Preparation method of phosphorylated chitosan and sulfonated polyetheretherketone blended proton exchange membrane

Abstract

The invention discloses a preparation method of a phosphorylated chitosan and sulfonated polyetheretherketone blended proton exchange membrane, and relates to the technical field of fuel cells, and the preparation method comprises the following steps: S1, preparing sulfonated polyetheretherketone SPEEK; s2, dropwise adding a phosphorous acid / formaldehyde solution into the chitosan / acetic acid solution for full reaction to obtain phosphorous acid grafted phosphorylated chitosan PCS, and adding p-toluenesulfonic acid TsOH to prepare PCS / TsOH; and S3, respectively dissolving SPEEK and PCS / TsOH in DMSO, dropwise adding and mixing to prepare a film, sequentially soaking the film in deionized water and sulfuric acid, and drying to obtain the SPEEK / PCS composite film. Compared with a pure SPEEK membrane with the same sulfonation degree, the composite membrane disclosed by the invention has better dimensional stability, more excellent thermal stability, mechanical property and conductivity, and also shows excellent alcohol resistance and battery performance.

Description

Technical Field

[0001] The present invention relates to fuel cells, and more particularly to a method for preparing a blended proton exchange membrane of phosphorylated chitosan and sulfonated polyether ether ketone. Background Art

[0002] Sulfonated polyether ether ketone (SPEEK) proton exchange membrane is a high-performance membrane material prepared by sulfonating polyether ether ketone (PEEK). PEEK itself is an engineering plastic with high temperature resistance and chemical corrosion resistance. After sulfonation, sulfonic acid groups (-SO 3 3H) are introduced, endowing it with proton conduction ability and making it suitable for fields requiring ion transport.

[0003] For pure sulfonated polyether ether ketone (SPEEK) membranes, a high degree of sulfonation is required to ensure high proton conductivity. However, a high degree of sulfonation will lead to an increase in membrane swelling and a decrease in alcohol resistance. Therefore, it must be further processed. Blending acid-base polymer electrolytes is a common method for preparing proton exchange membranes with excellent performance at present: mixing acid-base polymers and promoting proton transfer through ionic cross-linking reactions. Compared with uncrosslinked polymers, such acid-base blended membranes show good performance in hydrogen fuel cells and direct methanol fuel cells.

[0004] Chitosan, as a natural cationic polyelectrolyte, is rich in reserves and low in price. Moreover, it has both hydroxyl and amino groups on its structural units, showing very flexible reaction adaptability; among them, the amino group (-NH 2) It has strong reactivity and can form ionic crosslinks with sulfonic acid groups in SPEEK, improving the stability of the composite proton exchange membrane in water and reducing swelling. There are reports on the synthesis of blends based on sulfonated polyether ether ketone (SPEEK) and chitosan. Chitosan is added during the preparation of sulfonated polyether ether ketone using concentrated sulfuric acid as the sulfonating reagent, and SPEEK / CS blend proton exchange membranes with different ratios are prepared by controlling the chitosan content and reaction time. The drawbacks of this method are as follows: Chitosan molecules with a high degree of deacetylation have more free amino groups and are usually dissolved in dilute acid solutions; to dissolve chitosan in concentrated sulfuric acid, it usually needs to be dissolved in an organic solvent (DMF) first, and concentrated sulfuric acid has strong oxidizing and dehydrating properties, making it extremely difficult to filter the sample and the operation process complex. The defect in the performance of this membrane is that the conductivity is still low at the optimal ratio of S-CS 10%. There are also reports on the preparation of crosslinked composite membranes of chitosan and sulfonated polyether ether ketone (SPEEK) using solution casting and ultraviolet curing methods. Sulfonated polyether ether ketone (SPEEK) and chitosan (CS) are respectively dissolved in dimethyl sulfoxide (DMSO) and acetic acid, and a sulfonated polyether ether ketone-chitosan (SPEEK-CS) membrane is directly blended and irradiated with ultraviolet light to induce crosslinking. However, the blending of different solvents in the dimethyl sulfoxide / acetic acid solution easily causes changes in the solubility of the sample and precipitation of the sample. The defect in the performance of this membrane is that as the CS content increases, the conductivity, ion exchange capacity, and water absorption rate decrease, and it is not suitable for proton exchange membranes.

