Method of improving efficiency to electrocatalyze co2 to form co by using pulse wave electrochemistry

Abstract

This disclosure provides a method for improving the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation via pulsed wave electrochemistry. The method includes the following steps: applying a voltage with a pulsed waveform over time to a metal-containing catalyst on an electrode to modify the metal-containing catalyst to form a modified metal-containing catalyst; and electrolyzing carbon dioxide in an electrolytic cell to form carbon monoxide, wherein the cathode electrode in the electrolytic cell includes an electrode and the modified metal-containing catalyst.

Description

[Technical Field]

[0001] This disclosure relates to a method for improving the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation by pulsed wave electrochemistry. [Previous Technology]

[0002] With the ever-increasing demand for energy, carbon dioxide produced from energy fuels has gradually become one of the main causes of global warming. To reduce carbon emissions, carbon dioxide can be reduced through electrochemical reactions (CO2RR), thus converting it into other materials or other energy materials that are more in line with the green economy, such as syngas (carbon monoxide and hydrogen). In other words, carbon dioxide emissions can not only be reduced by converting it into other materials, but also promote economic growth in a more environmentally friendly way by forming energy materials such as syngas. However, there are still many problems to be solved in the technology of converting carbon dioxide using electrochemical methods. For example, the efficiency of converting carbon dioxide at low potentials may be very low, and the reaction current may be very low (equivalent to a very low yield). Moreover, the catalytic materials used to improve the conversion efficiency of carbon dioxide at low potentials, such as gold, silver, and platinum, may be too expensive to be economically viable for industrial applications. Therefore, given the limitations of industrial development, it is necessary to develop a new electrochemical method to reduce carbon dioxide emissions, which can not only reduce costs, but also stably convert a relatively large amount of green energy materials at relatively low potentials with higher efficiency. [Summary of the Invention]

[0003] This disclosure provides a method for improving the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation. The method includes the following operations: applying a voltage with a pulsed waveform that varies with time to a metal-containing catalyst on an electrode to modify the metal-containing catalyst to form a modified metal-containing catalyst. Using the modified metal-containing catalyst together with the electrode as the cathode electrode in an electrolytic cell to electrolyze carbon dioxide to form carbon monoxide.

[0004] In some embodiments, when a metal-containing catalyst is modified by applying a voltage with a pulsed waveform that varies over time to the metal-containing catalyst on the electrode, a portion of the metal-containing catalyst is reduced.

[0005] In some embodiments, the voltage changes over time from an initial voltage to a negative voltage and then to an ending negative voltage.

[0006] In some embodiments, the starting voltage is 0 V to -1.6 V, and the ending negative voltage is -1.2 V to -2.8 V.

[0007] In some embodiments, the voltage change over time includes at least one forward square pulse and at least one reverse square pulse, wherein the at least one forward square pulse changes the voltage in the negative voltage direction and the at least one reverse square pulse changes the voltage in the positive voltage direction.

[0008] In some embodiments, the voltage variation over time includes a plurality of square pulses, and the amplitude of each of the square pulses is from 10 mV to 1400 mV.

[0009] In some embodiments, the voltage change over time includes a plurality of pulses, and the width of each pulse is from 2 ms to 250 ms.

[0010] In some embodiments, applying a voltage with a pulsed waveform over time to the metal-containing catalyst on the electrode to modify the metal-containing catalyst includes repeatedly applying a voltage with a pulsed waveform over time to the metal-containing catalyst on the electrode at least twice to modify the metal-containing catalyst.

[0011] In some embodiments, the total execution time for applying a voltage with a pulsed waveform to the metal-containing catalyst on the electrode to modify the metal-containing catalyst is less than or equal to 8 hours.

[0012] In some embodiments, the metal-containing catalyst includes a zinc-containing ceramic compound.

Implementation Method

[0014] To make the description of this disclosure more detailed and complete, various embodiments are described below in an illustrative manner, but this is not to limit the embodiments of this disclosure to the only form. The embodiments of this disclosure may be combined with and / or substituted for each other where advantageous, and other embodiments may be added without further explanation.

