Interaction between CO and PtSn alloy: a theoretical study on understanding selective CO oxidation

Abstract

The adsorption properties of CO on PtSn(110) surface were investigated via quantum mechanical calculations. The adsorption energies and the geometries of CO molecule for all possible adsorption sites were calculated. The energetically most favourable CO adsorption site was found as Pt-Pt bridge site, site B. The adsorption properties of CO on PtSn(110) were compared with those on Pt3Sn(110) and Pt(110). The CO adsorption strength of bridge sites on three surfaces decreased with increasing Sn content. The adsorption properties of other PROX reactants and products, namely H2, CO2 and O2, were also investigated on PtSn(110) surface. Pt-Pt bridge site B was found as the only site adsorbing H atom stably. Stable CO2 adsorption was observed only on Pt-Sn bridge site C on PtSn(110) surface. For atomic oxygen adsorption, Sn-Sn bridge site F was the most favourable adsorption site on PtSn(110) surface. The adsorption properties of H2, CO2 and O2 gases were also compared for the three surfaces, namely PtSn(110), Pt3Sn(110) and Pt(110). In order to understand electronic interactions between the surface metals and the adsorbates, local density of states (LDOS) profiles were examined for bare and adsorbed states of the metal atoms and the adsorbate involved in the adsorption process. The common behaviour observed for all adsorbates was that electronic density around surface Pt atom increased with increasing Sn content in the alloy and the electronic interactions occurred in lower energy levels as Sn concentration in the alloy was increased.