Highly effective catalysis of the double-icosahedral Ru(19) cluster for dinitrogen dissociation - a first-principles investigation.

The N-2 bond cleavage is the rate-limiting step in the synthesis of ammonia, and ruthenium is a catalyst well known for this reaction. The double-icosahedral (D-5h) Ru-19 cluster is famous as an active catalyst, and has a remarkable stability towards the adsorption of H-2, N-2 and CO. Using first-principles calculations, we have investigated the adsorption and dissociation of dinitrogen on a double-icosahedral Ru-19 cluster. Our results show that the hollow site in the rhombus region (BHB site) of the Ru-19 cluster possesses the greatest catalytic activity to dissociate N-2, with the reaction barrier of 0.89 eV and an exothermicity of -1.45 eV. Multiple coadsorption of N-2 on the cluster (i.e. coadsorption of 2N(2) and 3N(2) on a single Ru-19 cluster) causes the barrier to dissociate N-2 to be less on a BHB site than for adsorption of a single N-2. To understand the catalytic properties of a Ru-19 cluster towards N-2 bond cleavage, we calculated the electron population, vibrational wavenumbers and local densities of states; the results are explicable.