Dimethyl oxalate synthesis via CO oxidation on Pd-doped Ag(111) surface: A theoretic study

Abstract

High-efficiency and low-cost Pd-based catalyst is of vital importance toward CO oxidation to dimethyl oxalate (DMO). Here, we design Pd monolayer, Pd stripe and Pd single atom embedded on Ag(111) surfaces, i.e. PdML/Ag(111), Pd4Ag8/Ag(111) and Pd1-Ag(111), to investigate the effect of different content of Pd atoms in Ag substrate toward DMO formation. The density functional theory (DFT) calculation illustrates that the optimal pathway to produce DMO is two COOCH3 intermediates coupling route on three catalyst surfaces, which is the same to the Pd(111) surface, showing that it has no influence on the favorable route of DMO formation. Additionally, the DFT combined with micro-kinetic analysis indicates that Pd1-Ag(111) exhibits the highest activity for DMO generation, PdML/Ag(111) is superior to Pd(111), while Pd4Ag8/Ag(111) is inferior to Pd(111). Among them, the high activity on the Pd1-Ag(111) is attributed to strain effect and ligand effect both reducing activation barrier of the rate-controlling step. Moreover, Pd1-Ag(111) shows high selectivity for DMO, whereas it is opposite on the PdML/Ag(111). Therefore, it is proposed that Pd1-Ag single atom surface alloy can be the promising candidate not only improving the noble Pd’s catalytic performance for DMO formation but also reducing its usage.