## 1 Introduction  
Considering the world's growing interest in producing green hydrogen, WE using RES appears as a promising solution. The two leading WE technologies to produce hydrogen are conventional alkaline and PEM electrolysis, where the ions crossing the diaphragm/membrane are hydroxide anions and hydrogen protons, respectively. The latter presents two main advantages: great flexibility (On/Off cycling and transient operation) and operation at high current densities. However, the high production cost related to the materials used (Platinum-Group Metals--PGM and titanium) is a limitation. Conventional alkaline WE with liquid electrolytes are notable among others due to their larger maturity and higher commercial outreach [1]. In the conventional configuration, a thick diaphragm is necessary to separate the electrodes with a liquid electrolyte, resulting in moderate current densities, lower hydrogen purity, and weak load cycling. Nevertheless, this technology allows the use of non-noble metals, reducing production costs, and has a higher lifetime. Recently, polymeric AEMs have been developed for electrochemical system applications [2]. They included advantages from both PEM and alkaline WE. The principal modification between conventional alkaline and AEMWE is the substitution of the diaphragm by an AEM, enabling the operation at higher current densities and preserving the opportunity of using non-noble metal catalysts. There is a research gap concerning the main components and integrated AEMWE that can be assigned to the system complexity and the lack of standard evaluation criteria. For instance, most of the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) electrocatalysts described with excellent activity are tested at room temperature, for a small period, at low voltages, but these conditions do not correspond to real applications [3]. To be a competitive technology, by 2050, AEMWEs must operate at current densities above 2 Acm\({}^{-2}\) with a voltage below 2 V [4]. Accelerated Stress Tests (ASTs) are decisive for determining the targeted lifetime of AEMWEs. Developments regarding the key electrolyzer components, such as the membrane, electrocatalyst, and their effects on electrolysis performance, have been reported in the literature [5]. The Membrane Electrode Assembly (MEA) is the main component that determines the performance of the electrolyzer, comprising the AEM, ionomer, anode, cathode catalyst layers, and Gas Diffusion Layers (GDLs). Although some membranes are commercially offered, they have two important weaknesses: the mobility of anions through the AEM is considerably lower than the mobility of protons through a PEM, and they do not demonstrate good chemical and/or mechanical stability. The alkaline media brings the advantage of using a wider variety of cheaper materials for AEMWE components compared to PEMWE. The feeding-water quality plays a vital role in the electrocatalytic activity and significantly affects the performance of the AEMWE. However, the use of impure water brings a great research opportunity considering the shortage of drinking water, but technical barriers for impure-water splitting need to be overcome [6].  
There are several reviews available in the literature concerning AEMWE technology from a global perspective [2; 3; 4; 7; 8; 9; 10] or addressing specific topics such as membranes [5; 11; 12] or electrocatalysts [13], which could be useful to readers who desire to deepen their knowledge of the topic.  
In this perspective paper, four research lines considered hot topics were selected: membrane and catalyst development, and durability and feeding solutions options, including the interesting possibility of using wastewater.