Theoretical Investigation of the Properties of Pd2Cu Intermetallics and CO2 Hydrogenation to Ethanol Catalyzed on Pd2Cu (110)

Intermetallics or ordered alloys are catalytically more advantageous than solid solution alloys. The B2 phase Pd2Cu intermetallics exhibit excellent catalytic properties for CO2 hydrogenation to ethanol and other reactions. However, the crystal structure of Pd2Cu is unknown. With a self-coded program based on symmetry and atomic ratio, we combed and identified the Pd2Cu structure. The calculated (110) interlayer distance agrees with the experimental result acceptably. Lattice dynamics and AIMD simulations demonstrate the identified structure is stable. The calculated bond strength indicates that among the five types of bonds, the shorter Pd–Cu bond (SPd–Cu) plays the most important role in stabilizing the structure. Crystal orbital Hamilton population (COHP) analyses reveal that the 5s(Pd)–4p(Cu) interaction dominates the Pd–Cu bonding and the 5s(Pd)–5s(Pd) or the 4p(Cu)–4p(Cu) interaction contributes the most in the homonuclear Pd–Pd and Cu–Cu bonds. Investigations on the reaction mechanism proposed for CO2 hydrogenation to CH3CH2OH show that CH2OH to CH2+OH is the key step determining the production of ethanol, followed by CO2+H to COOH and COOH to CO+OH.