A catalyst for the electrocatalytic synthesis of multi-carbon products from CO2 and its preparation method.

Abstract

This invention belongs to the technical field of CO2 electrochemical reduction, specifically relating to a catalyst for the electrocatalytic synthesis of multi-carbon products from CO2 and its preparation method. The catalyst is CuInS with Cu-In dual active centers. 2‑x Nanomaterials. This catalyst exhibits both high electrocatalytic activity for CO2RR and high activity for C. 2+ The high selectivity of the product can significantly improve the energy efficiency of CO2 utilization.

Description

Technical Field

[0001] This invention belongs to the technical field of CO2 electrochemical reduction, specifically relating to a catalyst for the electrocatalytic synthesis of multi-carbon products from CO2 and its preparation method. Background Technology

[0002] Electrocatalytic CO2 reduction reaction (CO2RR) is an energy conversion technology that converts CO2 into economically viable small-molecule fuels. These small-molecule fuels include C1 (such as CO, CH3OH, etc.) and C2O2. 2+ (e.g., C2H4, C2H6, C2H5OH, etc.). Small molecule fuels can be coupled with unstable renewable energy sources (such as solar, wind, and hydropower) to achieve peak shaving for new energy sources, and are expected to form a sustainable artificial carbon cycle system, providing a sustainable and carbon-neutral method for storing intermittent renewable electricity.

[0003] In promoting CO2RR, C-C bond coupling occurs, and the synthesized product contains multi-carbon products (C-C). 2+ Compared to C1 products, it has higher energy density and wider applicability, and therefore higher economic value.

[0004] For C 2+ There are two main pathways for the formation of the product: (1) *CO dimerizes at low overpotential to form *OCCO species; (2) *CO is hydrogenated to form *CHO substances, which is a common intermediate for the formation of methane and occurs at high overpotential.

[0005] CC-C bond coupling is highly sensitive to the structure of both the catalyst and the electrolyte. Currently, the catalysts promoting CC-C bond coupling are standalone Cu-based catalysts; however, the optimal conditions for their electrocatalytic CO2RR require relatively high overpotentials, such as -1.4V vs. RHE for CuO-BN (vs. RHE represents the voltage relative to the reference electrode (reversible hydrogen electrode)). Furthermore, most existing Cu-based catalysts exhibit high overpotential (FE). C2+ Lower (FE is used to evaluate product selectivity), FE C2+ The range is ≤50%, so C is visible. 2+ The product selectivity is low. The high operating voltage and low selectivity of currently used electrocatalysts limit the synthesis of C from CO2RR. 2+ Further development of the product.

[0006] Therefore, there is an urgent need for a catalyst with low operating voltage and high selectivity for the electrocatalytic synthesis of multi-carbon products from CO2. Summary of the Invention

[0007] The purpose of this invention is to provide a catalyst for the electrocatalytic synthesis of multi-carbon products from CO2 and its preparation method. This catalyst exhibits both high electrocatalytic activity for CO2RR and high activity for C... 2+ The high selectivity of the product can significantly improve the energy efficiency of CO2 utilization.

[0008] The technical solution of this invention is: a catalyst for the electrocatalytic synthesis of multi-carbon products from CO2 is CuInS with Cu-In dual active centers. 2-x Nanomaterials.

[0009] Where 2-x represents the coordination number of S, and because there is an S defect, the coordination number of S is less than 2.

[0010] Furthermore, the aforementioned CuInS 2-x The nanomaterials have a flower-shaped, folded cluster structure.

[0011] One method for preparing the above-mentioned catalyst involves first synthesizing In2S3 with a flower-shaped, folded cluster structure via a solvothermal reaction, and then doping Cu into the defect sites of the flower-shaped, folded cluster In2S3 using an electrochemical ion substitution method to obtain CuInS3 with Cu-In dual active centers. 2-x catalyst.

[0012] The preparation method first utilizes a solvothermal synthesis approach using ionic liquids. Ionic liquids possess abundant and dispersed tridentate sites and anion coordination. Through the interaction between the ionic liquid and In ions, the thermodynamic and kinetic properties of In ion reduction are modulated, enhancing the solvothermal reaction to prepare In2S3 with a unique flower-like, ruffled cluster structure. This flower-like, ruffled cluster structure significantly increases the specific surface area of ​​the catalyst, provides more electron channels, and offers sufficient active sites for subsequent ion substitution.

