A method for in-situ preparation of polyphenylene sulfide-based membrane electrode

Abstract

The present invention discloses a method for preparing a polyphenylene sulfide-based membrane electrode in situ, comprising: subjecting a polyphenylene sulfide cloth to plasma treatment, then soaking it in an acidic solution or an alkaline solution, then washing and drying it to obtain a hydrophilic polyphenylene sulfide membrane; then pouring a layer of PAN or PVP solution doped with rare earth ions or iron-based element ions on the surface of the hydrophilic polyphenylene sulfide membrane, and drying it to obtain a composite polyphenylene sulfide membrane; using carbon dioxide laser engraving to laser engrave the PAN or PVP polymer layer containing rare earth ions or iron-based element ions in the composite polyphenylene sulfide membrane to form graphene doped with rare earth ions or iron-based element ions, and obtain a polyphenylene sulfide-based membrane electrode for alkaline water electrolysis. The present invention has a relatively loose requirement on temperature, is simple and feasible, safe and controllable, has low energy consumption, generates electrode materials in situ on the membrane surface, and reduces the possibility of electrode shedding during later use.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen production by electrolyzing water, and specifically to a method for in-situ preparation of a polyphenylene sulfide-based membrane electrode. Background Art

[0002] Although traditional fossil fuels can meet the current energy demand, their non-renewability and environmental impact are a concern. Finding renewable and clean alternative energy sources has become a focus of current research in the energy field. Hydrogen energy, as a green and pollution-free energy carrier, enables efficient conversion between hydrogen energy and electrical energy through electrolysis of water technology. Currently, hydrogen production by electrolyzing water technologies include alkaline water electrolysis, proton exchange membrane (PEM) electrolysis, anion exchange membrane (AEM) electrolysis, and solid oxide electrolysis cell (SOEC) electrolysis, etc. Among these technologies, alkaline water electrolysis for hydrogen production is the most mature and commercially available electrolytic hydrogen production technology at present, with advantages such as simple operation and relatively low production costs.

[0003] The diaphragm is one of the key components of an alkaline electrolytic cell. It not only separates the positive and negative electrodes of the cell to prevent short circuits, but also avoids the mixing of gas products at both electrodes, and provides high ionic conductivity for hydroxide ions to transfer from the cathode to the anode. The early used asbestos diaphragm has been phased out due to its carcinogenicity, easy decomposition, pollution of the electrolyte, high resistance, and high energy consumption. Then, the polyphenylene sulfide (PPS) diaphragm was developed as the second-generation diaphragm. The PPS diaphragm has excellent acid, alkali, and solvent resistance and can operate stably in a wet state at 200°C for a long time, making it an ideal choice for the diaphragm of an alkaline electrolytic cell. However, the PPS diaphragm is essentially a hydrophobic diaphragm, resulting in poor airtightness of the diaphragm, difficulties in hydroxide ion transport, high membrane resistance, and low current density, which greatly increases the energy consumption of electrolytic hydrogen production. At the same time, to reduce the impedance between the electrode and the membrane, currently, a non-precious metal catalyst material is pressed on the surface of the membrane. Although this technology can greatly reduce the impedance of charge transfer, during long-term use, the electrode will show a peeling phenomenon, thereby reducing the efficiency of electrolyzing water.

[0004] Currently, the hydrophilic modification of PPS mainly includes: 1) Oxidation method. Strong oxidants such as strong acids or hydrogen peroxide are used to oxidize polyphenylene sulfide. Although this method can increase the hydrophilicity of polyphenylene sulfide, it also destroys the molecular chain of polyphenylene sulfide itself during the oxidation process to introduce hydrophilic groups, which will reduce the service life of polyphenylene sulfide in a high-concentration alkaline solution. In a high-concentration alkaline solution, hydroxide ions will attack the carbon atoms on the damaged molecular chain, thereby causing the decomposition of polyphenylene sulfide. 2) Surface grafting of some hydrophilic molecular chains, but most of the polar molecular chains are not alkali-resistant. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a method for in-situ preparation of polyphenylene sulfide-based membrane electrodes.

