A zinc-based catalyst for the electrochemical reduction of carbon dioxide, its preparation method and application
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2022-10-20
- Publication Date
- 2026-06-30
Smart Images
Figure CN115478283B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalysis, specifically to a zinc-based catalyst for the electrochemical reduction of carbon dioxide, its preparation method, and its application. Background Technology
[0002] The extensive use of fossil fuels has led to an unprecedented increase in atmospheric carbon dioxide concentration, a contributing factor to global warming and climate change. Electrochemical reduction of carbon dioxide, combined with renewable energy sources such as solar and wind power, can convert carbon dioxide into high-value-added chemicals and fuels, representing an effective method for achieving carbon neutrality. Electrocatalysts, crucial for carbon dioxide reduction, are currently the focus of research, primarily on precious metals (such as gold and silver), which are very expensive. Furthermore, electrocatalysts face challenges such as low activity, low selectivity, and poor stability. Therefore, the development of efficient and low-cost electrocatalysts is of great significance for the industrial application of electrochemical carbon dioxide reduction.
[0003] Zinc is an abundant and inexpensive metal that exhibits some activity in the reduction of carbon dioxide to carbon monoxide. However, compared to precious metals (such as gold and silver), zinc still suffers from drawbacks such as low selectivity and poor stability. Summary of the Invention
[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a zinc-based catalyst for the electrochemical reduction of carbon dioxide, its preparation method and application, so as to solve the technical problems of low selectivity and poor stability of zinc-based catalysts.
[0005] To achieve the above objectives, the present invention employs the following technical solution:
[0006] This invention discloses a method for preparing a zinc-based catalyst for the electrochemical reduction of carbon dioxide, comprising the following steps:
[0007] 1) Using a zinc sheet as the working electrode and an Ag / AgCl electrode as the reference electrode, a three-electrode system is formed with the counter electrode. An electrolyte is added, and then carbon dioxide gas is introduced into the system and an oxidation voltage is applied. A white film is generated on the surface of the zinc sheet as the main component of the zinc-based oxide electrode.
[0008] 2) Using the zinc-based oxide electrode generated in step 1) as the reduction electrode and the Ag / AgCl electrode as the reference electrode, a three-electrode system is formed with the counter electrode. Electrolyte is added, carbon dioxide gas is introduced into the system and a reduction voltage is applied, and the zinc-based oxide electrode is reduced to obtain a zinc-based catalyst.
[0009] Preferably, the zinc sheet used as the working electrode is a zinc sheet that has been polished to remove the oxide layer.
[0010] Preferably, the electrolyte is a potassium bicarbonate solution saturated with carbon dioxide, which is consistent with the electrolyte used for the electrochemical reduction of carbon dioxide.
[0011] More preferably, the concentration of the potassium bicarbonate solution used in steps 1) and 2) is 0.1 to 2 mol / L.
[0012] Preferably, in step 1), the applied oxidation voltage is 0.5V to 2V (relative to the silver / silver chloride reference electrode), and the treatment time is 5 to 20 minutes.
[0013] Preferably, in step 2), the applied reduction voltage is -2V to -1.2V (relative to the silver / silver chloride reference electrode), and the treatment time is 0.5 hours to 4 hours.
[0014] The present invention also discloses a zinc-based catalyst for electrochemical reduction of carbon dioxide prepared by the above preparation method. The zinc-based catalyst is a layered stacked structure dotted with hexagonal zinc nanosheets, and the width of the hexagonal zinc nanosheets is 200-400 nm.
[0015] Preferably, the zinc-based catalyst can be prepared and applied in situ.
[0016] Preferably, the zinc-based catalyst can be repeatedly activated and reused.
