PROTON EXCHANGE MEMBRANE AND MANUFACTURING METHOD THEREOF

Abstract

A manufacturing method of a proton exchange membrane is provided, which includes the steps as follows. The hydroxyl groups are disposed on the surface of a substrate by a hydrophilic treatment. The hydroxyl groups on the substrate are chemically modified with a coupling agent by a sol-gel process. The substrate is exposed to an amino acid with a phosphonate radical so that the amino acid containing a phosphonate radical can be chemically bonded with the coupling agent. The chemically bonded substrate is immersed in phosphoric acid for absorbing the phosphoric acid. The substrate blended with the phosphoric acid is placed between at least two leak-proof films for the purpose of preventing the leakage of the absorbed phosphoric acid. The proton exchange membrane manufactured by this method enable to retain the phosphoric acid in organic/inorganic complex form and micron/nano complex pore size.

Claims

1. A method of manufacturing a proton exchange membrane, comprising the following steps of: disposing hydroxyl groups on a surface of a substrate by a hydrophilic treatment; chemically modifying the hydroxyl groups disposed on the substrate with a coupling agent by a sol-gel process; chemically bonding an amino acid containing a phosphonate radical with the coupling agent chemically modifying the substrate; making the substrate which is chemically bonded to absorb phosphoric acid; and placing the substrate blended with the phosphoric acid between at least two leak-proof films for preventing the leakage of the absorbed phosphoric acid.

2. The method of manufacturing the proton exchange membrane of claim 1, wherein the substrate comprises glass fiber, polybenzimidazoles, polyolefin, or polyacrylamide/polyvinyl alcohol.

3. The method of manufacturing the proton exchange membrane of claim 1, wherein the coupling agent comprises (3-glycidyloxypropyl)trimethoxysilane.

4. The method of manufacturing the proton exchange membrane of claim 1, wherein the amino acid containing a phosphonate radical comprises O-phospho-DL-serine, O-phospho-L-threonine, O-phospho-L-tyrosine, or N-phosphonomethylglycine.

5. The method of manufacturing the proton exchange membrane of claim 1, wherein the least two leak-proof films comprise a polytetrafluoroethylene film, a graphene oxide, or a polycarbonate membrane.

6. A proton exchange membrane, comprising: a substrate; a coupling agent chemically modifying the substrate by a sol-gel process; serine containing a phosphonate radical chemically bonded with the coupling agent; phosphoric acid absorbed on the substrate; and at least two leak-proof films, wherein the substrate blended with the phosphoric acid is placed between the least two leak-proof films for preventing the leakage of the absorbed phosphoric acid.

7. The proton exchange membrane of claim 6, wherein the substrate comprises glass fiber, polybenzimidazoles, polyolefin, or polyacrylamide/polyvinyl alcohol.

8. The proton exchange membrane of claim 6, wherein the coupling agent comprises (3 -glycidyloxypropyl)trimethoxysilane.

9. The proton exchange membrane of claim 6, wherein the serine containing a phosphonate radical comprises O-phospho-DL-serine, O-phospho-L-threonine, O-phospho-L-tyrosine, or N-phosphonomethylglycine.

10. The proton exchange membrane of claim 6, wherein the least two leak-proof films comprise a polytetrafluoroethylene film, a graphene oxide, or a polycarbonate membrane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a flow chart of an embodiment of a method of manufacturing a proton exchange membrane in accordance with the present disclosure.

[0020] FIG. 2A is a schematic diagram illustrating an embodiment of a proton exchange membrane processed with hydrophilic treatment in accordance with the present disclosure.

[0021] FIG. 2B is a schematic diagram illustrating an embodiment of a proton exchange membrane modified by GPETMS in accordance with the present disclosure.

[0022] FIG. 2C is a schematic diagram illustrating an embodiment of the ring-opening and grafting reaction of a proton exchange membrane in accordance with the present disclosure.

[0023] FIG. 3A is a photo showing an embodiment of an unprocessed silicon wafer in accordance with the present disclosure.

