A method for preparing a hydrophilic porous electrode

Abstract

This invention belongs to the field of porous electrode technology, and specifically relates to a method for preparing a hydrophilic porous electrode. The method for preparing the hydrophilic porous electrode of this invention includes the following steps: applying a voltage to both ends of a porous conductive carbon-based material and performing Joule heating to obtain the hydrophilic porous electrode. This invention uses Joule heating to modify the porous conductive carbon-based material, which can increase the content and hydrophilicity of oxygen-containing hydrophilic functional groups on the electrode surface, resulting in good surface wettability. When the obtained hydrophilic porous electrode is used as a single continuous conductive porous electrothermal element, the current mainly conducts heat along the carbon skeleton, resulting in good underwater thermal contact. Water mainly exchanges heat with the carbon skeleton, thereby reducing electrolytic bubbles and current fluctuations when water is the main electrolysis pathway, and exhibiting good heating stability.

Description

Technical Field

[0001] This invention belongs to the field of porous electrode technology, and specifically relates to a method for preparing a hydrophilic porous electrode. Background Technology

[0002] Porous carbon materials such as carbon felt, graphite felt, carbon cloth, carbon paper, carbon fiber felt, and carbon foam possess excellent electrical conductivity, high porosity, strong thermal stability, and low cost, making them promising candidates for electrothermal conversion devices. However, commercially available porous carbon materials often suffer from hydrophobicity or insufficient wetting on their surfaces, resulting in limited effective contact area when in contact with water, which can easily lead to localized dry zones, high interfacial thermal resistance, uneven temperature distribution, and decreased heating efficiency.

[0003] Therefore, providing a method for preparing a hydrophilic porous electrode to solve the problems of insufficient surface wettability, poor underwater thermal contact, easy generation of obvious bubbles and insufficient heating stability of existing porous carbon heating elements is of great significance. Summary of the Invention

[0004] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a method for preparing a hydrophilic porous electrode, wherein the prepared hydrophilic porous electrode has good surface wettability, good underwater thermal contact, is not prone to bubble generation during DC heating, and has good thermal stability.

[0005] The inventive concept of this invention: The method for preparing the hydrophilic porous electrode of this invention includes the following steps: applying voltage to both ends of a porous conductive carbon-based material and performing Joule heating to obtain a hydrophilic porous electrode.

[0006] Rapid Joule heating, a fast heat treatment method that generates Joule heat within a conductive material by passing an electric current through it, offers advantages such as high energy utilization, rapid heating, short processing time, and ease of continuous application. It can be used to control the microstructure and surface chemical state of carbon materials. This invention employs Joule heating to treat porous conductive carbon-based materials. During treatment, the porous conductive carbon-based materials undergo surface oxidation modification, thereby increasing the content and hydrophilicity of oxygen-containing hydrophilic functional groups and improving surface wettability. When the resulting hydrophilic porous electrode is used as a single continuous conductive porous electrothermal element, the current primarily conducts heat along the carbon skeleton, resulting in good underwater thermal contact. Water mainly exchanges heat with the carbon skeleton, thus reducing electrolytic bubbles and current fluctuations that occur when water is the primary electrolysis pathway, and improving heating stability.

[0007] Therefore, a first aspect of the present invention provides a method for preparing a hydrophilic porous electrode.

[0008] Specifically, the method for preparing the hydrophilic porous electrode includes the following steps: A voltage is applied across the ends of a porous conductive carbon-based material, and Joule heating is performed to obtain the hydrophilic porous electrode.

[0009] Specifically, existing technologies typically use rapid Joule heating for carbon material synthesis, graphitization, or general surface functionalization, but an integrated technical solution combining rapid hydrophilic modification of porous conductive carbon-based materials, continuous DC heating of the carbon skeleton, and underwater suppression of visible bubble precipitation has not yet been formed.

[0010] Preferably, the two ends of the porous conductive carbon-based material are fixed to conductive clamps, and the two conductive clamps are respectively connected to the positive and negative terminals of the power supply; a voltage is applied to the two ends of the porous conductive carbon-based material to perform Joule heating, thereby obtaining the hydrophilic porous electrode.

[0011] Specifically, this invention does not have any particular limitation on the type of conductive clamp; conventional conductive clamps can be used.

