Proton Exchange Membrane,PEM）YesProton exchange membrane fuel cell(Proton Exchange Membrane Fuel Cell, PEMFC) plays a key role in battery performance.It not only has the function of blocking, but also has the function of conducting protons.The whole proton exchange membrane is mainly usedFluorosulfonic acidType proton exchange membrane;Nafion recast film;wrongFluoropolymerProton exchange membrane;New composite proton exchange membrane, etc.
Proton exchange membrane fuel cellIt has become the most competitive clean alternative power source for gasoline internal combustion engine powerPEMThe material of shall meet the following conditions:
At present, it is divided into: allFluorosulfonic acidType proton exchange membrane;Nafion recast film;wrongFluoropolymerProton exchange membrane;New composite proton exchange membrane, etc
classification
Announce
edit
Fixed long-life power supply
Provided within the longest service lifepower density It is the largest. It has been proved that it can be used continuously for more than 10000 hours, and the design is constantly improved. It is a fixed typeProton exchange membrane fuel cellContribute to the commercial success of the industry.
Portable power supply
Make portablefuel cellThe device is smaller and more powerful. These components enable the fuel cell to work well with dry reaction gas, and achieve a durable power density that can meet the requirements of the most challenging applications.
Power supply for vehicles
Maximum power density and durability in harsh (hot and dry) automotive environments.These components can operate under hotter and drier working conditions, realizing smaller fuel with more simplified system and higher powerBattery pack。
application
Announce
edit
Improvement and application of proton exchange membrane materials
Proton exchange membrane fuel cellIt has the advantages of low operating temperature, fast starting, high specific power, simple structure, convenient operation, etc., and is recognized as the preferred energy for electric vehicles, fixed power stations, etc.stayfuel cellInternally, the proton exchange membrane provides a channel for the migration and transportation of protons, enabling protons to pass through the membrane from the anode to the cathode, forming a circuit with the electron transfer of the external circuit, and providing current to the outside. Therefore, the performance of the proton exchange membrane plays a very important role in the performance of the fuel cell, and its quality directly affects the service life of the battery.
Until now, the most commonly used proton exchange membrane (PEMFC) is still DuPont's Nafion®Membrane, with protonsconductivityHigh andchemical stabilityGood advantage. At present, most PEMFCs use Nafion®IsochronousFluorosulfonic acidMembrane, PEM used for domestic assembly of PEMFC mainly depends on imports.But Nafion®The membrane still has the following disadvantages: (1) It is difficult to make, high cost, synthesis andsulfonationIt is very difficulthydrolysisSulfonation is easy to denature and degrade the polymer, making it difficult to form the film, resulting in high cost;(2) The requirements for temperature and water content are high. The best operating temperature of Nafion® series membranes is 70~90 ℃. Exceeding this temperature will sharply reduce their water content,ConductivityRapid decline, which hinders the increase of working temperatureelectrode reaction Speed and overcomingCatalyst poisoningDifficult problems;(3) Some hydrocarbons, such as methanol,permeability High, not suitable forDirect methanol fuel cell(DMFC).
Therefore, in order to improve the performance of proton exchange membrane, the improvement research of proton exchange membrane is ongoing.According to the literature reports in recent two years, the following methods can be used for improvement:
(1) Organic/inorganic nano composite proton exchange membrane, depending on the small size of nanoparticles andSpecific surface areaMajor features improvedcomposite membraneTo expand the water retention capacity ofProton exchange membrane fuel cellThe purpose of the operating temperature range;
(2) The framework material of proton exchange membrane was improved, aiming at Nafion®Membrane, or in Nafion®Improved on the basis of membrane, or new skeleton materials are selected;
(3) Adjust the internal structure of the membrane, especially increase the micropores, so as to facilitate membrane formation and solve theCatalyst poisoningProblems.
In addition, in addition to these three improvements, many existing studies have more or less adopted nanotechnology, making materials smaller and better performance.
Production method
Announce
edit
The following is a brief introduction to the literature using these three methods.
Columbia Chemical Company disclosed on December 4, 2003World patentsA kind of sulfonic acid conducting polymer grafted carbon material was disclosed.The manufacturing process is to oxidize and polymerize the conductor polymer monomer containing heteroatoms in the carbon material, andsulfonationGrafting, the method can also further metallize the polymergraftCarbon materials.Carbon containing materials can be carbon blackgraphite, nano carbon or fullerenes, etc.The polymer ispolyaniline 、PolypyrroleEtc.Its protonconductivity8.9 × 10-2S/cm (tested with Nafion sulfonated polyaniline).