[0005] The phosphorylation of chitosan introduces phosphite groups that contain both hydroxyl groups and can carry electrons, which is expected to further improve proton conductivity. At the same time, low swelling needs to be ensured. There is no reported scheme in the prior art for blending phosphorylated chitosan and sulfonated polyether ether ketone to prepare proton exchange membranes. Therefore, a preparation method for a blend proton exchange membrane of phosphorylated chitosan and sulfonated polyether ether ketone needs to be developed to prepare a proton exchange membrane with excellent proton conductivity, alcohol resistance, and low swelling. Summary of the Invention

[0006] The object of the present invention is to solve the deficiencies of the above-mentioned background technology and provide a preparation method for a blend proton exchange membrane of phosphorylated chitosan and sulfonated polyether ether ketone, and prepare a proton exchange membrane with excellent proton conductivity, alcohol resistance, and low swelling.

[0007] The technical solution of the present invention is as follows: A preparation method for a blend proton exchange membrane of phosphorylated chitosan and sulfonated polyether ether ketone, comprising the following steps:

[0008] S1. Prepare sulfonated polyether ether ketone SPEEK with a sulfonation degree of 75% - 80%;

[0009] S2, adding the phosphorous acid / formaldehyde solution dropwise to the chitosan / acetic acid solution for sufficient reaction to obtain phosphorous acid-grafted phosphorylated chitosan PCS, and blending with p-toluenesulfonic acid TsOH to prepare PCS / TsOH;

[0010] S3, the sulfonated polyetheretherketone SPEEK obtained in step S1 and the PCS / TsOH obtained in step S2 are fully cross-linked in DMSO solvent to prepare a membrane, which is then soaked in deionized water and sulfuric acid in sequence and dried to obtain a SPEEK / PCS composite membrane.

[0011] Preferably, in step S1, the SPEEK preparation process specifically includes:

[0012] Under the condition of 45-55° C. in a water bath, PEEK is added to concentrated sulfuric acid to react for 4-4.5 hours. The reaction solution is cooled to room temperature and then placed in ice water to precipitate a solid, which is then washed and dried to obtain sulfonated polyetheretherketone SPEEK.

[0013] Preferably, in step S2,

[0014] The chitosan / acetic acid solution is obtained by adding solid chitosan to an acetic acid solution and stirring and dissolving it;

[0015] The phosphorous acid / formaldehyde solution is obtained by adding solid phosphorous acid into a formaldehyde aqueous solution and mixing thoroughly;

[0016] The amino-NH 2 , phosphorous acid H 3 PO 3 、Formaldehyde CH 2 The molar ratio of the chitosan raw material is 1:0.8-1.2:0.8-1.2. The viscosity of the chitosan raw material is 100-200 mPa·s, the degree of deacetylation is ≥95%, the volume fraction of acetic acid in the acetic acid solution is 2-3 wt.%, preferably 2 wt.%, and the concentration of the formaldehyde aqueous solution is 35-40 wt.%, preferably 37.5 wt.%. As a more preferred embodiment, the amino-NH 2 , phosphorous acid H 3 PO 3 、Formaldehyde CH 2 The molar ratio of the three is 1:1:1.

[0017] Preferably, in step S2, the step of preparing PCS comprises:

[0018] The phosphorous acid / formaldehyde solution was added dropwise to the chitosan / acetic acid solution, and the reaction was carried out at 65-75°C for 20-24 hours. The reaction solution was filtered, dialyzed, and dried to obtain phosphorylated chitosan PCS.

