Octahedral Ni-nanocluster (Ni 85) for Efficient and Selective Reduction of Nitric Oxide (NO) to Nitrogen (N 2)

Abstract

Nitric oxide (NO) reduction pathways are systematically studied on a (111) facet of the octahedral nickel (Ni 85) nanocluster in the presence/absence of hydrogen. Thermodynamic (reaction free energies) and kinetic (free energy barriers, and temperature dependent reaction rates) parameters are investigated to find out the most favoured reduction pathway for NO reduction. The catalytic activity of the Ni-nanocluster is investigated in greater detail toward the product selectivity (N 2 vs. N 2 O vs. NH 3). The previous theoretical (catalyzed by Pt, Pd, Rh and Ir) and experimental reports (catalyzed by Pt, Ag, Pd) show that direct N-O bond dissociation is very much unlikely due to the high-energy barrier but our study shows that the reaction is thermodynamically and kinetically favourable when catalysed by the octahedral Ni-nanocluster. The catalytic activity of the Ni-nanocluster toward NO reduction reaction is very much efficient and selective toward N 2 formation even in the presence of hydrogen. However, N 2 O (one of the major by-products) formation is very much unlikely due to the high activation barrier. Our microkinetic analysis shows that even at high hydrogen partial pressures, the catalyst is very much selective toward N 2 formation over NH 3.