Reaction 1 is highly endothermic, and at ambient conditions in air, the equilibrium lies far to the left (Supplementary Fig. ). The equilibrium shifts towards NO with increasing temperature, a fact exploited in the Birkeland-Eyde (B-E) process for thermally fixing N 2 at high temperatures achieved within a thermal plasma. At these high temperatures, N 2 and O 2 are partially atomized, and NO is produced by O and N radical reactions with N 2