{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/106372"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/106372","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"In-situ electron imaging of oxidation and reduction of rutile (TiO2) nanocrystals and interaction with palladium","abstract":"Metal nanoparticles supported on oxides exhibit excellent catalytic properties for chemical reactions that impact several industries, for example, Pd/CeO2 is used in the catalytic converters of automobiles for environmental remediation, Rh/ZrO2 is used for fuel refinement, and Pt/TiO2 is an excellent photocatalyst. Since chemical reactions take place at surfaces and interfaces, the catalytic reactions are highly dependent on the oxide surface structure and the interface with metal nanoparticles. Further, the oxides undergo the oxidation and reduction reactions as environment changes, the oxide surface structure also evolves dynamically during chemical reactions. The dynamic changes include the shape of nanocrystals, surface reconstruction, and the formation and rearrangements of defects. Here, we demonstrate that such structural changes can be directly observed using the new and improved environmental transmission electron microscopy (ETEM) methods. We focus on the surface and interface of TiO2 nanocrystals and Pd nanoparticles supported on TiO2 and observe their structural dynamics by direct electron imaging. In our experimental setup, we flow the gas directly into the sample area in a TEM column, while we heat the sample using a heating stage to the desired temperature. To reduce the TiO2 nanocrystals, high temperature heating under the TEM column vacuum of several 10-5 Pa is used. To oxidize the TiO2 nanocrystals, high purity oxygen gas is introduced into the TEM column to reach the pressure higher than 1x10-3 Pa at the same sample temperature. Under these reduction and oxidation conditions, the surface reconstruction of TiO2 nanocrystals is observed, as well as the defect evolution in the TiO2 nanocrystals, and changes on the surface of Pd nanoparticles supported on the TiO2 nanocrystals. To determine the shape and surface structure of the TiO2 nanocrystals, the high resolution electron microscopy (HREM) image analysis technique is developed based on the high-throughput multislice HREM image simulations and template matching. Using this technique, we determine the crystals orientation, the crystal thickness, and the image defocus from a single HREM image. In our study of TiO2 surface, we identified the TiO2 (110) surface has 2x1 reconstruction with the Ti3O5 sub-stoichiometry during reduction. The TiO2 (110) surface has a different reconstruction of 1x1 structure during oxidation. The reconstructions on other TiO2 surfaces are also observed. To visualize the defect evolution in TiO2 nanocrystals, we introduce a large amount of defects in the TiO2 nanocrystals by electron beam irradiation at 550 °C in vacuum. The electron beam induced reduction leads the creation of the planar defects, called crystallographic shear planes (CSPs). The CSPs transform from {101} to {211} orientations when the oxygen partial pressure is increased. Ex-situ observation of the CSP structures using scanning TEM (STEM) show that the {211} CSPs contain a high concentration of the titanium interstitials. The titanium interstitial diffusion mediated mechanism of CSP rotation is proposed. Pd nanocrystals of 1 to 2 nm size on TiO2 nanocrystals support of the average 50 nm size are examined to study interfacial interaction. The over-layer formation on the surface of the Pd nanocrystals is identified. The over-layer formation shows a support-facet dependency, which we attribute to the surface reducibility of the TiO2. We further suggest that the over-layer formation is due to the titanium interstitial defects migrating to the Pd nanocrystal surface during reduction.","abstract_html":"Metal nanoparticles supported on oxides exhibit excellent catalytic properties for chemical reactions that impact several industries, for example, Pd/CeO2 is used in the catalytic converters of automobiles for environmental remediation, Rh/ZrO2 is used for fuel refinement, and Pt/TiO2 is an excellent photocatalyst. Since chemical reactions take place at surfaces and interfaces, the catalytic reactions are highly dependent on the oxide surface structure and the interface with metal nanoparticles. Further, the oxides undergo the oxidation and reduction reactions as environment changes, the oxide surface structure also evolves dynamically during chemical reactions. The dynamic changes include the shape of nanocrystals, surface reconstruction, and the formation and rearrangements of defects. Here, we demonstrate that such structural changes can be directly observed using the new and improved environmental transmission electron microscopy (ETEM) methods. We focus on the surface and interface of TiO2 nanocrystals and Pd nanoparticles supported on TiO2 and observe their structural dynamics by direct electron imaging. In our experimental setup, we flow the gas directly into the sample area in a TEM column, while we heat the sample using a heating stage to the desired temperature. To reduce the TiO2 nanocrystals, high temperature heating under the TEM column vacuum of several 10-5 Pa is used. To oxidize the TiO2 nanocrystals, high purity oxygen gas is introduced into the TEM column to reach the pressure higher than 1x10-3 Pa at the same sample temperature. Under these reduction and oxidation conditions, the surface reconstruction of TiO2 nanocrystals is observed, as well as the defect evolution in the TiO2 nanocrystals, and changes on the surface of Pd nanoparticles supported on the TiO2 nanocrystals. To determine the shape and surface structure of the TiO2 nanocrystals, the high resolution electron microscopy (HREM) image analysis technique is developed based on the high-throughput multislice HREM image simulations and template matching. Using this technique, we determine the crystals orientation, the crystal thickness, and the image defocus from a single HREM image. In our study of TiO2 surface, we identified the TiO2 (110) surface has 2x1 reconstruction with the Ti3O5 sub-stoichiometry during reduction. The TiO2 (110) surface has a different reconstruction of 1x1 structure during oxidation. The reconstructions on other TiO2 surfaces are also observed. To visualize the defect evolution in TiO2 nanocrystals, we introduce a large amount of defects in the TiO2 nanocrystals by electron beam irradiation at 550 °C in vacuum. The electron beam induced reduction leads the creation of the planar defects, called crystallographic shear planes (CSPs). The CSPs transform from {101} to {211} orientations when the oxygen partial pressure is increased. Ex-situ observation of the CSP structures using scanning TEM (STEM) show that the {211} CSPs contain a high concentration of the titanium interstitials. The titanium interstitial diffusion mediated mechanism of CSP rotation is proposed. Pd nanocrystals of 1 to 2 nm size on TiO2 nanocrystals support of the average 50 nm size are examined to study interfacial interaction. The over-layer formation on the surface of the Pd nanocrystals is identified. The over-layer formation shows a support-facet dependency, which we attribute to the surface reducibility of the TiO2. We further suggest that the over-layer formation is due to the titanium interstitial defects migrating to the Pd nanocrystal surface during reduction.","abstract_has_math":false,"creators":["Yoon, Aram"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Materials Science & Engr","degree_department":null,"school":null,"contributors":["Zuo, Jian-Min","Bellon, Pascal","Huang, Pinshane","Perry, Nicolar Helen"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-03-02T22:15:07Z","date_published":"2020-03-02T22:15:07Z","updated_at":"2026-07-22T22:24:45Z","subjects":["in-situ imaging, environmental TEM, HREM, catalyst, oxidation, reduction, nanocrystal, surface, defect, CSP, crystallographic shear plane, SMSI, strong metal support interaction, titanium oxide, TiO2, rutile, Magneli, Palladium, Pd"],"languages":["en"],"rights":["All rights are reserved."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/106372","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Zuo, Jian-Min","Bellon, Pascal","Huang, Pinshane","Perry, Nicolar Helen"]},{"key":"dc:creator","label":"Author","values":["Yoon, Aram"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-03-02T22:15:07Z","2022-03-03T10:15:22Z","2019-12-06","2019-12"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science & Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["in-situ imaging, environmental TEM, HREM, catalyst, oxidation, reduction, nanocrystal, surface, defect, CSP, crystallographic shear plane, SMSI, strong metal support interaction, titanium oxide, TiO2, rutile, Magneli, Palladium, Pd"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["All rights are reserved."