Ammonia oxidation is being considered as a viable technology for hydrogen production for use in fuel cells. This study was undertaken to gain insight into current issues related to catalytic inactivity with time. Density Functional Theory was used in modeling the chemical species present during ammonia oxidation: NHx (x = 0 - 3), OHy (y = 1 & 2) and N2Hz (z = 0 - 4) and the adsorption of these molecules on the surface of platinum clusters. Using comparison with experimental measurements where possible, it was found that the strength of adsorption for these molecules followed this trend: N2 < H2O < NH3 < N2H2 < N2H4 < N2H < N2H3 < OH < NH2 < NH < N. This suggests that the species present towards the right of this spectrum were especially relevant to surface blockage and could play a role in catalytic inactivity.
In addition, the formation and oxidation of the N2Hz molecules could possibly be tracked by spectrochemical analysis of the position of the N - N bond, which went from single (N2H4) to double (N2H2) to triple (N2) as the oxidation of ammonia progressed. The presence or absence of this peak is an indicator of the orientation of the molecule formed and an indicator of the progress of the reaction.
Finally, an exploratory investigation of a mechanism of ammonia oxidation, where ammonia is deprotonated in successive steps, predicted that the conversion of the imide radical to nitrogen, although thermodynamically favorable, exhibits slow kinetics in comparison to deprotonation of ammonia or amidogen