Nafion/g-C3N4Composite membrane and preparation method and application thereof
阅读说明：本技术 一种Nafion/g-C3N4复合膜及其制备方法与应用 (Nafion/g-C3N4Composite membrane and preparation method and application thereof ) 是由 周利 栾邹杰 黄河 邵志刚 于 2019-11-15 设计创作，主要内容包括：本发明提供一种Nafion/g-C-3N-4复合膜及其制备方法与应用,具体表现为将一种质子化氮化碳与Nafion树脂复合制备复合膜,属于质子交换膜燃料电池技术领域。本发明先将Nafion树脂溶解在高沸点溶剂中,然后再向Nafion溶液中加入分散好的g-C-3N-4悬浮液,搅拌、超声均匀,倒入模具中,在一定温度下烘干成膜,得到复合膜。掺杂了g-C-3N-4的复合膜电导率有明显提高,且单电池极化性能优于商业化Nafion 211膜。(The invention provides Nafion/g-C 3 N 4 The composite membrane and the preparation method and the application thereof are particularly characterized in that a composite membrane is prepared by compounding protonated carbon nitride and Nafion resin, and belong to the technical field of proton exchange membrane fuel cells. The invention firstly dissolves Nafion resin in a high boiling point solvent, and then well dispersed g-C is added into the Nafion solution 3 N 4 And stirring and ultrasonically homogenizing the suspension, pouring the suspension into a mold, and drying the suspension at a certain temperature to form a film to obtain the composite film. Is doped with g-C 3 N 4 The conductivity of the composite membrane is obviously improved, and the single cell polarization performance is superior to that of a commercial Nafion211 membrane.)
1. A composite membrane comprising Nafion resin and g-C3N4(ii) a The g to C3N4The mass ratio of the Nafion resin to the Nafion resin is 0.001-0.2: 1.
2. A method of making the composite membrane of claim 1, comprising the steps of:
(1) preparing a casting solution: taking a Nafion solution, evaporating to obtain Nafion resin, dissolving the Nafion resin in a high-boiling-point solvent, and stirring at room temperature for 1-24h to obtain a mixed solution A;
(2) preparing a composite membrane: adopting a solution casting method to obtain a mixed solution A and g-C3N4And mixing the suspension, stirring for 1-24h, and performing ultrasonic treatment for 1-24h to obtain a mixed solution B, pouring the mixed solution B into a mold, and drying to obtain the composite film.
3. The preparation method according to claim 2, wherein the evaporating temperature in the step (1) is 60-200 ℃, and the evaporating time is 10-48 h; the stirring temperature in the step (1) is room temperature, and the stirring time is 1-24 h; the stirring time in the step (2) is 1-24 h; the ultrasonic time is 1-24 h.
4. The production method according to claim 2, wherein the solute content in the mixed solution a is 1 to 20% by mass.
5. The method of claim 2, wherein g-C is3N4g-C in suspension3N4The mass fraction of (A) is 0.01-5%.
6. The method of claim 2, wherein: the high boiling point solvent is one or more of N, N-Dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO).
7. The method of claim 2, wherein g-C is3N4The precursor used for preparation is any one of melamine, dicyandiamide and urea.
8. The method according to claim 2, wherein the drying temperature in the step (2) is 50 to 140 ℃ and the drying time is 6 to 48 hours.
9. Use of a composite membrane according to claim 1 in a fuel cell, a flow battery, a lead acid battery or a water electrolyser.
Technical Field
The invention relates to Nafion/g-C3N4A composite membrane and a preparation method and application thereof, belonging to the technical field of proton exchange membrane fuel cells
Background
The Proton Exchange Membrane Fuel Cell (PEMFC) isThe efficient, clean and environment-friendly power generation device is a reliable power source of an electric automobile, can also be used as a civil and military power source of a decentralized power station, a submarine, a spacecraft, an aircraft and the like, a portable small power source and the like, and has wide application prospects. Is widely used at presentTypical proton exchange membranes of perfluorosulfonic acid type have excellent proton transfer performance, but their use under high temperature and low humidity conditions is limited, and researchers often modify them by organic-inorganic composite strategies to improve their performance in some aspects.