[0013] Then, a simple and green dual-active-site composite method is used, namely, the direct substitution of Cu and In elements by electrochemical ion substitution. Cu can quickly and effectively embed into the defect sites on the In surface to construct a fine micro-nano structure of the catalyst layer and prepare Cu-In dual-active-site catalyst.

[0014] Furthermore, the method for preparing the catalyst includes the following steps:

[0015] (1) Preparation of In2S3 precursor solution: Indium source and sulfur source are dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to form a milky white solution;

[0016] (2) Synthesis of In2S3: The In2S3 precursor solution obtained in step (1) is heated at 100-120℃ for 15-20h to carry out a solvothermal reaction; after the reaction is completed, it is separated by centrifugation, collected, washed, and freeze-dried to obtain In2S3 with a flower-shaped folded cluster structure.

[0017] (3) Preparation of In2S3 carbon paper electrode: First, the In2S3 powder obtained in step (2) is mixed with isopropanol, deionized water and Nafion solution with a mass fraction of 5% to prepare a catalyst ink solution; then the catalyst ink solution is uniformly sprayed onto the carbon paper electrode substrate, dried and set aside.

[0018] (4) Synthesis of CuInS 2-x CuCl₂·2H₂O was dissolved in deionized water to prepare a 0.02-0.04 mol / L CuCl₂ electrolyte, labeled as solution A. An In₂S₃ carbon paper electrode was immersed in solution A, with the reaction time controlled at 10-20 min, and the CuCl₂ concentration controlled at a constant level. 2+ When the concentration is between 0.02-0.04 mol / L, and the open-circuit voltage (OCV) is between 0.1V and 0.4V, Cu... 2+ Cu atoms undergo an elemental substitution reaction with In. This simple and environmentally friendly ion exchange method allows for the direct doping of Cu atoms into defect sites of flower-shaped, ruffled In-based materials, yielding CuInS after the reaction. 2-x The catalyst is the Cu-In dual-active-center electrocatalyst.

[0019] Furthermore, in step (1) of the catalyst preparation method, the mass ratio of indium source to sulfur source is 0.3-0.5:1; the mass ratio of indium source to 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid is 0.05-0.08:1.

[0020] Preferably, the mass ratio of indium source to sulfur source is 0.4:1; and the mass ratio of indium source to 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid is 0.07:1.

[0021] When synthesizing In2S3, controlling the S source content will generate S defects. At the same time, the S defects will have a reaction effect on the coordination environment of In, triggering the generation of In defects.

[0022] Furthermore, in step (1) of the catalyst preparation method, the indium source is selected from one of InCl3·4H2O, In(NO3)3·H2O, and In2(SO4)3; the sulfur source is selected from Na2S·9H2O or K2S·5H2O.

[0023] Furthermore, in step (2) of the catalyst preparation method, the centrifugal speed for centrifugation is 7000-9000 rpm; the washing is performed three times with deionized water and ethanol respectively; and the freeze-drying time is 24 h.

[0024] Furthermore, in step (3) of the catalyst preparation method, the amount of In2S3 powder is 0.01-0.02g; the volume of Nafion solution is 0.05-0.10ml; the volume of isopropanol is 0.3-0.5ml; and the volume of deionized water is 0.7-0.8ml.

[0025] The beneficial effects of this invention are as follows: the catalyst described in this invention is CuInS with Cu-In dual active centers. 2-x In the CO2RR application process, In is thermodynamically favorable for the adsorption of HCO3* and H*. - It is also an effective proton donor; the In active site helps enhance proton transport and adsorption, lowers the energy barrier of the RDS reaction, and facilitates the formation of the CHO* intermediate. Cu promotes subsequent C-C bond coupling, forming the *OHCCHO* intermediate, achieving a continuous electron and proton transfer reaction, synergistically promoting the CO2→CHO*→*OHCCHO*→C 2+ The product's reaction pathway involves highly selective catalytic reduction of CO2 to C under low operating voltage. 2+ The product exhibits synergistic effects of Cu and In in multiple ways. The dual active catalytic sites accelerate the formation of reaction intermediates and promote C / C bond coupling, thereby effectively enhancing the C-reaction reaction. 2+ The product conversion efficiency was improved, and the conversion of CO2 to C was significantly increased. 2+ Product selectivity,

