Nitrogen oxidation on a plasma-exposed surface

TL;DR

This study investigates nitrogen fixation via plasma catalysis on iron oxide surfaces, revealing formation of nitrates and NOx species, and proposing a mechanism involving plasma-created NOx adsorption as an intermediate step.

Contribution

It provides experimental insights into surface chemistry and intermediate processes during nitrogen fixation in plasma catalysis, highlighting nitrate formation on iron oxide surfaces.

Findings

Surface nitrates form during plasma exposure.

Bidentate nitrates are identified on the surface.

NOx species are involved as intermediates.

Abstract

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.