A method for shutting down a carbon dioxide electrocatalytic reactor

Abstract

The application relates to the technical field of energy sources, and discloses a closing method of a carbon dioxide electro-catalytic reactor, which comprises the following steps: step 1, starting a reduction circuit to perform reduction and impurity removal treatment; step 2, starting a cleaning circuit to perform cleaning treatment; and step 3, injecting carbon dioxide gas into a cathode chamber and injecting electrolyte into an anode chamber, and then sealing and storing; the reduction circuit adopts three-stage voltage treatment, one-stage voltage treatment can oxidize metal impurities on an electrode catalyst of the cathode into corresponding metal oxides; two-stage voltage treatment converts salt crystals into carbon monoxide and carbon dioxide, and meanwhile, salt ions are transferred into an anode electrolyte; and three-stage voltage treatment reduces all metal oxides on the surface of the cathode into elemental metal to realize electrode renewal; the cleaning circuit adopts volatile substances as cleaning liquid, and can quickly remove generated insoluble impurities; and the method can significantly inhibit the technical effect of the deterioration of the carbon dioxide electro-catalytic reactor.

Description

Technical Field

[0001] This invention relates to the field of energy technology, and in particular to a method for shutting down a carbon dioxide electrocatalytic reactor. Background Technology

[0002] Carbon-based fuels primarily produce carbon dioxide upon combustion. In recent years, low-carbon energy has garnered significant attention, prompting researchers in the energy technology field to conduct in-depth studies on carbon dioxide reduction and reuse technologies. Current carbon dioxide reduction and reuse technologies mainly include photocatalysis and electrocatalysis. Photocatalysis uses light energy as its driving force, but the limitations of light usage prevent it from becoming a mainstream method for carbon dioxide reduction. Electrocatalysis, on the other hand, uses electricity as its driving force, has fewer limitations, and is currently the primary method for carbon dioxide reduction and reuse.

[0003] The apparatus for implementing the electrocatalytic carbon dioxide reduction and reuse method is a carbon dioxide electrocatalytic reactor. Existing carbon dioxide electrocatalytic reactors mainly consist of an electrolytic cell and an ion exchange membrane. The ion exchange membrane divides the electrolytic cell into an anode chamber and a cathode chamber. The anode chamber contains an anode electrode, which includes metal electrodes such as gold and copper. The cathode chamber contains a cathode electrode, which includes metal electrodes such as iridium oxide. During use, an electrolyte is injected into the anode chamber, and carbon dioxide and water are introduced into the cathode chamber. The positive and negative terminals of a DC power supply are electrically connected to the anode and cathode electrodes, respectively. Under the action of DC current, the electrocatalytic reduction of carbon dioxide is achieved. Examples include the thermal management air inlet structure of a carbon dioxide electrocatalytic reactor disclosed in publication number CN115449831A and the large-size electrocatalytic carbon dioxide reactor with co-current anode and cathode flow disclosed in publication number CN115572992A.

[0004] Carbon dioxide electrocatalytic reactors suffer from cell degradation after use, with metallic and salt impurities forming on the surface of the electrode catalyst. These impurities coat the catalyst surface, while insoluble impurities such as formic acid and acetic acid are generated in the cathode chamber. This leads to a significant decrease in the catalytic efficiency of the electrode catalyst during subsequent use. CN112593258A discloses a carbon dioxide electrolysis device and method, which effectively solves the cell degradation problem during operation by adding a flushing circuit. The flushing circuit in this application uses a flushing liquid control circuit to clean the generated volatile liquid and addresses the problem of metal electrode coating by timely replacement of electrode materials. However, this method suffers from low cleaning efficiency, high energy consumption, and high cost, hindering industrial-scale promotion. Summary of the Invention

[0005] To overcome the problems existing in the prior art, this application provides a method for shutting down a carbon dioxide electrocatalytic reactor. The method includes three steps: reduction and impurity removal, cleaning, and sealing. The reduction and impurity removal can remove the generated salt crystals and impurity metals and refresh the electrode catalyst. The cleaning can quickly remove the generated non-volatile impurities, and the cleaning solution is a volatile substance that evaporates quickly after cleaning. The sealing can ensure that the refreshed electrode catalyst is not oxidized, which can effectively inhibit the deterioration of the carbon dioxide electrocatalytic reactor.

