Quaternized chitosan-based anion exchange membrane for alkaline direct methanol fuel cells

Abstract

We synthesized a novel quaternized anion exchange membrane (AEM) that exhibits high ionic conductivity and structural stability, even under high pH conditions, by copolymerizing a chitosan-based membrane with vinylimidazole derivatives. During the process, a quaternized poly[O-(2-imidazolyethylene)-N-picolylchitosan (QPIENPC) was synthesized by modifying chitosan with a 4-pyridinecarboxaldehyde derivative and then copolymerizing the modified chitosan with 1-vinylimidzaole. The results revealed that the degree of quaternization is correlated with ionic exchange capacity, water absorption ability, linear expansion ratio, and hydroxide conductivity of the resulting membrane. The QPIENPC membrane was characterized by a high ionic conductivity of 10.15mScm−1, 14 times greater that of the unfunctionalized chitosan membrane, as well as by low water absorption ability (36.17%) and linear expansion ratio (20.49%) at 80°C. An alkaline direct methanol fuel cell (ADMFC) was fabricated using the prepared QPIENPC membrane as an anion exchange electrolyte membrane, with PtRu/C and Pt/C as the anode and cathode, respectively. The performance of this ADMFC is promising even under high pH conditions, with the peak power density of 10.42mWcm−2 and corresponding current density of 28.76mAcm−2. Moreover, the thermochemical and mechanical strengths of the QPIENPC membrane were higher than those of the chitosan membrane.