Many domestic patents adopt similar methods.For example, Tsinghua University's Chinese patent CN1476113, published in June 2003, contains sulfonic acid in the membrane matrixLateral baseOfAromatic heterocyclic polymerAdd to solvent to formHomogeneous mixtureAfter that, inorganic substances are added to formSuspended solids。The suspended solids are crushed by nano crushing technology to obtain evenly dispersed slurry, which is then coated by casting method.The membrane structure formed is uniform and quite dense.It not only has good resistance to methanol penetration, but also has goodchemical stabilityAnd proton conductivity, methanolpermeability Less than 5%.
Journal of Membrane Science publishedUniversity of Hong KongPublished papers, which are in situAcid catalysisPolymerization method, combining Nafion withFurfuryl alcoholCopolymerization. The proton exchange membrane prepared from this material significantly improves the flow rate of reducing methanolconductivity0.0848S/cm.
The Chinese patent CN1585153 of Sun Yat sen University published in 2004 introduced a directalcoholsfuel cellPreparation method of modified proton exchange membrane.The preparation method is commercially availablesulfonationResin as raw material, and addInorganic nanomaterials, viaTape casting method, calendering, slurry coating or dipping to prepare proton exchange membrane.
(3) Adjust the internal structure of the membrane
In 2004, the magazine Elctrochimica Acta published the paper of Gwangju Institute of Science and Technology in South Korea, which adopted the modified polymer as the proton exchange membrane, and selected sulfonated polystyrene b-poly（ethylene-γ - butene) - b-polystyrenecopolymer(SSEBS), in microscopic form, shows a nanostructured ion channel, and the reactance of this proton exchange membrane is better than that of ordinary proton exchange membrane.
In 2001, the Chinese invention patent CN1411085, which was applied by Huazhong University of Science and Technology, was disclosedCeramic filmThere are several micropores orderly distributed on the structure, whose pore diameter is n ≤ 2mm. The micropores are all over the entire ceramic film, and the micropores of the ceramic film are filled with highconductivityElectrolyte.Aperture n should preferably be nanometerOrder of magnitude。The preparation method of the proton exchange membrane is as follows: firstly, orderly micropores are prepared on the metal film with thickness h ≤ 1mm;Then the ceramic film is oxidized by electrochemical method or other methods;Then, the micropores of the ceramic film are filled with electrolytes with high conductivity.This method is characterized by easy membrane formation and low manufacturing cost, and can be solved by increasing the working temperature of the proton exchange membraneCatalyst poisoningProblems.
In addition, some proton exchange membrane manufacturing methods reported abroad recently include:
WO200545976 is related to the application of Renault Company on May 19, 2005Ionic conductorPatent of composite proton exchange membrane, which discloses an ionic conductorcomposite membraneThe manufacturing method of, including a) combined electronic and ionicNonconductivePolymer, or in solution or molten stateBi-Sn The salt is mixed with at least two polymers;b) AndSilicahydrolysisOrganoidPrecursorcombination;c) Suitable forHeteropolyacidThe organic solution is mixed and cast to form a film, especially in the form of a film, with a thickness of 5~500 μ m, a smooth surface, and the ionic conductor channels are nanometer sized.The polymer is selected aspolysulfoneClass andPolyimide resin。Final Protonconductivity433k, 100% RH, reaching (1.1 ～ 3.8) × 10-2S/cm.
SABANCI University World Patent WO200521845, published on March 10, 2005, uses aMetallic coatingOfNanofiberIn addition, the invention also relates to a metal coating process of electronic spinning nanofibers.
Table 1 and Table 2 respectively list the materials, proton conductivity and finalfuel cellPerformance.
However, the research on the new method is not yet mature, and there are some shortcomings that need to be further improved.For example: after adding inorganic substancescomposite membraneIt will become brittle and hard, and the film-forming property will become poor, so the appropriate proportion between organic and inorganic substances in the composite membrane becomes particularly important, which is also one of the research directions in the future. In addition, after adding nano particles, the research on the comprehensive properties of the membrane, such as the dispersion performance of nano particles and the control of reaction energy, also deserves further attention.