[0019] Preferably, in step S2, the step of preparing PCS / TsOH by blending comprises:

[0020] Phosphorylated chitosan PCS and p-toluenesulfonic acid are co-dissolved in water, and the molar ratio of -NH contained in phosphorylated chitosan PCS 2 : TsOH = 1:0.9 - 1.1. After forming a transparent and homogeneous solution, it is dried to obtain PCS / TsOH. More preferably, the molar ratio of -NH contained in PCS 2 : TsOH = 1:1. In the present invention, -NH contained in phosphorylated chitosan PCS 2 refers to the uncrosslinked -NH remaining after chitosan is phosphorylated 2 , and its quantity can be calculated by verifying the grafting degree through nuclear magnetic resonance.

[0021] Preferably, in step S3, the preparation of the film after crosslinking includes:

[0022] Sulfonated polyether ether ketone SPEEK is placed in DMSO solvent and stirred to obtain solution A. Then, PCS / TsOH is added to DMSO to form solution B at 40 - 60 °C, where the mass ratio of PCS / TsOH to SPEEK is 2 - 8:100. Solution B is added dropwise to solution A and stirred for 12 h for crosslinking. After filtering the reaction solution, it is formed into a film on a hot stage.

[0023] Preferably, the mass ratio of PCS / TsOH to SPEEK is 4 - 6:100.

[0024] Preferably, in step S3,

[0025] It is soaked in deionized water for 10 - 30 min, and then soaked in 2 - 2.5 M sulfuric acid for 24 - 36 h to achieve sufficient crosslinking. 2 - 2.5 M refers to a concentration of 2 - 2.5 mol / L.

[0026] The present invention also provides a phosphorylated chitosan and sulfonated polyether ether ketone blended proton exchange membrane, which is prepared by the above method.

[0027] The present invention also provides an application of the phosphorylated chitosan and sulfonated polyether ether ketone blended proton exchange membrane in hydrogen fuel cells or methanol fuel cells.

[0028] The beneficial effects of the present invention:

[0029] 1. Compared with pure SPEEK membranes with the same sulfonation degree, the composite membranes have lower dimensional swelling and thickness swelling in water and methanol fuel, but higher water absorption / fuel absorption rate and ion exchange capacity. This is because the grafted phosphite groups can participate in the proton conduction process to a certain extent. At the same time, the amino groups in the ungrafted chitosan have strong ionic cross-linking with the sulfonate groups in sulfonated polyether ether ketone, and the protonation of amino groups is also beneficial to proton conduction. Due to the ionic cross-linking effect, the dimensional stability of the composite membrane is better than that of the pure membrane. The composite membrane has lower thickness swelling and dimensional swelling compared with the pure SPEEK membrane. The thickness swelling and dimensional swelling of the SPEEK-6% PCS membrane are 53% and 75% of the pure SPEEK membrane respectively.

[0030] 2. The composite membrane has more excellent mechanical properties than the pure SPEEK membrane, and the tensile strength can be as high as 70 - 80 MPa. This is because SPEEK itself has excellent mechanical properties, and the blending with phosphorylated chitosan forms acid-base ionic cross-linking, further enhancing its mechanical properties. It should be noted that the solubility of phosphorylated chitosan in water is greatly improved, enabling it to be mixed with p-toluenesulfonic acid in a similar molar ratio. While if pure chitosan is mixed with p-toluenesulfonic acid in a similar molar ratio, it is difficult to completely dissolve, and the excess p-toluenesulfonic acid will leave a large number of holes in the membrane, resulting in defects in the composite membrane.

[0031] 3. The conductivity of the composite membrane is greatly improved compared with the pure membrane, and the binding energy is relatively lower. This is because the grafted phosphite groups on chitosan can promote proton conduction to a certain extent. At the same time, the protonated amino groups due to ionic cross-linking and soaking in sulfuric acid provide an efficient proton transport channel, greatly improving the proton conductivity. At 80 °C, the proton conductivity of the SPEEK-4% PCS composite membrane is 139.75 mS / cm, and the proton conductivity of the SPEEK-6% PCS composite membrane is 148.35 mS / cm, which is 24% higher than that of the pure SPEEK membrane (119.2 mS / cm).