Patent document CN201910140036.2 mainly comprises sulfonated polyether ether ketone, and g-C3N4Compounding to obtain a composite reinforced membrane; SPEEK and g-C from Mingyue Gang et al3N4Blending to prepare a composite membrane for a methanol fuel cell; cuicui Dong et al combined SPEEK with g-C3N4And phosphotungstic acid are blended to prepare a composite membrane for a methanol fuel cell; the sulfonated polyether ether ketone resins used in the above patent documents and articles have main chains each composed of C-H bonds and a bond energy of 86KJ mol-1During battery operation, H is generated2O2OH and other free radical substances are easy to attack the main chain of the sulfonated polyether ether ketone resin to cause the degradation of the resin, thereby greatly reducing the service life of the battery.
In addition, in order to obtain sulfonated polymers and chemically modify the blended inorganic substances, researchers often need to use dangerous chemicals such as concentrated sulfuric acid (strong corrosivity and strong irritation), dichloromethane (2A carcinogen) or chlorosulfonic acid (strong corrosivity and strong irritation), and the invention can avoid the use of the dangerous chemicals. Huijuanan Bai et al general g-C3N4The composite membrane is added into PES-PVP to be applied to a high-temperature proton exchange membrane fuel cell, although good effect is achieved, the composite membrane cannot be applied to a low-temperature system, the use potential is only obtained when the operation temperature of the cell is higher than 120 ℃, and the highest power of the cell assembled by the composite membrane is 634mW cm-2Far lower than the highest work of the battery assembled by the composite film of the patentRate density 1.38W cm-2。
Disclosure of Invention
The invention aims to provide Nafion/g-C3N4A method for preparing a composite membrane. g-C3N4The proton conductivity of the composite membrane can be improved.
In one aspect, the invention provides Nafion/g-C3N4The composite membrane material is prepared by using Nafion resin as a matrix and doping g-C in the matrix3N4In mass percent, g-C3N4Accounting for 0.1 to 20 percent of the mass of the Nafion resin matrix.
The invention also provides a preparation method of the composite film, which comprises the following steps:
A) preparing a casting solution: weighing Nafion D520 solution with proper mass, evaporating to dryness at a certain temperature to obtain Nafion resin, dissolving the resin in a high-boiling-point solvent, and stirring for proper time to obtain uniform and transparent mixed solution A with different solute mass fractions;
B) preparing a composite membrane: taking a mixed solution A prepared in the step A) with proper mass by adopting a solution casting method, and mixing the mixed solution A with the g-C which is dispersed in advance3N4Mixing the suspension, stirring, performing ultrasonic treatment for a period of time to obtain a mixed solution B, pouring the mixed solution B into a glass plate mold or a polytetrafluoroethylene mold, drying in an oven at a proper temperature for a proper time to obtain the composite film, and forming the composite film at 80 ℃ of 0.5M H2SO4Boiling the solution for 1h, then washing the solution by using deionized water at the temperature of 80 ℃ until the washing solution is neutral, and finally drying the composite membrane for later use. The g to C3N4The suspension is prepared from g-C3N4Dispersing in solvent same as Nafion solution, stirring for 6 hr, and ultrasonic treating with ultrasonic cell disruptor for several times to promote g-C3N4Dispersion of (2)
Based on the technical scheme, preferably, the evaporation temperature in the step A) is 60-200 ℃, and the evaporation time is 10-48 h; the stirring temperature in the step (1) is room temperature, and the stirring time is 1-24 h; the stirring time in the step (2) is 1-24h, and the ultrasonic time is 1-24 h.
Based on the technical scheme, the solute mass fraction of the mixed solution A in the step A) is preferably 1-20%.
Based on the technical scheme, preferably, the g-C3N4The mass ratio of the Nafion resin is 0.1-20%.
Based on the technical scheme, preferably, the high boiling point solvent is one or more of N, N-Dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO).
Based on the technical scheme, the g-C of the invention is preferable3N4The synthesis steps are preferably as follows: taking any one of melamine, dicyandiamide or urea as a precursor, weighing the precursor with proper mass, calcining the precursor for 4 hours at 550 ℃ in an air atmosphere, grinding the product to obtain light yellow powder, stirring the light yellow powder in a hydrochloric acid solution for 4 hours, centrifuging, washing and filtering the mixed solution, and collecting solids to obtain protonated g-C3N4And drying for later use.
