@article{99444b34d4074c79acf0c0a2f63f90ab,
title = "Understanding Pore Formation in ALD Alumina Overcoats",
abstract = "AlOX thin films deposited by atomic layer deposition (ALD) have previously been used to increase both stability and selectivity of supported palladium catalysts and are known to develop nanoscale porosity upon heating. Understanding the factors that affect ALD thin-film porosity enables future design of layered catalytic structures with tunable nanoscale features on industrially-relevant high-surface-area materials. In this study, porous and nonporous aluminum oxide supports with and without palladium nanoparticles were overcoated with thin films of 2-7 nm AlOX by ALD deposited at temperatures of 100, 200, and 300 °C. Hydroxyl loss and changes in surface chemistry were observed upon heating the films, and changes in surface area and pore volume of the annealed films were correlated to AlOX deposition temperature and the presence of Pd. Crystallization of the overcoat to γ-Al2O3 is shown to occur separately from hydroxyl loss and pore formation. A mechanistic understanding of pore formation in AlOX ALD films is obtained by reference to studies of the structural transformations accompanying the formation of transition aluminas from hydroxide precursors. Additionally, a direct and tunable correlation is established between pore development and the overall hydroxyl content of AlOX ALD coatings.",
keywords = "ALD, nanoparticles, porosity, selective catalysis, thin films",
author = "Cassandra George and Patrick Littlewood and Stair, {Peter C.}",
note = "Funding Information: This work was jointly funded by Northwestern University Institute for Catalysis in Energy Processes (ICEP) on Grant DOE DE-FG02-03ER15457 and Qatar National Research Fund NPRP exceptional grant award [NPRP-EP X-100-2-024]. Funding Information: This material is based on work supported as part of the Institute for Atom-efficient Chemical Transformations (IACT), an Energy Frontiers Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. We acknowledge funding from Northwestern University Institute for Catalysis in Energy Processes (ICEP) on Grant DOE DE-FG02-03ER15457. ICEP was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. P.L. gratefully acknowledges financial support of the QNRF: This work was made possible by a NPRP exceptional grant award [NPRP-EP X-100-2-024] from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. In addition, the electron microscopy work made use of the EPIC, Keck-II, and/or SPID facility(ies) of Northwestern University{\textquoteright}s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. We would also like to acknowledge the use of facilities within the umbrella of REACT center for Catalysis led by Prof. Neil Schweitzer. The authors thank Sheel Sanghvi for LaB6 PXRD data. Finally, the authors would like to thank the Notestein group, a part of the Chemical Engineering Department at Northwestern University, for advice and use of instrumentation. Funding Information: This material is based on work supported as part of the Institute for Atom-efficient Chemical Transformations (IACT) an Energy Frontiers Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. We acknowledge funding from Northwestern University Institute for Catalysis in Energy Processes (ICEP) on Grant DOE DE-FG02-03ER15457. ICEP was supported by the Chemical Sciences, Geosciences, and Biosciences Division Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. P.L. gratefully acknowledges financial support of the QNRF: This work was made possible by a NPRP exceptional grant award [NPRP-EP X-100-2-024] from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. In addition, the electron microscopy work made use of the EPIC, Keck-II, and/or SPID facility(ies) of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. We would also like to acknowledge the use of facilities within the umbrella of REACT center for Catalysis led by Prof. Neil Schweitzer. The authors thank Sheel Sanghvi for LaB6 PXRD data. Finally, the authors would like to thank the Notestein group, a part of the Chemical Engineering Department at Northwestern University, for advice and use of instrumentation.",
year = "2020",
month = may,
day = "6",
doi = "10.1021/acsami.9b23256",
language = "English (US)",
volume = "12",
pages = "20331--20343",
journal = "ACS applied materials & interfaces",
issn = "1944-8244",
publisher = "American Chemical Society",
number = "18",
}