[0032] 4. The pure SPEEK membrane with high sulfonation degree has a high methanol permeation during the test of battery performance and will rupture during the test, while the composite membrane of this application has more excellent battery performance than the commercial 211 membrane. This benefits from the better methanol barrier ability, excellent mechanical stability and high proton conductivity of the composite membrane; the ionic cross-linking effect makes the composite membrane have a denser structure, thus increasing the diffusion resistance and tortuous path of methanol and also improving the mechanical properties of the composite membrane; in terms of proton conduction, the protonated amino groups further provide a proton transport channel, and the grafted phosphite groups in PCS can also play a role in transferring protons. The special ionic cross-linking structure does not affect proton conduction while making the structure stable, and the battery performance is also greatly improved. Brief Description of the Drawings

[0033] Figure 1 To obtain the 1H NMR spectrum of sulfonated poly(ether ether ketone) (SPEEK)

[0034] Figure 2 To obtain the 1H NMR spectrum of phosphorylated chitosan (PCS)

[0035] Figure 3 To obtain the thermoanalysis curve of the SPEEK / PCS composite membrane

[0036] Figure 4 To obtain the mechanical property diagram of SPEEK / PCS

[0037] Figure 5 To obtain the conductivity diagram of the SPEEK / PCS composite membrane

[0038] Figure 6 To obtain the binding energy diagram of SPEEK / PCS

[0039] Figure 7 To obtain the power density curve of SPEEK / PCS using 2 M methanol as fuel

[0040] Figure 8 To obtain the methanol permeation limiting current density curve of SPEEK / PCS using 2 M methanol as fuel Detailed Description of the Invention

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The drugs used in the following embodiments are all commercially available products without special instructions, and the methods used are all conventional methods in the art without special instructions.

[0042] Example 1

[0043] This example discloses a method for preparing a phosphorylated chitosan and sulfonated poly(ether ether ketone) blended proton exchange membrane, and the steps are as follows:

[0044] S1. Sulfonation of PEEK

[0045] Sulfonated polyether ether ketone (SPEEK) was prepared by reacting concentrated sulfuric acid with polyether ether ketone (PEEK) under mechanical stirring at 50 °C for 4 h and 10 min. The specific operation was as follows: Under the condition of a 50 °C water bath, 190 mL of concentrated sulfuric acid was added to a three-necked flask, and then 10 g of polyether ether ketone PEEK was added. After reacting for 4 h and 10 min, an orange-yellow reaction solution was obtained. The temperature of the reaction solution was lowered to room temperature, and it was slowly poured into ice water for precipitation to obtain a white thread-like solid. It was repeatedly filtered and washed with deionized water until the pH of the washing solution was neutral, and then dried in a drying oven at 60 °C for 24 h to obtain sulfonated polyether ether ketone (SPEEK). Its sulfonation degree was verified by nuclear magnetic resonance. From Figure 1 it can be seen that the sulfonation degree was 76%.

[0046] S2. Synthesis of PCS / TsOH

[0047] 2.8 g of chitosan with a viscosity of 100 - 200 mPa·s and a degree of deacetylation ≥ 95% was dissolved in 100 mL of 2 vt.% acetic acid solution, and stirred at 600 rpm at room temperature for 6 h to obtain a light yellow homogeneous chitosan / acetic acid solution; 100 mL of the above solution was taken and placed in a 250 mL three-necked flask, and mechanically stirred and heated to 70 °C.

