# Technology for Green Hydrogen Production: Desk Analysis
## 4 Results and Discussion
### Current Technologies Used for Green Hydrogen Production
#### 4.2.2 Proton Exchange Membrane Electrolyzers
Additionally, doping strategies that minimize the formation of secondary phases and maintain structural integrity under operating conditions are essential for achieving high chemical stability. Research into NASICON-type oxides for proton-conducting electrolytes in H-SOEs is an active area of study. Scientists are exploring new compositions, doping strategies, and processing techniques to further enhance their proton conductivity and stability under operating conditions [165; 166; 167]. The goal is to develop materials that can improve the efficiency and cost-effectiveness of green hydrogen production through electrolysis. Each of these oxide families has unique structural features and properties that can be tailored through doping and processing to enhance proton conductivity [166; 167; 67; 67]. The choice of material depends on various factors, including conductivity, stability, cost, and compatibility with other cell components. The use of H-SOEs offers several potential advantages as lower operating temperatures, higher efficiency, better integration with certain fuels, and simplified system design [165; 166; 167]. Proton-conducting electrolytes can operate at lower temperatures than oxygen-ion-conducting electrolytes, which can reduce thermal stresses and potentially allow for the use of less expensive materials. The proton-conducting mechanism can be more efficient because it avoids the need for the electrolyte to transport bulky oxygen ions, which can lead to lower energy losses. H-SOEs can be designed to co-electrolyte water and carbon dioxide, producing syngas as a mixture of hydrogen and carbon monoxide, which is a valuable feedstock for the production of synthetic fuels and chemicals. In H-SOEs, the direct production of hydrogen at the cathode can simplify the gas separation process, as there is no need to separate hydrogen from water vapor as in the case of oxygen-ion-conducting electrolyzers. Despite these advantages, H-SOEs also face challenges, such as finding materials that can withstand the harsh conditions of high-temperature operation while maintaining proton conductivity. Research and development in this area are ongoing with the aim of developing materials that offer higher conductivity, operate at lower temperatures, and are more durable and cost-effective [166; 167; 67]. This research is critical for the advancement of clean energy technologies and reducing greenhouse gas emissions. To sum up, SOEs are high-temperature devices offering several advantages [14; 16; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91; 92; 93; 94; 95; 96; 97; 98; 99; 100; 101; 102; 103; 104; 105; 106; 107; 108; 109; 101; 106; 107; 108; 109; 110; 111; 111; 111; 1112; 1113; 1114; 115; 1116; 117; 1117; 1118; 1119; 1120; 1121; 1122; 1123; 1124; 1125; 1126; 1127; 1128; 1129; 1130; 114; 1146; 1147; 1148; 1149; 1150; 1160; 1161; 1162; 1163; 1164; 1165; 1166; 1167]. The elevated temperatures facilitate favorable chemical reactions, allowing for the use of inexpensive nickel electrodes and a reduction in electricity demand due to the utilization of waste heat, which can lead to apparent efficiencies exceeding 100%. Additionally, SOEs have the potential to operate in reverse as fuel cells and can facilitate the co-electrolysis of CO\({}_{2}\) and water to produce syngas, a critical feedstock for the chemical industry [31; 36; 38; 40; 42; 146; 150; 162]. Despite these benefits, SOEs face challenges such as accelerated degradation and reduced lifespan due to thermo-chemical cycling, particularly during shutdowns and ramping periods. Other issues include difficulties with sealing at high differential pressures, electrode contamination from sealants like silica, and other contaminants from system components. Currently, SOEs are deployed at a small scale, with some demonstration projects reaching 1 MW.