Crosslinking poly(aryl-imidazolium) as anion exchange membrane fuel cells(AEMFCs)

Fuel cells have recently received much interest as green and renewable energy conversion systems sincethey can directly convert chemical energy into electrical energy without generating any pollutants.Fuel cells and electrolyzers depend on electrolytes as a central ingredient. Two major types ofelectrolytes are anion exchange membranes (AEMs) and proton exchange membranes (PEMs). Due tothe lower self-diffusion coefficient of OH- and weaker ionic functionality dissociation (low pKb) intypical AEMs compared to proton exchange membranes, decreased ion conductivity is frequently seenin these membranes, which is a main disadvantage of AEMs. To address this problem, a substitutemanner to improve the conductivity is to create channels through interconnected hydrogen-bondingnetworks. Ion-dipole interactions display another force that is the ideal method for boosting OHconductivityin AEMs. An ion and a neutral dipolar molecule are attracted to one anotherelectrostatically, creating this force [۱,۲]. In this work, the amorphous poly(arylene-imidazolium)(PAIm۱) was cross-linked with PVP using ۱,۱۰- dibromodecane (DBD) as a crosslinking agent. ThisAEM creates channels via potent cation-dipole interaction between imidazolium cations and polarpoly(vinylpyrrolidone) (PVP).The existence of ion channels was checked by SEM images, which confirmed the existence of ionchannels. The key problem of AEMs is insufficient long-time chemical stability in an alkalinecondition, which is a significant barrier to the construction of robust AEMFCs. In this investigation, thealkaline stability of the membranes was examined which shows high alkaline stability. As listed in Table۱, the Cross-PAIm۱-PVP membranes show ion exchange capacity (IEC) values of ۲.۰۲ meq g-۱. AEMwater uptake (WU) is fairly important because water molecules can convey hydroxide ions via theGrotthuss mechanism through the formation/cleavage of covalent bonds. On the other hand, excessivewater uptake could lead to undesirable swelling ratio (SR) and poor mechanical properties. Theswelling ratio and water uptake of the Cross-PAIm۱-PVP membrane are desirable and increase withrising temperature, as indicated in Table ۱. The mechanical properties of AEMs are important factorsin their use in water electrolysis and fuel cells because they should be able to preserve their desirableproperties over time. As listed in Table ۱, the Cross- PAIm۱-PVP membrane displayed tensile strengthof ۷.۲۵ MPa, elongation at break of ۹.۱۴ %, and Young's modulus of ۹۵.۳۲ MPa.The ionic conductivity of the prepared membrane was measured and showed a very high ionicconductivity due to the presence of channels formed through cation-dipole. The efficiency of theprepared AEMs was tested at ۳۰ °C in a direct ethanol fuel cell (DEFC) using a mixture of ۲M ethanol and۲M KOH solution. The open-circuit voltage of the Cross-PAIm۱-PVP at ۳۰ °C was ۰.۸۱ V, indicatinga superior fuel barrier ability. Overall, the approach described here points to a promising future for theuse of next-generation AEMs in fuel cells, electrolyzers, and particularly as electrolytes for batteries thathave lower ionic conductivity.

کلیدواژه ها:

Ion-dipole interactions ، DEFC ، High conductive ، AEMs