[0017] The present invention also discloses the application of the above-mentioned zinc-based catalyst in the electrochemical reduction of carbon dioxide to produce carbon monoxide.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] This invention discloses a method for preparing a zinc-based catalyst for the electrochemical reduction of carbon dioxide. Using zinc sheets as raw material, the method involves two steps: electrochemical oxidation and reduction, to obtain a zinc-based oxide electrode with a layer of neatly arranged hexagonal prism-shaped nanowires on its surface and a layered, stacked zinc-based catalyst dotted with hexagonal metallic zinc nanosheets. This method for preparing the zinc-based catalyst is rapid and simple, and the environmental conditions for both steps are identical to those of the electrochemical carbon dioxide reduction system. This allows for in-situ preparation of the zinc-based catalyst within the electrochemical carbon dioxide reduction system, enabling its direct application as a reduction electrode in the electrochemical reduction of carbon dioxide. This method is suitable for large-scale preparation and application.
[0020] The zinc-based catalyst prepared by the method of this invention provides a larger electrochemical active area and more active sites due to the advantageous crystal orientation and layered stacking structure of its hexagonal zinc nanosheets. This results in excellent catalytic performance for the electrochemical reduction of carbon dioxide, exhibiting good selectivity and stability for carbon monoxide. Furthermore, this zinc-based catalyst can be repeatedly activated and reused, and the reactivated catalyst still maintains good selectivity for carbon monoxide and catalytic activity for the electrochemical reduction of carbon dioxide. Based on these advantages, this zinc-based catalyst has promising prospects for industrial applications. Attached Figure Description
[0021] Figure 1 This is the X-ray diffraction (XRD) pattern of the zinc-based catalyst provided in Example 1 of this invention. The horizontal axis represents the diffraction angle 2θ, in degrees; the vertical axis represents the diffraction intensity, in relative intensity.
[0022] Figure 2 These are scanning electron microscope (SEM) images of the raw material zinc sheet a provided in Example 1 of this invention, as well as the prepared zinc-based oxide electrode b and zinc-based catalysts c and d.
[0023] Figure 3 The linear sweep voltammetry curves of the zinc-based catalyst provided in Example 1 of this invention, used as the working electrode, in 0.1 M KHCO3 electrolyte, were obtained at a scan rate of 5 mV / s. The black curve (top) a represents the linear sweep voltammetry curve of the working electrode under nitrogen saturation, and the red curve (bottom) b represents the linear sweep voltammetry curve of the working electrode under carbon dioxide saturation. The horizontal axis represents the potential relative to the reversible hydrogen electrode, in volts (V); the vertical axis represents the current density, in milliamperes per square centimeter (mA / cm²). 2 ).
[0024] Figure 4 The results are as follows: using the zinc-based catalyst provided in Example 1 of this invention as the working electrode, the product was tested in a carbon dioxide-saturated 0.1 MkHCO3 electrolyte. The horizontal axis represents the potential relative to the reversible hydrogen electrode, in volts (V); the vertical axis represents the Faraday efficiency of carbon monoxide, in %.
[0025] Figure 5 The figures provided in Example 1 of this invention, using the zinc-based catalyst as the working electrode, are time-current density and time-carbon monoxide Faradaic efficiency curves in a carbon dioxide-saturated 0.1M KHCO3 electrolyte at a constant voltage of -1.6V. The horizontal axis represents time in hours; the vertical axis represents current density (right) and carbon monoxide Faradaic efficiency (left), in milliamperes per square centimeter (mA / cm²). 2 ) (right) and % (left).
[0026] Figure 6 The images are scanning electron microscope (SEM) images of the zinc-based oxide electrode a prepared by oxidation for 20 min and the zinc-based catalyst b obtained after reduction, provided in Example 2 of this invention.
[0027] Figure 7 This is a scanning electron microscope (SEM) image of zinc-based oxide electrode a and zinc-based catalyst b after reactivation, using the zinc-based catalyst prepared in Example 2 and participating in the electrochemical reduction of carbon dioxide as raw material, as provided in Example 3 of the present invention. Detailed Implementation
[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0030] The present invention will now be described in further detail with reference to the accompanying drawings:
[0031] This invention provides a highly efficient and re-activatable zinc-based catalyst and a rapid, low-cost, and simple method for preparing the zinc-based catalyst suitable for large-scale production.