[0024] FIG. 3B is a photo showing an embodiment of a silicon wafer processed with KOH hydrophilic treatment in accordance with the present disclosure.

[0025] FIG. 3C is a photo showing an embodiment of silicon wafer reacted with GPTMS by 2 hours in accordance with the present disclosure.

[0026] FIG. 3D is a photo showing an embodiment of silicon wafer reacted with GPTMS by 3 hour in accordance with the present disclosure.

[0027] FIG. 3E is a photo showing an embodiment of silicon wafer reacted with GPTMS by 4 hours in accordance with the present disclosure.

[0028] FIG. 4A is a top view of a structural model of AFM surface of an embodiment of silicon wafer in accordance with the present disclosure.

[0029] FIG. 4B is a side view of a structural model of AFM surface of an embodiment of silicon wafer in accordance with the present disclosure.

[0030] FIG. 5 is a SEM photo showing an embodiment of a substrate of a proton exchange membrane processed with hydrophilic treatment in accordance with the present disclosure.

[0031] FIG. 6 is a SEM photo showing an embodiment of a substrate of a proton exchange membrane modified by GPTMS in accordance with the present disclosure.

[0032] FIG. 7A is a SEM photo showing another embodiment of a substrate of a proton exchange membrane modified by GPTMS in accordance with the present disclosure.

[0033] FIG. 7B is an EDX chemical analytical diagram of FIG. 7A.

[0034] FIG. 8A is a XPS result diagram illustrating an embodiment of a substrate of a proton exchange membrane processed with hydrophilic treatment in accordance with the present disclosure.

[0035] FIG. 8B is a XPS result diagram illustrating an embodiment of a substrate of a proton exchange membrane modified by GPTMS in accordance with the present disclosure.

[0036] FIG. 9A is a XPS result diagram illustrating an embodiment of a substrate of a proton exchange membrane modified by GPTMS in accordance with the present disclosure.

[0037] FIG. 9B is a XPS result diagram illustrating an embodiment of a substrate of a proton exchange membrane exposed to an amino acid with a phosphonate radical after ring-opening and grafting reaction in accordance with the present disclosure.

[0038] FIG. 10 is a SEM photo showing an embodiment of a substrate of a proton exchange membrane exposed to an amino acid with a phosphonate radical after ring-opening and grafting reaction in accordance with the present disclosure.

[0039] FIG. 11A is a SEM photo showing an embodiment of a substrate of a proton exchange membrane exposed to an amino acid with a phosphonate radical after ring-opening and grafting reaction in accordance with the present disclosure.

[0040] FIG. 11B is an EDX chemical constitution analytical diagram of large block shown in FIG. 11A.

[0041] FIG. 12A is a SEM photo showing an embodiment of a substrate of a proton exchange membrane exposed to an amino acid with a phosphonate radical after ring-opening and grafting reaction in accordance with the present disclosure.

[0042] FIG. 12B is an EDX chemical constitution analytical diagram of the plates shown in FIG. 12A.

[0043] FIG. 13 is a schematic diagram illustrating an embodiment of the proton conductivity of a proton exchange membrane varying with temperatures in accordance with the present disclosure.

[0044] FIG. 14 is a schematic diagram illustrating a comparison and an embodiment of a proton exchange membrane in accordance with the present disclosure.

[0045] FIG. 15A is a schematic diagram illustrating an embodiment of the pore distribution of the glass fiber.

[0046] FIG. 15B is schematic diagram illustrating an embodiment of the pore distribution of the PTFE film.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Please refer to FIGS. 1, 2A, 2B and 2C, which are flow charts of a method of manufacturing a proton exchange membrane in accordance with the present disclosure. The method of manufacturing a proton exchange membrane is feasible to be applied to all the embodiments of the present disclosure. In the present embodiment, the hydrophilic treatment may include KOH immersion treatment, hydro plasma treatment or methanol immersion treatment, but it shall be not limited thereto. The substrate may be made of glass fiber, polybenzimidazoles, polyolefin, or polyacrylamide/polyvinyl alcohol, but it shall be not limited thereto. The amino acid with a phosphonate radical may include O-phospho-DL-serine, O-phospho-L-threonine, O-phospho-L-tyrosine, or

[0048] N-phosphonomethylglycine, but it shall be not limited thereto. As shown in FIG. 1, the process may include the following steps.