[0006] The specific technical solution of this invention is as follows: A method for shutting down a carbon dioxide electrocatalytic reactor, the reactor comprising a main power supply, a cathode chamber, an anode chamber, a reduction circuit, and a cleaning flow path, the method comprising the following steps: Step 1: Turn on the restoration circuit to perform restoration and impurity removal; Step 2: Open the cleaning flow path to perform the cathode chamber cleaning process; Step 3: Inject carbon dioxide gas into the cathode chamber and electrolyte into the anode chamber, then seal and store. The reduction circuit includes an auxiliary DC power supply, the positive terminal of which is electrically connected to the cathode chamber, and the negative terminal of which is electrically connected to the anode chamber. The cleaning flow path includes a cleaning device, a conductivity device, a carbon dioxide device, and a humidity detection device, and the cleaning flow path is connected to the cathode chamber.

[0007] Preferably, the reduction and impurity removal process in step 1 includes: several stages of first-stage voltage processing, second-stage voltage processing, and third-stage voltage processing.

[0008] Preferably, the voltage processing conditions are: voltage 1-1.5V, time 1-2min.

[0009] Preferably, the two-stage voltage processing conditions are: voltage 3-3.5V, time 2-3min.

[0010] Preferably, the three-stage voltage processing conditions are: voltage -1.5 to -1V, time 1 to 2 minutes.

[0011] Preferably, the cleaning device contains a cleaning solution.

[0012] Preferably, the volatile organic solvent is ethanol.

[0013] Preferably, the cleaning process in step 2 includes: turning on the cleaning device and the conductivity device; turning off the cleaning device and turning on the carbon dioxide device and the humidity detection device when the conductivity of the conductivity device changes from 0 to 0.15 μs / cm; and turning off the cleaning circuit when the humidity of the humidity detection device is from 0 to 30%.

[0014] Preferably, the humidity detection device includes a humidity detector.

[0015] This application provides a method for shutting down a carbon dioxide electrocatalytic reactor, comprising three steps: reduction and impurity removal, cleaning, and protective sealing. The first step, reduction and impurity removal, aims to activate the electrode and remove salt crystals, impurity metals, and residual liquid products precipitated on the cathode surface. Repeated oxidation and reduction of the cathode catalyst via a reduction circuit facilitates the removal of adsorbed species from the electrode surface during oxidation, and subsequent reduction of the oxide layer enhances the active sites for the reaction. Salt crystals are primarily bicarbonate / carbonate deposits formed by metal ions diffused from the anode and on the cathode surface. These deposits block the pores of the gas diffusion layer and cause the pressure within the cathode chamber to increase with salt deposition. The formation of salt crystals also restricts carbon dioxide from entering the catalyst layer, leading to reduced carbon dioxide utilization. Impurity metals mainly originate from small amounts of impurity metals in the anode solution. During the reaction, some metal ions migrate to the cathode surface under the influence of an electric field and deposit on the cathode under negative potential conditions. These impurity metals can cover the original active sites of the catalyst, thus affecting the catalyst's reaction performance. The residual liquid products are mainly non-volatile liquid reduction products, such as formic acid and acetic acid. Through a first-stage voltage treatment, the catalyst at the cathode is oxidized into the corresponding metal oxides. Through a second-stage voltage treatment, the original cathode undergoes an electrolytic oxygen release reaction, and the original anode undergoes an electrolytic hydrogen release reaction. The hydrogen ions produced react with bicarbonate and carbonate on the cathode surface to generate carbon dioxide and water, consuming the salt crystals. The metal ions migrate to the anolyte under the influence of the electric field. The residual products on the cathode surface can create some resistance to the mass transfer of carbon dioxide to the reaction interface. Some products may occupy the active sites of the catalyst, leading to a decrease in reactor performance. Under the influence of a positive potential, the remaining liquid products on the surface undergo electrocatalytic oxidation to generate carbon monoxide or carbon dioxide molecules that escape from the system. Through a third-stage voltage treatment, the metal oxides formed on the cathode surface are reduced back to elemental metals, and the electrode is renewed. With subsequent restoration of the positive and negative electrodes to their working state, all oxides formed on the catalyst surface during this process can be reduced.

