An electrocatalytic carbon dioxide reduction method utilizing tensile and compressive strain synergistically driven asymmetric C–C coupling

Abstract

This invention belongs to the technical field of electrocatalytic CO2 reduction reaction (ECO2RR), specifically relating to an electrocatalytic CO2 reduction method that utilizes tensile and compressive strain to synergistically drive asymmetric C–C coupling. The method includes the following steps: First, loading a catalyst with tensile and compressive strain onto a gas diffusion electrode to prepare a working electrode; Second, assembling the working electrode prepared in the first step with a counter electrode and a reference electrode to form a three-electrode flow electrolysis cell system; Third, introducing carbon dioxide gas and using an alkaline or neutral solution as the electrolyte to carry out ECO2RR, generating multi-carbon (C2) carbon dioxide. 2+ The product is obtained by using a catalyst, preferably a copper-based catalyst, which is a metallic material. Compared to existing technologies, this invention solves the problems of slow C–C coupling kinetics and the inability to achieve high current densities for C… 2+ Technical problems include low product selectivity and poor long-term operational stability.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic carbon dioxide reduction reaction (ECO2RR) technology, specifically relating to an ECO2RR method that utilizes tensile strain and compressive strain (hereinafter referred to as "tension and compression") to synergistically drive asymmetric C–C coupling. It is particularly suitable for the efficient preparation of multi-carbon (C2R) compounds at industrial-grade current densities. 2+ )product. Background Technology

[0002] Copper-based catalysts in the production of C from ECO2RR 2+ This product has significant application value, but its core bottleneck lies in the slow C–C coupling kinetics. Traditional understanding mainly focuses on the symmetrical *CO–*CO coupling pathway, considering it to be the C–C coupling pathway. 2+ The rate-determining step in product formation is often overlooked, however, as this view ignores an inherent contradiction: on the one hand, high *CO coverage is needed to provide sufficient coupling precursors; on the other hand, high coverage exacerbates the dipole-dipole repulsion effect between *CO molecules, thus inhibiting subsequent C-C coupling. Recent theoretical studies indicate that asymmetric coupling pathways mediated by intermediates such as *CHO or *COH have significant advantages: firstly, they can break the symmetry of the coupling electron pairs, effectively lowering the C-C coupling energy barrier; secondly, they can expand product diversity (such as more complex oxygen-containing products like ethanol and propanol). However, achieving asymmetric coupling pathways requires simultaneous control of *CO adsorption strength, surface coverage, and hydrogenation kinetics; the synergistic control of these parameters far exceeds the design capabilities of traditional copper catalysts.

[0003] In practical applications of ECO2RR, existing technologies face key challenges: when the current density is increased to industrial-grade levels, due to mass transfer limitations and the intensification of competitive hydrogen evolution reactions, C 2+ Product selectivity decreases sharply. Furthermore, existing electrocatalytic systems struggle to maintain stable C–C coupling kinetics at high current densities, resulting in poor long-term operational stability. 2+ The Faraday efficiency of the product decays significantly within a few hours. These theoretical bottlenecks and practical application challenges together restrict the industrialization process of ECO2RR technology.

[0004] Lattice strain engineering, as an effective means of controlling the electronic structure of catalysts, has shown unique advantages in the field of electrocatalysis. Different types of strain (compressive and tensile strain) have drastically different regulatory effects on catalytic performance. In recent years, methods for constructing copper-based catalysts with tensile and compressive strain fields have been reported; however, their application value in ECO2RR has not been fully recognized, and the regulatory mechanism of spatially separated tensile and compressive strain fields on the C–C coupling pathway lacks systematic research. Existing studies mostly focus on the effect of single strain on catalytic performance, and research on the synergistic effect of tensile and compressive strain fields has not been reported. Therefore, how to utilize the spatial synergistic effect of tensile and compressive strain fields to drive asymmetric C–C coupling and achieve high selectivity and high stability in ECO2RR for C production at industrial-grade current densities is a key research area. 2+ The product has become a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an ECO2RR method that utilizes the synergistic driving of tensile and compressive strain to propel asymmetric C–C coupling, thereby solving the problems of slow C–C coupling kinetics and the limitations of C–C coupling at high current densities in existing technologies. 2+ Technical problems include low product selectivity and poor long-term operational stability.