[0049] Step 1: acetone, isopropanol and deionized water are used to clean a glass fiber 10 through supersonic vibration by 5 minutes, and then the glass fiber 10 is immersed in the potassium hydroxide (KOH) solution of 10% concentration at room temperature through supersonic vibration by 40 minutes, such that the glass fiber 10 is cleaned and has hydrophilic effect. As shown in FIG. 2A, the glass fiber 10 made according to the process mentioned above has hydroxyl groups. The following reaction is shown as follows.

[0050] Step 2: 3-glycidoxypropyl-trimethoxysilane (GPTMS) is disposed on the glass fiber 10 by a sol-gel process. The GPTMS is added dropwise to ethanol to prepare the GPTMS in ethanol solution of 1 vol. %, and then a magnetic stirrer is sued to stir the solution. The addition of acetic acid is used to adjust the PH value of the solution to be 3 to 5, and acid catalysis is used to facilitate the hydrolysis of the GPTMS. The glass fiber 10 processed with hydrophilic treatment is added to the prepared GPTMS solution to perform dehydration reaction by 4 hours. The step facilitates the GPTMS to be disposed on the glass fiber 10, as shown in FIG. 2B.

[0051] Step 3: O-phospho-DL-serine of 2 grams is solved in the deionized water with 200 ml at a temperature of 80 C. The glass fiber 10 disposed with the GPTMS is placed in the O-phospho-DL-serine solution at a temperature of 80 C. to react by one hour. The step is to perform the ring-opening and grafting reaction by using epoxy group of the GPTMS and amino group of the O-phospho-DL-serine, so as to achieve the purpose of chemically bonding phosphonate radicals on the glass fiber 10, as shown in FIG. 2C.

[0052] Step 4: the prepared glass fiber 10 is immersed in the phosphoric acid of 86% concentration at a temperature of 150 C. by 20 minutes, and baked at a temperature of 60 C. to remove the unwanted water. Afterwards, the glass fiber 10 is placed between two polytetrafluoroethylene films to form the desired proton exchange membrane of the present disclosure. The polytetrafluoroethylene film used herein is to prevent the leakage of the phosphoric acid absorbed by the glass fiber 10.

[0053] In accordance with the present embodiment, the proton exchange membrane transfers proton in organic/inorganic complex form. The organic form means that the proton is transferred by the phosphonate radicals chemically bonded (containing C-P bond) on the substrate. The inorganic form is that the proton is transferred through electrolyte such as the phosphoric acid adhered to the substrate by capillary action, Van der Waals force, or hydrogen bond. The organic/inorganic complex form is characterized of better proton conductivity due to the inorganic form and stronger C-P bonding that performs by the organic form. Besides, it can avoid losing electrolyte resulted from the inorganic form. As a result, the defect of the proton conductivity degrading with time can be improved.

[0054] The sequence shown in FIG. 1 explains the process of substrate. For example, when the substrate is modified by the GPTMS, that means the substrate has also been processed with the hydrophilic treatment, or when the substrate is processed with ring-opening and grafting reaction, that means the substrate has also been processed by the hydrophilic treatment and modified by the GPTMS, the unnecessary details are no longer provided hereinafter for the concise manner.

