Poly(alkyl-biphenyl pyridinium)-Based Anion Exchange Membranes with Alkyl Side Chains Enable High Anion Permselectivity and Monovalent Ion Flux

Abstract

Poly(alkyl-biphenyl pyridinium)-based anion exchange membranes with alkyl side chains were synthesized for permselective anion separation. By altering the length of the grafted side chain, the hydrophilicity and other attributes of the membranes could be controlled. The QDPAB-C5 membrane with the best comprehensive performance exhibited a Cl− ion flux of 3.72 mol m−2 h−1 and a Cl−/SO42− permselectivity of 15, which are significantly better than the commercial Neosepta ACS membrane. The QDPAB-C5 membranes with distinct microscopic phase separation structures formed interconnected hydrophilic/hydrophobic ion channels and exhibited excellent ion flux and permselectivity for other anionic systems (NO3−/SO42−, Br−/SO42−, F−/SO42−, NO3−/Cl−, Br−/Cl−, and F−/Cl−) as well. Furthermore, the influence of alkyl side chain length on the membranes’ ion flux and permselectivity in electrodialysis was investigated, which may be attributed to the alterations in ion channels and hydrophobic regions of the membranes. This work provides an effective strategy for the development of monovalent anion permselective membranes.

Recent Advances and Challenges in Anion Exchange Membranes Development/Application for Water Electrolysis: A Review

“…Typical polymer backbones include polybenzimidazole (PBI) [31,32], polyether ether ketone (PEEK) [33], polysulfone (PSF) [34][35][36], polystyrene (PS) [37][38][39], polyphenylene ether (PPO) [32,[40][41][42], and polyolefins [43], as shown in Figure 3. Common cationic functional groups include trimethylamine (TMA) [31,38], imidazolium (TMI) [32,44], pyridinium (PYR), piperidinium (PIP) [45,46], quaternary ammonium groups [47], 6-Azonia-spiro [5.5]undecane (ASU) [48][49][50][51], and quaternary phosphonium [52], which offer the function of anion exchange to the AEM via electrostatic interaction in water electrolysis,as shown in Figure 4. In a water electrolysis cell, AEM plays a role in ion conduction while preventing the crossover of hydrogen and oxygen.…”

“…Additionally, due to the lower OHmigration rate, the ion conductivity of AEM is much lower than that of PEM. Most AEMWE exhibits a sharp decline in performance after extended operation periods [49,53] Common cationic functional groups include trimethylamine (TMA) [31,38], imidazolium (TMI) [32,44], pyridinium (PYR), piperidinium (PIP) [45,46], quaternary ammonium groups [47], 6-Azonia-spiro [5.5]undecane (ASU) [48][49][50][51], and quaternary phosphonium [52], which offer the function of anion exchange to the AEM via electrostatic interaction in water electrolysis, as shown in Figure 4.…”

Crosslinked high-performance anion exchange membranes based on poly(dibenzyl N-methyl piperidine) and pentafluorobenzoyl-substituted SEBS

“…Polyarylene-based AEMs incorporating piperidinium as an ion-conducting head group, termed poly(aryl piperidinium) (PAP)-based AEMs, demonstrate a high ion exchange capacity (IEC) providing exceptional ionic conductivity. Various polymers, including polybiphenylene, 15,16 polyterphenylene, 14,17,18 and polydibenzylene 19,20 are used in their fabrication, resulting in a cell performance equivalent to that of PEM-based WE cells. 8,17,21 However, due to their high IEC, some PAP-based AEMs exhibit excessively high water uptake (WU) values and swelling ratios (SRs), dilution effects which inhibit rather than enhance phase separation and ultimately result in reduced ionic conductivity.…”

Understanding the Effect of Triazole on Crosslinked PPO–SEBS-Based Anion Exchange Membranes for Water Electrolysis

“…Both aryl ether-type and non-aryl ether-type polymers have been employed as polymer backbones, including poly(arylene ether ketone) (PEK) [ 22 , 23 , 24 ], poly(arylene ether sulfone) (PES) [ 25 , 26 ], poly(phenylene oxide) (PPO) [ 27 , 28 , 29 , 30 ], styrene ethylene butylene styrene (SEBS) [ 27 , 31 , 32 , 33 , 34 , 35 ], polyphenylene (PP) [ 12 , 32 , 33 , 36 , 37 ], and polyethylene (PE) [ 38 , 39 , 40 , 41 ]. Ion-conducting groups are often quaternary ammonium [ 12 , 32 , 33 , 34 ], morpholinium [ 42 , 43 ], pyridinium [ 32 , 33 , 44 ], imidazolium [ 45 , 46 ], phosphonium [ 47 , 48 ], and metal coordination compounds [ 49 ]. In particular, the most popular aryl ether-type and non-aryl ether-type polymer backbones are PPO and SEBS because they are commercial polymers with respectable physicochemical features.…”