| AVS 63rd International Symposium & Exhibition | |
| In-Situ and Operando Spectroscopy and Microscopy for Catalysts, Surfaces, & Materials Focus Topic | Thursday Sessions |
| Session IS-ThM |
| Session: | In-situ and Operando Spectroscopy and Microscopy with Infrared Absorption Spectroscopy |
| Presenter: | Lawrence Allard, Oak Ridge National Laboratory |
| Authors: | L.F. Allard, Oak Ridge National Laboratory S. Duan, Arizona State University J. Liu, Arizona State University |
| Correspondent: | Click to Email |
In recent years, catalysis by single-atom species dispersed on supports has been shown to be an exciting and viable possibility, for catalytic reactions in many systems [e.g. ref. 1]. The stability of single metal atoms on a support during elevated temperatures typically seen in “real” reaction processes is a critical issue, and is necessary to characterize appropriately in order to develop robust single-atom catalysts (SACs). Imaging single heavy atoms on lower Z supports via aberration-corrected high-angle annular dark-field (HAADF) imaging techniques in modern electron microscopy has become routine over the past decade, and extending this imaging capability into the realm of in situ gas-reaction technology is a natural goal for the catalytic scientist to better understand dynamical movement and the anchoring of noble metal atoms on specific support sites. This understanding will allow the ability to synthesize SACs with significant loadings of catalytic species while maintaining the full dispersion at the single-atom level.
Novel in situ gas-reaction technologies that utilize MEMS-based heater devices retained in a “closed-cell” reactor specimen holder for use in aberration-corrected (S)TEM instruments have shown the remarkable ability for imaging atomic columns in a crystal structure even at elevated temperatures and at pressures up to a full atmosphere [e.g. ref 2]. The possibility to extend this imaging capability to SACs has been a goal of our work, and will be demonstrated in this talk. The effects of the electron beam on the sample, and the effects of electron scattering processes within the gas and window materials that comprise the gas-cell are problematical questions that are being addressed. An “ideal” SAC catalyst comprising Pt atoms on NiO nanocrystals has been used as the model sample for HAADF images to demonstrate cases from material on a standard TEM grid to material in the full geometry of the closed gas-cell reactor.
References:
1. B. Qiao, A. Wang, X. Yang, L.F. Allard, Z. Jiang, Y. Cui, J. Liu, J. Li and T. Zhang, "Single-atom catalysis of CO oxidation using Pt1/FeOx,” NatureChemistry3 August 2011, pp. 634-641.
2. L.F. Allard, S.H. Overbury, W.C. Bigelow, M.B. Katz, D.P. Nackashi and John Damiano; “Novel MEMS-Based Gas-Cell/Heating Specimen Holder Provides Advanced Imaging Capabilities for In Situ Reaction Studies,” Microsc. Microanal.18, 2012, pp. 656–666.