[0032] In a first aspect, the present invention provides a highly efficient zinc-based catalyst for the electrochemical reduction of carbon dioxide, which is prepared by a two-step method using zinc sheets as raw material to obtain a zinc-based oxide electrode and a zinc-based catalyst for the electrochemical reduction of carbon dioxide.
[0033] In an embodiment of the present invention, the surface of the zinc-based oxide electrode is a hexagonal prism-shaped, neatly arranged nanowire. The nanowire has a diameter of about 100 nm and a length of about 1 μm. The composition is several zinc-containing compounds, including basic zinc carbonate (Zn5(CO3)2(OH)6), zinc hydroxide (Zn(OH)2), and zinc carbonate (ZnCO3).
[0034] In embodiments of the present invention, the zinc-based catalyst for the electrochemical reduction of carbon dioxide exhibits a layered stacked structure dotted with hexagonal zinc nanosheets, the width of which is 200-400 nm. Due to the advantageous crystal orientation of the hexagonal zinc nanosheets and the larger electrochemical active area and more active sites provided by the layered stacked structure, the zinc-based catalyst of the present invention possesses excellent catalytic performance.
[0035] Figure 1 This is the X-ray diffraction (XRD) pattern of the zinc sheet, zinc-based oxide electrode, and zinc-based catalyst material provided by this invention. As can be seen from the figure, the zinc sheet generates some zinc compounds through the first electrochemical reaction. In the second electrochemical reaction, these zinc compounds are completely reduced to metallic zinc, i.e., the zinc-based catalyst described in this invention.
[0036] Figure 2 Scanning electron microscope (SEM) images of the zinc sheet a, zinc-based oxide electrode b, and zinc-based catalysts c and d provided for this invention. As can be seen from the images, the surface of the zinc-based oxide electrode consists of neatly arranged hexagonal prism nanowires with a diameter of approximately 100 nm and a length of approximately 1 μm; the surface of the zinc-based catalyst exhibits a layered stacked structure dotted with hexagonal zinc nanosheets, the width of which is 200-400 nm.
[0037] Secondly, this invention provides a rapid, low-cost, and simple method for preparing a zinc-based catalyst suitable for large-scale production. Specifically, the electrocatalyst is prepared using zinc sheets as raw material through a two-step electrochemical method. The specific preparation steps and applications are as follows:
[0038] (1) Using a zinc sheet after the oxide layer has been removed by grinding as the working electrode, KHCO3 solution as the electrolyte, and an Ag / AgCl electrode as the reference electrode, a three-electrode system is formed with a counter electrode. A certain amount of carbon dioxide gas is continuously passed through the system, and a certain oxidation voltage is applied to the system. At this time, the following reaction occurs on the surface of the working electrode:
[0039] Zn–2e - =Zn 2+
[0040] Zn 2+ +2H₂O=Zn(OH)₂+2H +
[0041] 5Zn 2+ +10HCO3 - =Zn5(CO3)2(OH)6 + 8CO2 + 2H2O
[0042] Zn 2+ +CO3 2- =ZnCO3
[0043] After a period of time, a white film can be observed to form on the surface of the zinc sheet, which is the main component of the zinc-based oxide electrode mentioned above.
[0044] (2) Using the above-mentioned zinc-based oxide electrode as the working electrode, KHCO3 solution as the electrolyte, Ag / AgCl electrode as the reference electrode, and counter electrode to form a three-electrode body, a certain amount of carbon dioxide gas is continuously passed through and a certain reduction voltage is applied, that is, placed in the electrochemical carbon dioxide reaction system. In the initial stage of the reaction, the zinc-based oxide electrode is reduced to obtain the zinc-based catalyst of the present invention.