[0006] To solve the above problems, the technical solution of the present invention is as follows: An electrocatalytic carbon dioxide reduction method utilizing tensile and compressive strain synergistically driving asymmetric C–C coupling, the method comprising the following steps: The first step is to load a catalyst with tensile and compressive strain onto a gas diffusion electrode to prepare the working electrode; The second step is to assemble the working electrode prepared in the first step with the counter electrode and the reference electrode into a three-electrode flow electrolysis cell system. The third step involves introducing carbon dioxide gas, using an alkaline or neutral solution as the electrolyte, at a temperature of 0.1–3.0 A·cm⁻¹. −2 ECO2RR is performed at current density to generate C 2+ product.

[0007] As an improvement to the method of the present invention, the catalyst with synergistic regulation of tensile and compressive strain is a metallic material.

[0008] In a preferred embodiment of the method of the present invention, the metal material is a copper-based catalyst. Under the synergistic regulation of tensile and compressive strain, the copper-based catalyst can achieve excellent ECO2RR performance.

[0009] As a further preferred embodiment of the method of the present invention, the copper-based catalyst has spatially separated compressive strain regions and tensile strain regions, which are distributed at nanoscale intervals. The compressive strain regions enhance *CO adsorption, while the tensile strain regions promote water dissociation and *CO hydrogenation to *COH. The spatial synergistic effect of the two drives the asymmetric coupling of *CO–*COH, significantly reducing the C–C coupling energy barrier.

[0010] As an improvement to the method of the present invention, the local strain degree of the compressive strain region and the tensile strain region is ±1% to ±10%.

[0011] As an improvement to the method of the present invention, the catalyst loading in the first step is 0.1–2.0 mg∙cm⁻¹. −2 .

[0012] As an improvement to the method of the present invention, the specific components of the gas diffusion electrode in the first step are carbon fiber, carbon black, polytetrafluoroethylene, etc.; in the second step, the counter electrode is at least one of nickel foam, iridium dioxide mesh, and carbon paper, and the reference electrode is an Ag / AgCl reference electrode.

[0013] As an improvement to the method of the present invention, the alkaline or neutral solution in the third step is at least one of KOH, KHCO3, and K2SO4 solutions, with a concentration of 0.1–5.0 M.

[0014] As an improvement to the method of the present invention, the C 2+ The product includes at least one of ethylene, ethanol, acetic acid, and propanol.

[0015] As an improvement to the method of the present invention, the preparation method of the copper-based catalyst with spatially separated tensile and compressive strain fields is a wet chemical reduction method, which includes at least the following steps: The first step is to dissolve the copper source and the nickel source in an organic solvent and stir until they are evenly mixed. The second step is to add an aqueous solution of sodium borohydride to the resulting solution so that the copper and nickel sources undergo a reduction reaction with it. The third step involves allowing the product obtained in the second step to stand, then washing, centrifuging and purifying it, followed by vacuum freeze-drying to obtain a copper-based catalyst with a spatially separated tensile and compressive strain field.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Effectively solved the technical problem of slow C–C coupling kinetics in traditional copper-based catalysts. Through the synergistic effect of tensile and compressive strain fields, an asymmetric coupling pathway from *CO to *COH was achieved. The Tafel slope for C2H4 formation was reduced to 62.6 mV·dec. −1 (Compared to 91.2 mV·dec for strain-free copper-based catalysts)−1 This indicates that the method of the present invention significantly accelerates the C–C coupling dynamics process; 2. Effectively solved the problem of C under high current density. 2+ The technical problem of low product selectivity. At 1.6 A∙cm −2 At industrial-grade current density, C 2+ The product achieves a Faraday efficiency of 88.9%, corresponding to a bias current density of 7103 A∙g. −1 (Corrected for catalyst loading mass), setting a new record high to date. And within 0.6–2.0 A∙cm⁻¹ −2 Over a wide current density range, C 2+ The product's Faraday efficiency remains stable at over 75%, which is significantly better than the defect of traditional copper-based catalysts where the selectivity drops sharply at high current densities, and it has excellent prospects for industrial application. 3. Effectively solved the technical problem of poor long-term operational stability. In a 17-hour long-term stability test (current density 0.6 A∙cm⁻¹), −2 The Faraday efficiency of C2H4 remained above 50%, while the Faraday efficiency of H2 remained below 10%, demonstrating good operational stability. Attached Figure Description