[0015] Spatial relative terms, such as up and down, are used in drawings to describe the relationship between one element (or feature) and another element (or feature). In addition to the directions described in the drawings, spatial relative terms are intended to cover different orientations of the device during use or operation. For example, the device may be oriented in other ways (e.g., rotated 90 degrees), and therefore the spatial relative terms can be interpreted accordingly. In this disclosure, unless otherwise stated, the same element symbols in different drawings refer to the same or similar elements formed from the same or similar materials by the same or similar methods.

[0016] The terms "approximately," "substantially," "truly," etc., used in this disclosure include values ​​(or characteristics) and deviations of said values ​​(or characteristics) as understood by those skilled in the art. For example, taking into account errors in values ​​(or characteristics), these terms may refer to values ​​within one or more standard deviations (e.g., values ​​within ±30%, ±20%, ±15%, ±10%, or ±5%), or may refer to deviations including those caused by practical operation (e.g., the description "truly parallel" may indicate practically close to parallel rather than ideally perfect parallel). Furthermore, an acceptable range of deviation may be selected depending on the nature or other properties of the measurement, and a single range of deviation may not apply to all values ​​(or characteristics).

[0017] This disclosure provides a method 100 for improving the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation, as shown in Figure 1. Method 100 includes operations 101 to 102. Operation 101 includes applying a voltage with a pulsed waveform to a metal-containing catalyst on an electrode over time to modify the metal-containing catalyst and form a modified metal-containing catalyst. Operation 102 includes electrolyzing carbon dioxide in an electrolytic cell to form carbon monoxide, wherein the cathode electrode in the electrolytic cell includes an electrode and the modified metal-containing catalyst. By applying a voltage with a pulsed waveform to the metal-containing catalyst over time, the metal-containing catalyst can be modified, for example, by changing the valence state of the metal in the metal-containing catalyst or changing the surface properties of the metal-containing catalyst, thereby improving the conductivity and active sites of the modified metal-containing catalyst. Therefore, it helps to make the modified metal-containing catalyst more easily adsorb carbon dioxide and improve catalytic efficiency. The method 100 of this disclosure will now be described in detail with reference to some embodiments.

[0018] In operation 101, a voltage with a pulsed waveform is applied to the metal-containing catalyst on the electrode over time to modify the metal-containing catalyst and form a modified metal-containing catalyst. Since the metal-containing catalyst is disposed on the electrode, the properties of the metal-containing catalyst thereon can be changed by voltage variation through the application of a voltage with a pulsed waveform over time to the electrode. In some embodiments, the application of a voltage with a pulsed waveform over time to the metal-containing catalyst on the electrode is performed by an electrochemical device (e.g., an electrochemical device with a three-electrode system). In some embodiments, when modifying the metal-containing catalyst by applying a voltage with a pulsed waveform over time to the metal-containing catalyst on the electrode, it is preferable to reduce a portion of the metal-containing catalyst (e.g., the surface portion) (e.g., the valence state of the metal in the metal-containing catalyst changes to a higher reduced state) without oxidizing the metal-containing catalyst. In some embodiments, the metal catalyst, along with the electrode, is disposed in the cathode cell at the cathode end (but not the anode end) of the electrochemical device to reduce the metal catalyst. Therefore, the electrode with the metal catalyst disposed thereon can be called the cathode electrode in the electrochemical device, and can also be called the working electrode when the electrochemical device is a three-electrode system. In some embodiments, the electrode with the metal catalyst disposed thereon includes any feasible electrode material, such as porous electrode materials. In embodiments where the electrode includes a porous electrode material, the electrode can be called a gas diffusion electrode, improving the reaction efficiency of gas-related electrochemical reactions. In some embodiments, porous electrode materials include carbon fibers (e.g., including carbon fiber paper, carbon fiber woven fabric, carbon fiber-containing nonwoven fabric, or combinations thereof), carbon black, activated carbon, acetylene black, porous metal materials (e.g., including a mesh structure made of nickel wire), or combinations thereof.

