High-performance COF-based composite anion exchange membrane sandwiched by GO layers for alkaline H2/O2 fuel cell application

Ether-Free Alkaline Polyelectrolytes for Water Electrolyzers: Recent Advances and Perspectives

Anion exchange membrane (AEM) water electrolyzers (AEMWEs) have attracted great interest for their potential as sustainable, environmentally friendly, low-cost sources of renewable energy. Alkaline polyelectrolytes play a crucial role in AEMWEs, determining their performance and longevity. Because heteroatom-containing polymers have been shown to have poor durability in alkaline conditions, this review focuses on ether-free alkaline polyelectrolytes, which are more chemically stable. The merits, weaknesses, and challenges in preparing ether-free AEMs are summarized and highlighted. The evaluation of synthesis methods for polymers, modification strategies, and cationic stability will provide insights valuable for the structural design of future alkaline polyelectrolytes. Moreover, the in situ degradation mechanisms of AEMs and ionomers during AEMWE operation are revealed. This review provides insights into the design of alkaline polyelectrolytes for AEMWEs to accelerate their widespread commercialization.

De Novo Design of Aminopropyl Quaternary Ammonium-Functionalized Covalent Organic Frameworks for Enhanced Polybenzimidazole Anion Exchange Membranes

Quaternary ammonium functionalized covalent organic frameworks (COFs) have great potential to enhance hydroxide transport owing to crystalline ordered 1D nanochannels, however, suffer from limited quaternary ammonium functional monomers and poor membrane-forming ability. In this work, a novel aminopropyl quaternary ammonium-functionalized COF (DCOF) is designed and synthesized via a bottom-up strategy. The self-supporting DCOF membrane exhibits high crystallinity with a dense and orderly arrangement of quaternary ammonium groups (IEC, 2.07 mmol g-1), achieving a high hydroxide conductivity of 172.5 mS cm-1 and an extremely low water swelling of 5.3% at 80 °C. The exfoliated DCOF colloidal suspension is further incorporated into quaternary ammonium di-cation grafted polybenzimidazoles (DPBI) matrix. Molecular simulations reveal strong electrostatic and van der Waals interfacial interactions between DCOF and DPBI, which enable a high doping content of 20 wt.% and interconnected ionic channels through the surface and nanochannels of the DCOF. The DCOF/DPBI-20% membrane exhibits a tensile strength of 29.7 MPa, a hydroxide conductivity of 135.3 mS cm-1, and a low swelling ratio of 37.2% at 80 °C. A H2/O2 single cell assembled with the membrane reaches a peak power density of 323 mW cm- 2, surpassing most recently reported COF-based membranes.

Recent Developments on Bioinspired Cellulose Containing Polymer Nanocomposite Cation and Anion Exchange Membranes for Fuel Cells (PEMFC and AFC)

Hydrogen fuel cell (FC) technologies are being worked on as a possible replacement for fossil fuels because they produce a lot of energy and do not pollute the air. In FC, ion-exchange membranes (IEMs) are the vital components for ion transport between two porous electrodes. However, the high production cost of commercialized membranes limits their benefits. Various research has focused on cellulose-based membranes such as IEM with high proton conductivity, and mechanical, chemical, and thermal stabilities to replace the high cost of synthetic polymer materials. In this review, we focus on and explain the recent progress (from 2018 to 2022) of cellulose-containing hybrid membranes as cation exchange membranes (CEM) and anion exchange membranes (AEM) for proton exchange membrane fuel cells (PEMFC) and alkaline fuel cells (AFC). In this account, we focused primarily on the effect of cellulose materials in various membranes on the functional properties of various polymer membranes. The development of hybrid membranes with cellulose for PEMFC and AFC has been classified based on the combination of other polymers and materials. For PEMFC, the sections are associated with cellulose with Nafion, polyaryletherketone, various polymeric materials, ionic liquid, inorganic fillers, and natural materials. Moreover, the cellulose-containing AEM for AFC has been summarized in detail. Furthermore, this review explains the significance of cellulose and cellulose derivative-modified membranes during fuel cell performance. Notably, this review shows the vital information needed to improve the ion exchange membrane in PEMFC and AFC technologies.