A theoretical study of coverage effects for ethylene epoxidation on Cu(111) under low oxygen pressure

摘要

The effect of oxygen coverage on the molecular mechanism of ethylene epoxidation on Cu(111)under ultra-high-vacuum conditions was studied by means of periodic density functional calculations.Oxygen coverages of 1/16 and 1/4 monolayer were considered.The results indicate that the barriers leading to ethylene oxide and acetaldehyde from a common oxametallacycle intermediate depend on the oxygen coverage.In particular,the decrease in the energy barrier leading to the epoxide with oxygen coverage can be correlated with a concomitant change in the formation energy of the desired product.It is also suggested that the optimum oxygen coverage for the epoxidation of a given olefin on Cu surfaces likely vary from one molecule to the other.