[0045] The aforementioned zinc-based catalyst uses zinc sheets as raw material, with the prepared zinc-based catalyst forming the catalytic surface. The zinc-based oxide electrode obtained in the first step can be directly used as a reduction electrode in the electrochemical reduction of carbon dioxide. The zinc-based oxide electrode undergoes in-situ reduction in the initial stage of the reaction, and the resulting zinc-based catalyst directly participates in the electrochemical reduction of carbon dioxide. As a carbon dioxide reduction electrode, this zinc-based catalyst exhibits a selectivity of up to 92% for carbon monoxide, significantly higher than that of a pure zinc sheet electrode.
[0046] Figure 3 The zinc-based catalyst provided in this invention was used as the reduction electrode, and linear sweep voltammetry curves were obtained in 0.1 M KHCO3 solutions saturated with carbon dioxide and nitrogen, at a scan rate of 5 mV / s. Curve a (top) shows the linear sweep voltammetry curve of the zinc-based catalyst as the reduction electrode under nitrogen saturation, and curve b (bottom) shows the linear sweep voltammetry curve of the zinc-based catalyst as the reduction electrode under carbon dioxide saturation. As can be seen from the figures, the zinc-based catalyst exhibits a higher current density and a lower onset potential under carbon dioxide saturation, indicating that the zinc-based catalyst has certain catalytic activity for the electrochemical reduction of carbon dioxide.
[0047] Figure 4The zinc-based catalyst provided in this invention was used as the working electrode for the electrochemical reduction of carbon dioxide. Product test results were obtained at different reduction voltages in a carbon dioxide-saturated 0.1 M KHCO3 solution. As shown in the figure, the main product of this zinc-based catalyst is carbon monoxide. At around -1.6 V, the Faraday efficiency for carbon monoxide can reach 92%, indicating that this zinc-based catalyst has high selectivity for carbon monoxide.
[0048] Figure 5 The zinc-based catalyst provided in this invention is used as a reducing electrode, and the time-current density / carbon monoxide Faraday efficiency curve is shown in the figure in a carbon dioxide-saturated 0.1M KHCO3 solution. As can be seen from the figure, under a constant voltage of -1.6V, the current density does not decrease significantly over 70 hours, remaining stable at -4.25 ± 0.2 mA cm⁻¹. -2 Furthermore, the Faraday efficiency remained around 90%, indicating that the zinc-based catalyst exhibits good stability during the electrochemical reduction of carbon dioxide.
[0049] Thirdly, this invention provides a method for repeatedly activating and reusing the above-mentioned zinc-based catalyst in the electrochemical reduction of carbon dioxide to produce carbon monoxide. Specific embodiments are as follows:
[0050] After the zinc-based catalyst used as the working electrode for the electrochemical reduction of carbon dioxide decays, steps (1) and (2) in the second aspect are repeated to obtain a reactivated zinc-based catalyst, which can then be used in the electrochemical reduction of carbon dioxide reaction.
[0051] Figure 7 The images show scanning electron microscope (SEM) images of the zinc-based oxide electrode a and zinc-based catalyst b generated during the reactivation process of the zinc-based catalyst described in this invention. As can be seen from the figures, the morphology of the reactivated zinc-based oxide electrode and the activated zinc-based catalyst is the same as that in the initial preparation process. The catalytic performance of the reactivated zinc-based catalyst at the preferred voltage of -1.6V is shown in Table 1. This indicates that the reactivated zinc-based catalyst also exhibits good selectivity and activity for the electrochemical reduction of carbon dioxide to carbon monoxide.
[0052] Example 1
[0053] (1) After mechanical grinding and polishing to remove the oxide layer, the zinc sheet is cut to a certain size and used as the working electrode. A 0.1M KHCO3 solution saturated with carbon dioxide is used as the electrolyte, and an Ag / AgCl electrode is used as the reference electrode to form a three-electrode system. A certain amount of carbon dioxide gas is continuously introduced, and a certain oxidation voltage (1V relative to the Ag / AgCl reference electrode) is applied to the three-electrode system for 5 minutes. A series of reactions occur on the surface of the working electrode. After the reaction is completed, a white film is formed on the surface of the zinc sheet, which is the main component of the zinc-based oxide electrode of the present invention.
