Nitrogen oxidation on a plasma-exposed surface

The elementary processes during the fixation of nitrogen by plasma catalysis are studied in a low-pressure plasma experiment using N${}_2$ and O${}_2$ as source gases. The formation of surface groups on an iron oxide foil are monitored with infrared reflection spectroscopy. Surface nitrates (NO${}_3$) are formed when the samples are exposed to a 1:1 N${}_2$:O${}_2$ plasma, as well as O${}_3$, NO${}_2$, NO, and N${}_2$O in the gas phase. During plasma exposure, bidentate nitrates are formed. The structure of this surface group changes after plasma exposure. It is postulated that adsorption plasma created NO${}_x$(g) yields the formation of these NO${}_3$ species. This constitutes an intermediate step for NO${}_x$ formation by plasma catalysis.