[0012] Preferably, the porous conductive carbon-based material includes any one of carbon felt, graphite felt, carbon cloth, carbon paper, carbon fiber felt, and carbon foam.

[0013] Preferably, the porous conductive carbon-based material is first cut, cleaned, and dried.

[0014] Preferably, the cut size is (8-12)cm × (4-6)cm; for example, 8cm × 4cm, 10cm × 5cm, 12cm × 6cm, etc.

[0015] Preferably, the cleaning agent used for the cleaning includes at least one of ethanol and water.

[0016] Specifically, the cleaning process removes impurities, dust, and loose fibers from the surface of the porous conductive carbon-based material.

[0017] Preferably, the drying temperature is 40-120℃; for example, the drying temperature is 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, etc.

[0018] Preferably, the Joule heating is performed using either DC or AC voltage.

[0019] More preferably, the Joule heating is performed using a DC voltage.

[0020] Specifically, the Joule heating of this invention is rapid Joule heating, preferably using DC voltage. This is because DC processing allows for easier control of the current path and end-temperature distribution, and ensures consistency with subsequent low-voltage DC electrothermal conversion applications. As an alternative, AC power can also be used to generate Joule heating; however, under the same effective voltage and processing time, AC processing may cause periodic fluctuations in instantaneous power and temperature distribution, and the uniformity of surface modification and compatibility with subsequent DC applications may be inferior to DC processing. Therefore, this invention preferably uses DC voltage for Joule heating.

[0021] Preferably, the voltage for Joule heating is 5-40V; for example, voltages of 5V, 10V, 15V, 20V, 25V, 30V, 35V, 40V, etc.

[0022] Preferably, the Joule heating time is 5-120 seconds.

[0023] More preferably, the Joule heating time is 5-40s; for example, the time is 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, etc.

[0024] According to some embodiments of the present invention, the voltage for Joule heating is 5-40V, and the Joule heating time is 5-40s.

[0025] According to some embodiments of the present invention, the voltage for Joule heating is 20V, and the Joule heating time is 5s.

[0026] According to some embodiments of the present invention, the voltage for Joule heating is 20V, and the Joule heating time is 10s.

[0027] According to some embodiments of the present invention, the voltage for Joule heating is 20V, and the Joule heating time is 20s.

[0028] According to some embodiments of the present invention, the voltage for Joule heating is 20V, and the Joule heating time is 40s.

[0029] Specifically, the degree of introduction of oxygen-containing hydrophilic functional groups on the surface of porous conductive carbon-based materials can be controlled through parameter "directional regulation." In this invention, "directional regulation" refers to using parameters such as voltage, time, material size, and treatment atmosphere to ensure that surface modification is mainly directed towards increasing the content of oxygen-containing functional groups such as hydroxyl, carboxyl, carbonyl, and / or CO, as well as improving water wettability.

[0030] Preferably, the Joule heating is carried out in an oxygen-containing atmosphere.

[0031] Preferably, the oxygen-containing atmosphere includes at least one of an inert gas mixed with air or air.

[0032] A second aspect of the present invention provides a hydrophilic porous electrode.

[0033] Specifically, the hydrophilic porous electrode is prepared by the method for preparing the hydrophilic porous electrode described in the first aspect of the present invention.

[0034] Preferably, the surface of the hydrophilic porous electrode has oxygen-containing hydrophilic functional groups.

[0035] Preferably, the oxygen-containing hydrophilic functional group includes at least one of hydroxyl, carboxyl, carbonyl, and CO.

[0036] A third aspect of the present invention provides an application of the hydrophilic porous electrode described in the first aspect of the present invention in low-pressure DC heating water.

[0037] Specifically, the hydrophilic porous electrode is used as a continuous porous carbon skeleton heating element for low-pressure DC water heating, and the current is mainly conducted along the continuous porous carbon skeleton to generate Joule heat.

[0038] Preferably, the DC voltage of the low-pressure DC heating water is 5-40V.

[0039] Preferably, the metal connection end of the hydrophilic porous electrode is located above the water surface, or the metal connection end and the non-working end are insulated and encapsulated to reduce the Faraday reaction caused by the metal connection end contacting water.

[0040] Specifically, the metal connection end and non-working end refer to the part that is not in contact with water.