[0026] A novel approach to enhance proton adsorption and lower the catalytic rate control barrier: Reduce the formation energy barrier of the rate-controlling step CHO*, promoting the reaction CO2→CHO*→*OHCCHO*→C 2+ The reaction pathway of the product enables the highly selective synthesis of C at low operating voltage. 2+ Products. In2S3 can only electrocatalyze the production of formic acid, CO, and hydrogen from CO2, but cannot reduce CO2 to C. 2+ Products such as Cu-InS2-x catalysts with dual Cu-In active sites can produce C with high selectivity at lower operating potentials. 2+ product.

[0027] This invention meticulously designs the structure of the final product during the preparation process, and obtains CuInS with Cu-In dual active centers through carefully designed steps and parameters. 2-zWhen used as an electrochemical reducing agent for carbon dioxide, the catalyst exhibits both high electrocatalytic activity and selectivity for carbon dioxide reduction, significantly improving C… 2+ The Faraday efficiency of the product. Attached Figure Description

[0028] Figure 1 Cu-In bimetallic sulfide CuInS prepared in Example 1 of this invention 2-x SEM images and elemental distribution images of the catalyst.

[0029] Figure 2 Cu-In bimetallic sulfide CuInS as described in Example 1 of this invention 2-x Catalytic performance (voltage-Faraday efficiency) graph from catalyst performance test chart.

[0030] Figure 3 This is a SEM image of the flower-shaped In monometallic sulfide In2S3 prepared in Comparative Example 1 of the present invention.

[0031] Figure 4 The image shows the performance test graph (voltage-Faraday efficiency graph) of the In monometallic sulfide In2S3 catalyst of Comparative Example 1 of this invention.

[0032] Figure 5 The CuInS obtained in Example 1 of this invention 2-x Catalyst and In2S obtained from Comparative Example 1 3-x A comparison graph showing the relationship between current density and voltage of a catalyst.

[0033] Figure 6 The CuInS obtained in Example 1 of this invention 2-x Catalyst and In2S obtained from Comparative Example 1 3-x A comparison of the relationship between the ethanol current density and voltage of the catalyst. Detailed Implementation

[0034] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0035] Example 1

[0036] The catalyst used for the electrocatalytic synthesis of multi-carbon products from CO2 is CuInS with Cu-In dual active centers. 2-x Nanomaterials.

[0037] The preparation method of this catalyst includes the following steps:

[0038] (1) Preparation of In2S3 precursor solution:

[0039] Using 1-butyl-3-methylimidazolium hexafluorophosphate as the solvent, 0.293 g of InCl3·4H2O and 0.721 g of Na2S·9H2O were dissolved in 4 g of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to form a milky white solution.

[0040] (2) Synthesis of In2S3:

[0041] In2S3, an In-based material substrate with flower-shaped, ruffled clusters, was initially synthesized using a solvothermal reaction. The milky-white In2S3 precursor solution obtained in step (1) was transferred to a 50 mL autoclave and heated at 120 °C for 16 h to conduct a solvothermal reaction under high temperature and pressure. After the reaction, the sample was collected by centrifugation and washed three times with deionized water and ethanol, respectively. Finally, the obtained product was freeze-dried to obtain the In-based material In2S3.

[0042] (3) Preparation of In2S3 carbon paper electrode:

[0043] Take 0.01g of the flower-shaped ruffled In2S3 powder obtained in step (2), mix it in a mixture containing 0.3mL isopropanol, 0.7mL deionized water, and 0.08mL of 5% Nafion, and sonicate for 15min to prepare a catalyst ink solution. Then take 0.1ml of the above ink solution and spray it evenly onto a carbon paper electrode substrate, and dry it in a vacuum drying oven for 12h. The area of ​​the carbon paper electrode is approximately 1*1cm. 2 The In2S3 loading on the carbon paper electrode is approximately 1 mg·cm³. -2 .