[0048] 1.353 g of solid phosphorous acid (amount used 16.5 mmol) was added to 1.321 g of 37.5 wt.% formaldehyde solution (containing 16.5 mmol of formaldehyde) and mixed thoroughly to obtain a homogeneous phosphorous acid / formaldehyde solution, which was then added dropwise to the chitosan / acetic acid solution. The reaction molar ratio -NH 2 :H 3 PO 3 :CH 2 O = 1:1:1 was ensured to maximize the degree of phosphorylation (16.5 mmol -NH 2 was contained in chitosan). After the addition was completed, the reaction was maintained at 70 °C for 24 h. Then, the reaction solution was filtered and dialyzed for 48 h, and dried in a petri dish to obtain phosphorous acid-grafted phosphorylated chitosan PCS. Its grafting degree was verified by nuclear magnetic resonance. From Figure 2 it can be seen that the grafting degree: 0.33 / 1 = 33%.

[0049] 0.5 g of the above phosphorylated chitosan PCS (molecular weight 187.56, amino group content 0.5 × 0.67 / 187.56 = 1.79 mmol) and 0.31 g of p-toluenesulfonic acid (molecular weight 172.2, amount used 1.79 mmol) were dissolved in 30 mL of water at a molar ratio of -NH 2 :TsOH = 1:1. After a transparent homogeneous solution was formed, it was poured into a petri dish and dried at 60 °C to obtain PCS / TsOH that was soluble in DMSO.

[0050] S3. Preparation of SPEEK / PCS composite membrane

[0051] Take 0.5 g of the above-mentioned sulfonated polyether ether ketone SPEEK and dissolve it in 20 mL of DMSO at room temperature (30 °C). Under the stirring condition of 400 revolutions per minute, make it form a homogeneous solution A; take PCS / TsOH equivalent to 2 wt.% of SPEEK (the specific mass of PCS / TsOH is 0.01 g) and dissolve it in 5 mL of DMSO at 60 °C to form a homogeneous solution B. Dropwise add solution B into solution A, and then stir and react at room temperature for 12 h to make it fully react. After filtering the reacted solution, coat it on a hot stage at 60 °C. Soak the dried film in deionized water for half an hour to remove small molecules of p-toluenesulfonic acid, and then soak it in 2 M sulfuric acid for 24 h to make the -NH on chitosan 2 Further cross-link with sulfuric acid, and dry to obtain the SPEEK / PCS composite membrane, denoted as SPEEK-2% PCS.

[0052] Examples 2-4

[0053] In this example, except that the dosage of PCS / TsOH in step S3 is changed to 4 wt.%, 6 wt.%, and 8 wt.% of SPEEK, the rest are the same as in Example 1. The prepared SPEEK / PCS composite membranes are denoted as SPEEK-4% PCS, SPEEK-6% PCS, and SPEEK-8% PCS respectively.

[0054] Comparative Example 1

[0055] Prepare the pure SPEEK membrane from the SPEEK obtained in step S1. The specific steps are as follows: take 0.5 g of SPEEK and dissolve it in 25 mL of DMSO under the stirring condition at room temperature. After forming a homogeneous solution, coat it on a hot stage at 60 °C and dry to obtain the SPEEK membrane.

[0056] Comparative Example 2

[0057] Prepare the pure PCS membrane from the phosphorylated chitosan PCS obtained in step S2. The specific operation steps are the same as those in Comparative Example 1 to obtain the PCS membrane.

[0058] Performance testing

[0059] a. Water absorption and swelling test

[0060] The SPEEK / PCS composite membranes obtained from Examples 1 to 4 and the pure SPEEK membrane of the comparative example were subjected to water absorption and swelling tests, and the test results are shown in Table 1. It can be seen from the test results that at 20 °C, the water absorption rate of the pure SPEEK membrane is about 16.1%, while SPEEK-6% PCS in the composite membrane has the highest water absorption rate of 26.8%, which is 66% higher than that of the pure membrane. At the same time, the composite membrane also has lower dimensional swelling and thickness swelling compared to the pure SPEEK membrane. The dimensional swelling of the SPEEK-6% PCS membrane is 21.7%, and the thickness swelling is 3.9%, which are 75% and 53% of the pure SPEEK membrane, respectively.