[0054] (2) The zinc-based oxide electrode mentioned above continues to be used as the working electrode, the 0.1M KHCO3 solution saturated with carbon dioxide is used as the electrolyte, the Ag / AgCl electrode is used as the reference electrode, and a counter electrode is added to form a three-electrode body. A certain amount of carbon dioxide gas is continuously passed through and a certain reduction voltage is applied.
[0055] In the early stage of the reduction reaction, the zinc-based oxide electrode prepared in (1) is reduced in situ to nano-zinc, i.e., the zinc-based catalyst described in this invention, whose microstructure is as follows. Figure 2 As shown in c and d, the zinc-based catalyst continues the electrochemical reduction of carbon dioxide in the system.
[0056] To further verify the catalytic effect of the zinc-based catalyst provided in Example 1 of the present invention on the electrochemical reduction of carbon dioxide, corresponding electrochemical tests were conducted.
[0057] Figure 3 Linear sweep voltammetry curves of the zinc-based catalyst provided in this embodiment as the working electrode in a 0.1 M KHCO3 electrolyte saturated with nitrogen a and carbon dioxide b are shown at a scan rate of 5 mV / s. Figure 3 It can be seen that the current density generated under carbon dioxide saturation conditions is significantly higher than that under nitrogen saturation conditions. This is because the hydrogen evolution reaction is dominant under nitrogen saturation conditions, while the carbon dioxide reduction reaction is dominant under carbon dioxide saturation conditions. This indicates that the zinc-based catalyst has significant catalytic activity for the electrochemical reduction of carbon dioxide. Figure 4 The figure shows the Faraday efficiency curves of the zinc-based catalyst for carbon monoxide at different potentials. As can be seen from the figure, the Faraday efficiency of carbon monoxide can reach 92% at a suitable potential, indicating that it has high selectivity for carbon monoxide. Figure 5 The figure shows the time / current density and time / carbon monoxide Faraday efficiency curves of the zinc-based catalyst. As can be seen from the figure, the zinc-based catalyst has good stability in the electrochemical reduction of carbon dioxide. The current density does not decrease significantly within 70 hours, and the carbon monoxide Faraday efficiency remains at around 90%.
[0058] Example 2
[0059] (1) After mechanical grinding and polishing to remove the oxide layer, the zinc sheet is cut to a certain size and used as the working electrode. A carbon dioxide-saturated 0.1M KHCO3 solution is used as the electrolyte, and an Ag / AgCl electrode is used as the reference electrode. A counter electrode is added to form a three-electrode system. A certain amount of carbon dioxide gas is continuously introduced, and a certain oxidation voltage (1V relative to the Ag / AgCl reference electrode) is applied to the three-electrode system for 20 minutes. A series of reactions occur on the surface of the working electrode. After the reaction, a white film is formed on the surface of the zinc sheet, which is the main component of the zinc-based oxide electrode of the present invention. Its microstructure is as follows: Figure 6 As shown in Figure a.
[0060] (2) The zinc-based oxide electrode described above continues to serve as the working electrode, with a carbon dioxide-saturated 0.1M KHCO3 solution as the electrolyte, an Ag / AgCl electrode as the reference electrode, and a counter electrode forming a three-electrode system. A certain amount of carbon dioxide gas is continuously passed through the electrode, and a certain reduction voltage is applied. In the early stage of the reduction reaction, the zinc-based oxide electrode prepared in (1) is reduced in situ to nano-zinc, i.e., the zinc-based catalyst described in this invention, whose microstructure is as follows: Figure 6 As shown in Figure b, the zinc-based catalyst continues the electrochemical reduction of carbon dioxide in the system. The catalytic performance of the zinc-based catalyst in the electrochemical reduction of carbon dioxide in this example is shown in Table 1.
[0061] Example 3
[0062] The zinc-based catalyst prepared in Example 2 and involved in the electrochemical reduction of carbon dioxide was reactivated. That is, the zinc-based catalyst prepared in Example 2 and involved in the electrochemical reduction of carbon dioxide was used as the working electrode, and steps (1) and (2) in Example 2 were repeated, but the time for applying the oxidation voltage was reduced to 5 minutes.