[0019] In some embodiments, the metal-containing catalyst preferably includes a zinc-containing catalyst, such as a zinc-containing ceramic compound, to achieve better electrocatalytic efficiency in the formation of carbon monoxide from carbon dioxide after the formation of the modified metal-containing catalyst (or modified zinc-containing catalyst or modified zinc-containing ceramic compound). Furthermore, zinc-containing catalysts are more readily available and less expensive than catalysts including, for example, gold, silver, or platinum. In some embodiments, the zinc-containing ceramic compound preferably includes zinc oxide, zinc fluoride, zinc sulfide, or combinations thereof. In some embodiments, the metal-containing catalyst is preferably present in the form of particles (e.g., nanoparticles). In some embodiments, the average particle size or average diameter is preferably 50 nm to 100 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm. In some embodiments, the particle size or diameter is uniform.

[0020] In some embodiments, a portion (e.g., the surface portion) of the modified metal-containing catalyst includes the reduced metal-containing catalyst, and another portion (e.g., the non-surface portion) includes the unreduced and unoxidized metal-containing catalyst. Compared to the complete reduction of the metal-containing catalyst, the reduction of a portion of the metal-containing catalyst and the unreduction of the other portion can increase the active sites for the electrocatalytic formation of carbon monoxide from carbon dioxide in the modified metal-containing catalyst. Moreover, the reduction of the portion of the metal-containing catalyst can also improve the conductivity of the modified metal-containing catalyst. For example, reducing the metal in the metal-containing catalyst to a zero-valent metal may improve conductivity, but zero-valent metals, such as zinc, tend to electrocatalyze carbon dioxide to formate, thus reducing the yield of carbon monoxide. In some embodiments, the valence state of the metal in the surface portion of the modified metal-containing catalyst is reduced compared to the valence state of the metal in the non-surface portion. In embodiments where the metal catalyst exists in the form of particles (e.g., nanoparticles), the average particle size or average diameter of the modified metal catalyst particles is smaller than that of the unmodified metal catalyst particles. In some embodiments, the modified metal catalyst particles include large particles and small particles smaller than the large particles, with small particles surrounding large particles. In some embodiments, the modified metal catalyst has more (101) crystal planes than the unmodified metal catalyst to increase the number of active sites for the electrocatalytic formation of carbon monoxide from carbon dioxide. In some embodiments, the yield (or selectivity) of the modified metal catalyst in electrocatalyzing the formation of carbon monoxide from carbon dioxide is greater than the yield (or selectivity) of formate formation.

[0021] In some embodiments, the electrochemical device further includes any feasible anode electrode disposed in the anode tank at the anode end of the electrochemical device to carry out the anodic reaction, relative to the electrode on which the metal catalyst is disposed. In embodiments where the electrochemical device is a three-electrode system, the anode electrode may also be referred to as the counter electrode. In some embodiments, the anode electrode includes platinum. In embodiments where the electrochemical device is a three-electrode system, the electrochemical device further includes a reference electrode disposed in the cathode tank at the cathode end of the electrochemical device. In some embodiments, the reference electrode includes Ag / AgCl. In some embodiments, the electrochemical device further includes an electrolyte located in the cathode tank and the anode tank to maintain the electroneutrality of the electrochemical device during the electrochemical reaction. In some embodiments, the electrolyte includes an aqueous solution of potassium chloride. In some embodiments, the oxidation reaction occurring at the anode end includes the oxidation of water to oxygen. In some embodiments, the cathode tank further includes gaseous carbon dioxide. In some embodiments, the electrochemical device further includes an ion exchange membrane disposed between the cathode tank and the anode tank.

