AVS 63rd International Symposium & Exhibition
    In-Situ and Operando Spectroscopy and Microscopy for Catalysts, Surfaces, & Materials Focus Topic Thursday Sessions
       Session IS-ThM

Invited Paper IS-ThM10
Characterizing Working Catalysts with Correlated Electron and Photon Probes

Thursday, November 10, 2016, 11:00 am, Room 101C

Session: In-situ and Operando Spectroscopy and Microscopy with Infrared Absorption Spectroscopy
Presenter: Eric Stach, Brookhaven National Laboratory
Authors: E. Stach, Brookhaven National Laboratory
Y. Li, Yeshiva University
S. Zhao, University of Illinois at Urbana Champaign
A. Gamalski, Brookhaven National Laboratory
D. Liu, University of Illinois at Urbana Champaign
R. Nuzzo, University of Illinois at Urbana Champaign
J.G. Chen, Columbia University/Brookhaven National Laboratory
A.I. Frenkel, Yeshiva University
Correspondent: Click to Email
Heterogeneous catalysts often undergo dramatic changes in their structure as the mediate a chemical reaction. Multiple experimental approaches have been developed to understand these changes, but each has its particular limitations. Electron microscopy can provide analytical characterization with exquisite spatial resolution, but generally requires that the sample be imaged both ex situ and ex post facto. Photon probes have superior depth penetration and thus can be used to characterize samples in operando (i.e when they are actively working). But they generally lack spatial resolution and thus give only ensemble average information.

We have taken advantage of the recent developments in closed-cell microscopy methods to develop an approach that allows us to successfully combine electron, x-ray and optical probes to characterize supported nanoparticle catalysts in operando. By measuring the reaction products at each stage of the reaction, we can directly correlate the information that can be obtained from each approach, and thus gain a deep insight into the structural dynamics of the system.

In this work, we will show how a combination of x-ray absorption near edge (XANES) and scanning transmission electron microscopy (STEM) can be used to characterize the changes that occur in a model NiPt bimetallic catalyst during oxidation and reduction. Bimetallics are of broad interest in heterogeneous catalysis as the provide the opportunity to selectively tune reactivity and selectivity. However, the characterization of their structure by averaged probes such as x-ray absorption spectroscopy is comprised by the heterogeneity that such systems may proscribe.

The presentation will focus on the development and application of experimental methods used to describe the morphological changes that occur in this model bimetallic system. These will include high temperature atmospheric pressure electron microscopy, the direct measurement of reaction products using gas chromatography-mass spectrometry and the ability of a newly developed electron microscope for operando microscopy (based on the FEI Talos platform) to characterize bimetallic nanoparticles through energy dispersive x-ray spectroscopy.