## 1 Introduction  
The water crisis is considered to be the most critical problem that requires attention and practical solutions, as more than one billion people do not have access to drinking water [1; 2]. The reasons for the limited access to drinking water are usually the unequal distribution of water on Earth, with only 2.5% freshwater in the total water, and water pollution by dissolved organic and mineral substances [3]. Groundwater is typically regarded as one of the purest sources of drinking water in many countries, such as India [4], and the Anti-Atlas in Morocco [5]. However, these water resources are facing serious problems due to rapid urbanization and industrialization. One of these issues is nitrate contamination, which presents a serious threat to ecosystems and human health. Broadly speaking, nitrate accumulation in groundwater is caused by various anthropogenic and geogenic activities [6]. In fact, it is commonly agreed that agricultural activities are the most important source of nitrate pollution in groundwater [7; 8; 9; 10]. Many regions of the world report a significant percentage of nitrates in groundwater that exceeds World Health Organization (WHO) standards. Hence, anthropogenic nitrate is an environmental handicap with serious consequences when it reaches the human body through water ingestion [11], especially a disease that occurs in the bloodstream of babies under 6 months of age, called infant cyanosis, methemoglobin, or blue babies [12]. The conversion process of nitrates to nitrates and then to nitrosamines in the human body leads to harmful effects, such as gastric cancer [13]. That is why the WHO considers drinking water safe in terms of nitrates when it has a quality ratio less than or equal to one (QR \(=\frac{\text{C}_{\text{uptake}}}{50}\leq 1\)) [14]. To meet the permissible standard of nitrate concentration in drinking water, many physicochemical techniques have been adopted to remove nitrates from the water, such as adsorption [15; 16], ion exchange [17; 18], biological denitrification [19; 20], anaerobic ammonium oxidation (Anammox) [21; 22], chemical denitrification [23; 24], catalytic denitrification [25; 26; 27], nanofiltration, and reverse osmosis [28; 29]. Nevertheless, these processes suffer from serious limitations, including high installation and maintenance costs, biofouling, brine generation, membrane sensitivity, and the need for post-treatment [30]. Currently, eNO\({}_{3}\)R can be perceived as the best way to treat contaminated water containing nitrogen compounds owing to their advantages, such as easy operation, remote control, minimal generation of secondary waste generation, and no potential for failure associated with high salinity, and these treatments can also be driven by renewable energy such as solar energy, hydropower, and wind power [31; 32]. On the other hand, some disadvantages can minimize their effectiveness, such as low efficiency for higher nitrate contents and very long reaction time [33; 34]. Numerous research investigations have centered their attention on the electrochemical synthesis of ammonia (NH\({}_{3}\)) through the reduction in nitrate (NO\({}_{3}^{-}\)) to ammonium (NH\({}_{4}^{+}\)) in nitrate-contaminated water. This focus emerges as a promising avenue to alleviate the substantial energy demands entailed by the conventional Haber-Bosch industrial process, which produces NH\({}_{3}\) from nitrogen (N\({}_{2}\)) and hydrogen (H\({}_{2}\)) [35]. Simultaneously, it offers a sustainable means of nitrogen recovery. The second strategy is eliminating NO\({}_{3}^{-}\) from groundwater while concurrently converting it into nitrogen gas. This pursuit assumes significance due to its pivotal role in maintaining equilibrium within the nitrogen cycle (N-cycle). From a thermodynamic standpoint, N\({}_{2}\) boasts the lowest solubility in water, simplifying its separation from aqueous mediums.