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

Abstract

In recent years, the microphase separation structure of ion-exchange membranes constructed by intermolecular interaction forces, such as hydrogen bond, cation−dipole interaction, and π−π interaction, has received extensive attention. Porphyrins can provide an active self-aggregation driving force through π−π interaction. Herein, a series of TMAP-Zn-PMHQ-X anion-exchange membranes (AEMs) were rationally designed in which the porphyrin was introduced to construct highly efficient ion channels. The as-prepared membranes are composed of functionalized fluorophobic polymers as the main chain and quaternized zinc porphyrin as the hydrophilic side chain. TMAP-Zn-PMHQ-13.5% with an ion-exchange capacity (IEC) of 0.35 meq•g −1 has an OH − conductivity of 152.5 mS•cm −1 and a swelling ratio of 53.3% at 80 °C. Meanwhile, the OH − conductivity of the membrane remains 95.76% after being tested in a 2 M NaOH solution at 80 °C for 500 h. A single cell based on the TMAP-Zn-PMHQ-13.5% AEM can achieve a power density of 631.6 mW•cm −2 at a current density of 998.9 mA•cm −2 at 80 °C. This kind of porphyrin selfassembled strategy provides an effective way to fabricate AEMs with good OH − conductivity and a relatively low IEC.