Silica Containing Composite Anion Exchange Membranes by Sol–Gel Synthesis: A Short Review

Abstract

This short review summarizes the literature on composite anion exchange membranes (AEM) containing an organo-silica network formed by sol–gel chemistry. The article covers AEM for diffusion dialysis (DD), for electrochemical energy technologies including fuel cells and redox flow batteries, and for electrodialysis. By applying a vast variety of organically modified silica compounds (ORMOSIL), many composite AEM reported in the last 15 years are based on poly (vinylalcohol) (PVA) or poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) used as polymer matrix. The most stringent requirements are high permselectivity and water flux for DD membranes, while high ionic conductivity is essential for electrochemical applications. Furthermore, the alkaline stability of AEM for fuel cell applications remains a challenging problem that is not yet solved. Possible future topics of investigation on composite AEM containing an organo-silica network are also discussed.

Anion Exchange Membranes with 1D, 2D and 3D Fillers: A Review

“…In this review, we will limit the description of the progress achieved to silica and derivatives not obtained via the sol-gel process. Sol-gel silica composites were described in a recent review by Sgreccia et al [94]. [95].…”

Recent progress in anion exchange membranes (AEMs) in water electrolysis: synthesis, physio-chemical analysis, properties, and applications

“…27,29,32,45,49,50,55,57,58,[150][151][152][153][154][155][156][157][158][159][160][161][162] In addition, there are reviews on AEMs such as molecular design and microscopy analysis of membranes for fuel cell and water electrolysis, dealing with alkaline durability of imidazoliumbased AEMs, synthesis of ion-exchange membranes for various applications, synthetic approaches for alkaline-stable AEMs, Friedel-Cras reaction-based synthesis of AEMs for fuel cell and electrolysis applications, click chemistry in AEMs for energy-based applications, the signicance of polymer ion exchange membrane structures and properties for hydrogen production by water electrolysis, synthesis of silica-AEMs composite, and anion exchange polyelectrolytes for the synthesis of AEMs and ionomers. 50,88,145,160,[163][164][165][166][167][168][169][170][171][172][173] However, no comprehensive review of AEMs from synthesis to application through physiochemical analysis and evaluation of properties has been identied in recent studies. This review is distinct from other contemporary works because it thoroughly reviews the synthesis of AEMs, such as hydrocarbon and uorine, with choices of homogeneous (organic/organic) and heterogeneous…”

Anion-Conducting Polymer Electrolyte without Ether Linkages and with Ionic Groups Grafted on Long Side Chains: Poly(Alkylene Biphenyl Butyltrimethyl Ammonium) (ABBA)

“…The E2 elimination produces an alkene when a hydrogen is available in β position [ 27 ]. Different strategies are proposed to mitigate the damaging effect of alkaline media [ 2 , 15 , 28 , 29 , 30 , 31 , 32 ], including a delocalization of the positive charge [ 10 , 29 ], a protection by steric hindrance [ 10 , 33 ], an introduction of a long chain to separate the charge from the backbone [ 28 , 34 , 35 ], a different architecture of the polymer backbone [ 31 , 36 , 37 , 38 ], or the formation of composites with inorganic materials stable in alkaline environments [ 39 , 40 ]. Theoretical studies by Pivovar and co-workers show that the most stable side chain length corresponds to four to five CH 2 groups [ 41 ]; most recently the comparison between benzyltrimethylammonium and long alkyl-tethered quaternary ammonium (hexyltrimethylammonium) shows a better chemical stability of the latter in alkaline conditions [ 42 ].…”

“…This precursor is poly-condensed with 1,1,1-trifluoroacetone and then quaternized using TMA. The resulting new ionomer poly(alkylene biphenyl butyltrimethyl ammonium) (ABBA) is blended with poly(vinylalcohol) (PVA) [ 40 , 50 ] or poly(vinylidene difluoride) (PVDF) [ 51 , 52 ]. PVA is chosen because of its nontoxicity, film forming properties and low cost, and PVDF for its low reactivity, high solubility in polar solvents and the ability to enhance the nanophase separation [ 53 , 54 , 55 ].…”