V, E vs. RHE), and the stable operation time is greater than 30h.

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