Ammonia synthesis using nitrogen/water vapor inductively coupled plasma

Ammonia synthesis by the Haber-Bosch process using gray hydrogen emits

carbon dioxide in the hydrogen production process, while using green hydrogen enhances the

production cost significantly.

To solve the issue, in this work, we investigate the synthesis of ammonia using inductively

coupled plasma with nitrogen/water vapor mixture.

We found that water vapor had no problem as the source of H atoms, since the H density

in the nitrogen/water plasma was higher than that in the nitrogen/hydrogen plasma.

A drawback of the nitrogen/water vapor plasma was the decrease in the production rate with

the water vapor pressure.

The decrease in the production rate correlated with the decrease in the N density,

which may be attributed to N + OH → NO + H.

On the other hand, the N atom flux toward the surface of the stainless-steel chamber wall, which was

the reaction place for the ammonia synthesis, was 100 times higher than the production rate,

even if the N atom density was decreased by the above reaction.

This suggests another possibility that the decrease in the production rate with the water vapor pressure

is related with the influence of OH on adsorption/reaction processes on the surface.