Piperidinium-functionalized anion exchange membranes and their application in alkaline fuel cells and water electrolysis

Abstract

A series of piperidinium-functionalized anion exchange membranes have been designed and fabricated for alkaline fuel cells and water electrolysis.

Ether-free polyfluorenes tethered with quinuclidinium cations as hydroxide exchange membranes

“…42 The high stability of the alicyclic QAs has been rationalized by a low ring strain combined with the constrained conformations imposed by the ring structure, which increase the transition state energy of both substitution and elimination reactions. 42 Later studies by us and others on AEMs functionalized with alicyclic cations such as piperidinium 25,26,44 and different spirocyclic QAs 32,37,[45][46][47][48][49][50][51] have conrmed a high alkaline stability. However, the results also indicate that the stability is highly dependent on precisely how the cations are attached to the polymer backbone.…”

“…However, the results also indicate that the stability is highly dependent on precisely how the cations are attached to the polymer backbone. 32,47,49,51 If the alicyclic cations are placed in positions where their ring conformation can be deformed, e.g., in a rigid polymer backbone, there is a tendency for the stability to decrease. 25,32 In the present work we have prepared and studied AEMs based on aryl ether-free uorene-based copolymers tethered with quinuclidinium (Qui) cations placed on exible hexyl spacers.…”

Density functional theory study on the degradation of fuel cell anion exchange membranes via removal of vinylbenzyl quaternary ammonium head group

“…The loss of NMP head group (Figure A(i)) occurs through nucleophilic substitution reaction (S N 2) via OH − ion attack on the bridging benzylic carbon with an EOB of 31.5 kcal/mol as shown in Figure B. It can be observed that the barrier energies for the detachment of different head groups investigated via nucleophilic attack, are essentially the same, suggesting similar governing degradation mechanism regardless of tethered functionality.…”

“…Even though DABCO and ABCO produce β‐carbons (consequently β‐hydrogens) upon reaction with benzylic chloride, Hofmann elimination will not proceed due to the impossibility of attaining the required stereoelectronics . NMP‐functionalised AEMs, on the other hand, can undergo degradation via any or combination of three possible mechanisms, namely, OH − ion attack through nucleophilic substitution, ring‐opening elimination, and ring‐opening substitution …”

Comb-shaped cardo poly(arylene ether nitrile sulfone) anion exchange membranes: significant impact of nitrile group content on morphology and properties

“…However, the existing AEMs still suffer from some challenges such as the trade-off between dimensional stability and conductivity, and the poor alkaline durability, which delayed the large-scale commercialization of AEMFCs. [8][9][10] To achieve high-performance AEMs, materials such as poly(phenylene oxide), 11 poly(styrene), 12 poly(ionic liquid), 13 poly(ether imide), 14 polyolen, 15 poly(arylene ether ketone) 16 and poly(arylene ether sulfone) 17,18 were modied by incorporating with hydroxide ion exchange groups such as imidazolium, 19 quaternary ammonium, 14,15 guanidinium, 20 pyridinium, 21 morpholinium, 22 piperidinium, 11,23 pyrrolidinium, 18,24 phosphonium 25 and metal ions, 26 etc. Furthermore, the microstructure of the AEMs also plays a key role in membrane's properties.…”