[0016] The second step of the cleaning process uses ethanol as the cleaning solution. Ethanol molecules can dissolve the small amount of non-volatile substances (such as formic acid and acetic acid) produced. Ethanol molecules are highly volatile and have good miscibility with water molecules and organic molecules, which can quickly carry the remaining molecules away from the reactor. These liquid products will dissolve in ethanol molecules and be carried away from the cathode surface together. The third step is to fill the cathode cavity with carbon dioxide to ensure that the electrode catalyst in the cathode cavity is not oxidized and produces impurities during the period when it is not in use.

[0017] Compared with the prior art, this application has the following technical effects: (1) The reduction circuit of this application adopts a three-stage voltage process. The first stage voltage process can oxidize the metal impurities on the cathode electrode catalyst into the corresponding metal oxides; the second stage voltage process converts salt crystals into carbon monoxide and carbon dioxide, while the salt ions are transferred to the anolyte; the third stage voltage process reduces all the metal oxides on the cathode surface into elemental metals to achieve electrode renewal. (2) The cleaning circuit of this application uses volatile substances as cleaning liquid, which can quickly remove the generated insoluble impurities; (3) The shutdown method provided by this application has the technical effect of low cost and significant inhibition of the deterioration of carbon dioxide electrocatalytic reactor. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the device structure of Embodiment 1 of this application. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments.

[0020] Example 1: (Ag / IrO2) like Figure 1As shown, a carbon dioxide electrocatalytic reactor includes a main power supply, an electrolytic cell, a reduction circuit, a purification circuit, and a dehumidification circuit. The electrolytic cell is equipped with an ion exchange membrane, which divides the cell into a cathode chamber and an anode chamber. The cathode chamber contains an anode electrocatalytic electrode, which is composed of iridium oxide nanoparticles. The cathode chamber contains a cathode electrocatalytic electrode, which is composed of silver nanoparticles. The electrolyte in the anode chamber is potassium hydroxide (0.1M). The ion exchange membrane is an anion exchange membrane. The reduction circuit includes an auxiliary DC power supply, which is a DC power supply. The positive electrode of the auxiliary DC power supply is connected to the cathode... The anode catalytic electrode is electrically connected, and the negative terminal of the auxiliary DC power supply is electrically connected to the anode catalytic electrode. The cathode chamber is provided with a cathode chamber outlet and a cathode chamber inlet. The cathode chamber inlet is connected to the impurity removal circuit, the dehumidification circuit, and the carbon dioxide gas source. The cleaning circuit includes a cleaning device, a conductivity device, a carbon dioxide device, and a humidity detection device. The cleaning device contains a volatile cleaning liquid (ethanol). The cathode chamber outlet is connected to a gas storage tank, a gas-liquid separator, and a liquid collection tank. The conductivity detection device is located in the liquid collection tank. The dehumidification circuit includes a humidity sensor and a carbon dioxide gas source. The anode chamber is connected to the electrolyte tank. A method for shutting down a carbon dioxide electrocatalytic reactor includes the following steps: Step 1: Turn on the restoration circuit to perform restoration and impurity removal. The restoration and impurity removal process includes: starting the auxiliary power supply to perform a first-stage voltage process, with the conditions for the first-stage voltage process being: voltage 1.5V for 2 minutes; then performing a second-stage voltage process, with the conditions for the second-stage voltage process being: voltage 3.5V for 3 minutes; and then performing a third-stage voltage process, with the conditions for the second-stage voltage process being: voltage -1.5V for 2 minutes. Step 2: Turn on the cleaning circuit to perform the cleaning process. The cleaning process includes: turning on the cleaning device and the conductivity device. When the conductivity of the conductivity device changes by 0.15 μs / cm, turn off the cleaning device and turn on the carbon dioxide device and the humidity detection device. When the humidity of the humidity detection device is 30%, turn off the cleaning circuit. Step 3: Inject carbon dioxide gas into the cathode chamber and electrolyte into the anode chamber, then seal and store.

