A Density Functional Theory Investigation of Ammonia Oxidation Pathways on Nickel Oxide

Abstract

Direct ammonia fuel cells (DAFCs) utilize ammonia’s chemical energy and converts it into electricity through the electrocatalyzed ammonia oxidation reaction (AOR). Currently, studies have focused on Pt-based anode materials, however due to limitations, research has shifted towards alternative materials. Previous research in our group has focused on oxidized Ni-based materials including Ni(OH)₂ and NiOOH which show promising catalytic activity. The current study used density functional theory to determine the catalytic activity of NiO. It was found that the rate-limiting step for all mechanisms associated with AOR is seen as the first deprotonation from *NH₃ to *NH₂, requiring 1.25 V. Additionally, the lattice oxygens in the surface provide alternate mechanistic routes compared to the previously studied Ni(OH)₂ and NiOOH. This work outlines the ability of NiO to drive various mechanisms toward N₂(g), N₂H₄(g), NO(g), NO₂^–(aq), NO₃^–(aq), and N₂O(g).