[0041] Specifically, by modifying porous conductive carbon-based materials using rapid Joule heating, the hydrophilicity of the resulting porous carbon electrode surface is improved, allowing water to wet the porous framework more quickly. When used as a single continuous conductive porous electrothermal element in water, the positive and negative terminals are connected to the two ends of the continuous carbon framework, respectively. Current is mainly conducted along the carbon framework, and Joule heat is generated within the carbon framework and transferred to the water. Since water molecules are not the main electrolyte pathway between the two separated electrodes, and the metal-water interface Faraday reaction can be reduced by placing the metal connection ends above the water surface or by insulating and encapsulating the ends, visible bubble precipitation can be significantly suppressed and the stability of DC heating can be improved.

[0042] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: This invention employs Joule heating to modify porous conductive carbon-based materials, increasing the content and hydrophilicity of oxygen-containing hydrophilic functional groups on the electrode surface, resulting in good surface wettability. When the resulting hydrophilic porous electrode is used as a single continuous conductive porous electrothermal element, current is primarily conducted along the carbon skeleton for heating, providing good underwater thermal contact. Water mainly exchanges heat with the carbon skeleton, thereby reducing electrolytic bubbles and current fluctuations when water is the primary electrolysis pathway, resulting in good heating stability. Specific beneficial effects are as follows: (1) It has a wide range of raw materials and can be applied to porous conductive carbon-based materials such as carbon felt, graphite felt, carbon cloth, carbon paper, carbon fiber felt or carbon foam.

[0043] (2) The voltage and processing time of rapid Joule heating are adjustable and can be adjusted according to actual conditions. At the same time, the degree of introduction of oxygen-containing functional groups on the surface can be controlled by adjusting the voltage, time, material size and processing atmosphere to achieve controllable improvement of hydrophilicity.

[0044] (3) The hydrophilic porous electrode is used as a continuous porous carbon skeleton heating element. The current mainly passes through the solid carbon skeleton rather than the water electrolyte path, which can reduce the visible bubble precipitation and current fluctuation during DC heating, improve the stability of DC heating, and has good heating stability.

[0045] (4) The present invention supports the modification effect from three aspects: surface chemistry, microstructure, and interfacial electrical behavior, through infrared spectroscopy, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) tests. Among them, infrared spectroscopy proved that the related signals of oxygen-containing functional groups on the surface were enhanced after treatment; SEM proved that the porous conductive carbon-based material still maintained a continuous fiber network and porous structure after rapid Joule heating treatment, without significant structural collapse; EIS proved that after rapid Joule heating treatment, the interfacial impedance of the hydrophilic porous electrode in the aqueous medium was reduced, and the electrode / water interface contact state was improved. These results together indicate that rapid Joule heating not only improves the surface hydrophilicity of the porous conductive carbon-based material, but also improves its interfacial stability when used as an underwater DC heating element.

[0046] (5) The porous structure and hydrophilic interface of the hydrophilic porous electrode can increase the contact area of ​​the water-electric heating element and reduce the interfacial thermal resistance, making it suitable for instant heating, flowing water heating and low-pressure portable water heating scenarios. Attached Figure Description

[0047] Figure 1 This is a schematic diagram illustrating the preparation of a hydrophilic porous electrode using Joule heating modified porous conductive carbon-based material in an embodiment of the present invention. Figure 2 The infrared spectra of the hydrophilic porous electrodes of Examples 1-4 of the present invention and the original commercial carbon felt of Comparative Example 1 are shown. Figure 3These are scanning electron microscope images of the hydrophilic porous electrode of Example 2 and the original commercial carbon felt of Comparative Example 1. Figure 4 The electrochemical impedance spectroscopy spectra of the hydrophilic porous electrodes of Examples 1-4 of the present invention and the original commercial carbon felt of Comparative Example 1 are shown. Figure 5 The figures show the hydrophilicity test results of the hydrophilic porous electrode of Example 2 and the original commercial carbon felt of Comparative Example 1. Figure 6 This is a photograph of the hydrophilic porous electrode of Embodiment 2 of the present invention being heated under a DC voltage of 40V. Detailed Implementation

[0048] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0049] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0050] The following examples illustrate the process of preparing hydrophilic porous electrodes using Joule heating-modified porous conductive carbon-based materials. Figure 1 As shown.

