Hydrogenation of Cyclohexene on the M/Pt(111) and Pt/M/Pt(111) (M = Fe, Co, Ni, and Cu) Surfaces from a Systematic DFT Study

The hydrogenation of cyclohexene on the M/Pt(111), Pt/M/Pt(111) (M = Fe, Co, Ni, and Cu), Pt(111), and Ni(111) surfaces has been studied using density functional theory calculation. The low hydrogenation barriers could explain high hydrogenation reactivity of the Pt/M/Pt(111) sandwich structure. The Pt/Cu/Pt(111) surface may be an efficient catalyst for speeding up cyclohexene hydrogenation because of its high standard turnover frequency (TOF degrees). However, the experimental results showed the opposite: almost no cyclohexane was detected on the Pt/Cu/Pt(111). The possible reason is the Pt-Cu alloy formed on the topmost layer of the Pt/Cu/Pt(111) actually influencing the hydrogenation process, meaning that the chemical property of the so-called Pt/Cu/Pt(111) might be sensitive to the surface Pt coverage. Besides, on the basis of a volcano-type relationship between the TOF degrees and the coadsorption energy of the cyclohexene and the hydrogen atoms, similar sandwich structures on which the corresponding adsorption energy is in the range of -0.4 to -1.6 eV may possess excellent hydrogenation reactivity.