[0017] Figure 1 The diagram shows the ECO2RR performance of the catalyst used in this invention in a three-electrode flow electrolyzer, where (a) is the linear sweep voltammetry (LSV) curve and (b) is the 0.8 A∙cm⁻¹ curve. −2 Product distribution at current density: (c) is the Tefel slope diagram of C2H4 formation, and (d) is the online differential electrochemical mass spectrometry (DEMS) test results. Figure 2 The following is a graph showing the ECO2RR performance of the method of the present invention in a thin liquid layer flow cell, where (a) is the product distribution under different current densities, (b) is a comparison with the performance of the catalyst reported in the literature, and (c) is the 17-hour stability test. Figure 3 Optimized structures for Cu(111) surfaces with different strain levels and adsorption coupling intermediates in theoretical calculations: (a) optimized structures for compressive strain Cu (ɛ = −5%), (b) strain-free Cu (ɛ = 0) and (c) tensile strain Cu (ɛ = 5%) Cu(111) surfaces; (d) optimized structures for ɛ = −5%, (e) ɛ = 0 and (f) ɛ = 5% Cu(111) surfaces *OCCO; (g) optimized structures for ɛ = −5%, (h) ɛ = 0 and (i) ɛ = 5% Cu(111) surfaces *OCCOH. Figure 4The figures show the theoretical calculation results, where (a) is the adsorption energy of *CO on the Cu(111) surface at different strain levels (−5%, 0 and +5%); (b) is the Gibbs free energy barrier for H2O dissociation; (c) is the Gibbs free energy barrier for the *CO hydrogenation pathway; (d) is the Gibbs free energy barrier for the C–C coupling step; and (e) is the reaction order analysis of CO generated from C2H4 on the catalyst. Figure 5 This is a schematic diagram of the mechanism of asymmetric C–C coupling driven by the synergistic tension-compression strain in the method of the present invention. Detailed Implementation

[0018] To make the above-mentioned objectives, technical solutions and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0019] It should be noted that the tension-compression synergistic regulation strategy of the present invention is applicable to various metal material systems, including but not limited to copper, silver, gold, nickel, iron, cobalt, zinc, and their alloys. The following examples use copper-based catalysts as a detailed description, but should not be construed as limiting the scope of protection of the present invention.

[0020] The copper-based catalyst with spatially separated tensile and compressive strain used in the examples was prepared by the following method: The first step is to dissolve the copper source and the nickel source in an organic solvent and stir until they are evenly mixed. The second step is to add an aqueous solution of sodium borohydride to the resulting solution so that the copper and nickel sources undergo a reduction reaction with it. The third step involves allowing the product obtained in the second step to stand, then washing, centrifuging and purifying it, followed by vacuum freeze-drying to obtain a copper-based catalyst with a spatially separated tensile and compressive strain field.

[0021] The copper source is at least one selected from copper nitrate, copper chloride, copper sulfate, and copper acetate; the nickel source is at least one selected from nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate; and the molar ratio of the copper source to the nickel source is 100:1–5000:1. The solvent is selected from at least one selected from ethylene glycol monoethyl ether, ethylene glycol, and propylene glycol. The concentration of the reducing agent aqueous solution in the second step is 100–300 mg·mL. −1 In the third step, the settling time is 1–10 hours, the washing frequency is 3–10 times, and the vacuum freeze-drying time is 12–24 hours to obtain a copper-based catalyst with spatially separated compressive and tensile strain. This catalyst has spatially separated compressive strain regions and tensile strain regions, which are distributed at nanoscale intervals with a local strain degree of ±5%.

