###### Abstract  
This review discusses the roles of anion exchange membrane (AEM) as a solid-state electrolyte in fuel cell and electrolyzer applications. It highlights the advancement of existing fabrication methods and emphasizes the importance of radiation grafting methods in improving the properties of AEM. The development of AEM has been focused on the improvement of its physicochemical properties, including ionic conductivity, ion exchange capacity, water uptake, swelling ratio, etc., and its thermo-mechano-chemical stability in high-pH and high-temperature conditions. Generally, the AEM radiation grafting processes are considered green synthesis because they are usually performed at room temperature and practically eliminated the use of catalysts and toxic solvents, yet the final products are homogeneous and high quality. The radiation grafting technique is capable of modifying the hydrophilic and hydrophobic domains to control the ionic properties of membrane as well as its water uptake and swelling ratio without scarifying its mechanical properties. Researchers also showed that the chemical stability of AEMs can be improved by grafting spacers onto base polymers. The effects of irradiation dose and dose rate on the performance of AEM were discussed. The long-term stability of membrane in alkaline solutions remains the main challenge to commercial use. graffing; irradiation; green hydrogen; alkaline fuel cell; alkaline water electrolysis 2021  
1 Fbruary 2021  
24 May 2021  
1 Fuel Cell Institute, Universit Kebangsan Malaysia, Bangi 43600, Malaysia; [EMAIL_ADDRESS] (C.Y.W. );  
[EMAIL_ADDRESS] (W.Y.W. );  
[EMAIL_ADDRESS] (W.Y.W. );  
skal..  
both technologies use strong alkaline aqueous solution (i.e., KOH) as an electrolyte that unfortunately can react with carbon dioxide in the air to produce insoluble precipitates (i.e., K\({}_{2}\)CO\({}_{3}\)), leading to the blockage of catalyst active sites and porous separator as well as the reduction of hydroxyl ions in anolyte, which eventually reduce the overall performance of the devices. In addition, the alkaline fuel cell and electrolyzer with liquid electrolyte [6] are inherently troublesome to shut down/start up, prone to leaking, have a high concentration gradient, and require consistent and stable output conditions. Leveraging on the knowledge of proton exchange membrane (PEM), solid-state anion exchange membrane (AEM), which offers the similar advantages of alkaline liquid fuel cell/electrolyte, has been proposed as the replacement for liquid electrolyte. With the recent announcement of the Green Deal by the European Union and gaining interest of green hydrogen production from water electrolysis, AEM electrolysis has been viewed as a potential technology that could reduce the hydrogen production cost significantly to the targeted price of USD 4/kg H\({}_{2}\)[7; 8]. [PERSON] et al. [9] have classified the AEMs into three categories: heterogenous membranes, interpenetrating polymer networks and homogeneous membranes. Heterogenous membrane can be prepared by embedding anion exchange material in an inert compound (either hydroxide salt or inorganic nanoparticles), whereas interpenetrating polymer networks is an amalgamation of two polymers in the form of a network, where both polymers are either partially or fully crosslinked. Most AEMs are homogeneous membranes and typically can be prepared via direct polymerization and crosslinking or the chemical modification of polymers by irradiation, grafting or chemical reactions. Homogeneous anion exchange membrane is defined by a semi-permeable membrane that consists of positively charged cation head groups that are immobilized in the polymer backbone that allow for the creation of conduction channels for the mobile, negatively charged anions to transport through the membrane [10]. The immobilization of cation head groups also limits their reaction and contact with carbon dioxide to reduce and prevent the formation of carbonate precipitates [11].