NOx Generation in Air Thermal Plasmas and Prospects for Decentralized Nitrogen Fixation

Nitrogen fixation is essential for modern food production, yet the conventional Haber–Bosch process requires high temperature and pressure and involves significant energy consumption and CO2 emissions. This article reviews nitrogen oxide (NOx) formation in air thermal plasmas generated by a direct-current arc, focusing on reaction field design and energy efficiency. Air thermal plasmas create high-temperature conditions that activate nitrogen and oxygen, leading to reactive nitrogen species. Key factors affecting NOx generation, including energy input, gas flow conditions, and energy consumption per unit nitrogen production, are outlined together with representative experimental trends relating arc current, NOx concentration, and energy consumption.