Green Electrocatalytical Synthesis of Ammonia Using Solid Oxide Electrolysis Cells

Ammonia is a very important chemical to human society, and its production mainly relies on the traditional Haber-Bosch (HB) method. However, the HB process is carried out under high temperature and pressure, resulting in a large amount of energy consumption and gas emissions. Electrochemical synthesis of ammonia (ESA) is a promising route due to its cleanliness and sustainability with low energy consumption. Solid oxide electrolysis cells (SOECs) working at high temperature have the advantages of increasing catalytic activity, easy to assemble and friendly to environment. Therefore, in this chapter recent experimental and theoretical studies on EAS using proton and oxygen ion conducting SOECs are reviewed. At the current stage, the ammonia production rates reported are in a range of 10^-13-10^-9 mol s^-1 cm^-2, which is far from the feasible commercial value. A lot of efforts have been made to further improve the ammonia production rate, including the development of new materials and microstructure design for electrode and electrolyte, plasma assisted ESA, and so on. Then we reviewed the recent progress of mechanism from experiments observation and density theoretical calculation (DFT) for the electrochemical nitrogen reduction reaction. In the end, the challenges and outlook for ESA using high-temperature SOEC are discussed. There is still a long way to go before the commercialization of ESA.