[0055] Please refer to FIGS. 3A through 3E, which are the photos of an embodiment of the silicon wafer in accordance with the present disclosure. The reason the silicon wafer is used to instead of the glass fiber in this assay is that the glass fiber is too soft to be analyzed for detecting the contact angle, so that the silicon wafer which has identical composition to glass fiber is selected as a replacement. Here, the silicon wafer shown in FIG. 3A is unprocessed and has a contact angle of 28. The silicon wafer in FIG. 3B is processed with hydrophilic treatment through the KOH solution and has a contact angle of 3. The silicon wafer shown in FIG. 3C reacts with the GPTMS by 2 hours and has a contact angle of 22. The silicon wafer shown in FIG. 3D reacts with the GPTMS by 3 hours and has a contact angle of 38. The silicon wafer shown in FIG. 3E reacts with the GPTMS by 4 hours and has a contact angle of 42.

[0056] According to the results derived from the processes mentioned above, it can be found that the silicon wafer processed with hydrophilic treatment through the KOH solution has a contact angle from 28 to 3, proving that the hydrophilic treatment processed with the KOH solution does have hydrophilic effect. When the silicon wafer processed with hydrophilic treatment reacts with the GPTMS, the contact angle varies with time from 3 to 42. Therefore, it can be found that the GPTMS is successfully disposed on the silicon wafer, achieving the effect of modifying the surface of the silicon wafer.

[0057] Please refer to FIG. 4A and FIG. 4B, which are the top view and side view of structural model of AFM surface of the silicon wafer, respectively. The reason the silicon wafer is used to instead of the glass fiber in this assay is that the glass fiber is too soft to be analyzed by AFM, so that the silicon wafer which has identical composition to glass fiber is selected as a replacement. Here, the silicon wafers respectively shown in FIG. 4A and 4B are both processed with hydrophilic treatment and then react with the GPTMS by 3 hours.

[0058] According to the aforementioned figures it can be found that surfaces of silicon wafers have a maximum loss by 1 nm, indicating that the GPTMS is evenly disposed on the silicon wafers to form the film of a nano size after the reaction.

[0059] Please refer to FIG. 5, which is the SEM photo showing an embodiment the substrate of the proton exchange membrane processed with hydrophilic treatment in accordance with the present disclosure. In the present embodiment, the substrate may include glass fiber, and hydrophilic treatment may be performed by KOH solution, but it shall be not limited thereto. Here, by means of hydrophilic treatment, the glass fiber has hydroxyl groups and is further combined with the GPTMS, enabling the GPTMS to be disposed on the glass fiber.

[0060] Please refer to FIG. 6, which is the SEM photo showing an embodiment of the substrate of the proton exchange membrane processed with the GPTMS in accordance with the present disclosure. In the present embodiment, the substrate may include glass fiber, but it shall be not limited thereto. Comparing FIG. 6 with FIG. 5 can find a minor difference. However, as the two figures are both of a nano size, it proves that the GPTMS is disposed on the glass fiber with a nano size.

[0061] Please refer to FIGS. 7A and 7B, which are respectively a SEM photo and an EDX chemical constitution analytical diagram showing another embodiment of the substrate of the proton exchange membrane modified by the GPTMS in accordance with the present disclosure. In the embodiment, the substrate may include glass fiber, but it shall be not limited thereto. The EDX chemical constitution of FIG. 7B is shown in table 1.

TABLE-US-00001 TABLE 1 Element Weight (%) Atomic (%) C 11.14 15.94 O 62.42 67.07 Na 5.64 4.22 Al 1.60 1.02 Si 19.20 11.75 Totals 100.00 100.00

[0062] As the table shows, the glass fiber without C atom has a weight percent of about 11% and an atom percentage of about 16%. The performance of the GPTMS containing C atom disposed on the glass fiber is therefore found. As a result, the data indicates that the GPTMS is successfully disposed on the glass fiber.

[0063] Please refer to FIG. 8A and FIG. 8B, which are respectively a XPS diagram of the substrate processed with hydrophilic treatment and a XPS diagram of the substrate modified by the GPTMS. In the present embodiment, the substrate may include glass fiber, but it shall be not limited thereto. As shown in the figures, after being modified by the GPTMS, the relative strength of C-C bond and C-H bond increases from 2000 C/S as shown in FIG. 8A to 4300 C/S as shown in FIG. 8B, and the relative strength of CHC bond increases from 1600 C/S as shown in FIG. 8A to 4000 C/S as shown in FIG. 8B.