[0022] Continuing with the explanation of operation 101, refer to the example of voltage change over time in Figure 2. A voltage change over time with a pulsed waveform can modify the metal-containing catalyst, thereby increasing the efficiency of carbon monoxide formation when the modified metal-containing catalyst is used to electrocatalyze carbon dioxide in subsequent operation 102, for example, by achieving higher yields or using smaller overpotentials for the electrochemical reaction. In some embodiments, the voltage change over time for each operation starts from the initial voltage V1 and increases towards a negative voltage until it ends at a negative voltage VX (note that the aforementioned "increase" refers to an increase in the absolute value of the voltage, not defined by the positive or negative value of the voltage) to ensure that the metal-containing catalyst does not react in the oxidation direction during the modification process. In some embodiments, the absolute value of the ending negative voltage VX is greater than the absolute value of the initial voltage V1. In some embodiments, the onset voltage V1 is preferably 0 V to -1.6 V (relative to the Ag / AgCl electrode), such as 0 V, -0.5 V, -1.0 V, or -1.6 V, and the termination negative voltage VX is preferably -1.2 V to -2.8 V (relative to the Ag / AgCl electrode), such as -1.2 V, -1.7 V, -2.2 V, or -2.8 V, to ensure that the onset voltage V1 results in the metal-containing catalyst being in a non-reduced state or a higher oxidized state before modification, and to ensure that the termination negative voltage VX ensures that the metal-containing catalyst is indeed reduced during the modification process. If the absolute value of the termination negative voltage VX is too small, sufficient metal-containing catalyst may not be reduced; if the absolute value of the termination negative voltage VX is too large, the potential required for the reduction reaction may saturate, thus failing to significantly increase the progress of the reduction reaction.

[0023] In some embodiments, the preferred voltage variation over time comprises a plurality of pulses, and the duration W of each pulse is preferably from 2 ms to 250 ms, for example, 2 ms, 5 ms, 10 ms, 50 ms, 100 ms, 150 ms, 200 ms, or 250 ms. In some embodiments, the duration W of each pulse is the same. In some embodiments, the amplitude of each pulse is preferably from 10 mV to 1400 mV, for example, 10 mV, 50 mV, 100 mV, 250 mV, 500 mV, 750 mV, 1000 mV, or 1400 mV. In some embodiments, the amplitude is a factor of the absolute value of the difference between the starting voltage V1 and the ending negative voltage VX to ensure the waveform integrity of each pulse, for example, having a complete amplitude. In some embodiments, the amplitude of each pulse is the same. In some implementations, the number of pulses between the initial voltage V1 and the final negative voltage VX during each execution is inversely proportional to the amplitude.

[0024] In some embodiments, the pulses are preferably square pulses, such that the voltage of each execution changes over time from a starting voltage V1 to a final negative voltage VX via square pulses in a stepped manner. In some embodiments, the square pulses preferably include at least one forward square pulse P1 (e.g., a square pulse changing from the starting voltage V1 to voltage V2, a square pulse changing from voltage V3 to voltage V4, etc.) and at least one reverse square pulse P2 (e.g., a square pulse changing from voltage V2 to voltage V3, a square pulse changing from voltage V4 to voltage V5, etc.), wherein at least one forward square pulse P1 changes the voltage in the negative voltage direction (e.g., increases the absolute value of the voltage), and at least one reverse square pulse P2 changes the voltage in the positive voltage direction (e.g., decreases the absolute value of the voltage). The negative voltage direction is the direction extending from zero voltage to negative voltage, and the positive voltage direction is the direction extending from zero voltage to positive voltage. In some embodiments, each of the at least one forward square pulse P1 and each of the at least one reverse square pulse P2 are alternately arranged.