[0006] The technical solution of the present invention to solve the above technical problem is to provide a method for in-situ preparation of polyphenylene sulfide-based membrane electrodes, which is characterized in that the method comprises the following steps:

[0007] Step 1: Perform plasma treatment on polyphenylene sulfide cloth to make the surface of polyphenylene sulfide have hydrophilic groups; then soak the treated polyphenylene sulfide cloth in an acidic solution or an alkaline solution, and then wash and dry it to obtain a hydrophilic polyphenylene sulfide separator;

[0008] Step 2: Pour a layer of PAN or PVP solution doped with rare earth ions or iron-based element ions on the surface of the hydrophilic polyphenylene sulfide separator obtained in Step 1, and after drying, obtain a composite polyphenylene sulfide separator;

[0009] Step 3: Use carbon dioxide laser engraving to engrave the PAN or PVP polymer layer containing rare earth ions or iron-based element ions in the composite polyphenylene sulfide separator obtained in Step 2 to form graphene doped with rare earth ions or iron-based element ions, and obtain a polyphenylene sulfide-based membrane electrode for alkaline electrolyzed water.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] (1) In the present invention, first by plasma treatment, oxygen-containing groups such as -OH, -CO-, -COOH, and -CHO, or groups such as -NH 2 etc. will be introduced on the surface of PPS, significantly improving the hydrophilic performance of PPS. Then, an acidic solution or an alkaline solution is used to lock the hydrophilic groups introduced by the plasma on the surface of the polyphenylene sulfide fiber, so that it can have good hydrophilicity without oxidation or grafting treatment, and the defect that the hydrophilic functional groups on the surface of the PPS membrane after plasma treatment have timeliness is improved.

[0012] (2) The present invention has relatively loose requirements for temperature, considers fewer factors than the traditional high-temperature carbonization method, has a mild experimental environment, is more convenient to prepare, is safe and controllable, and only needs to perform laser sintering for dozens of seconds to prepare an electrode material with catalytic function, has a shorter production cycle and lower energy consumption, and solves the problem of high energy consumption caused by the relatively high temperature requirements for synthesis in the traditional CVD method.

[0013] (3) The present invention is simple and feasible, uses raw materials with relatively low costs, and the laser engraving process is simple. At the same time, electrode materials are in-situ generated on the membrane surface, reducing the possibility of electrode detachment during later use. This method is suitable for batch production and has stronger application potential in the commercial application field. Description of the Drawings

[0014] Figure 1Hydrophilicity test diagram of the hydrophilic polyphenylene sulfide separator prepared in step 1 of Example 1 of the present invention;

[0015] Figure 2 Hydrophilicity test diagram of the polyphenylene sulfide separator prepared in step 1 of Comparative Example 1 of the present invention;

[0016] Figure 3 Photo of the composite polyphenylene sulfide separator prepared in step 2 of Example 1 of the present invention;

[0017] Figure 4 Photo of the polyphenylene sulfide-based membrane electrode prepared in step 3 of Example 1 of the present invention;

[0018] Figure 5 Resistance test diagram of the composite polyphenylene sulfide separator prepared in step 2 of Example 1 of the present invention;

[0019] Figure 6 Resistance test diagram of the polyphenylene sulfide-based membrane electrode prepared in step 3 of Example 1 of the present invention;

[0020] Figure 7 Electrochemical performance diagram of the polyphenylene sulfide-based membrane electrodes prepared in Example 1 and Comparative Example 1 of the present invention. Detailed description of the invention

[0021] The following are specific examples of the present invention. The specific examples are only used to further illustrate the present invention in detail and do not limit the protection scope of the claims of the present invention.

[0022] The present invention provides a method for in-situ preparing a polyphenylene sulfide-based membrane electrode (hereinafter referred to as the method), which is characterized in that the method includes the following steps:

[0023] Step 1: Perform plasma treatment on the polyphenylene sulfide cloth to make the surface of the polyphenylene sulfide have hydrophilic groups; then soak the treated polyphenylene sulfide cloth in an acidic solution or a basic solution to lock the hydrophilic groups on the surface with the acidic solution or the basic solution, and then wash and dry to obtain a hydrophilic polyphenylene sulfide separator (hereinafter referred to as the hydrophilic polyphenylene sulfide separator) with hydrophilic groups on the fiber surface;

[0024] Preferably, in step 1, the polyphenylene sulfide cloth uses a commercial polyphenylene sulfide cloth.

[0025] Preferably, in step 1, the plasma treatment time is 100 - 400 s, the temperature is room temperature, and the frequency is 10 - 15 MHz.

[0026] Preferably, in step 1, the hydrophilic groups are -OH, -CO-, -COOH, -CHO, and -NH 2 .

[0027] Preferably, in step 1, the treated polyphenylene sulfide cloth is quickly placed in an acidic solution or an alkaline solution to minimize the loss of surface hydrophilic groups.

[0028] Preferably, in step 1, the acidic solution is an acidic aqueous solution, and the alkaline solution is an alkaline aqueous solution.