[0061] Table 1 Data table of water absorption and swelling test

[0062]

[0063] b. Thermal analysis

[0064] The SPEEK / PCS composite membranes obtained from Examples 1 to 4, the pure SPEEK membrane of the comparative example, and the pure PCS membrane were subjected to thermal analysis tests, and the results are as Figure 3 shown. It can be seen from Figure 3 that the thermal degradation behavior of the SPEEK membrane sample is divided into three parts. The first stage (around 180 °C) is the evaporation of the remaining solvent and the bound water locked by hydrogen bonds. The second weight loss of the pure SPEEK membrane occurs at 250 °C, which is mainly attributed to the thermal decomposition of -SO 3 H. The third weight loss occurs at around 450 °C, which is attributed to the decomposition of the SPEEK main chain. The pure PCS membrane has a weight loss stage at around 200 °C due to the decomposition of functional groups (CH 2 , NH 2 and PO 3 H) in the biopolymer. However, the composite membrane shows an obvious weight loss only near 300 °C, and the decomposition of the polymer main chain occurs at 520 °C, indicating that the ionic cross-linking effect improves the thermal stability of the composite membrane.

[0065] c. Mechanical property test

[0066] The SPEEK / PCS composite membranes obtained from Examples 1 to 4 and the pure SPEEK membrane of the comparative example were subjected to mechanical property tests, and the results are as Figure 4 shown. The test conditions were to cut the membrane into a rectangle of 1×4 cm, and its mechanical properties in the wet state were tested using a tensile tester (AG-IC 5KN, Shimadzu Corporation, Japan), and the tensile rate used was 50 mm min -1 . From Figure 4It can be seen that the tensile strength of pure SPEEK is about 49.8 MPa. The tensile strength of the composite membrane is higher than that of the pure SPEEK membrane and first gradually increases (71.2 - 76.5 MPa) with the increase of the PCS doping amount, and drops to 51.3 MPa when the doping amount reaches 8 wt.%. At the same time, the elongation at break of the composite membrane also has a relatively large increase compared to the pure membrane and also decreases at a doping amount of 8 wt.%. This is attributed to the -SO 3 H in SPEEK and -NH 2 in PCS

[0067] d. Proton conductivity test

[0068] The SPEEK / PCS composite membranes obtained in Examples 1 - 4 and the pure SPEEK membrane in the comparative example were subjected to proton conductivity tests. The test conditions were to measure the ionic conductivity of the membrane in a fully wet state using the electrochemical impedance spectroscopy (EIS) (frequency range: 1 Hz - 10 6 Hz) recorded by an electrochemical workstation (Autolab PGSTAT 302N, Netherlands). The membrane (width × length = 2 × 3 cm) was soaked in deionized water at room temperature for 24 h to achieve complete hydration, and then the resistance R, width, and thickness of the membrane were measured at different temperatures.

[0069] The results are as Figure 5 shown. It can be seen from Figure 5 that with the increase of temperature, due to the thermal activation characteristics of proton movement, the conductivity of all comparative samples gradually increases. The conductivity of SPEEK with a sulfonation degree of 76% is 33.9 mS / cm (20 °C). With the addition of PCS, the ionic crosslinking and hydrogen bond formation between SPEEK and PCS are enhanced; -NH 2 / -N(CH 3 ) 3 and -SO 3 H in the composite membrane partially reduce the amount of -SO 3 H, but the protonated amino group enables the transfer of protons through an ordered dynamic network by constructing a crosslinking network; at the same time, the introduced -H 2 PO 3The group also enables proton vehicle-borne transfer. With the increase of the PCS doping amount, the proton transfer channels generated by ionic crosslinking increase. However, when the doping amount reaches 8 wt.% (32.0 mS / cm at 20 °C), the proton conductivity of the composite membrane at this time is lower than that of the composite membrane with a filling amount of 6 wt.% (39.9 mS / cm at 20 °C). At 80 °C, the proton conductivity of the SPEEK-4% PCS composite membrane is 139.75 mS / cm, and the proton conductivity of the SPEEK-6% PCS composite membrane is 148.35 mS / cm, which is 24% higher than that of the pure SPEEK membrane (119.2 mS / cm).