[0044] (4) Synthesis of CuInS 2-x catalyst:

[0045] 0.136 g of CuCl₂·2H₂O was dissolved in 40 mL of deionized water to prepare a 0.02 mol / L CuCl₂ electrolyte, labeled as solution A. Finally, an In-based In₂S₃ carbon paper electrode was immersed in solution A, and the reaction time (10 min) and Cu precursor concentration (0.02 mol / L) were controlled to maintain an open-circuit voltage (OCV) between 0.1 V and 0.4 V. 2+ Cu atoms undergo an elemental substitution reaction with In, doping them into the defect sites of the flower-shaped, ruffled clusters of In-based materials. The reaction then yields CuInS. 2-x The catalyst is the Cu-In dual-active-center electrocatalyst.

[0046] Among the key factors that affect the number of defect sites on the In surface are the mass ratio of indium source to sulfur source, the temperature of solvothermal reaction, and the reaction time. Only by properly controlling these parameters can flower-shaped folded clusters of In2S3 be prepared.

[0047] Cu in the process of effectively embedding In surface defect sites 2+ The choice of electrolyte concentration and the reaction time of the ion exchange reaction play important roles.

[0048] pass Figure 1 Scanning electron microscopy (SEM) images show that CuInS obtained after ion exchange 2-x The structure remains largely unchanged, exhibiting a flower-shaped, folded cluster structure. Analysis of the mapping results shows that Cu, In, and S are uniformly distributed in the catalyst, proving that the reaction between Cu and In₂S₃ is complete, and the Cu-In dual active sites are distributed throughout the catalyst.

[0049] like Figure 2 As shown, CuInS with Cu-In dual active centers 2-x Catalysts can produce C 2+ The product, in which the selectivity of ethanol (FE) C2H5OH At -0.63V, it reaches 80%, accompanied by the formation of ethylene, ethane, carbon monoxide and a small amount of methane.

[0050] Comparative Example 1

[0051] The comparative example uses In2S as the electrochemical reduction catalyst for CO2. 3-x catalyst.

[0052] The method for preparing the carbon dioxide electrochemical reduction catalyst is characterized by comprising the following steps:

[0053] (1) Preparation of In2S3 precursor solution:

[0054] 0.293g InCl3·4H2O and 0.721g Na2S·9H2O were dissolved in 4g 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to form a milky white solution.

[0055] (2) Synthetic flower-shaped ruffled clusters In2S 3-x catalyst:

[0056] A solvothermal reaction was used to synthesize flower-shaped ruffled clusters of In2S. 3-xThe milky white In₂S₃ precursor solution obtained in step (1) was transferred to a 50 mL autoclave and heated at 120 °C for 16 h to carry out a solvothermal reaction under high temperature and high pressure. After the reaction was completed, the sample was collected by centrifugation and washed three times with deionized water and ethanol, respectively. Finally, the obtained product was freeze-dried to obtain In₂S₃. 3-x catalyst.

[0057] (3) Preparation of In2S 3-x Catalyst carbon paper electrode:

[0058] Take 0.01g of the flower-shaped ruffled In2S3 powder obtained in step (2), mix it in a mixture containing 0.3mL isopropanol, 0.7mL DDI and 0.08mL Nafion (5% by mass), and sonicate for 15min to prepare a catalyst ink solution. Then take 0.1ml of the above ink solution and spray it evenly onto a carbon paper electrode substrate, and dry it overnight in a vacuum drying oven to obtain In2S3. 3-x Electrodes. The carbon paper electrode has an area of ​​approximately 1*1 cm². 2 In2S on carbon paper electrodes 3-x The loading capacity is approximately 1 mg·cm³. -2 .

[0059] pass Figure 3 Scanning electron microscopy (SEM) images showed that the obtained In2S3 exhibited a flower-shaped, frilled cluster structure. This flower-shaped, frilled cluster structure significantly increased the specific surface area of ​​the catalyst, provided more electron channels, and offered sufficient defect sites for subsequent ion substitution.

[0060] like Figure 4 As shown, at -0.93V vs. RHE, the formic acid selectivity of In2S3 reached 82%, while the formic acid selectivity of the other two products was FE. CO It is 9%, FE H2 It is 8%.

