Unveiling alloying effects on the catalytic activities of Cu3Pt and Cu3Pd for nonoxidative dehydrogenation and esterification of ethanol

Abstract

To investigate the alloying effects of the Cu catalyst, we performed extensive density functional theory (DFT) calculations to study the reaction mechanisms of ethanol dimerization to form ethyl acetate (EA) on Cu(111) and CuM(111) with M = Pt or Pd. Specifically, thirty-three reactions along the minimum energy reaction pathways were studied by calculating the energy barrier and reaction energy. To evaluate catalytic performance and determine the rate-determining step (RDS), we calculated reaction rate constants based on the harmonic transition state theory. The DFT results showed that the most widely recognized Colley mechanism for ethanol dimerization to form EA should be revised by including CH3CHO hydrogenation to form CH3CH2O. While the first dehydrogenation was found to be the RDS on Cu(111) and Cu3Pt(111), CH3CHO hydrogenation was identified to be the RDS on Cu3Pd(111). Furthermore, Cu3Pt(111) is about 3 orders of magnitude faster than Cu(111) and Cu3Pd(111) for ethanol nonoxidative dehydrogenation and esterification. This work also provides a benchmark for further examination of ethanol dimerization over other Cu alloys.