Plasma nitrogen chemistry from NOx removal to nitrogen fixation: Personal perspective

Plasma is an electricity-driven chemical process which can replace the conventional high-temperature and high-pressure processes, achieving greener production for strengthening renewable energy in the pursuit of carbon neutrality. The adaptability of plasma technology to temporal power variations, along with its rapid startup and shutdown capabilities, can provide a promising solution for renewable energy, which suffers from fluctuations in power output. Various plasma technologies are being investigated in seeking this possibility for various chemical conversion such as CO₂ decomposition, CO₂ methanation, dry and steam reforming, NH₃ synthesis and NO_x production. Remarkable advancements have been made in plasma NOx production during the last decade, and some startup companies are expanding social implementation of plasma technology for decentralized small- or medium scale power-to-X applications. This short review focuses on the basic but often overlooked aspects in plasma nitrogen chemistry. Fundamentals of N₂ and O₂ molecules related with the plasmas will be first addressed and then removal and formation of NO_x will be presented for an important applications of plasma nitrogen chemistry.