Ao Nan Lai

Phenolphthalein-based Poly(arylene ether sulfone nitrile)s Multiblock Copolymers As Anion Exchange Membranes for Alkaline Fuel Cells

A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s (PESN) multiblock copolymers containing 1-methylimidazole groups (ImPESN) were synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. The ion groups were introduced selectively and densely on the unit of phenolphthalein as the hydrophilic segments, allowing for the formation of ion clusters. Strong polar nitrile groups were introduced into the hydrophobic segments with the intention of improving the dimensional stability of the AEMs. A well-controlled multiblock structure was responsible for the well-defined hydrophobic/hydrophilic phase separation and interconnected ion-transport channels, as confirmed by atomic force microscopy and small angle X-ray scattering. The ImPESN membranes with low swelling showed a relatively high water uptake, high hydroxide ion conductivity together with good mechanical, thermal and alkaline stability. The ionic conductivity of the membranes was in the range of 3.85-14.67×10(-2) S·cm(-1) from 30 to 80 °C. Moreover, a single H2/O2 fuel cell with the ImPESN membrane showed an open circuit voltage of 0.92 V and a maximum power density of 66.4 mW cm(-2) at 60 °C.

Imidazolium-Functionalized Poly(arylene ether sulfone) Anion-Exchange Membranes Densely Grafted with Flexible Side Chains for Fuel Cells

With the intention of optimizing the performance of anion-exchange membranes (AEMs), a set of imidazolium-functionalized poly(arylene ether sulfone)s with densely distributed long flexible aliphatic side chains were synthesized. The membranes made from the as-synthesized polymers are robust, transparent, and endowed with microphase segregation capability. The ionic exchange capacity (IEC), hydroxide conductivity, water uptake, thermal stability, and alkaline resistance of the AEMs were evaluated in detail for fuel cell applications. Morphological observation with the use of atomic force microscopy and small-angle X-ray scattering reveals that the combination of high-local-density-type and side-chain-type architectures induces distinguished nanophase separation in the AEMs. The as-prepared membranes have advantages in effective water management and ionic conductivity over traditional main-chain polymers. Typically, the conductivity and IEC were in the ranges of 57.3-112.5 mS cm(-1) and 1.35-1.84 mequiv g(-1) at 80 °C, respectively. Furthermore, the membranes exhibit good thermal and alkaline stability and achieve a peak power density of 114.5 mW cm(-2) at a current density of 250.1 mA cm(-2). Therefore, the present polymers containing clustered flexible pendent aliphatic imidazolium promise to be attractive AEM materials for fuel cells.

Comb-shaped phenolphthalein-based poly(ether sulfone)s as anion exchange membranes for alkaline fuel cells

A series of novel comb-shaped phenolphthalein-based poly(ether sulfone)s was synthesized for preparing anion exchange membranes (AEMs). Hexadecyldimethylamine with a long alkyl chain was used as the quaternization reagent to form a comb-shaped architecture of the copolymers. Due to the presence of a long alkyl side chain with hydrophobicity, the as-synthesized comb-shaped AEMs possess a self-anti-swelling property resulting in a low water uptake and swelling ratio. The PES-B100-C16 membrane exhibits excellent alkaline stability due to the presence of large volumetric β-alkyl chains linking to the cationic group that resist the attack of OH−, and retain available ionic conductivity in a 2 M KOH solution at 60 °C for 360 h. An open circuit voltage of the single cell reached 0.67 V, and the maximum power density was 43 mW cm2 at a current density of 125 mA cm−2 without optimization in a single H2/O2 alkaline fuel cell at 50 °C.

Influence of phenolphthalein groups on the structure and properties of poly(arylene ether sulfone nitrile)-based anion exchange membranes for fuel cells

Two series of novel poly(arylene ether sulfone nitrile) (PESN) multiblock copolymers are synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. To study the effect of phenolphthalein groups on the structure and properties of the membranes, the ion groups facilitating the formation of ion clusters are selectively and densely located on the phenolphthalein-sulfone segments of one and on the bisphenol A-sulfone segments of the other. The morphology and structure of the membranes are observed by atomic force microscopy and small angle X-ray scattering. The phenolphthalein-containing type endows the AEMs with a much clearer and more-defined microphase-separated structure leading to the formation of much larger and more developed interconnected ion-transport channels. As a result, high hydroxide conductivity (in the range of 2.04–12.98 × 10−2 S cm−1 from 30 to 80 °C) and H2/O2 fuel cell performance (an open circuit voltage of 0.92 V and a maximum power density of 66.4 mW cm−2 at 60 °C) can be achieved. Furthermore, the phenolphthalein-containing AEMs also show higher water uptake and mechanical strength, lower swelling ratio, and higher thermal and alkaline stability than the phenolphthalein-free AEMs.