Based on the technical scheme, preferably, the drying temperature in the step B) is 50-140 ℃, and the drying time is 6-48 h.
The invention also provides an application of the composite membrane, and the composite membrane can be used in a fuel cell, a flow battery, a lead-acid battery or a water electrolyzer.
Advantageous effects
(1) The invention prepares Nafion/g-C3N4The operation method of the composite membrane is simple, and only Nafion resin and g-C are needed3N4The components are uniformly mixed in a high-boiling point solvent and then dried to form a film at a certain temperature, and the synthetic method is simple.
(2) The invention compares g-C3N4Compared with the SPEEK prepared composite membrane, the invention selects the Nafion resin as the matrix, and the Nafion resin main chain is formed by C-F bonds, because the main chain (formed by C-H bonds) and the side chain of the SPPEK are easily degraded by free radical attack in the long-term operation process of the battery, thereby greatly reducing the service life of the batteryHas strong resistance to free radical attack and can meet the requirement of long-term use.
(3) The composite membrane prepared by the invention has higher conductivity, the conductivity of the composite membrane is obviously higher than that of a commercial Nafion211 membrane (see table 1) at 30 ℃, and the higher conductivity usually means higher power density of a battery.
(4) The composite membrane prepared by the invention has better battery performance, 0.25 percent of g-C3N4The highest power density of a single cell assembled by the Nafion composite membrane is 1.38W cm-2The highest power density of the single cell is obviously higher than that of a commercial Nafion211 membrane assembled single cell by 1.18W cm-2。
Drawings
Fig. 1a and 1b are SEM images of the surface and cross-section of the composite film obtained in example 1, respectively.
FIG. 2a and FIG. 2b are g-C, respectively3N4XRD patterns of the composite films obtained in examples 1 to 3 and the Nafion211 film.
Fig. 3 is a graph of the cell performance of the composite membrane obtained in example 1 and the Nafion211 membrane.
Detailed Description
Example 1
Evaporating 100.1017g Nafion D520 solution at 80 deg.C for 24 hr to obtain resin, dissolving 95.0247g DMF to obtain Nafion solution with solute mass fraction of 5%, collecting 8.0124g Nafion solution with solute mass fraction of 5%, adding 1.0 mg-C3N4(obtained by calcining dicyandiamide as a precursor, g-C3N4Dispersing in 2g of DMF), stirring for 2h, ultrasonically dispersing for 4h uniformly, and drying at 80 ℃ for 24h to obtain a composite film, wherein g-C in the composite film3N4The mass ratio of the Nafion resin was 0.25%, and the resin was named 0.25% g-C3N4Nafion. The prepared composite membrane is 0.5M H at 80 DEG C2SO4Boiling the solution for 1h, then washing the solution by using deionized water at 80 ℃ until the washing solution is neutral, and drying the solution in an oven at 80 ℃ for later use.
Fig. 1a and 1b are SEM images of the surface and cross-section of the composite film obtained in example 1, respectively. The surface and the section of the composite membrane are compact, and no obvious crack or pinhole exists, which shows that the prepared composite membrane can meet the requirement of air tightness in the operation process of the battery.
FIG. 2a and FIG. 2b are g-C, respectively3N4XRD patterns of the composite films obtained in examples 1 to 3 and the Nafion211 film. FIG. 2a demonstrates g-C3N4Was successfully synthesized and FIG. 2b shows the addition of g-C to Nafion resin3N4Thereafter, the degree of crystallinity of the film was reduced, and as the amount added was increased, the degree of crystallinity of the composite film was also reduced more, which was also laterally confirmed by g-C3N4Was successfully added to the Nafion resin.
Fig. 3 shows the cell performance of the composite membrane obtained in example 1 and the Nafion211 membrane. In comparison with a single cell assembled from commercial Nafion211 membrane, the same test conditions were applied (65 ℃, 100% RH, H)2-O2，0.05MPa)0.25％g-C3N4The single cell assembled by the Nafion composite membrane has higher power density, and reflects the superiority of the composite membrane used for proton exchange membrane fuel cells.
