The elementary processes during the fixation of nitrogen by plasma catalysis are studied in a low-pressure plasma experiment with N \(_2\) and O \(_2\) as source gases. The formation of surface groups on an iron oxide foil is monitored with infrared reflection absorption spectroscopy. Surface nitrates (NO \(_3^-\) ) are formed when the substrate is exposed to a 1:1 N \(_2\) :O \(_2\) plasma, as well as N \(_2\) O(g), NO(g), NO \(_2\) (g), and O \(_3\) (g) in the gas phase. It is postulated that NO \(_{1,2}\) (g) species created by the plasma, adsorb at the surface and create these nitrates. This constitutes an intermediate step for nitrogen oxidation by plasma catalysis.
