Improving the conductivity and dimensional stability of anion exchange membranes by grafting of quaternized dendrons

Abstract

High conductivity is critical for the practical applications of anion exchange membranes (AEMs) in fuel cells. In this study, a new strategy for enhanced conductivity and dimensional stability of AEMs by incorporating quaternized dendrons is proposed. Thanks to the introduced quaternized dendrons, distinct nanoscale phase separation and well-connected ion conductive channels are formed in the as-prepared membranes (PPO-QG-x). As a result, PPO-QG-x AEMs achieve high hydroxide conductivities up to 65.5 mS cm À1 at 20 C and 121.5 mS cm À1 at 80 C (IEC = 1.95 mmol g À1 ), while possessing good dimensional stability. Meanwhile, PPO-QG-x AEMs show good alkaline stability with the maximum loss in conductivity of 15.1% after treated in 2 M NaOH at 80 C for 960 h. In addition, the single-cell assembled with PPO-QG-12 membrane exhibit a peak power density of 249.4 mW cm À2 at 60 C. Overall, this work provides a new insight to achieve high conductivity of AEMs.

Elastic and Conductive Cross‐linked Anion Exchange Membranes Based on Polyphenylene Oxide and Poly(vinyl alcohol) for H2‐O2 Fuel Cells

“…While the peak power density of sc DQPPO‐40 single cell is 0.577 W cm −2 with a current density of 1.1 A cm −2 . The fuel cell performances of PPO‐based AEMs may still have some distance to achieve the reported best levels, such as the >3 W cm −2 data obtained with norbornene‐based AEMs, [47,48] however, compared to the PPO‐based AEMs reported in recent years [49–60] (Table 2), the AEM developed in the present work demonstrates competitive cell performance. The excellent performance is attributable to the fact that the cross‐linked polymer network to make the compact membrane, higher IEC and better phase separation to promote the conduction of ions, and the hydrophilic of PVA made it possible to effectively transport water in a humidified condition to alleviate flooding in anode.…”

Poly(phenylene oxide)-Based Anion Exchange Membranes Having Linear Cross-Linkers or Star Cross-Linkers

“…Because advanced AEMs have been reported in recent years, the peak power density of AEMFCs has exceeded 1000 mW/cm 2 , such as fluoropoly­(olefin)-based AEMs of Hickner’s group, QAPPT-based AEMs of Zhuang’s group, PAP-based AEMs of Yan’s group, PDTP-basd AEMs of Lee’s group, and norbornene-based AEMs of Kohl’s group . However, as shown in Table , sc DQPPO-40 shows competitive fuel cell performance in PPO-based AEMs. ,,,,− In fact, in addition to AEMs, there are many other factors that affect AEMFCs performance, such as MEA preparation technology and fuel cell operation conditions. Following work will be focused on how to improve the performance and long-term stability of AEMFCs.…”

Highly Ion-Conductive and Alkaline Stable Anion Exchange Membranes Containing Bulky Aryl Units and Symmetric bis-Piperidinium Branches

“…The QPTPDP-30-OH membrane with thickness of 40 μm and an ionomer (QPTPDP-40-OH prepared in this work) were used to fabricate membrane electrode assembly (MEA) for the single-cell test. The MEA was fabricated according to our previous work . The test was carried out at 60 °C and 100% relative humidity using a Scribner 890e fuel cell testing system.…”

“…The MEA was fabricated according to our previous work. 11 The test was carried out at 60 °C and 100% relative humidity using a Scribner 890e fuel cell testing system. Both H 2 and O 2 were supplied at a flow rate of 200 mL/min with backpressure of 0.1 MPa.…”

“…The challenge in developing high-performance AEMs involves achieving high conductivity while maintaining sufficient alkaline and mechanical stability. , AEMs are usually composed of polymer skeletons with tethered cationic groups . Under strong alkaline conditions, OH – will preferentially attack polymer skeletons and the cationic groups of AEMs, resulting in the degradation of AEMs. − To address this issue, diverse polymer skeletons and cationic groups have been developed with N , N -dimethylpiperidinium (DMP) and 6-azonia-spiro[5.5]­undecane being the most promising cationic group candidates for AEMs, due to their excellent alkaline stability. , In addition, various polymers have been explored to prepare AEMs. − Among them, aryl ether-free polyaromatics, including poly­(arylene alkylene)­s and poly­(arylene piperidine)­s, serve as the most promising polymer skeletons for AEMs , due to their high alkaline stability. In recent years, several outstanding AEMs have been prepared by combining the advantages of DMP and aryl ether-free polyaromatics. − …”