# Technology for Green Hydrogen Production: Desk Analysis
## 2 Background of Analysis
### Water Electrolysis Process
The electrode material must be chemically stable in the electrolyte under operating conditions to prevent corrosion and degradation, and have good mechanical properties to withstand the stresses of operation, including changes in pressure and temperature [33; 34; 38; 39; 40; 41; 68]. The electrodes should maintain their performance over long periods without significant degradation. The cost of the electrode material is a significant factor, especially for large-scale applications [16; 91]. Noble metals are expensive, so there is a push toward developing low-cost alternatives [16; 17; 18; 20; 29]. The availability of the material and the sustainability of its supply chain are also important considerations to ensure long-term viability and scalability. The electrode material must be also compatible with the electrolyte pH (acidic, neutral, or alkaline). The material should maintain a stable interface with the electrolyte to ensure consistent performance over time and be easily processable into the desired electrode shape and structure. The manufacturing process for the electrode material should be scalable to meet the demands of large-scale hydrogen production [16; 72]. The environmental impact and toxicity of the electrode material and its manufacturing process are important considerations. The sustainability of the material, including its end-of-life recycling and disposal, should be considered [100]. Finally, the material should be able to withstand the operating temperature and pressure conditions of the electrolysis process, and be able to handle the desired current density without significant degradation [33; 34; 38; 39; 40; 41; 68]. Emerging trends in electrode materials include the use of nanomaterials, which can enhance catalytic activity and stability due to their  
Figure 6: Electrolysis of water [101]. high surface area and tunable properties [20; 27; 44; 97]; two-dimensional (2D) materials like graphene [102] and transition metal dichalcogenides (TMDs), which have been investigated for their unique properties and potential for high performance [103]; and bio-inspired catalysts like enzyme-inspired catalysts and other bio-inspired materials, explored for their efficiency and sustainability [104]. Table 2 summarizes the key components and materials of various types of electrolyzers, such as AEs, PEM electrolyzers, AEM electrolyzers, and SOEs, used in the production of green hydrogen [16]. The cells colored grey represent conditions or components that show significant variation across manufacturers or R&D institutions. Based on the data obtained by the International Renewable Energy Agency depicted in Table 2[16], it can be observed that AEM electrolyzers and SOEs are less mature at lab scale compared to other types, such as already commercial AEs or PEM electrolyzers, which might have more standardized or optimized components and conditions across different manufacturers. For AEM electrolyzers, the technology is relatively new and still under development, which could lead to a wide range of materials and operating conditions being explored by different institutions. AEM electrolyzers operate in an alkaline environment, which can offer advantages in terms of catalyst activity and durability but also presents challenges in terms of membrane stability and performance. SOEs operate at high temperatures, which creates challenges in material selection, thermal expansion mismatch, and durability. The significant variation in these technologies could indicate that they are still in the research phase, with many institutions experimenting with different approaches to improve performance, durability, and cost-effectiveness. This diversity of approaches is typical in the early stages of technology development and is essential for the eventual maturation and commercialization of these technologies. Each type has specific materials and configurations for its electrolyte, separator, electrodes/catalysts, and bipolar plates (Table 2) [16].