[0070] e. Binding energy test

[0071] The SPEEK / PCS composite membranes obtained in Examples 1 to 4 and the pure SPEEK membrane in the comparative example were subjected to binding energy tests, as Figure 6 shown. The activation energies of all samples were calculated by the Arrhenius formula, ranging from 18.82 to 20.09 kJ / mol. The activation energy of SPEEK is relatively low (18.82 kJ / mol), which is mainly because the H + conductivity mainly depends on the -SO 3 H groups in the membrane, allowing H + to be mainly transported in the form of hydrated H + through the carrier mechanism. However, the activation energies of the composite membranes with different doping ratios show a trend of first decreasing and then increasing, reaching the lowest (18.94 kJ / mol) at 6 wt.%, which is higher than that of the pure SPEEK membrane. This is attributed to the low-energy barrier proton transport channels generated by ionic crosslinking. Therefore, as the PCS doping amount increases, the binding energy gradually decreases, but the binding energy becomes larger at 8 wt.% (20.08 kJ / mol), which may be attributed to the excessive crosslinked structure.

[0072] f. Power density test

[0073] The 6 wt.% SPEEK / PCS composite membrane obtained in the example was compared with the commercial membrane 211 for power density testing, and the test results are as Figure 7 shown. The membrane was sandwiched between the anode (Pt-ru, 4.0 mg cm -2 ) and the cathode (Pt, 2.0 mg cm -2 ) catalyst layers to form a membrane electrode assembly (MEA) with an effective area of 4 cm 2 . A methanol solution with a concentration of 2 M was flowed to the anode side at a flow rate of 0.31 mL / min, and oxygen was flowed at 100 mL min -1The flow rate flows to the cathode side for measurement at 80 °C. The current density (I) and potential (V) of the DMFC polarization curve are recorded on an electrochemical workstation to calculate the power density. From Figure 7 The results show that the commercial 211 has a maximum power density of 89.3 mW / cm 2 , while the maximum power density of the SPEEK / PCS composite membrane can reach 160.3 mW / cm 2 , which is about 80% higher than that of 211.

[0074] g. Methanol permeability test

[0075] The 6 wt.% SPEEK / PCS composite membrane obtained in the example was compared with the commercial membrane 211 for methanol permeability test, and the test results are as Figure 8 shown. Assemble the above membrane electrode assembly (MEA), apply a positive voltage of 0 V to 1.0 V on an electrochemical workstation (Autolab PGSTAT302N, Netherlands), inject 2 M methanol into the anode side at a flow rate of 1 mL min -1 , and input nitrogen into the cathode side at a rate of 100 mL min -1 . The methanol permeability is evaluated by measuring the cross current density of complete electrooxidation of methanol through the cathode side.

[0076] Figure 8 It shows that the methanol permeation limiting current density of the composite membrane is lower than that of 211 membrane. The methanol permeation limiting current density value of SPEEK-6% PCS is 136 mA / cm 2 , only 25.3% of 2 211 (538.3 mA / cm 2 ), indicating that the crosslinked structure in the composite membrane can act as a barrier to prevent methanol permeation, increase the diffusion path of methanol, and thus reduce methanol permeation.

Claims

1. A method for preparing a proton exchange membrane of phosphorylated chitosan and sulfonated polyetheretherketone blend, characterized in that: The following steps are involved: S1, preparing sulfonated polyetheretherketone SPEEK with a sulfonation degree of 75% to 80%; S2, adding the phosphorous acid / formaldehyde solution dropwise to the chitosan / acetic acid solution for sufficient reaction to obtain phosphorous acid-grafted phosphorylated chitosan PCS, and blending with p-toluenesulfonic acid TsOH to prepare PCS / TsOH; S3, the sulfonated polyetheretherketone SPEEK obtained in step S1 and the PCS / TsOH obtained in step S2 are fully reacted and cross-linked in DMSO solvent to prepare a membrane, which is then soaked in deionized water and then soaked in sulfuric acid and dried to obtain a SPEEK / PCS composite membrane.

