Theoretical Investigation of the Properties of Pd<sub>2</sub>Cu Intermetallics and CO<sub>2</sub> Hydrogenation to Ethanol Catalyzed on Pd<sub>2</sub>Cu (110)
Hui Guo, Tao-Tao Shi, Ji-Tian Chen, Zhao‐Xu Chen
Abstract
Intermetallics or ordered alloys are catalytically more advantageous than solid solution alloys. The B 2 phase Pd 2 Cu intermetallics exhibit excellent catalytic properties for CO 2 hydrogenation to ethanol and other reactions. However, the crystal structure of Pd 2 Cu is unknown. With a self-coded program based on symmetry and atomic ratio, we combed and identified the Pd 2 Cu 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 (S Pd–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 CO 2 hydrogenation to CH 3 CH 2 OH show that CH 2 OH to CH 2 +OH is the key step determining the production of ethanol, followed by CO 2 +H to COOH and COOH to CO+OH.