Font Size: a A A

Preparation And Applied Research Of Anion Exchange Membranes For Alkaline Fuel Cell

Posted on:2021-02-13Degree:MasterType:Thesis
Country:ChinaCandidate:J J ZhangFull Text:PDF
GTID:2381330602999069Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Fuel cell is a clean and efficient energy conversion technology.In recent decades,the application and development of perfluorosulfonic acid membrane(Nafion(?))and Pt-based catalyst have led to the milestone progress of proton exchange membrane fuel cells(PEMFCs).Various commercial PEMFC-based vehicles have been reported with competitive performance.Currently,the operation of the commercial PEMFCs mainly relies on the efficient Pt-based catalytic reactions and fluorocarbon contained membranes(such as Nafion(?))due to the harsh acidic environment.However,both the membranes and catalysts are too expensive for the practical application of this technology.Recently,more and more researchers are focusing on anion exchange membrane fuel cells(AEMFCs),which have lower oxygen reduction reaction overpotential and faster kinetics due to the alkaline operating environment.Thus,it is possible to use cheaper silver-based,cobalt-based,nickel-based,and other non-platinum-based metal catalysts.In addition,AEMFCs also have the advantages of low metal catalyst poisoning probability,abundant fuel sources,and convenient water management compared to PEMFCs.However,the current research in this field is not mature enough and anion exchange membranes(AEMs)with high ion conductivity and excellent chemical stability were desperately needed.As we know,the AEMs are composed of a polymer backbone and the attached ion-exchange groups,which can realize selective permeation of anions.Various topological structures such as side-chain type,local density type,and comb type have been applied to increase the ion conductivity by constructing ion-conducting channels in the membrane.As a result,the ion conductivity of AEMs have been greatly improved,but still far away from the commercialization goal.To address this problem,the ion channel should be built in a more regular and continuous way.And this paper mainly focuses on this by enhancing the driving force that can induce the self-assembly of the ionic species.By careful structural design,the driving force derived from the polarity difference between the ionic and non-ionic segments,as well as the weak interaction between the ionic segments can be enhanced,so that the ion conductivity and alkali stability can be improved.The details are as follows:(1)Inspired by the attractive features of the side chain type and local density type AEMs,AEMs with densely grafted side chains were designed.We prepare the membranes by densely introducing multiple ionic side chains to specific structural units of polymers.As we know,the flexible side chains can improve the freedom of ion-exchange groups,and the densely distributed ionic side chains can strengthen the polarity difference between different segments.The synergistic effect can further enhance the driving force for the aggregation of ionic segments.Thereby constructing a regular ion-conducting channel for improved ion conductivity.(2)By analyzing the essence of channel construction,we decided to introduce the additional driving force.The polyethylene glycol(PEG)dipole macromolecule was grafted on the quaternized poly(2,6-dimethyl-1,4-phenylene oxide)(PPO),using the cation-dipole interaction between PEG and the quaternary ammonium cationic group as the driving force.It can promote the effective aggregation of ion-exchange groups and build a regular and continuous ion channel.Also,this ion-dipole interacted network has typical non-covalent stimulus responsiveness.Under thermal disturbance,the interaction network experienced the dynamic transition,which undoubtedly provides a dynamic ion-conducting environment that can increase ion transfer kinetics.Molecular dynamics simulation and experiments were performed,and the results show that the conceptual design can promote the aggregation of ion-exchange groups for channel construction,and greatly improve the ion conductivity and the corresponding fuel cell performance.(3)To further optimize the comprehensive performance of the membrane by a simple structure with ion-dipole interaction.We incorporate dipole ethylene oxide spacers into the ionic side-chains to a more alkaline-resistant poly(aryl piperidinium)backbone.In the process,the ion-dipole interaction between the ionic side chains act as a driving force to promote the aggregation of ionic side chains to build an alkali-stable ion channel.The resultant membranes present higher ion conductivity,superior alkali stability,and better single fuel cell performance.Through the above research works,we have proved the feasibility of constructing highly efficient ion-conducting channels by introducing interactions into the AEMs.This understanding breaks the limitations of the existing ion exchange membrane structure design and provides us with new research breakthroughs.In this paper,the role of ion-dipole interactions in promoting ion conduction is initially explored.In the future,other interactions such as hydrogen bonding,metal coordination,cation-?,and other non-covalent bonding effects can be further explored.
Keywords/Search Tags:Fuel cells, Anion exchange membrane, Ion channels, Ion conductivity, Alkaline stability
PDF Full Text Request
Related items