[0025] In some embodiments, when at least one forward square pulse P1 is a plurality of forward square pulses, the voltage at the end of time of each of the forward square pulses continuously decreases over time. For example, the voltage at the end of time of an earlier forward square pulse (e.g., voltage V2) decreases over time to the voltage at the end of time of a later forward square pulse (e.g., voltage V4), and the absolute value of the difference between the voltages at the end of time of adjacent forward square pulses (e.g., |V4-V2|) is preferably from 1 mV to 20 mV, such as 1 mV, 5 mV, 10 mV, 15 mV, or 20 mV. In some embodiments, the absolute value of the difference between the voltages at the end of time of each adjacent forward square pulse is the same. In some embodiments, when at least one reverse square pulse P2 is a plurality of reverse square pulses, the voltage at the end of time of each of the reverse square pulses continuously decreases over time. For example, the voltage at the end of time of an earlier reverse square pulse (e.g., voltage V3) decreases over time to the voltage at the end of time of a later reverse square pulse (e.g., voltage V5), and the absolute value of the difference between the voltages at the end of time of adjacent reverse square pulses (e.g., |V5-V3|) is preferably between 1 mV and 20 mV, such as 1 mV, 5 mV, 10 mV, 15 mV, or 20 mV. In some embodiments, the absolute value of the difference between the voltages at the end of time of each adjacent reverse square pulse is the same. In some embodiments, the absolute value of the difference between the voltages at the end of time of adjacent forward square pulses is the same as the absolute value of the difference between the voltages at the end of time of adjacent reverse square pulses.

[0026] In some embodiments, applying a voltage with a pulsed waveform over time to the metal-containing catalyst on the electrode to modify the metal-containing catalyst is performed only once, from the start voltage V1 to the end negative voltage VX, for example, only once as shown in Figure 2. In some embodiments, applying a voltage with a pulsed waveform over time to the metal-containing catalyst on the electrode to modify the metal-containing catalyst is performed repeatedly, from the start voltage V1 to the end negative voltage VX, at least twice and less than or equal to 60,000 times (or preferably 100 to 60,000 times, or more preferably 100 to 12,000 times), for example, repeatedly performing the voltage change over time as shown in Figure 2 twice. In some embodiments, the voltage change over time is the same each time. In some embodiments, the frequency of performing the voltage change over time is preferably 2 to 50 times per second, for example, 2 times per second, 5 times per second, 10 times per second, 20 times per second, 30 times per second, 40 times per second, or 50 times per second. In some embodiments, the period of voltage variation over time is preferably from 0.02 seconds to 0.5 seconds, for example, 0.02 seconds, 0.05 seconds, 0.1 seconds, 0.2 seconds, 0.3 seconds, 0.4 seconds, or 0.5 seconds. In some embodiments, the total execution time for applying a voltage with a pulsed waveform to the metal-containing catalyst on the electrode to modify the metal-containing catalyst is preferably less than or equal to 8 hours and greater than or equal to 0.02 seconds (or preferably 0.5 minutes to 6 hours, or more preferably 10 minutes to 4 hours).

[0027] In operation 102, the modified metal-containing catalyst, along with the electrodes, is used as the cathode electrode in an electrolytic cell to electrolyze carbon dioxide to form carbon monoxide. The modified metal-containing catalyst can improve the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation, for example, by increasing the Faradaic efficiency, reaction current, and yield of carbon monoxide formation, and by conducting the electrochemical reaction to form carbon monoxide at a lower overpotential. In some embodiments, the electrolytic cell used in operation 102 may be the same as the electrochemical device used in operation 101, except that operation 101 modifies the metal-containing catalyst by using the aforementioned voltage variation over time, while operation 102 electrolyzes carbon dioxide located at the cathode by applying an electrolytic voltage between the cathode and anode of the electrolytic cell using the modified metal-containing catalyst obtained from operation 101. In some embodiments, the electrolytic cell includes any feasible electrochemical device, such as a three-electrode system electrochemical device. In some embodiments, the modified metal catalyst, along with the electrode, is used as a cathode electrode in the cathode cell (but not the anode cell) to reduce gaseous carbon dioxide introduced into the cathode cell and form carbon monoxide. In embodiments where the electrode comprises a porous electrode material, this cathode electrode can also be called a gas diffusion electrode, and can improve the reaction efficiency of gas-related electrochemical reactions. In some embodiments, saturated gaseous carbon dioxide is introduced into the cathode cell. In some embodiments, the cathode cell further includes an electrolyte, such as an aqueous solution of potassium chloride. In some embodiments, in addition to the formation of carbon monoxide, the reduction reaction occurring at the cathode cell further includes the formation of hydrogen gas.

