Synthesis And Property Of PVA Quaternary Ammonium Functionalizedalkaline Anion-exchange Membranes And Their Application To Fuel Cell

Anion exchange membrane?AEM?fuel cell have attracted considerable attentions owing to the advantages of use of non-precious metal catalysts such as silver?Ag?,nickel?Ni?,their higher electrode reaction kinetics,reduced CO poisoning and perovskite,and etc..However,the membrane conductivity of alkaline PEMFCs is considered to be one of the most challenging problem,duo to the mobility of OH-is only a quarter of that of the H+ transportation in membranes of acidic PEMFCs.Therefor it's particularly important for the study of anion exchange membrane to achieve excellent mechanical properties,thermal / chemical stability,higher conductivity,cost-effective and environmentally-benign fabrication methods.This article reports a new type of alkaline anion-exchange membranes based on poly?vinyl alcohol??PVA?and poly bis?2-chloroethyl?ether-1,3-bis[3-?dimethylamino?propyl] urea copolymer?PUB?as anion charge carriers.PUB is not only a water soluble quaternized copolymer,but also can offer a large number of OH-species as charge carriers.The technique of chemical cross-linking was used to modify the blended polymer membrane,the dense network structure formed in the membrane makes higher conductivity.On the other hand,PUB is a kind of copolymer composed of a completely aliphatic skeleton with linear structure,on which quaternized comonomers feature two anion groups,which has a more excellent resistance to alkali stability and mechanical stability.The membranes are characterized in detail at structural,mechanical stability,oxidation,alkaline stability,??OH-?conducting,water uptake?WU?,property by FTIR spectroscopy,AFM,SEM,TG,and AC impedance technique to evaluate their applicability in alkaline fuel cells.The five summarized as follows:?1?The pictures of The FT-IR spectra and SEM showed that the PVA/PUB-OH-membranes showed excellent thermal stability even though the temperature high above 235 ?.The membranes are found very stable without losing any integrity and ionic conductivity.And the PVA/PUB-OH-membranes present excellent methanol resistance.PVA/PUB-OH-membrane shows the high tensile strength of 30.88 MPa and tensile elongation of 300%.?2?High ??OH-?was achieved of PVA/PUB-OH-membranes.The ??OH-?initially increased with increasing PUB content,at a PVA/PUB =1:0.5 by mass,??OH-?of membranes reached a plateau(7.6×10^-3S cm^-1).Further addition of PUB to the polymer,The ??OH-?of membranes decrease.In addition,the ion exchange capacity is among 0.92¹.27 mmol g-1.?3?PUB is a kind of copolymer composed of a completely aliphatic skeleton with linear structure,on which quaternized comonomers feature two anion groups.So PVA/PUB membranes show excellent mechanical properties,thermal / mechanical stability and resistance to alkali stability.In particular,the high alkaline stability was achieved for the PVA/PUB membranes in hot 8.0 M KOH at 85 ? without losing their integrity and OH-conductivity during 300 hours of evaluation,and also a relatively high oxidative stability.?4?After the addition of PVA,the mechanical properties and conductivity of the Chitosan/ PVA/PUB membrane have much improved.The conductivity of Chitosan/PVA/PUB membrane reached 1.12×10^-2 S cm^-1 With Chitosan/PVA/PUB ratio at 1:1:0.5 by mass,the stability of membranes and the ??OH-?improve a lot,especially tensile elongation reached 312%.The membranes based on QHECE/PVA,the??OH-?reached 8.22×10^-3S cm^-1.?5?The MEAs fabricated H₂/O₂ fuel cell application with PVA/PUB-OH-membranes showed the power densities around 28.6?PVA/PUB=1:0.5 by mass?along with the OCV at 1.0V.With the addition of Chitosan,showed the peak power density of 13.2 m W cm^-2?Chitosan/ PVA/PUB=1:1:0.5 by mass?at room temperature on a low metal loading on both the anode and the cathode of 0.5 mg?Pt?cm^-2.