CO在Pd平板与Pd38团簇表面上的催化氧化机理研究

采用密度泛函理论(DFT)计算模拟Pd平板和Pd_(38)团簇上的CO催化氧化过程,分析了CO在Pd催化剂表面上的氧化反应机理。结果表明,在Pd_(38)团簇模型上CO催化氧化的决速步骤是O_2的解离,反应能垒为0.65 eV,而在Pd平板模型上的决速步骤是CO的氧化,其反应能垒为0.87 eV。对比决速步骤的活化能发现,CO在Pd_(38)团簇上的氧化反应更易进行,说明CO氧化更易在小颗粒催化剂表面上进行,即Pd催化剂的活性与活性组分颗粒大小相关,活性组分颗粒越小,暴露的活性位点越多,其催化活性也越高。

Catalytic oxidation of CO on Pd38 cluster and Pd slab,a computational study

The catalytic oxidation of CO was comparatively investigated on the Pd slab and Pd₃₈ cluster models by density functional theory (DFT) calculation, in order to reveal the mechanism of CO oxidation over Pd catalysts. The results show that the rate-determining step of CO oxidation on the Pd₃₈ cluster is the dissociation of O₂, with the energy barrier of 0.65 eV, whereas the oxidation of CO turns to be the rate-determining step on Pd slab, with the energy barrier of 0.87 eV. Obviously, the oxidation of CO on the Pd₃₈ cluster is much easier than that on the Pd slab, suggesting that the activity of Pd catalysts is related to the dispersion of active Pd species; the Pd catalyst with higher Pd dispersion also exhibits higher activity in CO oxidation.