[0022] This invention details one of the preparation methods: (1) Prepare chemical raw materials: copper nitrate trihydrate, nickel nitrate hexahydrate, sodium borohydride, ethylene glycol monoethyl ether; instruments and equipment: electronic balance, ultrasonic cleaner, magnetic stirrer, centrifuge, vacuum freeze dryer.

[0023] (2) Dissolve 241.6 mg of copper nitrate trihydrate and 0.30 mg of nickel nitrate hexahydrate in an appropriate amount of ethylene glycol monoethyl ether solvent. Under ultrasonic conditions, add the nickel nitrate solution dropwise to the copper nitrate solution and stir vigorously for 30 minutes to mix thoroughly.

[0024] (3) Dissolve 378.4 mg of sodium borohydride in 2 mL of deionized water, and quickly add the solution to the above mixture. A black precipitate will be produced immediately.

[0025] (4) Let the mixture obtained in step (3) stand for 3 hours, wash the precipitate with deionized water 5 times, centrifuge each time, and finally freeze dry in vacuum at −65℃ for 18 hours to obtain a black powder material, which is a copper-based catalyst with a spatially separated tensile and compressive strain field. Example 1

[0026] Electrode preparation and electrochemical testing (1) Preparation of chemical raw materials: copper-based catalyst with spatial separation tensile and compressive strain field, isopropanol, Nafion (5wt%) solution, Ag / AgCl reference electrode, nickel foam, anion exchange membrane, potassium hydroxide; Instruments and equipment: electronic balance, ultrasonic cleaner, electrochemical workstation, gas chromatograph, nuclear magnetic resonance hydrogen spectrometer.

[0027] (2) Electrode preparation: 10.0 mg of copper-based catalyst powder with tensile and compressive strain fields was weighed and mixed with 500 μL of isopropanol and 500 μL of deionized water. 30 μL of Nafion (5 wt%) solution was added as a binder. The mixture was ultrasonically treated in an ice-water bath for 30 minutes to form a uniformly dispersed ink. Subsequently, it was loaded onto a 3 cm × 3 cm commercial gas diffusion electrode by spraying and dried at 60 °C for 30 minutes. The catalyst loading was 0.2 mg∙cm⁻¹. −2 The electrode prepared is denoted as Cu-BLS.

[0028] (3) Electrolytic cell assembly: The working electrode, nickel foam counter electrode and Ag / AgCl reference electrode prepared in step (2) are assembled into a three-electrode flow electrolytic cell system, with the anolyte tank and the cathode tank separated by an anion exchange membrane.

[0029] (4) Electrochemical test: CO2 was introduced (flow rate of 20 sccm), and 1.0 M KOH solution was used as electrolyte. ECO2RR test was performed at different current densities. The reaction products were quantitatively analyzed by gas chromatography and nuclear magnetic resonance hydrogen spectroscopy.

[0030] Comparative Example 1 The ECO2RR test was performed according to the method in Example 1, but a strainless copper-based catalyst was used instead of a copper-based catalyst with a tensile and compressive strain field. All other conditions were the same, and the resulting electrode was denoted as Cu-ref.

[0031] Performance test results In a three-electrode flow electrolysis cell system, Cu-BLS with tensile and compressive strain fields exhibited a significantly higher current density under CO2 atmosphere than under Ar atmosphere, and the activity initiation potential was more positive, confirming its excellent CO2 catalytic activity. Figure 1 a). At 0.8 A·cm −2 At current density ( Figure 1 b) Cu-BLS achieves a Faraday efficiency of 60.2% for C2H4, C 2+ The overall Faraday efficiency of the product was 84.3%, significantly better than that of Cu-ref (C₂H₄) and (C₂H₄) (C₂H₄). 2+ Through in-depth analysis of reaction kinetics, it was found that ( Figure 1 c), the Tafel slope of C2H4 formation in Cu-BLS is significantly reduced (62.6 vs. 91.2 mV dec). −1 This indicates that its C–C coupling kinetics are more favorable. DEMS test results ( Figure 1 d) Further, it is shown that the onset potential of C2H4 generation on the Cu-BLS surface shifts positively by about 290 mV (−0.31 V vs. −0.60 V vs. RHE).

