Anion-conducting polysulfone membranes containing hexa-imidazolium functionalized biphenyl units

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

In recent years, anion exchange membranes (AEMs) have aroused widespread interest in hydrogen production via water electrolysis using renewable energy sources. The two current commercial low-temperature water electrolysis technologies used are alkaline water electrolysis (AWE) and proton exchange membrane (PEM) water electrolysis. The AWE technology exhibited the advantages of high stability and increased cost-effectiveness with low hydrogen production efficiency. In contrast, PEM water electrolysis exhibited high hydrogen efficiency with low stability and cost-effectiveness, respectively. Unfortunately, the major challenges that AEMs, as well as the corresponding ion transportation membranes, including alkaline hydrogen separator and proton exchange membranes, still face are hydrogen production efficiency, long-term stability, and cost-effectiveness under working conditions, which exhibited critical issues that need to be addressed as a top priority. This review comprehensively presented research progress on AEMs in recent years, providing a thorough understanding of academic studies and industrial applications. It focused on analyzing the chemical structure of polymers and the performance of AEMs and established the relationship between the structure and efficiency of the membranes. This review aimed to identify approaches for improving AEM ion conductivity and alkaline stability. Additionally, future research directions for the commercialization of anion exchange membranes were discussed based on the analysis and assessment of the current applications of AEMs in patents.

Synthesis of gemini basic ionic liquids and their application in anion exchange membranes

A gemini-type basic morpholine ionic liquid ([Nbmd][OH]) was synthesized via a two-step method with morpholine, bromododecane and 1,4-dibromobutane as raw materials, and its structure was characterized by 1H NMR and FT-IR spectroscopy. Meanwhile, a series of anion exchange membranes ([Nbmd][OH] x -QCS) were prepared with quaternized chitosan (QCS) as the polymer matrix and [Nbmd][OH] as the dopant owing to its strong alkalinity and good solubility. The structures of the [Nbmd][OH] x -QCS composite membranes were characterized in detail by FT-IR spectroscopy, the OH- conductivity by AC impedance spectroscopy, and the morphological features by scanning electron microscopy (SEM), thermal gravity analysis (TGA), etc. The results show that the [Nbmd][OH] x -QCS composite membranes have uniform surfaces and cross-section morphology. Increasing the content of [Nbmd][OH] not only enhances the thermal stability but also increases the OH- conductivity; the thermal decomposition temperature of the [Nbmd][OH]40-QCS membrane is nearly 20 °C higher than that of the pristine QCS membrane, and the maximum OH- conductivity is approximately 1.37 × 10-2 S cm-2 at 70 °C. The methanol permeability of the [Nbmd][OH]40-QCS membrane in 1 M methanol at room temperature is 2.21 × 10-6 cm-2 s-1, which is lower than that of Nafion®115, indicating a promising potential use in alkaline direct methanol fuel cells. Moreover, the [Nbmd][OH]40-QCS membrane exhibits the best alkaline stability of all the membranes prepared in this work, retaining approximately 81% of its initial conductivity after immersion in 3 M KOH solution for 120 h at 70 °C.

Imidazolium-functionalized anion exchange membranes using poly(ether sulfone)s as macrocrosslinkers for fuel cells

The incompatibility of the hydrophilic imidazolium cations from the functionalized poly(vinyl imidazole) with the long hydrophobic poly(ether sulfone) chain promoted the phase separation. The PES/PVIIL-0.4 membrane displayed good single cell performance.