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/106372"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Metal nanoparticles supported on oxides exhibit excellent catalytic properties for chemical reactions that impact several industries, for example, Pd/CeO2 is used in the catalytic converters of automobiles for environmental remediation, Rh/ZrO2 is used for fuel refinement, and Pt/TiO2 is an excellent photocatalyst. Since chemical reactions take place at surfaces and interfaces, the catalytic reactions are highly dependent on the oxide surface structure and the interface with metal nanoparticles. Further, the oxides undergo the oxidation and reduction reactions as environment changes, the oxide surface structure also evolves dynamically during chemical reactions. The dynamic changes include the shape of nanocrystals, surface reconstruction, and the formation and rearrangements of defects. Here, we demonstrate that such structural changes can be directly observed using the new and improved environmental transmission electron microscopy (ETEM) methods. We focus on the surface and interface of TiO2 nanocrystals and Pd nanoparticles supported on TiO2 and observe their structural dynamics by direct electron imaging. In our experimental setup, we flow the gas directly into the sample area in a TEM column, while we heat the sample using a heating stage to the desired temperature. To reduce the TiO2 nanocrystals, high temperature heating under the TEM column vacuum of several 10-5 Pa is used. To oxidize the TiO2 nanocrystals, high purity oxygen gas is introduced into the TEM column to reach the pressure higher than 1x10-3 Pa at the same sample temperature. Under these reduction and oxidation conditions, the surface reconstruction of TiO2 nanocrystals is observed, as well as the defect evolution in the TiO2 nanocrystals, and changes on the surface of Pd nanoparticles supported on the TiO2 nanocrystals. To determine the shape and surface structure of the TiO2 nanocrystals, the high resolution electron microscopy (HREM) image analysis technique is developed based on the high-throughput multislice HREM image simulations and template matching. Using this technique, we determine the crystals orientation, the crystal thickness, and the image defocus from a single HREM image. In our study of TiO2 surface, we identified the TiO2 (110) surface has 2x1 reconstruction with the Ti3O5 sub-stoichiometry during reduction. The TiO2 (110) surface has a different reconstruction of 1x1 structure during oxidation. The reconstructions on other TiO2 surfaces are also observed. To visualize the defect evolution in TiO2 nanocrystals, we introduce a large amount of defects in the TiO2 nanocrystals by electron beam irradiation at 550 °C in vacuum. The electron beam induced reduction leads the creation of the planar defects, called crystallographic shear planes (CSPs). The CSPs transform from {101} to {211} orientations when the oxygen partial pressure is increased. Ex-situ observation of the CSP structures using scanning TEM (STEM) show that the {211} CSPs contain a high concentration of the titanium interstitials. The titanium interstitial diffusion mediated mechanism of CSP rotation is proposed. Pd nanocrystals of 1 to 2 nm size on TiO2 nanocrystals support of the average 50 nm size are examined to study interfacial interaction. The over-layer formation on the surface of the Pd nanocrystals is identified. The over-layer formation shows a support-facet dependency, which we attribute to the surface reducibility of the TiO2. We further suggest that the over-layer formation is due to the titanium interstitial defects migrating to the Pd nanocrystal surface during reduction.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01","The student, Aram Yoon, accepted the attached license on 2019-12-04 at 14:30.","The student, Aram Yoon, submitted this Dissertation for approval on 2019-12-06 at 11:18.","This Dissertation was approved for publication on 2019-12-06 at 15:47.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14694 on 2020-02-28 at 17:23:25","Made available in DSpace on 2020-03-02T22:15:07Z (GMT). No. of bitstreams: 3 YOON-DISSERTATION-2019.pdf: 12555017 bytes, checksum: 64080a0ca70e23a23847b0fd7e170963 (MD5) LICENSE.txt: 4206 bytes, checksum: 3ea5cb1ad4e58fa2361c333e599708c9 (MD5) RightsLink Printable License.pdf: 148136 bytes, checksum: c156ffab97bf317d2b4ceef7be1ac3d3 (MD5) Previous issue date: 2019-12-06","Embargo set by: Seth Robbins for item 113914 Lift date: 2022-03-02T22:15:21Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 113914 Lift date: 2022-03-02T22:18:25Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only Restriction Lifted for Item 113914 on 2022-03-03T10:15:22Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["In-situ electron imaging of oxidation and reduction of rutile (TiO2) nanocrystals and interaction with palladium"]}]}],"canonical_facts":{"dc:contributor":["Zuo, Jian-Min","Bellon, Pascal","Huang, Pinshane","Perry, Nicolar Helen"],"dc:creator":["Yoon, Aram"],"dc:date":["2020-03-02T22:15:07Z","2022-03-03T10:15:22Z","2019-12-06","2019-12"],"dc:description":["Metal nanoparticles supported on oxides exhibit excellent catalytic properties for chemical reactions that impact several industries, for example, Pd/CeO2 is used in the catalytic converters of automobiles for environmental remediation, Rh/ZrO2 is used for fuel refinement, and Pt/TiO2 is an excellent photocatalyst. Since chemical reactions take place at surfaces and interfaces, the catalytic reactions are