[0028] In some embodiments, the electrolytic cell further includes an anode cell in which any feasible anode electrode is disposed at the anode end of the electrolytic cell for an anodic reaction, relative to the cathode electrode disposed at the cathode end of the electrolytic cell. In some embodiments, the anode electrode includes platinum. In some embodiments, the anode cell includes an electrolyte, such as an aqueous solution of potassium chloride. In some embodiments, the oxidation reaction occurring at the anode end includes the oxidation of water to oxygen. In some embodiments, the electrolytic cell further includes an ion exchange membrane disposed between the cathode cell and the anode cell. In some embodiments, the electrolysis voltage (potential difference between the cathode and anode ends) used to electrolyze carbon dioxide to form carbon monoxide is preferably 0.5V to 2V.

[0029] The present disclosure will now be further described with reference to some embodiments. It should be noted that the embodiments are provided to enable those skilled in the art to better understand the present disclosure and are not intended to limit the scope of the appended claims to the scope covered by the embodiments.

[0030] Example 1 in Figure 3A is a scanning electron microscope (SEM) image of the modified zinc oxide containing a metal catalyst obtained through operation 101 described above. The metal catalyst is zinc oxide. The voltage variation over time used in Example 1 includes a plurality of forward square pulses and a plurality of reverse square pulses as shown in Figure 2. Other parameters are shown in Table 1. Example 1 repeats the voltage variation over time at a frequency of 50 times per second until the total execution time is 20 minutes, as shown in Table 1. Comparative Example 1 in Figure 3B is a SEM image of unmodified zinc oxide. Comparative Example 2 in Figure 3C is a SEM image of zinc oxide modified using a voltage fixed over time. Comparative Example 3 in Figure 3D is a SEM image of zinc oxide modified using a voltage such as cyclic voltammetry. Comparing Figures 3A to 3D, it can be seen that the zinc oxide modified using operation 101 in Figure 3A has a significantly different shape and size from the unmodified or otherwise modified zinc oxide in Figures 3B to 3D.

[0031] Table 1 Starting voltage V1 Finish negative voltage V X amplitude Adjacent pulses End of time voltage difference absolute value frequency General Executive time -0.1 V -1.2 V 10 mV 10 mV per second 50 times 20 minutes

[0032] Figure 4 compares the carbon monoxide faradaic efficiencies obtained by electrolyzing carbon dioxide in Examples 1, 1, 2, and 3 after operation 102. In Figure 4, regardless of the voltage used for electrolyzing carbon dioxide, Example 1 exhibits a higher (e.g., 2 to 4 times) carbon monoxide faradaic efficiency compared to Comparative Examples 1, 2, and 3. For example, Example 1 achieves a carbon monoxide faradaic efficiency of up to 98% when electrolyzing carbon dioxide at a higher voltage (e.g., -1.05 V), and Example 1 still achieves a carbon monoxide faradaic efficiency of up to 60% even when electrolyzing carbon dioxide at a lower voltage (e.g., -0.85 V).

[0033] Figures 5 and 6 compare the total geometric current and carbon monoxide geometric current obtained after electrolysis of carbon dioxide in Examples 1, 1, 2, and 3, respectively, following operation 102. In the comparison of Figures 5 and 6, regardless of the voltage used for carbon dioxide electrolysis, Example 1 exhibits a significantly higher proportion of carbon monoxide geometric current in its total geometric current compared to Comparative Examples 1, 2, and 3.

[0034] The method disclosed herein modifies a metal-containing catalyst by varying a voltage with a pulsed waveform over time to form a modified metal-containing catalyst. The modified metal-containing catalyst has more active sites for adsorbing carbon dioxide compared to the unmodified catalyst, thus improving the efficiency of the modified metal-containing catalyst in electrocatalyzing the formation of carbon monoxide from carbon dioxide. This includes increasing the Faradaic efficiency, reaction current, and yield of carbon monoxide formation, and allowing the electrochemical reaction to proceed with a lower overpotential. Therefore, it helps reduce carbon dioxide emissions and can generate cleaner energy materials by forming syngas. Furthermore, the method disclosed herein is easy to implement and low in cost.

