Preparation method of amphiphilic polybenzimidazole and azide ionic liquid for phosphoric acid stabilized high-temperature proton exchange membrane

Abstract

The invention firstly provides a phosphoric acid stable type high-temperature proton exchange membrane with amphiphilic polybenzimidazole and azide type ionic liquid, the ionic liquid in the composite membrane accounts for 30% by mass, and the prepared OHPBI-PIL-Px membrane exchanges anions into H2PO4 <-> through acid-base doping reaction, so that ion pairs are formed, and the proton exchange membrane has the advantages of high-temperature proton exchange, high-temperature proton exchange, high-temperature proton exchange and the like. The composite membrane constructs a proton transfer channel in a system, promotes proton transfer and transfer, provides alkaline quaternary ammonium sites, has strong acid-base interaction with PA, and can effectively reduce PA leakage. The long-term performance of the high-temperature proton exchange membrane can be enhanced. The invention further provides a preparation method of the stable high-temperature proton exchange membrane with the amphiphilic polybenzimidazole and azide ionic liquid phosphoric acid. The OHPBI-PIL-Px membrane is formed by crosslinking through an in-situ free radical polymerization method. The formed high-temperature proton exchange membrane is excellent in electrochemical performance and controllable in cost, has a production prospect and can be applied to the field of high-temperature proton exchange membrane fuel cells.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer materials and fuel cells, and relates to a preparation method of a high-temperature proton exchange membrane with amphiphilic polybenzimidazole and azide type ionic liquid. BACKGROUND

[0002] Proton exchange membrane fuel cells have many advantages and potentials, mainly including high efficiency, low emission and simple structure. As a kind of proton exchange membrane, high-temperature proton exchange membrane fuel cells can operate at a relatively high temperature (120-200℃) without external humidification, and can improve carbon monoxide poisoning, improve the tolerance of impurities, improve energy conversion efficiency, have higher reaction activity and faster reaction rate. Among them, the high-temperature proton exchange membrane is the most important component, which can transport protons and block the cathode and anode, and has been studied more and more. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of a phosphoric acid stable high-temperature proton exchange membrane with amphiphilic polybenzimidazole and azide type ionic liquid for fuel cells, which has good proton conductivity, phosphoric acid retention capacity and output power. The proton conductivity of the prepared OHPBI-PIL-P30 can reach 151.9 mS cm -1 , 87.5% at 160℃ under anhydrous conditions after 240 hours, and 73.4% under 80℃ / 40% relative humidity conditions. The present application first provides a phosphoric acid stable high-temperature proton exchange membrane with amphiphilic polybenzimidazole and azide type ionic liquid, which comprises the following components by mass percentage: OHPBI-PIL-Px: 70% [CPDOc]Br2: 15% AMB: 15%

[0004] The present application further provides a preparation method of a phosphoric acid stable high-temperature proton exchange membrane with amphiphilic polybenzimidazole and azide type ionic liquid, comprising the following steps:

[0005] Step one: mix polyphosphoric acid and DAB thoroughly. Then add IPA, HyIPA and P2O5 into a round-bottom flask, and then pour the generated polymer into deionized water containing sodium bicarbonate. Finally, cut the polymer, boil and dry to obtain OHPBI.

[0006] Step two: graft OHPBI with 2-isocyanate pyridine under the catalysis of triethylamine to form amphiphilic polybenzimidazole OHPBI-Px.

[0007] Step three: synthesis of [CPDOc]Br2ionic liquid by equimolar reaction.

[0008] Step four: add amphiphilic polybenzimidazole OHPBI-Px in DMSO. After the polymer is completely dissolved, add two kinds of ionic liquid respectively, mix until completely dissolved. Then, add initiator AIBN, wait for complete dissolution, pour the casting solution evenly on the glass plate. At a certain temperature, wait for the solvent to completely evaporate. Subsequently, crosslinking is carried out at 150°C to obtain OHPBI-PIL-Px film. Preferably, the OHPBI-PIL-Px film is crosslinked by the method of in-situ radical polymerization, and the prepared OHPBI-PIL-Px film is exchanged into H2PO4 - , thereby forming an ion pair, the purpose of which is to (1) construct a proton transport channel to promote proton transfer and transfer; (2) provide a basic quaternary ammonium site and have a strong acid-base interaction with PA, which can enhance the long-term performance of high-temperature proton exchange membranes. Preferably, the preparation method of the phosphoric acid stable high-temperature proton exchange membrane with two functional nitrogen cation pair ionic liquids comprises the following steps: mixing amino type polybenzimidazole and ionic liquid in a ratio of 7:3. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 The preparation process of OHPBI, [CPDOc]Br2and AMB is shown; Figure 2 The phosphoric acid retention rate of OHPBI-PIL-Px film after 240 hours at 160°C / 0% relative humidity (RH) and at 80°C / 40% RH, respectively, is shown. Figure 3 The proton conductivity of OHPBI-PIL-Px film at 100-180°C is shown.

[0010] The technical solutions of the present application will be described clearly and completely below, and detailed embodiments and specific operation processes are given. It must be pointed out that for researchers in this technical field, a number of improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

[0011] Example 1 comprises the following steps:

[0012] ​Into a round bottom flask at 140 °C, 78 g of polyphosphoric acid was gradually added. Then, 0.015 mol of DAB was added to the reaction system and mixed well. Subsequently, IPA, OHIPA and P2O5 were gradually added to the round bottom flask. When the reactants were viscous, the temperature was increased to 200 °C at a specific speed, and 75 ml of phosphoric acid was added and stirred at 75 °C for 12 h. To neutralize the polymer, the resulting polymer was poured into deionized water containing hydrogen peroxide. After that, the polymer was cut, boiled and dried to obtain OHPBI.