2. The method for preparing a proton exchange membrane of phosphorylated chitosan and sulfonated polyetheretherketone blend according to claim 1, characterized in that: In step S1, the SPEEK preparation process specifically includes: In a water bath at 45-55° C., polyetheretherketone (PEEK) was added to concentrated sulfuric acid for reaction for 4-4.5 hours. The reaction solution was cooled to room temperature and then placed in ice water to precipitate a solid, which was then washed and dried to obtain sulfonated polyetheretherketone (SPEEK).

3. The method for preparing a proton exchange membrane of phosphorylated chitosan and sulfonated polyetheretherketone blend according to claim 1, characterized in that: In step S2, The chitosan / acetic acid solution is obtained by adding solid chitosan to an acetic acid solution and stirring and dissolving it; The phosphorous acid / formaldehyde solution is obtained by adding solid phosphorous acid into a formaldehyde aqueous solution and mixing thoroughly; The molar ratio of amino group-NH2, phosphorous acid H3PO3 and formaldehyde CH2O contained in the chitosan is 1:0.8-1.2:0.8-1.

2.

4. The method for preparing a proton exchange membrane blended with phosphorylated chitosan and sulfonated polyetheretherketone according to claim 1, characterized in that: In step S2, the step of preparing PCS includes: The phosphorous acid / formaldehyde solution was added dropwise to the chitosan / acetic acid solution, and the reaction was carried out at 65-75° C. for 20-24 hours. The reaction solution was filtered, dialyzed, and dried to obtain phosphorylated chitosan PCS.

5. The method for preparing a proton exchange membrane blended with phosphorylated chitosan and sulfonated polyetheretherketone according to claim 1, characterized in that: In step S2, the step of preparing PCS / TsOH by blending includes: Phosphorylated chitosan PCS and p-toluenesulfonic acid are dissolved in water at a molar ratio of -NH2 contained in phosphorylated chitosan PCS:TsOH=1:0.9-1.

1. After forming a transparent uniform solution, the solution is dried to obtain PCS / TsOH.

6. The method for preparing a proton exchange membrane blended with phosphorylated chitosan and sulfonated polyetheretherketone according to claim 1, characterized in that: In step S3, preparing a film after sufficient reaction and cross-linking includes: Sulfonated polyetheretherketone SPEEK is placed in DMSO solvent and stirred to obtain solution A, and then PCS / TsOH is added to DMSO at 40-60°C to form solution B, wherein the mass ratio of PCS / TsOH to SPEEK is 2-8:100; solution B is added dropwise into solution A and stirred for reaction for 12 hours to cross-link it, and the reaction liquid is filtered and then formed into a film on a hot stage.

7. The method for preparing a proton exchange membrane blended with phosphorylated chitosan and sulfonated polyetheretherketone according to claim 1, characterized in that: The mass ratio of PCS / TsOH to SPEEK is 4-6:

100.

8. The method for preparing a proton exchange membrane blended with phosphorylated chitosan and sulfonated polyetheretherketone according to claim 1, characterized in that: In step S3, the substrate is immersed in deionized water for 10 to 30 minutes, and then immersed in 2 to 2.5 M sulfuric acid for 24 to 36 hours to achieve full cross-linking.

9. A proton exchange membrane blended with phosphorylated chitosan and sulfonated polyetheretherketone, characterized in that: The membrane is prepared by the method for preparing any one of the proton exchange membranes of phosphorylated chitosan and sulfonated polyetheretherketone as described in claims 1 to 8.

10. An application of the phosphorylated chitosan and sulfonated polyetheretherketone blended proton exchange membrane as claimed in claim 9, characterized in that: Applicable to hydrogen fuel cells or methanol fuel cells.

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