Atomic-Scale Compositional Mapping and 3-Dimensional Electron Microscopy of Dealloyed PtCo3 Catalyst Nanoparticles with Spongy Multi-Core/Shell Structures

作者：Liu Zhongyi^*; Xin Huolin; Yu Zhiqiang; Zhu Ye; Zhang Junliang; Mundy Julia A; Muller David A; Wagner Frederick T

来源：Journal of the Electrochemical Society, 2012, 159(9): F554-F559.

DOI：10.1149/2.051209jes

Advanced electron microscopy techniques, i.e., high angle annular dark field (HAADF) imaging, elemental mapping based on electron energy loss spectroscopy (EELS), and three-dimensional (3D) reconstructions from electron tomography, have been used to characterize the complex spongy core-shell structures observed in a high-performing fuel cell catalyst, a dealloyed PtCo3 catalyst supported on high surface carbon (or D-PtCo3/HSC). HAADF imaging showed that multiple dark-contrast patches were randomly decorated on the D-PtCo3 nanoparticles, a type of image that had previously been reported for other catalysts and had been referred to as a spongy structure. In this work, EELS-based elemental mapping revealed that not all of the dark-contrast patches were simple holes (as had been reported for other catalysts). Rather, in this material, while some of the dark-contrast patches corresponded to voids or divots, others were Co-rich cores. The probability of a dark-contrast patch in an HAADF being a Co-rich core was statistically determined to be 58% +/- 15%. 3D tomography further confirmed the existence of voids and divots in the multi-core/shell-structured D-PtCo3 nanoparticles. Possible formation mechanisms of the spongy multi-core/shell structure are discussed.

• 出版日期2012