Compared with that of proton exchange membrane fuel cells (PEMFCs), alkaline anion exchange membrane fuel cells (AEMFCs) with alkaline anion exchange membranes (AEMs) as electrolytes are attracting increased attention due to their potential use as non-precious catalysts. As one of the key components of AEMFCs, an ideal AEM must possess high hydroxide conductivity, good thermal stability, sufficient mechanical stability, and excellent long-term durability at elevated temperatures in an alkaline environment. Until now, a large number of AEMs with various chemical structures and properties have been prepared, and studied in detail, and it has been found that the microphase separation structure greatly affected the performance of AEMs. This minireview provides recent progress made of AEMs with hydrophilic/hydrophobic microphase separation structure. The hydroxide conductivity, alkaline stability, and mechanical properties of AEMs could be improved due to the formation of hydrophilic/hydrophobic microphase separation in the membranes. The relationship among the microphase separation, the chemical structure of the polymers, and the performance of membranes has been discussed in detail. This article attempts to give an overview of some key factors for the future design of novel AEMs with excellent performance such as high conductivity and improved chemical stability.

A series of ether-bond free polybenzimidazole (PBI) bearing pendant imidazolium groups (HIm-PBI and PIm-PBI) are synthesized via a low cost preparation process under mild reaction conditions. HIm-PBI and PIm-PBI show excellent membrane forming property, and flexible HIm-PBIand PIm-PBI-based membranes are prepared by casting the polymer/dimethyl sulfoxide solution. For a comparison, etherbond free PBI without pendant imidazolium groups (I-PBI) was synthesized and characterized in detail, and I-PBI shows poor membrane forming ability under the same conditions. HIm-PBI-based anion exchange membranes (AEMs) with the longer pendant alkyl side chain exhibit larger ionic clusters than that of PIm-PBI with the shorter one. Both HIm-PBIand PIm-PBI-based AEMs show excellent alkaline stability, and the HIm-PBI-based AEMs show a high conductivity of 63.4 mS cm −1 at 80 °C, while the value for PIm-PBI-based AEMs is 57.6 mS cm −1 . The H 2 /O 2 single-cell assembled with HIm-PBI shows a maximum power density of 444.5 mW cm −2 at 60 °C, which is higher than the one with PIm-PBI (337.5 mW cm −2 ). A feasible approach to the synthesis of ether-bond free PBI-based AEMs is proposed, and these results indicate that the etherbond free PBI-based AEMs are promising materials for fuel cell applications.

In the present work, a novel series of quaternized polystyrene-bpolybutadiene-b-polystyrene (SBS-QA) is designed and prepared successfully via feasible and inexpensive synthetic procedure. The SBS-QA-based anion-exchange membranes (AEMs) with various ion-exchange capacities (IECs) are prepared and characterized, and the membranes exhibit good thermal stability and mechanical properties due to the elastomer-like nature of SBS. These AEMs show a very slow swell ratio with normal water uptake and IEC, and the SBS-QA25 membrane shows the conductivity of 17.97 and 30.87 mS cm −1 at 20 and 80 °C, respectively. The AEMs exhibit a robust alkaline stability due to its unique structure of ether-free backbone with side-chain cation groups. The high conductivity, enhanced alkaline stability, improved swelling resistance, and excellent mechanical properties of the SBS-QA-based AEMs indicate that they are promising materials for fuel cell applications.

A series of cross-linked piperidinium-based anion-exchange membranes (AEMs) with an aliphatic main chain was prepared by UV-initiated polymerization of 1-methyl-1-(4-vinylbenzyl)­piperidinium chloride ([MVBPip]­[Cl]). The chemical structures of [MVBPip]­[Cl] and piperidinium-based membranes were studied by nuclear magnetic resonance (NMR) and IR spectroscopy, respectively. The piperidinium cation showed excellent alkaline stability, demonstrated by 1H NMR spectroscopy. The water uptake and conductivity of the piperidinium-based AEMs were enhanced by an increase in [MVBPip]­[Cl] content. A hydrophilic/hydrophobic microphase-separated structure was clearly detectable in the piperidinium-based AEMs. The transparent and mechanically robust piperidinium-based AEMs exhibited excellent chemical stability in 2 M KOH solution with the conductivity reaching 57.4 mS cm–1 (80 °C). The maximum power density of the single cell fabricated with piperidinium-based AEMs achieved 108.8 mW cm–2. These results indicate that the cross-linked piperidinium-based AEMs with an aliphatic main chain are promising materials for application in fuel cells.

Blending hydrogen into the natural gas pipeline is considered as a feasible way for large-scale and long-distance delivery of hydrogen. However, the blended hydrogen can exert major impacts on the Joule–Thomson (J–T) coefficient of natural gas, which is a significant parameter for liquefaction of natural gas and formation of natural gas hydrate in engineering. In this study, the J–T coefficient of natural gas at different hydrogen blending ratios is numerically investigated. First, the theoretical formulas for calculating the J–T coefficient of the natural gas–hydrogen mixture using the Soave–Redlich–Kwong (SRK) equation of state (EOS), Peng–Robinson EOS (PR-EOS), and Benedict–Webb–Rubin–Starling EOS (BWRS-EOS) are, respectively, derived, and the calculation accuracy is verified by experimental data. Then, the J–T coefficients of natural gas at six different hydrogen blending ratios and thermodynamic conditions are calculated and analyzed using the derived theoretical formulas and a widely used empirical formula. Results indicate that the J–T coefficient of the natural gas–hydrogen mixture decreases approximately linearly with the increase of the hydrogen blending ratio. When the hydrogen blending ratio reaches 30% (mole fraction), the J–T coefficient of the natural gas–hydrogen mixture decreases by 40–50% compared with that of natural gas. This work also provides a J–T coefficient database of a methane–hydrogen mixture with a hydrogen blending ratio of 5–30% at a pressure of 0.5–20 MPa and temperatures of 275, 300, and 350 K as a reference and a benchmark for interested readers.