[0021] Example 2: (Ag / IrO2) The carbon dioxide electrocatalytic reactor used in Example 2 is the same as the carbon dioxide electrocatalytic reactor in Example 1.

[0022] A method for shutting down a carbon dioxide electrocatalytic reactor includes the following steps: Step 1: Turn on the restoration circuit to perform restoration and impurity removal. The restoration and impurity removal process includes: starting the auxiliary power supply to perform a first-stage voltage process, with the conditions for the first-stage voltage process being: voltage 1V, duration 1min; then performing a second-stage voltage process, with the conditions for the second-stage voltage process being: voltage 3V, duration 2min; and then performing a third-stage voltage process, with the conditions for the second-stage voltage process being: voltage -1V, duration 1min. Step 2: Turn on the cleaning circuit to perform the cleaning process. The cleaning process includes: turning on the cleaning device and the conductivity device. When the conductivity of the conductivity device changes by 0.1 μs / cm, turn off the cleaning device and turn on the carbon dioxide device and the humidity detection device. When the humidity of the humidity detection device is 15%, turn off the cleaning circuit. Step 3: Inject carbon dioxide gas into the cathode chamber and electrolyte into the anode chamber, then seal and store.

[0023] Example 3: (Cu / IrO2) The difference between the carbon dioxide electrocatalytic reactor used in Example 3 and that in Example 1 is that the cathode in Example 3 is Cu; a method for shutting down a carbon dioxide electrocatalytic reactor includes the following steps: Step 1: Turn on the restoration circuit to perform restoration and impurity removal. The restoration and impurity removal process includes: starting the auxiliary power supply to perform a first-stage voltage process, with the conditions for the first-stage voltage process being: voltage 1.2V, duration 2min; then performing a second-stage voltage process, with the conditions for the second-stage voltage process being: voltage 3V, duration 2min; and then performing a third-stage voltage process, with the conditions for the second-stage voltage process being: voltage -1.5V, duration 2min. Step 2: Turn on the cleaning circuit to perform the cleaning process. The cleaning process includes: turning on the cleaning device and the conductivity device. When the conductivity of the conductivity device changes by 0.1 μs / cm, turn off the cleaning device and turn on the carbon dioxide device and the humidity detection device. When the humidity of the humidity detection device is 15%, turn off the cleaning circuit. Step 3: Inject carbon dioxide gas into the cathode chamber and electrolyte into the anode chamber, then seal and store.

[0024] Comparative Example 1: Compared with Example 1, in Comparative Example 1, step 1 involved cleaning the cathode chamber with deionized water, while all other conditions were the same as in Example 1.

[0025] Comparative Example 2: Compared with Example 1, in Comparative Example 2, no segmented voltage processing was performed for cleaning in step 1. The voltage of the restoration circuit in step 1 was 3V, and the duration was 8min. All other conditions were the same as in Example 1.

[0026] Comparative Example 3: Compared with Example 1, Step 1 and Step 2 were not performed in Comparative Example 3, and all other conditions were the same as in Example 1.

[0027] Comparative Example 4: Compared with Example 1, step 3 was not performed in Comparative Example 4, and all other conditions were the same as in Example 1.

