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NM04.06.08 : Development of Ultrathin Hierarchical Co3O4 Flowers for Low-Temperature CO Oxidation

5:00 PM–7:00 PM Apr 4, 2018

PCC North, 300 Level, Exhibit Hall C-E

Description
Yafeng Cai1 2 Jia Xu1 Yun Guo2 Jingyue Liu1

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

Free-standing and ultrathin, hierarchical porous two-dimensional polycrystalline Co3O4 flowers were synthesized by a topotactic transformation of CoOx precursor systems. The synthesis processes and the structure of the final Co3O4 flowers were fully characterized by electron microscopy (SEM and aberration-corrected STEM) and spectroscopy (FTIR, XPS) techniques. The electron microscopy results showed that the CoOx flowers possess sizes ranging from ~ 1 mm to 5 µm and the average grain size is about 1.8 nm. The Co3O4 flowers possess abundant grain boundaries and surface steps, and the 2D-sheets range from about 1 nm to 5 nm in thickness. By detailed analyses of numerous aberration-corrected STEM images, we concluded that the 2D-sheets mainly exposed {211} and {100} surfaces. The XPS results revealed that compared with those of the bulk Co3O4 the core level energy of the Co 2p of the Co3O4 flowers showed a 0.8 eV redshift, caused by the enhanced electron density around the surface cobalt ions, resulting in the reduction of Co-O coordination [1]. Low-temperature CO oxidation over the synthesized 2D-Co3O4 flowers showed high activity due to high surface area and abundant surface defects. Dispersion of single metal atoms (e.g., Pt, Pd, and Ir) onto the 2D-Co3O4 flowers significantly modifies their catalytic performances for CO oxidation and other selected catalytic reactions [2].
References
[1] Y. Sun, S. Gao, Y. Xie, Chem. Soc. Rev. 43 (2014) 530–546.
[2] This work was supported by the National Science Foundation under CHE-1465057. The authors acknowledge the use of facilities within the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University. Yafeng Cai gratefully acknowledges financial support from the China Scholarship Council.

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