Adsorption and dehydrogenation of ammonia on Ru 55 , Cu 55 and Ru@Cu 54 nanoclusters: role of single atom alloy catalyst

Hydrogen production by the catalytic decomposition of ammonia (NH ) is an important process for several important applications, which include energy production and environment-related issues. The role of single Ru-atom substitution in a Cu nanocluster (NC) has been illustrated using the NH decomposition reaction as a model system. The structural stability of Ru@Cu NC has been evaluated using Ru and Cu NCs for comparison. Ru@Cu prefers an icosahedron structure ( ), like Ru and Cu NCs, with almost comparable average binding energies of -5.55 eV per atom. The adsorption of NH ( = 0-3) on different adsorption sites of the icosahedron Ru@Cu NC has also been studied and the corresponding adsorption energies have been estimated. The site-preference investigation suggested that NH prefers to adsorb vertically to the Ru@Cu . The stable geometries of the N and H atoms on the high symmetry adsorption sites of Ru@Cu NC have been studied. Although the N atom favours top and hollow sites, the H atom prefers to stay in the Ru-Cu bridge site along with the hollow sites. The adsorption energy of N on the Ru@Cu NC fcc site is found to be -5.42 eV, which is very close to the optimal value (-5.81 eV) of the ammonia decomposition volcano curve. The reaction energies for stepwise H atom elimination from an adsorbed NH molecule have been estimated. Finally, NH adsorption and decomposition on Ru@Cu have been illustrated in terms of electronic structure analysis. The energetics calculations for the dehydrogenation of NH suggest that Ru@Cu NC can be a suitable catalyst.