[0029] Preferably, in step 1, the pH of the acidic solution is 1 - 6, and the pH of the alkaline solution is 8 - 14.

[0030] Preferably, in step 1, the acid source of the acidic solution is a weak acid, specifically formic acid, acetic acid or phosphoric acid; the base source of the alkaline solution is a water-soluble strong base or weak base, specifically sodium hydroxide, potassium hydroxide or ammonia water.

[0031] Preferably, in step 1, the soaking time is 24 - 48 h, and the soaking temperature is 30 - 60 °C.

[0032] Preferably, in step 1, the cleaning process is: cleaning with deionized water to remove the acid and base ions on the surface until the surface of the polyphenylene sulfide diaphragm is neutral.

[0033] Preferably, in step 1, the drying process is: drying at 40 - 60 °C for 0.5 - 5 h (preferably 1 - 3 h) to remove the water molecules on the surface.

[0034] Step 2: Pour a layer of PAN or PVP solution doped with rare earth ions or iron-based element ions on the surface of the hydrophilic polyphenylene sulfide diaphragm in step 1, and after drying, a composite polyphenylene sulfide diaphragm is obtained;

[0035] Preferably, in step 2, the pouring process is scraping, coating or knife coating.

[0036] Preferably, in step 2, the pouring temperature is room temperature, and the pouring thickness is 50 - 100 μm.

[0037] Preferably, in step 2, in the PAN or PVP solution doped with rare earth ions or iron-based element ions, the mass fraction of the rare earth ion salt or iron-based element ion salt is 0.5% - 2 wt%, and the mass fraction of PAN or PVP is 10 - 15 wt%.

[0038] Preferably, in step 2, the rare earth ion is cerium ion, and the rare earth ion salt is cerium nitrate; the iron-based element ion is at least one of ferrous ion (Fe 2+ ), divalent cobalt ion (Co 2+ ), and divalent nickel ion (Ni 2+ ), and the iron-based element ion salt is ferrous nitrate, cobalt nitrate and nickel nitrate.

[0039] Preferably, in step 2, the drying process is: drying at 30-70°C for 2-12 h (preferably 3-6 h) to remove the organic solvents and water molecules in the membrane.

[0040] Step 3: Use carbon dioxide laser engraving to engrave the PAN or PVP polymer layer containing rare earth ions or iron-based element ions in the composite polyphenylene sulfide separator obtained in step 2. Decompose carbon dioxide into carbonyl radicals, which interact with -CN of PAN or -CO of PVP and rare earth ions or iron-based element ions in the polymer layer. After the interaction, the polymer layer rapidly carbonizes at high temperature to form graphene doped with rare earth ions or iron-based element ions, obtaining a polyphenylene sulfide-based membrane electrode for alkaline electrolyzed water (abbreviated as polyphenylene sulfide-based membrane electrode).

[0041] Preferably, in step 3, the process of carbon dioxide laser engraving is: the power is 10-20 W, and the engraving speed is 200-500 mm / s.

[0042] Example 1: Step 1: At room temperature, perform plasma treatment on commercial polyphenylene sulfide cloth for 100 s at a frequency of 13 MHz; then immerse the treated polyphenylene sulfide cloth in a formic acid solution with pH = 1 at 50°C for 24 h, wash it with deionized water until neutral, and place it in an oven to dry at 40°C for 5 h to obtain a hydrophilic polyphenylene sulfide separator;

[0043] Step 2: Dissolve cerium nitrate and PAN in DMF to prepare a PAN solution doped with cerium ions, where the mass fraction of cerium nitrate is 2 wt% and PAN is 10 wt%; then use a coater to coat a PAN solution doped with cerium ions with a thickness of 50 μm on the surface of the hydrophilic polyphenylene sulfide separator, and dry it at 30°C for 12 h to obtain a composite polyphenylene sulfide separator;

[0044] Step 3: Use a carbon dioxide laser engraving machine to engrave the surface of the composite polyphenylene sulfide separator, with an engraving power of 10 W and an engraving speed of 200 mm / s, to obtain a polyphenylene sulfide-based membrane electrode.

[0045] After testing, the water contact angle of the hydrophilic polyphenylene sulfide separator significantly decreases, and the wetting time is shortened. The membrane electrode made into an alkaline electrolyzed water electrolytic cell shows good performance.

[0046] From Figure 1 It can be seen that after the hydrophilic polyphenylene sulfide separator obtained in step 1 of Example 1 is placed for 3 h and then the contact angle is measured, it is obtained that: the contact angle is 85° and the wetting time is 10 s.