[0028] Detection example For Example 1 above, the carbon dioxide electrocatalytic reactors of Comparative Examples 1-5 were restarted after treatment, and the carbon dioxide catalytic performance at startup was recorded. The results are shown in Table 1. Catalytic performance calculation: the ratio of the carbon dioxide catalytic efficiency after restarting the carbon dioxide electrocatalytic reactor to the carbon dioxide catalytic efficiency at the time of initial use. The cleaning time for step 2 in Example 1 and Comparative Example 1 was recorded, and the results are shown in Table 1. Table 1: Test Results As shown in Table 1, compared with Example 1, Comparative Example 1 used deionized water for cleaning, while Example 1 used ethanol. The cleaning time required for Comparative Example 1 was significantly longer than that for Example 1, indicating that using ethanol as the cleaning solution can improve the cleaning speed of non-volatile impurities and achieve higher cleaning efficiency. Comparative Example 2 did not use segmented voltage treatment, and its catalytic performance was lower than that of Example 1. The above results show that after segmented voltage treatment, this application can more effectively remove impurities on the electrode catalyst and renew the electrode catalyst, enabling the catalytic efficiency of the carbon dioxide electrocatalytic reactor to reach the initial carbon dioxide catalytic efficiency after restarting. Comparative Example 3 did not include reduction and cleaning circuits, and the results show that its catalytic performance was significantly lower than that of Example 1. Comparative Example 4 did not undergo sealing treatment, and the results show that its catalytic performance was lower than that of Example 1. The above results indicate that sealing treatment can protect the electrode catalyst. The above structures show that the shutdown method of the carbon dioxide electrocatalytic reactor of this application can effectively inhibit the deterioration of the carbon dioxide electrocatalytic reactor and ensure that the carbon dioxide electrocatalytic reactor has the best carbon dioxide catalytic efficiency when it is restarted after shutdown.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for shutting down a carbon dioxide electrocatalytic reactor, the carbon dioxide electrocatalytic reactor comprising a main power supply, a cathode chamber, an anode chamber, a reduction circuit, and a cleaning flow path, characterized in that, The shutdown method includes the following steps: Step 1: Turn on the restoration circuit to perform restoration and impurity removal processing; the restoration and impurity removal processing includes: several first-stage voltage processing, second-stage voltage processing and third-stage voltage processing. The conditions for the first-stage voltage processing are: voltage 1~1.5V, time 1~2min; the conditions for the second-stage voltage processing are: voltage 3~3.5V, time 2~3min; the conditions for the third-stage voltage processing are: voltage -1.5~-1V, time 1~2min. Step 2: Open the cleaning flow path to perform the cathode chamber cleaning process; Step 3: Inject carbon dioxide gas into the cathode chamber and electrolyte into the anode chamber, then seal and store. The reduction circuit includes an auxiliary DC power supply, the positive terminal of which is electrically connected to the cathode chamber, and the negative terminal of which is electrically connected to the anode chamber. The cleaning flow path includes a cleaning device, a conductivity device, a carbon dioxide device, and a humidity detection device, and the cleaning flow path is connected to the cathode chamber.

2. The closing method according to claim 1, characterized in that, The cleaning device contains a cleaning solution.

3. The closing method according to claim 2, characterized in that, The cleaning solution is ethanol.

4. The closing method according to claim 1, characterized in that, The cleaning process described in step 2 includes: turning on the cleaning device and the conductivity device to flush the cathode chamber with the cleaning fluid; turning off the cleaning device and turning on the carbon dioxide device and the humidity detection device when the conductivity of the conductivity device changes from 0 to 0.15 μs / cm; and turning off the cleaning circuit when the humidity of the humidity detection device is 0 to 30%.

5. The closing method according to claim 4, characterized in that, The humidity detection device includes a humidity detector.

6. The closing method according to claim 1, characterized in that, The cathode electrocatalytic electrode is made of silver nanoparticles.

7. The closing method according to claim 1, characterized in that, The anodic electrocatalytic electrode is made of iridium oxide nanoparticles.

8. The closing method according to claim 1, characterized in that, The electrolyte is a 0.1M potassium hydroxide solution.

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