[0032] In a thin-layer flow electrolytic cell, Cu-BLS is used at a current of 0.6–2.0 A·cm⁻¹. −2 It exhibits excellent C over a wide current density range. 2+ Product selectivity, its Faraday efficiency remains consistently above 75% ( Figure 2 a). At 1.6 A·cm −2 At that time, C 2+ The product achieved a Faradaic efficiency of 88.9%, with the C2H4 Faradaic efficiency reaching as high as 61.4%. This performance significantly surpasses that of most similar catalysts reported in the literature. Figure 2 b), created 7103 A·g −1 C 2+ A new record for product bias current density was achieved. In a 17-hour long-term stability test (current density 0.6 A·cm⁻¹), a new record was set. −2 , Figure 2c) The Faraday efficiency of Cu-BLS C2H4 remains above 50%, while the Faraday efficiency of H2 is consistently below 10%, indicating that it has excellent long-term operational stability.

[0033] Example 2 Unlike Example 1, the catalyst loading in step (2) is 0.3 mg∙cm⁻¹. −2 .

[0034] The rest is the same as in Example 1, and will not be repeated here.

[0035] Example 3 Unlike Example 1, the catalyst loading in the first step was 1.0 mg∙cm⁻¹. −2 .

[0036] The rest is the same as in Example 1, and will not be repeated here.

[0037] Example 4 Unlike Example 1, the counter electrode in step (3) is an iridium dioxide mesh.

[0038] The rest is the same as in Example 1, and will not be repeated here.

[0039] Example 5 Unlike Example 1, the counter electrode in step (3) is carbon paper.

[0040] The rest is the same as in Example 1, and will not be repeated here.

[0041] Example 6 Unlike Example 1, the alkaline or neutral solution in step (4) is 1.0 M K2SO4.

[0042] The rest is the same as in Example 1, and will not be repeated here.

[0043] Example 7 Unlike Example 1, the alkaline or neutral solution in step (4) is 1.0 M KHCO3.

[0044] The rest is the same as in Example 1, and will not be repeated here.

[0045] Example 8 Unlike Example 1, the alkaline or neutral solution in step (4) is 3.0 M KOH.

[0046] The rest is the same as in Example 1, and will not be repeated here.

[0047] Mechanism analysis To elucidate the mechanism of asymmetric C–C coupling driven by synergistic tensile and compressive strain, we performed density functional theory (DFT) calculations. Simulations were performed on a Cu(111) surface with controllable strain levels (ɛ = −5%, 0, +5%). Figure 3 The influence of surface strain state on the adsorption behavior of key intermediates was systematically evaluated.

[0048] Calculation results ( Figure 4 a) This shows that compressive strain (ɛ = −5%) enhances the adsorption energy of *CO on the Cu surface to −0.74 eV, while on unstrained Cu (ɛ = 0), the adsorption energy is −0.56 eV, and on the tensile strained surface (ɛ = +5%), it weakens to −0.47 eV. This indicates that the compressive strain region has a stronger adsorption capacity for *CO, which is beneficial for providing a key intermediate for subsequent C–C coupling. On the other hand, tensile strain lowers the free energy barrier for H2O dissociation to only 0.02 eV (while the free energy barrier on unstrained Cu is 0.13 eV). After the formation of *H, hydrogenation of *CO preferentially forms *COH (ΔG = 0.14 eV) on tensile strained Cu, rather than *CHO (ΔG = 0.37 eV). Figure 4 c). The subsequent asymmetric *CO–*COH coupling is determined to be the rate-determining step, with its Gibbs free energy becoming ΔG = 0.71 eV. Figure 4 d), while the symmetric *CO–*CO coupling path exhibits a higher kinetic energy barrier (ΔG ≥ 1.02 eV) on Cu surfaces with different strain levels.