[0064] As the data shows, after the glass fiber is modified by the GPTMS, the relative strength of CC bond, CH bond and CHC bond of the GPTMS increases, meaning that the bonding number increases. Hence, it proves that the GPTMS is indeed disposed on the glass fiber.

[0065] Please refer to FIG. 9A and FIG. 9B, which are respectively a XPS diagram of the substrate of the proton exchange membrane modified by the GPTMS and a XPS diagram showing the ring-opening and grafting reaction of the substrate containing phosphonate radicals. In the present embodiment, the substrate may include glass fiber and the amino acid with a phosphonate radical may include O-phospho-DL-serine, but it shall be not limited thereto. As shown in the figures, after the ring-opening and grafting reaction, the relative strength of nitrogen element increases from 0 C/S as shown in FIG. 9A to 1.23 C/S as shown in FIG. 9B, and the relative strength of phosphor element increases from 0 C/S as shown in FIG. 9A to 1.34 C/S as shown in FIG. 9B.

[0066] As the data shows, after the ring-opening and grafting reaction, the relative strength of nitrogen element and phosphor element of O-phospho-DL-serine increase from 0 as shown in FIG. 9A to a certain strength as shown in FIG. 9B. Hence, it shows that the GPTMS is indeed disposed on the glass fiber.

[0067] Please refer to FIG. 10, which is a SEM photo showing the proton exchange membrane and the substrate exposed to the amino acid with a phosphonate radical after the ring-opening and grafting reaction. In the present embodiment, the substrate may include glass fiber and the amino acid with a phosphonate radical may include O-phospho-DL-serine, but it shall be not limited thereto. The difference between FIG. 5, FIG. 6 and FIG. 10 lies that there are numerous plate-shaped substances of nano size disposed among the glass fibers shown in FIG. 10, compared the substrate processed with hydrophilic treatment shown in FIG. 5 and the substrate modified by the GPTMS shown in FIG. 6. The chemical constitution of the plate-shaped substances will be described in the following paragraphs.

[0068] Please refer to FIG. 11A and FIG. 11B, which are respectively a SEM photo showing the substrate of the proton exchange membrane exposed to the amino acid with a phosphonate radical after ring-opening and grafting reaction and an analytical diagram of EXD chemical constitution thereof. In the present embodiment, the substrate may include glass fiber and the amino acid with a phosphonate radical may include O-phospho-DL-serine, but it shall be not limited thereto. The EDX chemical constitution of FIG. 11B is shown in table 2.

TABLE-US-00002 TABLE 2 Element Weight (%) Atomic (%) C 22.96 30.33 N 3.95 4.48 O 57.62 57.14 Al 0.28 0.17 Si 2.02 1.14 P 13.16 6.74 Totals 99.99 100

[0069] Compared with table 1 it can be found that the carbon element is not present in O-phospho-DL-serine before the ring-opening and grafting reaction, while it has a weight percentage of about 13% and an atom percentage of about 7% after the reaction. As a result, the data indicates that the O-phospho-DL-serine is successfully bonded on the glass fiber.

[0070] Please refer to FIG. 12A and FIG. 12B, which are respectively a SEM photo showing the substrate of the proton exchange membrane exposed to the amino acid with a phosphonate radical after ring-opening and grafting reaction and an analytical diagram of EXD chemical constitution thereof. In the present embodiment, the substrate may include glass fiber and the amino acid with a phosphonate radical include O-phospho-DL-serine, but it shall be not limited thereto. The EDX chemical constitution of FIG. 12B is shown in table 3.

