Mechanistic Investigation of the Catalytic Decomposition of Ammonia (NH 3 ) on an Fe(100) Surface: A DFT Study

Catalytic decomposition of ammonia (NH 3 ) is a promising chemical reaction in energy and environmental applications. Density functional theory (DFT) calculations were performed to clarify the detailed catalytic mechanism of NH 3 decomposition on an Fe(100) surface. Specifically, the elementary steps of the mechanism were calculated for the general dehydrogenation pathway of NH 3 . The adsorption of two types of ammonia dimers (2NH 3 ), locally adsorbed NH 3 and hydrogen-bonded NH 3, were then compared, revealing that locally adsorbed NH 3 is more stable than hydrogen-bonded NH 3 . By contrast, the dehydrogenation of dimeric NH 3 results in a high energy barrier. Moreover, the catalytic characteristics of NH 3 decomposition on a nitrogen (N)-covered Fe surface must be considered because the recombination of nitrogen (N 2 ) and desorption have an extremely high energy barrier. Our results indicate that the catalytic characteristics of the NH 3 decomposition reaction are altered by N coverage of the Fe surface. This study primarily focused on energetic and electronic analysis. Finally, we conclude that Fe is an alternative catalyst for the decomposition of NH 3 in CO x -free hydrogen production.