Jia Xu1 Yafeng Cai1 2 Jingyue Liu1

1, Arizona State University, Tempe, Arizona, United States
2, East China University of Science and Technology, Shanghai, , China

Aberration-corrected scanning transmission electron microscopy (STEM) has proved indispensable for understanding the atomic structures of nanomaterials and heterogeneous catalysts [1]. Nanoscale architectures of individual nanocomponents can provide synergistic and unique physicochemical properties that would not be possible with the individual components. We have previously developed a robust process to produce well faceted ZnO nanowires (NWs) as support materials for nanostructured catalysts or solar cell applications [2]. The ultraclean ZnO NWs primarily consist of ZnO {10-10} and {11-20} nanoscale facets. We have reported that Bi2O3 selectively deposit on the {11-20} nanofacets of the ZnO NWs with an epitaxial relationship [2]. We recently discovered individual Ir atoms self-assemble into single-atom size chains onto the {10-10} nanoscale facets of the ZnO NWs. Such self-assembly of Ir atom-size chains occurs under calcination treatment at selected temperatures. Aberration-corrected STEM-HAADF (high-angle annular dark-field) imaging technique was extensively used to help optimizing the synthesis processes, determine the atomic structure of the Ir/ZnO system, and to investigate the stability of the Ir atom chains under various gas treatment. By tiling the ZnO NWs both profile and plan view STEM-HAADF images were obtained which help determine the 3D structural relationship of the Ir atom chains with respect to the surface structure of the ZnO NWs. The catalytic properties of the newly discovered Ir/ZnO system were also evaluated for selected catalytic reactions [3].

[1] J Liu, ChemCatChem 3 (2011), p. 934.
[2] J Xu and J Liu, Chemistry of Materials 28 (2016), p. 8141.
[3]This work was funded by NSF under CHE-1465057. We acknowledge the use of facilities in the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University.