[0047] From Figure 3 It can be seen that the surface of the hydrophilic polyphenylene sulfide separator is evenly coated with a PAN solution doped with cerium ions.

[0048] FromFigure 4 It can be seen that the surface of the film is rapidly carbonized after laser engraving.

[0049] From Figure 5 It can be seen that the composite polyphenylene sulfide separator in Step 2 is non-conductive.

[0050] From Figure 6 It can be seen that the polyphenylene sulfide-based membrane electrode in Step 3 is conductive and exhibits a small resistance of 42.2 Ω.

[0051] From Figure 5 and Figure 6 It can be seen that through carbon dioxide laser engraving treatment, the non-conductive composite polyphenylene sulfide separator is carbonized, and the obtained polyphenylene sulfide-based membrane electrode is conductive.

[0052] Comparative Example 1:

[0053] It is exactly the same as Example 1, except that: in Step 1, only plasma treatment is carried out. Specifically: in Step 1, at room temperature, a commercial polyphenylene sulfide cloth is subjected to plasma treatment for 100 s at a frequency of 13 MHz to obtain a polyphenylene sulfide separator.

[0054] From Figure 2 It can be seen that after the polyphenylene sulfide separator obtained in Step 1 of Comparative Example 1 is placed for 3 h and then subjected to a contact angle test, it is obtained that: the contact angle is 121°, the surface shows superhydrophobicity and is not wetted. Therefore, the performance of the membrane electrode made into an alkaline electrolytic water electrolyzer is poor.

[0055] From Figure 1 and Figure 2 By comparison, it can be seen that after plasma treatment, soaking in an acidic solution or an alkaline solution can lock the hydrophilic groups on the surface.

[0056] From Figure 7 It can be seen that the surface resistance of the membrane electrode of Example 1 shows an obvious downward trend as the current density increases, and the surface resistance of the membrane electrode of Comparative Example 1 decreases less as the current density increases. Therefore, the membrane electrode made in Example 1 shows better performance when made into an alkaline electrolytic water electrolyzer.

[0057] Example 2: Step 1: At room temperature, a commercial polyphenylene sulfide cloth is subjected to plasma treatment for 200 s at a frequency of 15 MHz; then the treated polyphenylene sulfide cloth is soaked in an acetic acid solution with a pH of 5 at 60 °C for 36 h, then washed with deionized water until neutral, and placed in an oven at 50 °C and dried for 2 h to obtain a hydrophilic polyphenylene sulfide separator;

[0058] Step 2: Dissolve cobalt nitrate and PAN in DMF to prepare a PAN solution doped with cobalt ions, where the mass fraction of cobalt nitrate is 0.5 wt% and PAN is 15 wt%. Then, use a coater to coat a 100-μm-thick PAN solution doped with cobalt ions on the surface of the hydrophilic polyphenylene sulfide separator. After drying at 70 °C for 2 h, a composite polyphenylene sulfide separator is obtained.

[0059] Step 3: Use a carbon dioxide laser engraver to laser engrave the surface of the composite polyphenylene sulfide separator with a engraving power of 10 W and an engraving speed of 300 mm / s to obtain a polyphenylene sulfide-based membrane electrode.

[0060] After testing, the water contact angle of the hydrophilic polyphenylene sulfide separator significantly decreases, and the wetting time shortens. The membrane electrode made into an alkaline electrolytic water electrolytic cell exhibits good performance.

[0061] Example 3: Step 1: At room temperature, subject commercial polyphenylene sulfide cloth to plasma treatment for 200 s at a frequency of 10 MHz. Then, immerse the treated polyphenylene sulfide cloth in a potassium hydroxide solution with a pH of 10 at 60 °C for 48 h, then wash it with deionized water until neutral, and place it in an oven to dry at 60 °C for 0.5 h to obtain a hydrophilic polyphenylene sulfide separator.

[0062] Step 2: Dissolve nickel nitrate and PAN in DMF to prepare a PAN solution doped with nickel ions, where the mass fraction of nickel nitrate is 0.5 wt% and PAN is 15 wt%. Then, use a coater to coat a 100-μm-thick PAN solution doped with nickel ions on the surface of the hydrophilic polyphenylene sulfide separator. After drying at 50 °C for 12 h, a composite polyphenylene sulfide separator is obtained.

[0063] Step 3: Use a carbon dioxide laser engraver to laser engrave the surface of the composite polyphenylene sulfide separator with an engraving power of 20 W and an engraving speed of 200 mm / s to obtain a polyphenylene sulfide-based membrane electrode.

[0064] After testing, the water contact angle of the hydrophilic polyphenylene sulfide separator significantly decreases, and the wetting time shortens. The membrane electrode made into an alkaline electrolytic water electrolytic cell exhibits good performance.