TABLE-US-00003 TABLE 3 Element Weight (%) Atomic (%) C 24.27 32.32 O 58.86 58.84 Si 2.63 1.50 P 14.23 7.35 Totals 99.99 100.01

[0071] As the data shows, the P element, which is derived from the plate in SEM photo, shown in table 3 has a higher weight percentage of about 1% and a higher atomic percentage of about 0.6% than that in table 2. Hence, it can be found that the plates are the main place where O-phospho-DL-serine reacts with glass fiber.

[0072] Please refer to FIG. 13, which is a schematic diagram illustrating an embodiment of the proton conductivity of a proton exchange membrane varying with temperatures in accordance with FIG. 1 of the present disclosure. As shown in the figure, the proton exchange membrane of the present embodiment has better proton conductivity, and the proton conductivity reaches to 0.84 S/cm at a temperature of 150 C. Here, the AC impedance analysis is applied to measure the proton conductivity.

[0073] FIG. 14 is a schematic diagram illustrating a comparison and an embodiment of a proton exchange membrane in accordance with the present disclosure. As shown in the figure, the proton conductivity of the proton exchange membrane of an embodiment and that of the comparison are measured in one minute. Here, the composition of the proton exchange membrane of the comparison is PTFE, phosphoric acid, and glass fiber processed with hydrophilic treatment. The hydrophilic treatment may include KOH immersion treatment, hydro plasma treatment or methanol immersion treatment, but it shall be not limited thereto. The proton exchange membrane of the embodiment is formed according to the process shown in FIG. 1. The detailed data of FIG. 14 is shown in table 4.

TABLE-US-00004 TABLE 4 Types of the proton exchange membranes Test types Embodiment Comparison Proton conductivity (S/cm) 0.83 0.71 Proton conductivity after 1 min (S/cm) 0.56 0.46 Decrease of Proton conductivity after 1 min 32% 35%

[0074] According to the result shown in table 4 it can be found that the proton conductivity of the proton exchange membrane of the embodiment after 1 minute is 32%, and the decrease of proton conductivity of the proton exchange membrane of the comparison after 1 minute is 35%. The degree of attenuation is 3%, meaning that the proton conductivity of the proton exchange membrane of the embodiment has a smaller decrease. In other words, the proton conductivity of the proton exchange membrane of the embodiment has a better capacity for retaining the phosphoric acid after a period of time. In addition, the initial proton conductivity of the proton exchange membrane of the embodiment is better than that of the comparison, indicating that the proton exchange membrane of the embodiment is able to retain more phosphoric acids which are served as proton conductor, so as to further promote the electrical efficiency of the fuel cell.

[0075] Please refer to FIG. 15A and 15B, which are schematic diagrams illustrating an embodiment of the pore distribution of the glass fiber and the PTFE film, respectively. As shown in the figure, the pore distribution of the glass fiber is about 1m to about 1.5 m, and the pore distribution of the PTFE film is about 50 nm to about 400 nm. In addition, the porosity of the glass fiber is about 93%, and the porosity of the PTFE film is about 70%. The above data were all measured by the mercury porosimeter. The difference of the pore size and the porosity between the substrate (e.g. the glass fiber) and the leak-proof film (e.g. the PTFE film) may facilitate to retain the phosphoric acid in the proton exchange membrane.

[0076] In conclusion, after the modified processes, the proton exchange membrane of the present disclosure is able to retain the phosphoric acid in organic/inorganic complex form and micron/nano complex pore size. Compared with the traditional proton exchange membrane which retains the phosphoric acid in inorganic form, the proton exchange membrane of the present disclosure has better proton conductivity and the proton conductivity can be maintained after a period of time, so that the electrical efficiency of fuel cell can be promoted completely. In addition, the contact angle, AFM, SEM, EDX and XPS are applied to validate the modification of the present disclosure, indicating that parameters such as contact angles, photos, chemical constitutions, bonding, and the relative strength of atoms, and so on all successfully achieve the desired effect after being modified.

[0077] While the means of specific embodiments in present disclosure has been described by reference drawings, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims. The modifications and variations should in a range limited by the specification of the present disclosure.