High Performance Anion Exchange Membranes with Confined Sub‐2‐nm Ion Channel

Abstract

As a key component of low‐cost anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) are far from commercial application, because of dissatisfactory alkaline stability and conductivity. Herein, a new insight is proposed to prepare high performance AEMs by constructing of confined ion channel. With an intermediate oligomer produced before the main copolymerization, novel poly(vinyl‐carbazolyl aryl piperidinium) AEMs with confined sub‐2‐nm ion channel are successfully prepared. The unique sub‐2‐nm ion channel enable membranes ultrahigh hydroxide conductivity of 261.6 mS cm−1, and the state‐of‐the‐art chemical stability over 5000 h. Moreover, the AEMs also exhibit good mechanical stability with lower water uptake and dimensional swelling. Based on the as‐prepared AEMs and ionomer, fuel cells exhibit outstanding peak power density of 1.8 and 0.2 W cm−2 with Pt‐based catalysts and completely non‐precious metal catalysts, respectively.

Development of highly conductive anion exchange membranes based on crosslinked PIM-SEBS with high free volume

“…These studies have focused on the development of not only non-noble metal catalysts but also AEM materials with improved physical, chemical, and electrochemical stability and enhanced conductivity comparable to the characteristics of perfluorocarbon-based PEMs, including Nafion. 8–12…”

“…In light of this, enhancing the performance and durability of AEMWE requires the development of AEMs with improved ionic conductivity and chemical stability. 10,13–15…”

“…Typically, high ionic conductivity is achieved for a membrane by increasing the ion exchange capacity (IEC). 10,16,17 However, excessively high IECs can lead to an increase in the membrane's water uptake and swelling, possibly resulting in reduced dimensional stability. Given this, scholars have proposed various methods for designing and synthesizing ion-conducting polymers with high ionic conductivity.…”

“…Notably, some have reported that the formation of a microphase separation between hydrophilic and hydrophobic domains by ion-conducting polymers may contribute to improved ionic conductivity in AEMs. 10,11,18–20 Such hydrophilic–hydrophobic microphase separations create ion-conducting channels that facilitate the transport of OH − , resulting in enhanced ionic conductivity. The enhancement in the hydrophobic unit also leads to improved dimensional and mechanical stability.…”

“…Examples of such polymers include polystyrene, polyethylene, polynorbornene, poly(arylene alkylene), poly(benzimidazole), and poly(styrene- b -ethylene- co -butylene- b -styrene). 10,11,20–23,26 Polyarylene-type AEMs, in particular, demonstrate remarkable alkaline and thermal stability, excellent mechanical properties, and improved IEC and ionic conductivity due to the ion-conducting head groups contained in their polymer backbone structure. In comparison, the side chains of typical existing polymers are grafted with ion-conducting head groups in most cases.…”