Adsorption of CO on surfaces of 4d and 5d elements in group VIII

Ab initio density functional theory (DFT) calculations with the all electron relativistic (AER) core treatment method were used to determine adsorption of CO on close-packed surfaces of Ru, Rh, Pd, Os, Ir, and Pt. The adsorption energy and work function orders are obtained, which are Pd > Pt > Rh > Ru > Os > Ir and Os > Ir > Ru > Rh > Pt > Pd, where the latter was interpreted through analyzing their densities of state (DOS). The CO/Ir(111) system with the most negative adsorption energy was considered in detail as a model system. In terms of the plot of electron density difference and the values of Mulliken analysis, it is found that charges transfer from metallic surfaces to CO molecules. The results correspond to available experimental and theoretical data.