The regulating effect of doping Cu on the catalytic performance of CO oxidative coupling to DMO on Pd_xCu_y/GDY: A DFT study

Rely on the density functional theory (DFT) calculation, the catalytic performance of PdxCuy/GDY (x = 1, 2, 3, 4; x + y ≤ 4) for CO oxidative coupling reaction was obtained. The Pd_x/GDY (x = 1, 2, 3, 4) are not ideal catalyst for dimethyl oxalate (DMO) formation because by-product dimethyl carbonate (DMC) is easily formed on Pd₁/GDY and Pd₂/GDY, and high activation energies are needed on Pd₃/GDY and Pd₄/GDY. Therefore the second metal Cu is doped to regulate the performance of Pd_x/GDY (x = 1, 2, 3, 4). Doping Cu not only improve the activity of DMO formation, but more importantly, controlling the ratio of Cu:Pd can effectively regulate the selectivity of DMO. Thus taking into account the activity and selectivity of the reaction for the preparation of DMO by CO oxidative coupling, the Pd₁Cu₁/GDY and Pd₁Cu₂/GDY with the activation energies of 105.2 and 99.2 kJ mol^-1 to generate DMO show excellent catalytic activity and high DMO selectivity, which are considered as good catalysts for CO oxidative coupling. The differential charge density analysis shows the decrease in the charge density of metal clusters is an important reason for improving the selectivity of the catalyst.