Accordingly, the highest ammonia synthesis rate (𝑟 𝑁𝐻 3 ) value reached was approximately 5.0 mmol.gcat -1 .h -1 , 1.5 times higher than that produced from N2/sea water vapor system with 3.2 mmol.gcat -1 .h -1 at similar plasma power of 6 W. Ammonia could not be detected from the reaction of N2/sea water vapor in the absence of catalyst, even when varying the plasma power.