Coadsorption of hydrazine and OH on the Ni(211) surface: A DFT study

Abstract

Hydrazine (N2H4) and hydroxyl (OH) coadsorption on the Ni(211) surface is investigated using Density Functional Theory (DFT) based calculations. Effects of the vicinal steps and edges on the stability of various N2H4-OH coadsorption configurations are investigated and compared with the case of individual adsorption of the respective molecules. Stabilizing interaction between N2H4 and OH coadsorbate is found to be mediated by hydrogen-bond. The most stable interaction of N2H4-OH is found perpendicular to the step direction, with N2H4 and OH occupying the terrace and edge sites, respectively. Swapping the position of N2H4 and OH reduce the relative stability. However, placing N2H4 on edge sites stabilizes its cis-conformation with noticeable N - H bond elongation. Finally, N2H4 and OH coadsorption with N2H4 and OH coadsorbed on edge-sites is moderate in terms of overall stability but exhibits the weakest N2H4 coadsorption and longest hydrogen bond interaction distance. Nevertheless, these N2H4-OH coadsorption structures are almost equally accessible thermodynamically due to the relatively small energy differences among them (less than 0.2 eV). In an ideal extended periodic system at specific coverage used in this study, the obtained coadsorption reveals the formation of a chain-like structure between N2H4-OH linked by hydrogen bonds. The results demonstrate the importance of steps and edges in effective formations of hydrogen bond stabilizing N2H4 coadsorption with prospects of promoting proton-transfer-reaction from N2H4 to OH.