Challenges and Strategies of Anion Exchange Membranes in Hydrogen‐electricity Energy Conversion Devices

Abstract

Alkaline hydrogen-electricity energy conversion technologies, involving anion exchange membrane fuel cells (AEMFCs) and anion exchange membrane water electrolyzers (AEMWEs) are more appealing than the acidic counterparts due to the elimination of precious metal catalysts. However, the physicochemical properties of anion exchange membrane (AEMs), i.e., ionic conductivity, mechanical strength, stability, etc., are inferior to that of proton exchange membranes (PEMs), thus hindering these alkaline technologies from practical employment. To promote their development, we summarize the main challenges and the corresponding strategies of AEMs for the application of AEMFCs and AEMWEs in this review. The hydroxide transportation mecha-nism, ion exchange capacity, hydration and microscopic morphology that are relevant to the ionic conductivity are discussed firstly. Following the ionic conductivity, another obstacle, stability of AEMs is comprehensively described in terms of alkaline stability, mechanical stability and electrochemical stability. Upon integrating into the devices, water management, carbonation effect and membrane-electrode interface that are critical to the cell performance are highlighted as well. This review is anticipated to provide insights into the AEM design for hydrogen-electric energy conversion devices, thus accelerating the widespread commercialization of these promising technologies.

Polyketone-Based Anion-Exchange Membranes for Alkaline Water Electrolysis

“…AEMs consist of polymers with positively charged functional pendant groups. Examples of starting polymers to fabricate AEMs include polysulfones, polystyrene and divinylbenzene or butadiene copolymers, polyethylene oxides, polychloroprenes, and polyketones (PKs) [2][3][4][5][6][7][8]. These membranes are characterized by the presence of positively charged groups, such as -NH 3 + , -NRH 2 + , -NR 2 H + , -NR 3 + , and -PR 3 + [9,10].…”

Understanding the Effect of Triazole on Crosslinked PPO–SEBS-Based Anion Exchange Membranes for Water Electrolysis

“…Moreover, the AEM’s polymer backbone and ion-conducting groups are vulnerable to OH − ion breakdown, which reduces durability. To get beyond these restrictions, high ionic conductivity and chemical stability AEMs must be developed [ 8 , 17 , 19 ].…”

Polyolefin‐Based Anion Exchange Membranes with Superior Performance and Long‐Term Durability for Green Hydrogen Production

“…In this regard, trimethylammonium positively charged groups are generally preferred to more complex functionalities, thanks to the easiness of quaternization reaction and its high chemical stability and conductivity. [2,3,11,12] The introduction of charged electro-withdrawing groups often leads to the instability of the backbone, especially when starting from polymers with heteroatoms in the repeating units, like polysulfones and polyethers. [13][14][15] Recently, most of the research focused on the preparation of membranes starting from aryl-ether free backbones, able to confer superior mechanical properties and adequate chemical stability over time.…”

“…[13][14][15] Recently, most of the research focused on the preparation of membranes starting from aryl-ether free backbones, able to confer superior mechanical properties and adequate chemical stability over time. [2,3,[16][17][18][19] One of the most common procedures is based on the radiation grafting of a mixture of vinyl benzyl chloride (VBC) and vinylbenzene onto LDPE/HDPE substrates, triggered by highly energetic X-, 𝛽or 𝛾rays. [20,21] Then, the grafted VBC is generally converted into a quaternary ammonium salt by reaction with trimethylamine (TMA) to form the anion exchange sites.…”

“…[ 5 ] Nowadays, the best way to produce green hydrogen is water electrolysis, coupled with renewable and environmentally sustainable energy resources like wind, hydro, and solar. [ 2,6 ]…”