highly dependent on the oxide surface structure and the interface with metal nanoparticles. Further, the oxides undergo the oxidation and reduction reactions as environment changes, the oxide surface structure also evolves dynamically during chemical reactions. The dynamic changes include the shape of nanocrystals, surface reconstruction, and the formation and rearrangements of defects. Here, we demonstrate that such structural changes can be directly observed using the new and improved environmental transmission electron microscopy (ETEM) methods. We focus on the surface and interface of TiO2 nanocrystals and Pd nanoparticles supported on TiO2 and observe their structural dynamics by direct electron imaging. In our experimental setup, we flow the gas directly into the sample area in a TEM column, while we heat the sample using a heating stage to the desired temperature. To reduce the TiO2 nanocrystals, high temperature heating under the TEM column vacuum of several 10-5 Pa is used. To oxidize the TiO2 nanocrystals, high purity oxygen gas is introduced into the TEM column to reach the pressure higher than 1x10-3 Pa at the same sample temperature. Under these reduction and oxidation conditions, the surface reconstruction of TiO2 nanocrystals is observed, as well as the defect evolution in the TiO2 nanocrystals, and changes on the surface of Pd nanoparticles supported on the TiO2 nanocrystals. To determine the shape and surface structure of the TiO2 nanocrystals, the high resolution electron microscopy (HREM) image analysis technique is developed based on the high-throughput multislice HREM image simulations and template matching. Using this technique, we determine the crystals orientation, the crystal thickness, and the image defocus from a single HREM image. In our study of TiO2 surface, we identified the TiO2 (110) surface has 2x1 reconstruction with the Ti3O5 sub-stoichiometry during reduction. The TiO2 (110) surface has a different reconstruction of 1x1 structure during oxidation. The reconstructions on other TiO2 surfaces are also observed. To visualize the defect evolution in TiO2 nanocrystals, we introduce a large amount of defects in the TiO2 nanocrystals by electron beam irradiation at 550 °C in vacuum. The electron beam induced reduction leads the creation of the planar defects, called crystallographic shear planes (CSPs). The CSPs transform from {101} to {211} orientations when the oxygen partial pressure is increased. Ex-situ observation of the CSP structures using scanning TEM (STEM) show that the {211} CSPs contain a high concentration of the titanium interstitials. The titanium interstitial diffusion mediated mechanism of CSP rotation is proposed. Pd nanocrystals of 1 to 2 nm size on TiO2 nanocrystals support of the average 50 nm size are examined to study interfacial interaction. The over-layer formation on the surface of the Pd nanocrystals is identified. The over-layer formation shows a support-facet dependency, which we attribute to the surface reducibility of the TiO2. We further suggest that the over-layer formation is due to the titanium interstitial defects migrating to the Pd nanocrystal surface during reduction.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01","The student, Aram Yoon, accepted the attached license on 2019-12-04 at 14:30.","The student, Aram Yoon, submitted this Dissertation for approval on 2019-12-06 at 11:18.","This Dissertation was approved for publication on 2019-12-06 at 15:47.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14694 on 2020-02-28 at 17:23:25","Made available in DSpace on 2020-03-02T22:15:07Z (GMT). No. of bitstreams: 3 YOON-DISSERTATION-2019.pdf: 12555017 bytes, checksum: 64080a0ca70e23a23847b0fd7e170963 (MD5) LICENSE.txt: 4206 bytes, checksum: 3ea5cb1ad4e58fa2361c333e599708c9 (MD5) RightsLink Printable License.pdf: 148136 bytes, checksum: c156ffab97bf317d2b4ceef7be1ac3d3 (MD5) Previous issue date: 2019-12-06","Embargo set by: Seth Robbins for item 113914 Lift date: 2022-03-02T22:15:21Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 113914 Lift date: 2022-03-02T22:18:25Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only Restriction Lifted for Item 113914 on 2022-03-03T10:15:22Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/106372"],"dc:language":["en"],"dc:rights":["All rights are reserved."],"dc:subject":["in-situ imaging, environmental TEM, HREM, catalyst, oxidation, reduction, nanocrystal, surface, defect, CSP, crystallographic shear plane, SMSI, strong metal support interaction, titanium oxide, TiO2, rutile, Magneli, Palladium, Pd"],"dc:title":["In-situ electron imaging of oxidation and reduction of rutile (TiO2) nanocrystals and interaction with palladium"],"dc:type":["text"],"thesis:degree_discipline":["Materials Science & Engr"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:45Z"}