Example 2
Evaporating 40.0047g Nafion D520 solution at 90 deg.C for 28 hr to obtain resin, dissolving 48.0522g DMAc again to obtain Nafion solution with solute mass fraction of 4%, collecting 10.0017g Nafion solution with solute mass fraction of 4%, adding 2.0 mg-C3N4(obtained by calcining melamine as a precursor, g-C3N4Dispersing in 2g of DMF), stirring for 5h, performing ultrasonic treatment for 10h, uniformly dispersing, and drying at 90 ℃ for 16h to obtain a composite film, wherein g-C in the composite film3N4The mass ratio of the Nafion resin was 0.5%, and the resin was named 0.5% g-C3N4Nafion. The prepared composite membrane is 0.5M H at 80 DEG C2SO4Boiling the solution for 1h, then washing the solution by using deionized water at 80 ℃ until the washing solution is neutral, and drying the solution in an oven at 80 ℃ for later use.
Example 3
Evaporating 100.1044g Nafion D520 solution at 90 deg.C for 20 hr to obtain resin, and dissolving with 45.0247g NMP to obtain soluteCollecting 4.0124g Nafion solution with solute mass percent of 10%, adding 3.0mg g-C3N4(obtained by calcining dicyandiamide as a precursor, g-C3N4Dispersing in 2g of DMF), stirring for 10h, performing ultrasonic treatment for 10h to uniformly disperse, and drying at 90 ℃ for 16h to obtain a composite film, wherein g-C in the composite film3N4The mass ratio of the Nafion resin was 0.75%, and the resin was named 0.75% g-C3N4Nafion. The prepared composite membrane is 0.5M H at 80 DEG C2SO4Boiling the solution for 1h, then washing the solution by using deionized water at 80 ℃ until the washing solution is neutral, and drying the solution in an oven at 80 ℃ for later use.
Example 4
Evaporating 40.0055g Nafion D520 solution at 100 deg.C for 28 hr to obtain resin, dissolving 48.0112g DMSO to obtain Nafion solution with solute mass fraction of 2%, collecting 20.0742g Nafion solution with solute mass fraction of 2%, adding 8.0mg g-C3N4(obtained by calcining melamine as a precursor, g-C3N4Dispersing in 2g of DMF), stirring for 16h, ultrasonically dispersing for 5h, drying at 100 ℃ for 12h to obtain a composite film, wherein g-C in the composite film3N4The mass ratio of the Nafion resin was 2%, and the resin was named 2% g-C3N4Nafion. The prepared composite membrane is 0.5M H at 80 DEG C2SO4Boiling the solution for 1h, then washing the solution by using deionized water at 80 ℃ until the washing solution is neutral, and drying the solution in an oven at 80 ℃ for later use.
Example 5
Evaporating 80.1209g Nafion D520 solution at 80 deg.C for 36h to obtain resin, dissolving 11.0321g DMF and 10.0711g NMP together to obtain Nafion solution with solute mass fraction of 16%, adding 2.0098g Nafion solution with solute mass fraction of 16%, adding 40.0mg g-C3N4(obtained by calcining urea as a precursor, g-C3N4Dispersing in 2g of DMF), stirring for 20h, performing ultrasonic treatment for 8h, uniformly dispersing, and drying at 60 ℃ for 36h to obtain a composite film, wherein g-C in the composite film3N4The mass ratio of Nafion resin was 10%, and the name was10% g-C3N4Nafion. The prepared composite membrane is 0.5M H at 80 DEG C2SO4Boiling the solution for 1h, then washing the solution by using deionized water at 80 ℃ until the washing solution is neutral, and drying the solution in an oven at 80 ℃ for later use. Table 1 shows the conductivity results of the composite proton exchange membranes prepared in examples 1-5.
TABLE 1 conductivity of proton exchange membranes at 30 deg.C
Proton exchange membrane
Conductivity (S/cm)
Example 1
0.25％g-C3N4/Nafion
0.111
Example 2
0.5％g-C3N4/Nafion
0.105
Example 3
0.75％g-C3N4/Nafion
0.089
Example 4
2％g-C3N4/Nafion
0.103
Example 5
10％g-C3N4/Nafion
0.105
Nafion 211
0.071