Concluding Remarks

Direct synthesis of ammonia from air and water is attractive for chemical energy storage of renewable electricity and for production of ammonia fertilizers as well. However, the conversion unit must be compact and efficient enough for economical production, because renewable energies such as wind and solar power are distributed over a wide range of territory. Electrochemical conversion at low temperature and low pressure is a promising approach. The literature studies on the subject will be reviewed and analyzed. Critical challenges will be delineated. A new catalytic membrane reactor based on low-temperature alkaline membrane separator and nano-/micro-structured electrodes will be introduced to address these challenges.