[0049] After the CO reaction order ( n CO Quantitative analysis further confirmed the regulatory mechanism of tensile-compressive strain engineering on the C–C coupling pathway. The results show that the catalyst with tensile-compressive strain fields influences the formation of C2H4. n CO A value of 1.07 reflects the dominance of asymmetric *CO–*COH coupling; while the uniaxial strain catalyst... n CO The value is 2.07, consistent with the reaction order characteristics of the *CO dimerization pathway. These findings suggest that *CO adsorbed at the compression site (enhanced adsorption) migrates to the stretching site (promoting *COH formation), which can facilitate asymmetric *CO–*COH coupling.

[0050] Mechanism verification Based on experimental results and theoretical calculations, the mechanism of asymmetric C–C coupling driven by synergistic tension and compression strain in the method of this invention is as follows ( Figure 5 ): The compressive strain region enhances *CO adsorption, providing ample precursors for C–C coupling; the tensile strain region promotes H2O dissociation, accelerating the hydrogenation of *CO to *COH. The spatial proximity of these two types of strain regions allows *CO adsorbed in the compressive region to migrate to the tensile region, undergoing asymmetric coupling with *COH to form the *OCCOH intermediate. The energy barrier of this process is more than 0.17 eV lower than that of the symmetric *CO–*CO coupling. This synergistic tensile-compressive strain mechanism effectively overcomes the kinetic bottleneck of traditional copper-based catalysts in C–C coupling, achieving high selectivity for C at industrial-grade current densities. 2+ Product synthesis.

[0051] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for electrocatalytic carbon dioxide reduction utilizing spatially separated tensile and compressive strain to synergistically regulate asymmetric C–C coupling, characterized in that, The method includes the following steps: The first step is to load a catalyst with tensile strain and compressive strain onto a gas diffusion electrode to prepare a working electrode; The second step is to assemble the working electrode prepared in the first step with the counter electrode and the reference electrode into a three-electrode flow electrolysis cell system. The third step involves introducing carbon dioxide gas, using an alkaline or neutral solution as the electrolyte, at a temperature of 0.1–3.0 A·cm⁻¹. −2 Electrocatalytic carbon dioxide reduction reaction is carried out at a certain current density to generate multi-carbon products.

2. The method according to claim 1, characterized in that, The catalyst is a metallic material.

3. The method according to claim 2, characterized in that, The catalyst is a copper-based catalyst.

4. The method according to claim 3, characterized in that, The copper-based catalyst has spatially separated compressive strain regions and tensile strain regions, which are distributed at nanoscale intervals.

5. The method according to claim 4, characterized in that, The strain degree of the compressive strain region and the tensile strain region is ±1% to ±10%.

6. The method according to claim 1, characterized in that, The catalyst loading in the first step is 0.1–2.0 mg∙cm⁻¹. −2。 7. The method according to claim 1, characterized in that, In the first step, the gas diffusion electrode is composed of at least one of carbon fiber, carbon black, and polytetrafluoroethylene; in the second step, the counter electrode is composed of at least one of nickel foam, iridium dioxide mesh, or carbon paper, and the reference electrode is an Ag / AgCl reference electrode.

8. The method according to claim 1, characterized in that, The alkaline or neutral solution mentioned in the third step is at least one of KOH, KHCO3 or K2SO4 solution, with a concentration of 0.1–5.0 M.

9. The method according to claim 1, characterized in that, The multicarbon product includes at least one of ethylene, ethanol, acetic acid, or propanol.

10. The method according to claim 4, characterized in that: The preparation method of copper-based catalysts with spatially separated tensile and compressive strain fields is a wet chemical reduction method, which includes at least the following steps: The first step is to dissolve the copper source and the nickel source in an organic solvent and stir until they are evenly mixed. The second step is to add an aqueous solution of sodium borohydride to the obtained solution, so that the copper source and nickel source can undergo a reduction reaction with sodium borohydride; The third step involves allowing the product obtained in the second step to stand, then washing, centrifuging and purifying it, followed by vacuum freeze-drying to obtain a copper-based catalyst with a spatially separated tensile and compressive strain field.

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