[0063] The microstructures of the zinc-based oxide electrode a and the zinc-based catalyst b obtained during the repeated activation process in this embodiment are as follows: Figure 7 As shown in the figure, the morphology of the reactivated zinc-based oxide electrode and the activated zinc-based catalyst is the same as that in the initial preparation process. The catalytic performance of the reactivated zinc-based catalyst in the electrochemical reduction of carbon dioxide in this embodiment is shown in Table 1.
[0064] Table 1 Catalytic performance of zinc-based catalysts
[0065]
[0066]
[0067] In summary, this invention provides a simple two-step electrochemical method for preparing a zinc-based oxide electrode with a layer of neatly arranged hexagonal prism-shaped nanowires and a layered stacked zinc-based catalyst dotted with hexagonal zinc nanosheets. The preparation method for this zinc-based catalyst is rapid and simple, and the two-step preparation process operates under the same environmental conditions as the electrochemical carbon dioxide reduction system. This allows for in-situ preparation of the zinc-based catalyst within the electrochemical carbon dioxide reduction system, enabling its direct application as a reduction electrode for large-scale preparation and application. Furthermore, this zinc-based catalyst exhibits excellent catalytic performance for the electrochemical reduction of carbon dioxide, demonstrating good selectivity for carbon monoxide and good stability. In addition, the zinc-based catalyst can be repeatedly activated and reused, and the repeatedly activated catalyst still exhibits good selectivity for carbon monoxide and catalytic activity for the electrochemical reduction of carbon dioxide. Based on these advantages, this zinc-based catalyst shows promising prospects for industrial applications.
[0068] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A method for the preparation of a zinc-based catalyst for the electrochemical reduction of carbon dioxide, characterized in that, Includes the following steps: 1) A zinc sheet with its oxide layer removed by polishing is used as the working electrode, and an Ag / AgCl electrode is used as the reference electrode. Together with the counter electrode, they form a three-electrode system. An electrolyte is added, which is a carbon dioxide-saturated potassium bicarbonate solution, consistent with the electrolyte used for the electrochemical reduction of carbon dioxide. Then, carbon dioxide gas is introduced into the system and an oxidation voltage of 0.5 V to 2 V is applied. The treatment time is 5 to 20 minutes. A white film composed of hexagonal prisms and neatly arranged nanowires is formed on the surface of the zinc sheet, which serves as the main component of the zinc-based oxide electrode. 2) Using the zinc-based oxide electrode generated in step 1) as the reduction electrode and the Ag / AgCl electrode as the reference electrode, a three-electrode system is formed with the counter electrode. Electrolyte is added, carbon dioxide gas is introduced into the system and a reduction voltage is applied. The applied reduction voltage is -2 V to -1.2 V, and the treatment time is 0.5 hours to 4 hours. The zinc-based oxide electrode is reduced to obtain a zinc-based catalyst.
2. The method for preparing the zinc-based catalyst for the electrochemical reduction of carbon dioxide according to claim 1, characterized in that, The concentration of potassium bicarbonate solution is 0.1~2 mol / L.
3. A zinc-based catalyst for the electrochemical reduction of carbon dioxide prepared by the preparation method according to any one of claims 1 to 2, characterized in that, The zinc-based catalyst is a layered stacked structure dotted with hexagonal zinc nanosheets, and the width of the hexagonal zinc nanosheets is 200~400 nm. The zinc-based catalyst can be repeatedly activated and reused, and the repeatedly activated zinc-based catalyst has carbon monoxide selectivity and electrochemical carbon dioxide reduction catalytic activity.
4. The zinc-based catalyst for the electrochemical reduction of carbon dioxide according to claim 3, characterized in that, This zinc-based catalyst can be prepared in situ.
5. The application of the zinc-based catalyst according to any one of claims 3 to 4 in the electrochemical reduction of carbon dioxide to produce carbon monoxide.