Active site of bimetallic heterogeneous catalyst by atomic resolution aberration-corrected STEM

Abstract

The localized defect of Au–Pd bimetallic heterogeneous nanoparticles catalyst was investigated using HRTEM and aberration-corrected HRSTEM. The phase plates were calculated from the aberration coefficients of the measured probe tableau for various outer tilt angle of the optical axis and the accuracy required for the compensation of the various residual aberration coefficients in order to achieve sub-angstrom resolution with the electron optics system was evaluated up to the fifth order aberrations. It is found that the interplanar spacing of the Au–Pd nanoparticle (111) planes observed along the [110] zone axis was approximately 0.24nm measured by HRTEM. In addition, the HRSTEM HAADF image demonstrated that the twin boundaries on the surfaces of heterogeneous nanoparticles catalysts at atomic scale. These defects might be introduced during the growth to alleviate the internal stress caused by the 4.6% lattice mismatch of Au–Pd bimetallic system. Current research could be applied to the study of active sites in nanocatalysts.