Gold nanoparticles (NPs) have attracted attention due to their superior catalytic performance in CO oxidation at low temperatures. Heterogeneous catalysts usually operate under dynamic conditions. Thus, understanding the reaction mechanism and the nature of the reactive species of heterogeneous catalysts under reaction conditions is the first step in the study of more consistent, reliable, and practical catalysts. Along with the size and shape of Au NPs, the catalytic function of Au-catalyzed CO oxidation can be further optimized by controlling the physicochemical properties of oxide-supporting materials. We applied a combinatorial approach of experimental analyses and theoretical interpretations to study the effect of a surface structure of supporting oxides and the corresponding CO oxidation activity of supported Au NPs. The catalysts were modeled as Au/CeO2(100) and Au/CeO2(111) via density functional theory (DFT) calculations. The DFT calculations showed that the O-C-O type reaction intermediate could be spontaneously formed at the Au-CeO2(100) interface upon sequential multi-CO adsorption, accelerating CO oxidation via the Mars-van Krevelen mechanism. We synthesized Au NPs (average d ≈ 3 nm) supported on shape-controlled CeO2 nanocrystals, Au/CeO2 cubes and Au/CeO2 octahedra for experimental analyses. The increasing TOF as a function of CO partial pressure and the positive correlation between the reducibility of CeO2 and the catalytic activity of Au/CeO2 catalysts confirmed the theoretical prediction that CO molecules occupy the surface of Au NPs and that the oxidation of Au-bound CO occurs at the Au-CeO2 interface. Through a comparative study of DFT calculations and in-depth experimental analyses, we provide insights into the catalytic function of CeO2-supported Au NPs towards CO oxidation depending on the shape of CeO2 and ratio of CO/O2.

DFT study for CO oxidation over Au nanoparticles supported on CeO2 under catalytic reaction condition

2019 Fall National Meeting

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