Jin-Xun Liu

Research Project Emiel Hensen / Jin-Xun Liu

Au particle size effect for CO oxidation

Background

Au catalysis have attracted much more attention since the discovery that small supported Au nanoparticles are quite active CO oxidation catalysts[1]. It is widely accepted that CO oxidation is Au particle size sensitive. Previous experimental works have demonstrated that the activity of Au nanoparticles supported on TiO2 catalysts for CO oxidation increases sharply with decreasing Au particle size below 4 nm, with Au clusters in the range of 2.5 ~ 3 nm exhibiting the maximum reactivity. Extremely small Au clusters (below 2 nm) have lower CO oxidation activity[2]. Therefore, it is impossible to improve the mass-specific activity of Au catalysts for CO oxidation by merely decreasing the particle size. Although many progresses have been made, the origin of Au particle size effect for CO oxidation is not clearly well understood. In order to clarify this scientific issue, CO oxidation is entirely investigated on lots of Au clusters and surfaces theoretically and micro-kinetic simulations have been conducted to quantify the activity of different clusters and surfaces

Project and objective

Identification of the exact structures of Au clusters is of great significance for designing highly active Au catalysts. Genetic algorithm together with density functional theory (DFT) calculations has been performed to find the global minimum structures of Au clusters (Figure 1). Furthermore, the facets exposed on the Au Wulff shape have been considered to simulate large particles. The complete CO oxidation cycle has been studied on Au clusters and surfaces. Based on DFT calculations results, it is found that CO and O2 adsorption energies are the descriptor for CO oxidation reaction and all the reaction barriers can be expressed by CO and O2 adsorption energies. Micro-kinetic simulations are conducted to quantify the CO oxidation reaction rate on Au clusters and surfaces, shown in Figure 2.

Our DFT calculation results can be used to predict the suitable bimetallic catalytic systems with high CO oxidation activity at specified particle size based on the calculated CO and O2 adsorption energies. To the best of our knowledge, our approach represents the first time that CO oxidation reaction rate can be tuned by only modifying CO or O2 adsorption energies through changing the particle size and composition by full micro-kinetic simulations combined with DFT calculations.                                                                      

For further information:

Emiel Hensen (Helix, STW 3.35, Tel 5178, e.j.m.hensen@tue.nl)

Jinxun Liu (Helix , STW 4.46, Tel 9601, j.x.liu@tue.nl)

 

References:

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