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Title: Interaction of Zinc Oxide Nanoparticles with Water: Implications for Catalytic Activity

Abstract

Novel technological applications in catalysis and bactericidal formulation have emerged for zinc oxide (ZnO) nanoparticles owing to their ability to generate reactive oxygen species by fostering H 2O dissociation. Rational improvement of those properties requires a mechanistic understanding of ZnO nanoparticle reactivity, which is currently lacking. In this work, we determine the structural and electronic properties of nanometer-sized ZnO, determine the binding energetics of H 2O adsorption, and compare to an extended macroscopic surface. We show that the electronic density of states of ZnO nanoparticles is size-dependent, exhibiting a decreasing bandgap with the increase of nanoparticle diameter. The electronic states near the Fermi energy dominantly arise from O 2p states, which are spatially localized on “reactive” surface O atoms on the nanoparticle edges that are doubly coordinated. The frontier electronic states localized at the low coordinated atoms induce a spontaneous dissociation of H 2O at the nanoparticle edges. The surface Zn and O atoms have inhomogeneous electronic and geometrical/topological properties, thus providing nonequivalent sites for dissociative and molecular H 2O adsorption. The free energy of H 2O binding is dominated by the electronic DFT interaction energy, which is site-dependent and correlated with the Bader charge of surface Zn atom. Entropymore » is found to stabilize the bound form, because the increase in the vibrational contribution is greater than the decrease in the translational and rotational contribution, whereas solvation stabilizes the unbound state. The absence of rough edges on an extended, macroscopic ZnO surface prevents spontaneous dissociation of a single H 2O. This study underlies the importance of coupling geometrical and electronic degrees of freedom in determining the reactivity of nanoparticles and provides a simple elucidation of the superior catalytic activity of ZnO nanoparticles compared to ZnO in macroscopic forms.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [3];  [4];  [2]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Central Florida, Orlando, FL (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Loyola Univ., Chicago, IL (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); U.S. Department of Agriculture (USDA); National Institute of Food and Agriculture (NIFA)
OSTI Identifier:
1530081
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
ACS Applied Nano Materials
Additional Journal Information:
Journal Volume: TBD; Journal Issue: TBD; Journal ID: ISSN 2574-0970
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; zinc oxide; ZnO; catalysis

Citation Formats

Rawal, Takat B., Ozcan, Ali, Liu, Shih-Hsien, Pingali, Sai Venkatesh, Akbilgic, Oguz, Tetard, Laurene, O’Neill, Hugh, Santra, Swadeshmukul, and Petridis, Loukas. Interaction of Zinc Oxide Nanoparticles with Water: Implications for Catalytic Activity. United States: N. p., 2019. Web. doi:10.1021/acsanm.9b00714.
Rawal, Takat B., Ozcan, Ali, Liu, Shih-Hsien, Pingali, Sai Venkatesh, Akbilgic, Oguz, Tetard, Laurene, O’Neill, Hugh, Santra, Swadeshmukul, & Petridis, Loukas. Interaction of Zinc Oxide Nanoparticles with Water: Implications for Catalytic Activity. United States. doi:10.1021/acsanm.9b00714.
Rawal, Takat B., Ozcan, Ali, Liu, Shih-Hsien, Pingali, Sai Venkatesh, Akbilgic, Oguz, Tetard, Laurene, O’Neill, Hugh, Santra, Swadeshmukul, and Petridis, Loukas. Wed . "Interaction of Zinc Oxide Nanoparticles with Water: Implications for Catalytic Activity". United States. doi:10.1021/acsanm.9b00714.
@article{osti_1530081,
title = {Interaction of Zinc Oxide Nanoparticles with Water: Implications for Catalytic Activity},
author = {Rawal, Takat B. and Ozcan, Ali and Liu, Shih-Hsien and Pingali, Sai Venkatesh and Akbilgic, Oguz and Tetard, Laurene and O’Neill, Hugh and Santra, Swadeshmukul and Petridis, Loukas},
abstractNote = {Novel technological applications in catalysis and bactericidal formulation have emerged for zinc oxide (ZnO) nanoparticles owing to their ability to generate reactive oxygen species by fostering H2O dissociation. Rational improvement of those properties requires a mechanistic understanding of ZnO nanoparticle reactivity, which is currently lacking. In this work, we determine the structural and electronic properties of nanometer-sized ZnO, determine the binding energetics of H2O adsorption, and compare to an extended macroscopic surface. We show that the electronic density of states of ZnO nanoparticles is size-dependent, exhibiting a decreasing bandgap with the increase of nanoparticle diameter. The electronic states near the Fermi energy dominantly arise from O 2p states, which are spatially localized on “reactive” surface O atoms on the nanoparticle edges that are doubly coordinated. The frontier electronic states localized at the low coordinated atoms induce a spontaneous dissociation of H2O at the nanoparticle edges. The surface Zn and O atoms have inhomogeneous electronic and geometrical/topological properties, thus providing nonequivalent sites for dissociative and molecular H2O adsorption. The free energy of H2O binding is dominated by the electronic DFT interaction energy, which is site-dependent and correlated with the Bader charge of surface Zn atom. Entropy is found to stabilize the bound form, because the increase in the vibrational contribution is greater than the decrease in the translational and rotational contribution, whereas solvation stabilizes the unbound state. The absence of rough edges on an extended, macroscopic ZnO surface prevents spontaneous dissociation of a single H2O. This study underlies the importance of coupling geometrical and electronic degrees of freedom in determining the reactivity of nanoparticles and provides a simple elucidation of the superior catalytic activity of ZnO nanoparticles compared to ZnO in macroscopic forms.},
doi = {10.1021/acsanm.9b00714},
journal = {ACS Applied Nano Materials},
number = TBD,
volume = TBD,
place = {United States},
year = {2019},
month = {6}
}

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This content will become publicly available on June 12, 2020
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