[0051] Example 1 This embodiment provides a method for preparing a hydrophilic porous electrode, the specific steps of which are as follows: Commercial carbon felt is cut to the target size (10cm×5cm), washed with deionized water to remove surface impurities and loose fibers, and dried at 80°C for later use. The dried carbon felt was fixed at both ends to conductive clamps, which were then connected to the positive and negative terminals of a DC power supply, respectively. A DC voltage of 20V was applied to both ends of the carbon felt for 5 seconds. After the treatment was completed, the power was turned off and the material was allowed to cool naturally to room temperature to obtain a hydrophilic porous electrode.

[0052] Example 2 The only difference between Example 2 and Example 1 is that the processing time for DC voltage is 10 seconds; otherwise, they are the same as in Example 1.

[0053] Example 3 The only difference between Example 3 and Example 1 is that the processing time for DC voltage is 20 seconds; otherwise, they are the same as in Example 1.

[0054] Example 4 The only difference between Example 4 and Example 1 is that the processing time for DC voltage is 40 seconds; otherwise, they are the same as in Example 1.

[0055] Comparative Example 1 Comparative Example 1 used original commercial carbon felt that had not undergone rapid Joule heating modification as the electrode.

[0056] Performance testing 1. Infrared spectroscopy test Infrared spectroscopy was performed on the original commercial carbon felt of Comparative Example 1 and the hydrophilic porous electrodes after rapid Joule heating treatment in Examples 1-4. The infrared spectra are shown below. Figure 2 As shown. Figure 2 In this context, 5s, 10s, 20s, and 40s represent Examples 1-4, respectively.

[0057] Depend on Figure 2 The test results show that, compared with the original commercial carbon felt, the hydrophilic porous electrode treated with rapid Joule heating exhibits enhanced signals in the characteristic absorption regions related to oxygen-containing functional groups such as hydroxyl, carbonyl, and / or CO. This indicates that rapid Joule heating can introduce or increase oxygen-containing hydrophilic functional groups on the surface of porous conductive carbon-based materials. These oxygen-containing functional groups are beneficial for enhancing the water wetting ability of the carbon fiber surface, thereby improving the water / electrode interface contact state.

[0058] Meanwhile, it can be seen that rapid Joule heating can enhance the infrared absorption peaks related to hydroxyl groups, adsorbed water, and oxygen-containing functional groups on the carbon felt surface within a certain processing time window, indicating that the hydrophilic structures on the carbon felt surface increase after Joule heating. When the processing time is further extended, the intensity of the related absorption peaks decreases. This indicates that the rapid Joule heating time needs to be controlled within a suitable range to avoid excessive heat treatment leading to a reduction in the oxygen-containing structures on the surface.

[0059] 2. SEM testing SEM characterization was performed on the original commercial carbon felt of Comparative Example 1 and the hydrophilic porous electrodes after rapid Joule heating treatment in Example 2. The results are as follows: Figure 3 As shown. Among them, Figure 3 The left and right images in the figure are SEM images of the hydrophilic porous electrodes of Comparative Example 1 and Example 2, respectively.

[0060] Figure 3 SEM results showed that the hydrophilic porous electrode after rapid Joule heating treatment maintained the continuous conductive network and porous structure formed by interwoven carbon fibers, and no obvious overall melting, fracture, or pore structure collapse was observed. Compared with the original sample of Comparative Example 1, the fiber surface can show a certain degree of roughening or surface morphology change after rapid Joule heating treatment, which is beneficial to water wetting and heat transfer contact in the porous network.

[0061] 3. EIS Testing Electrochemical impedance spectroscopy (EIS) tests were performed on the original commercial carbon felt of Comparative Example 1 and the hydrophilic porous electrodes after rapid Joule heating treatment in Examples 1-4, respectively, in an aqueous medium. The results are as follows: Figure 4 As shown. Among them, Figure 4 The horizontal axis Z' / ohm represents the real impedance (ohms), and the vertical axis -Z'' / ohm represents the imaginary impedance (ohms); 5s, 10s, 20s, and 40s represent Examples 1-4, respectively.

