Plasma catalytic ammonia synthesis: state of the art and future directions

This review describes the history and development of ammonia synthesis from its discovery to the early development of the Haber-Bosch process to the current use of plasma catalysis as an alternative to the possible process decentralization of this essential commodity. Proposed reaction mechanisms to-date for vacuum and atmospheric pressure discharges are summarized and discussed. The use of different discharges and materials employed as catalysts as well as the observed interactions between the plasma and the catalyst that can modify and activate the catalytic surface and the possible effects of the catalyst on plasma are herein summarized. Moreover, important differences between thermal catalysis and plasma catalysis are contrasted. It is intended that this review can also help to develop an understanding of the current knowledge and gaps for the ammonia synthesis through plasma catalysis with an emphasis on the challenges presently faced.