Rate-Limiting Reaction of Dehydrogenative Dimerization of Ethanol to Ethyl Acetate and Hydrogen on Cu, Cu2, and Cu13 Clusters: Size Dependence

The reaction mechanisms of hydrogen and ethyl acetate formation from ethanol dehydrogenation in the presence of a single Cu atom, Cu2, and Cu13 were studied using density functional theory (DFT) calculations. The rate-limiting step was found to be dependent on the Cu cluster size. The acetaldehyde prefers desorbing from Cu clusters due to its low adsorption energy on Cu, rather than dehydrogenating to acetyl. The vibrational frequencies of the system and temperature also affect the reaction mechanism. The HOMO-LUMO gap of the Cu13 cluster rarely altered by adsorption species while that of a single Cu and Cu2 changed substantially when reactive species adsorbed on a single Cu atom or Cu2 cluster. This work also illustrates that the reaction mechanisms are sensitive to the size of Cu clusters.