Ionic Conductivity Of Anion Exchange Membranes Research Articles

High‐performance Poly(biphenyl piperidinium) Type Anion Exchange Membranes with Interconnected Ion Transfer Channels: Cooperativity of Dual Cations and Fluorinated Side Chains

AbstractThe performance of alkaline fuel cells is severely limited by substandard anion exchange membranes (AEMs) due to the lower ionic conductivity compared to the proton exchange membranes. The ionic conductivity of AEMs can be effectively improved by regulating the microphase structure, but it still cannot meet the practical use requirements. Here, enhanced microphase‐separated structures are constructed by the cooperativity of highly hydrophilic dual cations and highly hydrophobic fluorinated side chains. Meanwhile, the introduction of O enhances the flexibility of side chains and facilitates the formation of ion transport channels. The dual piperidinium cation functionalized membrane (PB2Pip‐5C8F) which is grafted with the ultra‐hydrophobic fluorocarbon chain exhibits a high conductivity of 74.4 mS cm−1 at 30 °C and 168.46 mS cm−1 at 80 °C. Furthermore, the PB2Pip‐5C8F membrane achieves the highest peak power density of 718 mW cm−2 at 80 °C under a current density of 1197 mA cm−2 without back pressure. A long‐term life cell test of this AEM shows a low voltage decay rate of 1.68 mV h−1 over 70 h of operation at 80 °C.

Self-Assembly of Porphyrin to Realize the High Ionic Conductivity of Anion-Exchange Membranes

Self-Assembly of Porphyrin to Realize the High Ionic Conductivity of Anion-Exchange Membranes

Degradation of guanidinium-functionalized anion exchange membrane during alkaline environment

A guanidinium-functionalized anion exchange membrane (AEM) was prepared and characterized. The AEM stability in an alkaline environment and transition structures during the degradation process were studied with DFT (density functional theory)/B3LYP method, 6-31 + G (d) basis set. Experimental results and theoretical analysis showed that the second step (Step 2′) of degradation reaction was the control procedure; guanidinium cation was unstable under alkaline condition. It had lower energy barriers, which decided it was easier for the degradation reaction to occur in high pH environment. The ionic conductivity of AEM was 2.4 × 10−2 S cm−1 at 80 °C. However, the AEM soaked in 1 M NaOH solution, fragments were found after 10 days. The FTIR analysis showed that the structure of the membrane had been changed due to the attack of hydroxide ion. A new substance, tetramethylurea, had produced.