| 1. |
Hajime Hojo, Minori Nakashima, Satoru Yoshizaki, Hisahiro Einaga, Lattice-Plane-Dependent Distribution of Ce3+ at Pt and CeO2 Interfaces for Pt/CeO2 Catalysts, ACS Nano, https://doi.org/10.1021/acsnano.3c09092, 18, 6, 4775-4782, 2023.12, The interaction between a metal and a support, which is known as the metal−support interaction, often plays a determining role in the catalytic properties of supported metal catalysts. Herein, we have developed model Pt/CeO2 catalysts, which enabled us to investigate the interface atomic and electronic structures between Pt and the {001}, {011}, and {111} planes of CeO2 using scanning transmission electron microscopy and electron energy-loss spectroscopy. We found that the number of Ce3+ ions around the Pt nanoparticles followed the order {001} > {011} > {111}, which was the opposite order of the generally accepted stability of low index surfaces of CeO2. Systematic first-principles calculations revealed that the presence of Pt nanoparticles facilitated the formation of oxygen vacancies and that the appearance of the Ptδ+ state was preferred when Pt nanoparticles were in contact with CeO2 {001} planes due to direct charge transfer from Pt to CeO2. These results provide important insights into the nature of the metal−support interaction for a comprehensive understanding of the properties of supported metal catalysts.. |
| 2. |
Hajime Hojo, Kazuki Hirota, So Ito, Hisahiro Einaga, Reduction Mechanism for CeO2 Revealed by Direct Observation of the Oxygen Vacancy Distribution in Shape-Controlled CeO2, Advanced Materials Interfaces, 10, 2201954, 2022.12.  |
| 3. |
Ryotaro Aso, Hajime Hojo, Yoshio Takahashi, Tetsuya Akashi, Yoshihiro Midoh, Fumiaki Ichihashi, Hiroshi Nakajima, Takehiro Tamaoka, Kunio Yubuta, Hiroshi Nakanishi, Hisahiro Einaga, Toshiaki Tanigaki, Hiroyuki Shinada, Yasukazu Murakami, Direct identification of the charge state in a single platinum nanoparticle on titanium oxide, Science, 378, 202-206, 2022.10, A goal in the characterization of supported metal catalysts is to achieve particle-by-particle analysis of the charge state strongly correlated with the catalytic activity. Here, we demonstrate the direct identification of the charge state of individual platinum nanoparticles (NPs) supported on titanium dioxide using ultrahigh sensitivity and precision electron holography. Sophisticated phase-shift analysis for the part of the NPs protruding into the vacuum visualized slight potential changes around individual platinum NPs. The analysis revealed the number (only one to six electrons) and sense (positive or negative) of the charge per platinum NP. The underlying mechanism of platinum charging is explained by the work function differences between platinum and titanium dioxide (depending on the orientation relationship and lattice distortion) and by first-principles calculations in terms of the charge transfer processes.. |
| 4. |
Hajime Hojo, Miki Gondo, Satoru Yoshizaki, and Hisahiro Einaga, Atomic and Electronic Structure of Pt/TiO2 Catalysts and Their Relationship to Catalytic Activity, Nano Letters, 22, 1, 145-150, 2021.12, Understanding the nature of the interaction between a metal and support, which is known as the metal−support interaction, in supported metal catalysts is crucial to design catalysts with desired properties. Here, we have
developed model Pt/TiO2 catalysts based on the deposition of colloidal Pt nanoparticles and studied their atomic and electronic structures before and after a postdeposition treatment that induces catalytic activity using aberration-corrected scanning transmission electron microscopy, electron energy loss spectroscopy, and first-principles calculations. Direct contact between Pt nanoparticles and TiO2 is realized after the postdeposition treatment, which is accompanied by the formation
of a Ti3+ state on the TiO2 surface close to the Pt nanoparticles and a Ptδ+ state on the Pt nanoparticles. The origin of these two states and their effect on the catalytic properties are discussed. These findings pave the way for a comprehensive understanding of metal−support interactions in supported metal catalysts.. |
| 5. |
Hajime Hojo, Ryo Kawabe, Keisuke Shimizu, Hajime Yamamoto, Ko Mibu, Kartik Samanta, Tanusri Saha-Dasgupta, Masaki Azuma, Ferromagnetism at Room Temperature Induced by Spin Structure Change in BiFe1−xCoxO3 Thin Films, Advanced Materials, 10.1002/adma.201603131, 29, 9, 2017.03. |
| 6. |
Keisuke Shimizu, Hajime Hojo, Yuichi Ikuhara, Masaki Azuma, Enhanced Piezoelectric Response due to Polarization Rotation in Cobalt-Substituted BiFeO3Epitaxial Thin Films, Advanced Materials, 10.1002/adma.201602450, 28, 39, 8639-8644, 2016.01. |
| 7. |
Hajime Hojo, Teruyasu Mizoguchi, Hiromichi Ohta, Scott D. Findlay, Naoya Shibata, Takahisa Yamamoto, Yuichi Ikuhara, Atomic structure of a CeO2 grain boundary: The role of oxygen vacancies, Nano Letters, 10.1021/nl1029336, 10, 11, 4668-4672, 2010.11. |
| 8. |
Hajime Hojo, Koji Fujita, Katsuhisa Tanaka, Kazuyuki Hirao, Room-temperature ferrimagnetic semiconductor 0.6FeTiO3 ̇ 0.4Fe2O3 solid solution thin films, Applied Physics Letters, 10.1063/1.2357547, 89, 14, 2006.10. |
