A theoretical study on the interaction of bimetallic Pt-Ni surface and the reactants of oxidative steam reforming reaction

Abstract

Pt-Ni bimetallic system is an efficient catalyst for Oxidative Steam Reforming (OSR) reaction; the detailed experimental test results obtained from Pt-Ni system have been already given in literature. In those research papers, the importance of understanding the bimetallic surface properties and the interaction between active sites and OSR reactants has been mentioned. In the current study (i) the properties of several bimetallic alloy surfaces having different Pt/Ni ratio, pseudomorphic Pt layers formed on Ni sublayers and monometallic Pt and Ni surfaces have been determined, (ii) the adsorption properties of all possible monometallic and bimetallic sites for oxygen and methane have been studied and (iii) the electronic interaction between metal atoms of the active sites and OSR reactant have been analyzed. The results showed that, Pt addition to Ni decreases the surface stress and the most stable site is found as 'five Ni layers containing 25 per cent Pt at topmost layer' surface alloy based on surface energy calculations. The adsorption studies indicate that oxygen adsorption energy does not only depend on surface concentrations of Pt and Ni but also the number of Pt-O and Ni-O bonds on the fcc site. Additionally, it was found that surface stress may be an important parameter in adsorption properties of the surface.