Hydrazine decomposition on nickel-embedded graphene

Abstract

In this article, the catalytic effect of the Ni-embedded graphene has been investigated for hydrazine (N2H4) decomposition reaction through Density Functional Theory (DFT) calculations with Grimme-D2 dispersion correction. Nickel embedded graphene systems are expected to be much cheaper than pristine nickel surfaces in the future because of relatively few numbers of Ni atom usage, experimentally synthesizable, and limit the Ni usage. The transformation of N2H4 has been taken into account in two different ways. The first way is sequential N–H and, the second one is the N–N bond cleavage from the gauche conformation which is the most stable conformation in gas phase and sole conformation observed on the Ni site. According to our findings, ·NH2 formation breaking the N–N bond in hydrazine has lower activation energy than hydrogen abstraction from hydrazine. The difficulty of breaking N–H bonds stems from the spatial accumulation of negative and positive charges, so it causes a mismatch between hydrogen atoms and negatively charges carbon atoms. NH3 formation pathway through the interaction of N2Hx (x = 1 → 4) species with co-adsorbed ·NH2 radicals is accompanied by much lower activation barriers and highly exothermic. Nevertheless, metal-embedded graphene systems are promising materials for hydrazine dehydrogenation and can be tailored to have more efficient charge distribution.