[0062] Figure 4 The EIS results showed that the interfacial impedance of the hydrophilic porous electrode after rapid Joule heating in aqueous medium was lower than that of the original carbon felt in Comparative Example 1. Specifically, the original carbon felt exhibited a significant impedance increase and polarization tailing in the low-frequency region, while the Joule-heat-treated sample curve shifted overall towards the low-impedance region, indicating a significant reduction in its electrode / water interfacial impedance. These results demonstrate that rapid Joule heating modification improves the interfacial contact state between the porous carbon electrode and water, resulting in a more stable current distribution and interfacial heat transfer, which helps reduce the risk of local current concentration and local bubble precipitation.

[0063] 5. Hydrophilicity test Water was added dropwise to the raw commercial carbon felt from Example 2 and the unmodified material, and the hydrophilicity effect was observed. The results are as follows: Figure 5 As shown. Since the locations of the metal connections (conductive clamp locations) on the same piece of material are not activated, the unactivated portions are equivalent to unmodified raw commercial carbon felt, allowing for hydrophilicity comparison.

[0064] Depend on Figure 5 As can be seen, the hydrophilic porous electrode prepared by Joule heating in Example 2 exhibits good hydrophilicity, allowing water droplets to wet and spread more quickly upon contact. In contrast, the unmodified commercial carbon felt has poor surface wettability, making it difficult for water droplets to wet and spread rapidly upon contact. This demonstrates that the present invention utilizes Joule heating to prepare the hydrophilic porous electrode, thereby improving the hydrophilicity of the electrode surface.

[0065] 6. Heating test under DC voltage The hydrophilic porous electrode of Example 2 was placed in water as a single continuous porous carbon heating element, with the metal connection end above the water surface. A heating test was conducted at 40V DC voltage. A photograph of the hydrophilic porous electrode of Example 2 under 40V DC voltage heating is shown below. Figure 6 As shown.

[0066] Depend on Figure 6 It can be observed that the visible bubble precipitation phenomenon is significantly suppressed, and no obvious visible bubble precipitation is observed. Since no local bubbles are observed, it indicates that the heating is relatively uniform and stable.

[0067] Using the same method as above, the original commercial carbon felt from Comparative Example 1 was used for DC voltage heating tests in water. It was observed that due to the lack of hydrophilic groups, the water-carbon skeleton contact was insufficient, resulting in bubble precipitation, i.e., uneven local heating, as well as problems such as high interfacial impedance and current fluctuations.

[0068] In summary, this invention utilizes Joule heating to modify porous conductive carbon-based materials, which increases the content and hydrophilicity of oxygen-containing hydrophilic functional groups on the electrode surface, resulting in good surface wettability. When the resulting hydrophilic porous electrode is used as a single continuous conductive porous electrothermal element, the current is mainly conducted along the carbon skeleton for heating, resulting in good underwater thermal contact. Water primarily exchanges heat with the carbon skeleton, thereby reducing electrolytic bubbles and current fluctuations when water is the main electrolysis pathway, and exhibiting good heating stability.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a hydrophilic porous electrode, characterized in that, The method for preparing the hydrophilic porous electrode includes the following steps: A voltage is applied across the ends of a porous conductive carbon-based material, and Joule heating is performed to obtain the hydrophilic porous electrode.

2. The preparation method according to claim 1, characterized in that, The porous conductive carbon-based material includes any one of carbon felt, graphite felt, carbon cloth, carbon paper, carbon fiber felt, and carbon foam.

3. The preparation method according to claim 1, characterized in that, The Joule heating is performed using either DC or AC voltage.

4. The preparation method according to claim 1, characterized in that, The voltage for Joule heating is 5-40V; And / or, the Joule heating time is 5-120s.

5. The preparation method according to claim 1, characterized in that, The Joule heating is carried out in an oxygen-containing atmosphere.

6. A hydrophilic porous electrode, characterized in that, The hydrophilic porous electrode is prepared by the preparation method according to any one of claims 1-5.

7. The hydrophilic porous electrode according to claim 6, characterized in that, The surface of the hydrophilic porous electrode has oxygen-containing hydrophilic functional groups.

8. The hydrophilic porous electrode according to claim 7, characterized in that, The oxygen-containing hydrophilic functional group includes at least one of hydroxyl, carboxyl, carbonyl, and CO groups.

9. The application of the hydrophilic porous electrode according to any one of claims 6-8 in low-pressure DC heating water.

10. The application according to claim 9, characterized in that, The DC voltage for the low-pressure DC heating water is 5-40V.

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