[0013] Into a 50 mL round bottom flask, 0.1 mol of OHPBI and 0.03 mol of 2- isocyanate pyridine and 0.1 microliters of triethylamine were added. The reaction was carried out at 65 °C for three. The product was poured into isopropyl alcohol and dried under vacuum to obtain amphiphilic polybenzimidazole— OHPBI-Px.

[0014] Into a 50 mL round bottom flask, 0.06 mol of 1,4-diazido bicyclo[2,2,2]octane and 5-bromo-1-pentene were added. The reaction was first carried out in an ice water bath for 3 h, then warmed to room temperature for 5-6 h, then warmed to 50 °C, and reacted under reflux condensation for 24 h until the solution became a white solid. The solid was poured into acetone and repeatedly washed with acetone to remove unreacted reactants. Then vacuumed at room temperature to obtain an ionic liquid intermediate with azide. The ionic liquid intermediate was weighed, then 0.023 mol of 1-bromo-4-chlorobutane was weighed, then reacted in a 25 °C oil bath for 3 h, then continued to react and warmed to 50 °C, and reacted under reflux condensation for 24 h until the solution became a white turbid liquid, which was poured into acetone and repeatedly washed with acetone to remove unreacted impurities, then vacuumed at room temperature to obtain an azide ionic liquid— [CPDOc]Br2.

[0015] First, 0.2 g of OHPBI-Px was dissolved in DMSO, after the polymer was completely dissolved, 15% by mass of AMB and [CPDOc]Br2 were added respectively, and stirred until completely dissolved. Then 1% by mass of AIBN was added and stirred for 30 min. The casting solution was poured onto a clean glass plate through a filter cloth until the casting solution evenly covered the entire glass plate, which was placed in an oven at 50 °C and waited for 4 h for AIBN to initiate double bond polymerization. Then the temperature was increased to 90 °C until the solvent was completely evaporated. The film was placed in an oven at 150 °C for crosslinking. OHPBI-PIL-Px film was obtained.

[0016] The phosphoric acid retention rate of OHPBI-PIL-Px composite membrane increases with the increase of 2-isocyanate pyridine content, and the phosphoric acid retention rate of OHPBI-PIL-P30 can reach 89.1% under the condition of 160℃ without humidity, and 73.4% under the condition of 80℃ / 40% relative humidity, which shows that the composite membrane can be applied to high-temperature proton exchange membrane.

[0017] The proton conductivity of OHPBI-PIL-Px composite membrane increases with the increase of 2-isocyanate pyridine content, and the proton conductivity of OHPBI-PIL-P30 membrane can reach 151.9mS cm -1 under the condition of 180℃, which shows that the composite membrane can be applied to high-temperature proton exchange membrane.

Claims

1. A phosphoric acid-stabilized high-temperature proton exchange membrane comprising amphiphilic polybenzimidazole and an azide-type ionic liquid, prepared by in-situ free radical polymerization of amphiphilic polybenzimidazole and an ionic liquid. The invention is further described in detail below with reference to embodiments: 1) Gradually pour 78g of polyphosphoric acid into a round-bottom flask at 140℃. Then, add 0.015mol of DAB to the reaction system and mix thoroughly. Subsequently, gradually add IPA, OHIPA, and P2O5 to the round-bottom flask. When the reactants become viscous, raise the temperature to 200℃ at a specific rate and add 75ml of phosphoric acid, stirring at 75℃ for 12 hours. To neutralize the polymer, pour the resulting polymer into deionized water containing hydrogen peroxide. Afterward, cut the polymer into small pieces, boil, and dry to obtain OHPBI. 2) In a 50 mL round-bottom flask, add 0.1 mol of OHPBI, 0.03 mol of 2-isocyanate pyridine, and 0.1 μL of triethylamine. The reaction is carried out at 65 °C. The product is poured into isopropanol and dried under vacuum to obtain amphiphilic polybenzimidazole-OHPBI-Px. 3) Add 0.06 mol of 1,4-diazidobicyclo[2,2,2]octane and 5-bromo-1-pentene to a 50 mL round-bottom flask. The reaction is first carried out in an ice-water bath for 3 h, then heated to room temperature and continued for 5-6 h, followed by heating to 50 °C and reacting under reflux for 24 h until the solution becomes a white solid. The solid is poured into acetone and repeatedly washed with acetone to remove unreacted reactants. Then, the mixture is vacuum-sealed at room temperature to obtain an ionic liquid intermediate containing azide. The ionic liquid intermediate is weighed, and then 0.023 mol of 1-bromo-4-chlorobutane is weighed. The mixture is then carried out in an oil bath at 25 °C for 3 h, followed by continued reaction at 50 °C and reflux for 24 h until the solution becomes a white turbid liquid. The turbid liquid is poured into acetone and repeatedly washed with acetone to remove unreacted impurities. Then, the mixture is vacuum-sealed at room temperature to obtain the azide ionic liquid—[CPDOc]Br2. 4) First, dissolve 0.2 g of OHPBI-Px in DMSO. After the polymer is completely dissolved, add AMB and [CPDOc]Br2 at a mass ratio of 15% respectively, and stir until completely dissolved. Then add AIBN at a mass ratio of 1% and stir for 30 min. Pour the casting solution through a filter cloth onto a clean glass plate until the casting solution evenly covers the entire glass plate. Place it in a 50°C oven and wait for 4 h to allow AIBN to initiate double bond polymerization. Then raise the temperature to 90°C until the solvent is completely evaporated. Place the membrane in a 150°C oven for crosslinking. The OHPBI-PIL-Px membrane is obtained.

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