[0035] This disclosure describes some embodiments in considerable detail, but other embodiments may also be feasible. Therefore, the description of embodiments in this disclosure is not intended to limit the scope and spirit of the appended claims. Modifications and alterations to this disclosure can be made by those skilled in the art without departing from the scope and spirit of this disclosure. When such modifications and alterations fall within the scope and spirit of the appended claims, this disclosure is intended to cover them. [Simplified Explanation of the Diagram]

[0013] When reading the figures of this disclosure, it is recommended to understand the various aspects of this disclosure from the following text. It should be noted that, according to industry standard practice, various feature dimensions may not be drawn to scale. Furthermore, for clarity of discussion, various feature dimensions may be arbitrarily increased or decreased. In addition, to simplify the figures, conventional structures and components may be shown in a simple schematic manner. Figure 1 is a flowchart of a method for improving the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation according to some embodiments of this disclosure. Figure 2 is a schematic diagram of voltage versus time according to some embodiments of this disclosure. Figures 3A to 3D are electron micrographs of modified metal-containing catalysts according to some embodiments of this disclosure, comparing them with electron micrographs of some comparative embodiments. Figure 4 is a comparison of the carbon monoxide Faraday efficiency of electrolyzing carbon dioxide using modified metal-containing catalysts according to some embodiments of this disclosure, comparing it with some comparative embodiments. Figure 5 is a comparison of the geometrical current density of electrolyzing carbon dioxide using modified metal-containing catalysts according to some embodiments of this disclosure, comparing it with some comparative embodiments. Figure 6 is a comparison of the carbon monoxide geometric current density of the modified metal-containing catalyst used in the electrolysis of carbon dioxide according to some embodiments of this disclosure with some comparative embodiments. [Biomaterial Storage]

[0037] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A method for improving the efficiency of electrocatalytic carbon dioxide to carbon monoxide formation by pulsed wave electrochemistry, comprising: Applying a voltage with a pulsed waveform to a metal-containing catalyst on an electrode and changing it over time to modify the metal-containing catalyst to form a modified metal-containing catalyst; and electrolyzing carbon dioxide in an electrolytic cell to form carbon monoxide, wherein a cathode electrode in the electrolytic cell includes the electrode and the modified metal-containing catalyst.

2. The method as claimed in claim 1, wherein when the metal-containing catalyst is modified by applying a voltage having the pulse waveform over time to the metal-containing catalyst on the electrode, a portion of the metal-containing catalyst is reduced.

3. The method as described in claim 1, wherein the voltage changes over time from an initial voltage to a negative voltage and then to a final negative voltage.

4. The method as described in claim 3, wherein the starting voltage is 0 V to -1.6 V and the ending negative voltage is -1.2 V to -2.8 V.

5. The method as claimed in claim 1, wherein the voltage change over time includes at least one forward square pulse and at least one reverse square pulse, the at least one forward square pulse changing the voltage in a negative voltage direction and the at least one reverse square pulse changing the voltage in a positive voltage direction.

6. The method as claimed in claim 1, wherein the voltage variation over time comprises a plurality of square pulses, and each of the square pulses has an amplitude of 10 mV to 1400 mV.

7. The method as described in claim 1, wherein the voltage variation over time comprises a plurality of pulses, and each of the pulses has a width of 2 ms to 250 ms.

8. The method as claimed in claim 1, wherein applying the voltage with the pulse waveform over time to the metal-containing catalyst on the electrode to modify the metal-containing catalyst comprises repeatedly applying the voltage with the pulse waveform over time to the metal-containing catalyst on the electrode at least twice to modify the metal-containing catalyst.

9. The method as claimed in claim 1, wherein the total execution time for applying the voltage having the pulse waveform to the metal-containing catalyst on the electrode to modify the metal-containing catalyst over time is less than or equal to 8 hours.

10. The method as claimed in claim 1, wherein the metal-containing catalyst comprises a zinc-containing ceramic compound.

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