Electrochemical Ammonia Synthesis and Ammonia Fuel Cells.

Ammonia is a promising platform molecule for the future renewable energy infrastructure owing to its high energy density (when liquefied) and carbon-free nature. In particular, the interconversion between the chemical and electrical energies leveraging the nitrogen cycle could be an effective approach in mitigating the intermittency of renewable electricity production. However, efficient methods to store and release energy into and from ammonia, respectively, are still under development. Here, the latest developments in electrochemical ammonia synthesis and ammonia fuel cells are presented, and perspectives in the technical challenges and possible remedies are outlined. N2 electrolysis, plasma-enabled N2 activation, and electro-thermochemical looping are three potential approaches for electrochemical ammonia synthesis; however, achieving high selectivity and energy efficiency remains challenging. Direct ammonia fuel cells are suitable for a broad range of mobile and transportation applications but are limited by the lack of active catalysts for ammonia oxidation.