Iron-nickel catalyst: study of the electronic structure and bonding during hydrogen adsorption phenomena

S. SIMONETTI; F. REY SARAVIA; G. CANTO

Cairo

Conferencia; 2nd International Conference on Energy Systems and Technologies - ICEST 2013; 2013

Hydrogen can be obtained from renewable sources through thermal or catalytic processes. Iron promoted nickel based catalyst has been developed for high yield hydrogen generation through ethanol reforming [1]. The reaction results show a remarkable improved durability in catalytic activity as well as selectivity to hydrogen in auto-thermal reforming. In this work we studied using the atom superposition and electron delocalization molecular orbital (ASED-MO) method [2, 3], the H chemisorption on a Fe50Ni50 catalyst. We analyzed the electronic structure and bonding during the adsorption phenomena. Different sites on the catalyst surface were selected in order to establish the preferential H adsorption location and the optimum H-surface distance. The two most stable sites for H on Fe50Ni50 are those where H bonds on top Fe at 1.50 Å to the surface and the H bonds on the Fe-Fe bridge site at 0.70 Å above the surface.  We found that the minimum energy site corresponds to the H bonding on top Fe. Fe-H bond is formed on the Fe50Ni50 surface and the interaction is mainly due to the overlaps between the H s orbital with the pz, s, dz2 and py Fe orbitals. As a consequence, it is observed a Fe-Fe bond weakening of 12 %. On the other hand, when the H is located on the Fe-Fe bridge site, the Fe-H interactions weaken the Fe-Fe nearest bonds to about 33% with mainly participation of pz, py, s and dyz Fe orbitals. In general, after H adsorption, the Fe-Ni and Ni-Ni bonds are slightly affected. The Ni-H interaction is not evidence on the Fe50Ni50 surface.     References   [1] Huang L,  Xie J,  Chen R, Chu D, Hsu A. Improved Durability of Iron Promoted Non-Precious Metal Catalysts for Hydrogen Generation through Bio-ethanol Reforming. Meet. Abstr. - Electrochem. Soc. 2008; 802:828 .   [2] Anderson A, Nath K. Atom-superposition and electron-delocalization tight-binding band theory. Phys. Rev. B 1990; 41: 5652–5660.   [3] Landrum G, Glassey W. Yet Another extended Hückel Molecular Orbital Package (YAeHMOP), Cornell University, Ithaca, NY, 2004.