文献类型：期刊文献

英文题名：Ultrathin, Polycrystalline, Two-Dimensional Co3O4 for Low-Temperature CO Oxidation

作者：Cai, Yafeng[1,2,3];Xu, Jia[1];Guo, Yun[2,3];Liu, Jingyue[1]

机构：[1]Arizona State Univ, Dept Phys, Tempe, AZ 85287 USA;[2]East China Univ Sci & Technol, Sch Chem & Mol Engn, Key Lab Adv Mat, Shanghai 200237, Peoples R China;[3]East China Univ Sci & Technol, Sch Chem & Mol Engn, Res Inst Ind Catalysis, Shanghai 200237, Peoples R China

年份：2019

卷号：9

期号：3

起止页码：2558

外文期刊名：ACS CATALYSIS

收录：;EI(收录号：20191006603019);WOS:【SCI-EXPANDED(收录号:WOS:000460600600088)】；

基金：This work was supported by the National Science Foundation under CHE-1465057. The authors gratefully acknowledge the use of facilities within the Eyring Materials Center and the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University. Y.C. gratefully acknowledges financial support from the China Scholarship Council.

语种：英文

外文关键词：catalysis; CO oxidation; two-dimensional materials; grain boundaries; Co3O4; electron microscopy

摘要：Free-standing, hierarchical, ultrathin, and two-dimensional (2D) polycrystalline Co3O4 flowers were synthesized by a hydrothermal and topotactic transformation process. Aberration-corrected electron microscopy study of both the CoOx precursor structure and the subsequent topotactic transformation processes revealed the nucleation and growth mechanisms of the 2D polycrystalline Co3O4 nanosheets. The free-standing flower-shaped CoOx powders (1-5 mu m) consist of numerous self-assembled nano-crystallites (average size similar to 1.8 nm). After the topotactic transformation, via a rapid calcination process, the powders maintained their hierarchical flower-like shape, but the CoOx nanocrystallites structurally transformed into ultrathin 2D Co3O4 nanoplates with thicknesses ranging from 1 to 5 nm (average thickness similar to 2.4 nm). The final, free-standing, ultrathin 2D polycrystalline Co3O4 flowers possess a BET surface area of 138 m(2)/g. Statistical structural analyses revealed that the exposed surfaces of the Co3O4 flowers are dominated by the Co3O4{112} (similar to 70%). The hierarchical Co3O4 flowers contain many grain boundaries, pockets, surface steps, and other types of surface defects. CO oxidation on the as-synthesized hierarchical Co3O4 flowers showed a specific activity (normalized to the surface area) of 0.377 mu mol.m(-2).s(-1), about 5 times that of the most active Co3O4 at 70 degrees C reported in literature. Furthermore, even under moisture-saturated condition (similar to 3% H2O), the ultrathin 2D Co3O4 catalyst demonstrated a high specific rate and is stable for at least 40 h at 90 and 150 degrees C. The abundance of accessible coordinatively unsaturated Co3+, active oxygen species, and surface defects on the polycrystalline Co3O4{112} nanosheets are responsible for the experimentally observed high catalytic activity.