[0061] like Figure 5 As shown, within the applied voltage range, CuInS with Cu-In dual active centers... 2-x The catalyst's current density is higher than that of In2S. 3-x The current density variation trend is even greater in CuInS 2-x The catalyst always maintains a ratio to In2S 3-x The higher current density indicates that CuInS 2-x The catalyst has higher electrochemical activity.

[0062] like Figure 6 As shown, at -0.73V vs. RHE, CuInS 2-xThe catalyst achieved a maximum current density of 17 mA·cm⁻¹ for ethanol. -2 At each operating voltage, In2S 3-x The ethanol current density was close to zero, indicating that In₂S₂ had not undergone Cu ion exchange. 3-x It cannot reduce CO2 to ethanol.

[0063] It is evident that In2S3 alone cannot generate C. 2+ product.

Claims

1. A catalyst for electrocatalytic CO2 synthesis of multi-carbon products, characterized in that, The catalyst is CuInS with Cu-In dual active centers 2-x Nanomaterials; The catalyst is prepared by the following steps: firstly, In2S3 with petaloid pleated cluster structure is synthesized by a solvothermal reaction, and then Cu is doped into the defect sites of the petaloid pleated cluster In2S3 by an electrochemical ion replacement method to obtain CuInS with Cu-In dual active centers 2-x catalyst The specific steps are as follows: (1) Preparation of In2S3 precursor solution: dissolve indium source and sulfur source into 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to form a milky white solution; (2) Synthesis of In2S3: heat the In2S3 precursor solution prepared in step (1) at 100-120℃ for 15-20h to perform a solvothermal reaction; after the reaction is completed, centrifugal separation is performed, and the product is collected, washed, and freeze-dried to obtain In2S3 with petaloid ruffled cluster structure; (3) Preparation of In2S3 carbon paper electrode: first, mix the In2S3 powder prepared in step (2) with isopropanol, secondary deionized water, and 5% Nafion solution to prepare a catalyst ink solution; then, uniformly spray the catalyst ink solution on a carbon paper electrode substrate, dry, and reserve for use; (4) synthesis of CuInS 2-x : CuCl2·2H2O is dissolved in deionized water to prepare a CuCl2 electrolyte with a concentration of 0.02-0.04 mol / L, which is marked as solution A; an In2S3 carbon paper electrode is immersed in solution A, the reaction time is controlled to be 10-20 min, and the Cu 2+ concentration is controlled to be 0.02-0.04 mol / L, Cu atoms are doped into defect sites of In2S3 with petaloid spherical pleat cluster structure under an open circuit voltage of 0.1-0.4 V, and CuInS 2-x catalyst, i.e., the CuInS with Cu-In dual active centers 2-x catalyst.

2. The catalyst for electrocatalytic CO2 synthesis of multi-carbon products of claim 1, wherein, The CuInS 2-x The nanomaterial is a flower ball-shaped ruffled cluster structure.

3. The catalyst for electrocatalytic CO2 synthesis of multi-carbon products of claim 1, wherein, The mass ratio of the indium source to the sulfur source in step (1) is 0.3-0.5:1; The mass ratio of the indium source to 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid is 0.05-0.08:

1.

4. The catalyst for electrocatalytic CO2 synthesis of multi-carbon products of claim 3, wherein, The mass ratio of the indium source to the sulfur source is 0.4:1; The mass ratio of the indium source to 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid is 0.07:

1.

5. The catalyst for electrocatalytic CO2 synthesis of multi-carbon products of claim 1, wherein, The indium source in step (1) is selected from one of InCl3·4H2O, In(NO3)3·H2O, and In2(SO4)3; and the sulfur source is selected from Na2S·9H2O or K2S·5H2O.

6. The catalyst for electrocatalytic CO2 synthesis of multi-carbon products of claim 1, wherein, The centrifugal speed for centrifugal separation in step (2) is 7000-9000rpm; the washing is performed with deionized water and ethanol for three times respectively; and the freeze-drying time is 24h.

7. The catalyst for electrocatalytic CO2 synthesis of multi-carbon products of claim 1, wherein, In step (3), the In2S3 powder is 0.01-0.02g; the volume of the Nafion solution is 0.05-0.10ml, the volume of isopropanol is 0.3-0.5ml, and the volume of secondary deionized water is 0.7-0.8ml.

Images