First Principles Investigation for H2 Dissociative Adsorption on Ni and Cr-Decorated Ni Surfaces - An Application to Alkaline Polymer Electrolyte Fuel Cell

Abstract

In this research, density functional theory (DFT) calculations for H2 dissociative adsorption on Ni(111) and Cr-decorated Ni surfaces are performed to compare and understand the adsorption mechanism on both surfaces as an application to alkaline polymer electrolyte fuel cell (APEFC). The Cr-decorated Ni (CrML/Ni(111)) surface is constructed by placing a monolayer of Cr atoms on the topmost layer of a Ni (111) surface. The potential energy scans for H2 dissociative adsorption on both surfaces reveal that the activation barrier of Cr-decorated Ni surface is lower than that of the pristine Ni surface. For both surfaces, the H atoms are dissociated with a distance of 1.8 A; but H2 on Cr-decorated Ni surface has greater adsorption energy than for H2 on Ni(111) surface. The density of states (DOS) shows that the presence of Cr increased the unoccupied states in the region around the Fermi level as compared to clean Ni surface. The increase in unoccupied states is supported by the computed total charges of the atoms before and after the Cr monolayer is added on the Ni surface which also implies a strong metal-to-metal interaction between Ni and Cr atoms. The difference in the charges of the H atoms and the surface atoms before and after the adsorption on the surfaces shows an easier transfer of charges between H atoms and surface atoms of Cr-decorated Ni surface than the surface atoms of Ni surface. [DOI: 10.1380/ejssnt.2010.325]