[0065] Example 4: Step 1: At room temperature, subject commercial polyphenylene sulfide cloth to plasma treatment for 200 s at a frequency of 12 MHz. Then, immerse the treated polyphenylene sulfide cloth in a sodium hydroxide solution with a pH of 14 at 30 °C for 48 h, then wash it with deionized water until neutral, and place it in an oven to dry at 50 °C for 3 h to obtain a hydrophilic polyphenylene sulfide separator.

[0066] Step 2: Dissolve ferrous nitrate and PAN in DMF to prepare a PAN solution doped with iron ions, where the mass fraction of ferrous nitrate is 2 wt% and PAN is 15 wt%; then use a coater to coat a PAN solution doped with iron ions with a thickness of 100 μm on the surface of the hydrophilic polyphenylene sulfide separator. After drying at 30 °C for 6 h, a composite polyphenylene sulfide separator is obtained.

[0067] Step 3: Use a carbon dioxide laser engraving machine to engrave the surface of the composite polyphenylene sulfide separator. The engraving power is 10 W and the engraving speed is 500 mm / s to obtain a polyphenylene sulfide-based membrane electrode.

[0068] After testing, the water contact angle of the hydrophilic polyphenylene sulfide separator is significantly reduced, and the wetting time is shortened. The membrane electrode made to form an alkaline electrolytic water electrolytic cell exhibits good performance.

[0069] Matters not described in the present invention are applicable to the prior art.

Claims

1. A method for in-situ preparation of a polyphenylene sulfide-based membrane electrode, characterized in that: The method comprises the following steps: Step 1, subjecting the polyphenylene sulfide cloth to plasma treatment to make the surface of the polyphenylene sulfide have hydrophilic groups; then immersing the treated polyphenylene sulfide cloth in an acidic solution or an alkaline solution, and then washing and drying to obtain a hydrophilic polyphenylene sulfide membrane; Step 2: pouring a layer of PAN or PVP solution doped with rare earth ions or iron-based element ions on the surface of the hydrophilic polyphenylene sulfide membrane in step 1, and drying to obtain a composite polyphenylene sulfide membrane; the rare earth ions are cerium ions; the iron-based element ions are at least one of ferrous ions, divalent cobalt ions and divalent nickel ions; Step 3: Use carbon dioxide laser engraving to laser engrave the PAN or PVP polymer layer containing rare earth ions or iron-based element ions in the composite polyphenylene sulfide membrane of step 2 to form graphene doped with rare earth ions or iron-based element ions, and obtain a polyphenylene sulfide-based membrane electrode for alkaline water electrolysis.

2. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 1, the plasma treatment time is 100-400 s, the temperature is room temperature, and the frequency is 10-15 MHz.

3. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 1, the treated polyphenylene sulfide cloth is quickly placed in an acidic solution or an alkaline solution to reduce the loss of surface hydrophilic groups.

4. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 1, the pH of the acidic solution is 1-6, and the pH of the alkaline solution is 8-14; In step 1, the acid source of the acidic solution is a weak acid; the alkali source of the alkaline solution is a water-soluble strong base or weak base; In step 1, the soaking time is 24-48 hours and the soaking temperature is 30-60°C; In step 1, the cleaning process is: cleaning with deionized water to remove acid and alkali ions on the surface until the surface of the polyphenylene sulfide diaphragm is neutral; In step 1, the drying process is: drying at 40-60°C for 0.5-5h.

5. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 4, characterized in that: The acid source of the acidic solution is formic acid, acetic acid or phosphoric acid; the alkali source of the alkaline solution is sodium hydroxide, potassium hydroxide or ammonia water.

6. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 2, the casting process is scraping, coating or scraping film; In step 2, the pouring temperature is room temperature and the pouring thickness is 50-100 μm.

7. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 2, in the PAN or PVP solution doped with rare earth ions or iron-based element ions, the mass fraction of the rare earth ion salt or the iron-based element ion salt is 0.5% to 2wt%, and the mass fraction of the PAN or PVP is 10 to 15wt%.

8. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 2, the rare earth ion salt is cerium nitrate; the iron element ion salt is ferrous nitrate, cobalt nitrate and nickel nitrate.

9. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 2, the drying process is: drying at 30-70°C for 2-12 hours.

10. The method for in-situ preparation of polyphenylene sulfide-based membrane electrode according to claim 1, characterized in that: In step 3, the process of CO2 laser engraving is: power is 10~20W, engraving speed is 200~500mm / s.

Images