Introducing and Controlling Water Vapor in Closed-Cell in Situ Electron Microscopy Gas Reactions

Kinga A. Unocic; Franklin S. Walden; Nelson L. Marthe; Abhaya K. Datye; Wilbur C. Bigelow; Lawrence F. Allard

doi:10.1017/S1431927620000185

Introducing and Controlling Water Vapor in Closed-Cell in Situ Electron Microscopy Gas Reactions

Kinga A. Unocic, Franklin S. Walden, Nelson L. Marthe, Abhaya K. Datye, Wilbur C. Bigelow, Lawrence F. Allard

Research output: Contribution to journal › Article › peer-review

14 Scopus citations

Abstract

Protocols for conducting in situ transmission electron microscopy (TEM) reactions using an environmental TEM with dry gases have been well established. However, many important reactions that are relevant to catalysis or high-temperature oxidation occur at atmospheric pressure and are influenced by the presence of water vapor. These experiments necessitate using a closed-cell gas reaction TEM holder. We have developed protocols for introducing and controlling water vapor concentrations in experimental gases from 2% at a full atmosphere to 100% at ∼17 Torr, while measuring the gas composition using a residual gas analyzer (RGA) on the return side of the in situ gas reactor holder. Initially, as a model system, cube-shaped MgO crystals were used to help develop the protocols for handling the water vapor injection process and confirming that we could successfully inject water vapor into the gas cell. The interaction of water vapor with MgO triggered surface morphological and chemical changes as a result of the formation of Mg(OH)2, later validated with mass spectra obtained with our RGA system with and without water vapor. Integrating an RGA with an in situ scanning/TEM closed-cell gas reaction system can thus provide critical measurements correlating gas composition with dynamic surface restructuring of materials during reactions.

Original language	English
Pages (from-to)	229-239
Number of pages	11
Journal	Microscopy and Microanalysis
Volume	26
Issue number	2
DOIs	https://doi.org/10.1017/S1431927620000185
State	Published - Apr 1 2020

Funding

The research was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle LLC, for the U.S. Department of Energy. Part of the capability to introduce water vapor into the in situ gas cell was developed in collaboration with ChemCatBio, a member of the Energy Materials Network, and was supported by the US Department of Energy Bioenergy Technology Office under Contract no. DE-AC05-00OR22725 with Oak Ridge National Laboratory. The publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Funders	Funder number
US Department of Energy Bioenergy Technology Office
UT-Battelle LLC
U.S. Department of Energy
Oak Ridge National Laboratory

Keywords

MgO
in situ STEM
residual gas analyzer
sclosed-cell gas reaction system
water vapor

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10.1017/S1431927620000185

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title = "Introducing and Controlling Water Vapor in Closed-Cell in Situ Electron Microscopy Gas Reactions",

abstract = "Protocols for conducting in situ transmission electron microscopy (TEM) reactions using an environmental TEM with dry gases have been well established. However, many important reactions that are relevant to catalysis or high-temperature oxidation occur at atmospheric pressure and are influenced by the presence of water vapor. These experiments necessitate using a closed-cell gas reaction TEM holder. We have developed protocols for introducing and controlling water vapor concentrations in experimental gases from 2% at a full atmosphere to 100% at ∼17 Torr, while measuring the gas composition using a residual gas analyzer (RGA) on the return side of the in situ gas reactor holder. Initially, as a model system, cube-shaped MgO crystals were used to help develop the protocols for handling the water vapor injection process and confirming that we could successfully inject water vapor into the gas cell. The interaction of water vapor with MgO triggered surface morphological and chemical changes as a result of the formation of Mg(OH)2, later validated with mass spectra obtained with our RGA system with and without water vapor. Integrating an RGA with an in situ scanning/TEM closed-cell gas reaction system can thus provide critical measurements correlating gas composition with dynamic surface restructuring of materials during reactions.",

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AU - Datye, Abhaya K.

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AB - Protocols for conducting in situ transmission electron microscopy (TEM) reactions using an environmental TEM with dry gases have been well established. However, many important reactions that are relevant to catalysis or high-temperature oxidation occur at atmospheric pressure and are influenced by the presence of water vapor. These experiments necessitate using a closed-cell gas reaction TEM holder. We have developed protocols for introducing and controlling water vapor concentrations in experimental gases from 2% at a full atmosphere to 100% at ∼17 Torr, while measuring the gas composition using a residual gas analyzer (RGA) on the return side of the in situ gas reactor holder. Initially, as a model system, cube-shaped MgO crystals were used to help develop the protocols for handling the water vapor injection process and confirming that we could successfully inject water vapor into the gas cell. The interaction of water vapor with MgO triggered surface morphological and chemical changes as a result of the formation of Mg(OH)2, later validated with mass spectra obtained with our RGA system with and without water vapor. Integrating an RGA with an in situ scanning/TEM closed-cell gas reaction system can thus provide critical measurements correlating gas composition with dynamic surface restructuring of materials during reactions.

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Introducing and Controlling Water Vapor in Closed-Cell in Situ Electron Microscopy Gas Reactions

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