Theoretical investigation of the mechanism of indirect decomposition of nitrous oxide (N₂O) by hydrogen (H₂) on Cu₇ cluster

Mechanism of the decomposition reaction between N₂O and H₂ molecules on the Cu₇ cluster was studied using density functional theory (DFT) with the BP86 functional in combination with the Aug-cc-pVDZ basis sets for N, O and H atoms, and the cc-pVDZ-PP basis set for Cu atom. The results show that the reaction undergoes via two successive steps. The first step involves adsorption of N₂O on the Cu₇ surface, followed by the decomposition of N₂O with an energy barrier of barely ~3 kcal/mol, producing an O atom, which subsequently binds to the cluster and a N₂ molecule. In the second step, the adsorped O atom couples with the H₂ molecule bound to a different Cu atom of the cluster leading to a release of H₂O molecule via two different pathways. The pathway corresponding to an adsorption of a N₂O molecule onto the most positively charged site of Cu₇ as turns out that the most energetically favorable with an energy barrier of ~22 kcal/mol, which is much lower than the barrier of 42 kcal/mol for the reaction without a catalyst. (author)