Metallurgical Abstracts on Light Metals and Alloys vol. 58

Amorphous alumina: an ideal material for advancing pentacoordinated aluminum chemistry and verifying its catalytic properties

Rei Okuno¹, Tetsuya Kinjo¹, Zen Maeno², Hirooki Kajiwara¹, Ayaka Ishi³, Naoto Kuwamura⁴, Yohei Onodera^5,6, Shinji Kohara^5,7, Koji Yazawa⁸,
Kenzo Deguchi⁹, Shinobu Ohki⁹, Shunsuke Shimizu¹⁰, Toshimasa Seki¹¹, Hiroki Nagai¹², Yuto Okawara¹, Ryuichi Maekawa¹,
Takeharu Yoshii^10,13, Kiyoshi Nakahara¹¹, Toshinori Okura³ and Hideki Hashimoto^3,5,13
¹ Applied Chemistry and Chemical Engineering Program, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
² Department of Environmental Chemistry and Chemical Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
³ Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
⁴ Division of Liberal Arts, Center for Promotion of Higher Education, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
⁵ Center for Basic Research on Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
⁶ Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashiro-nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
⁷ Graduate School of Science and Technology, Tokyo University of Science, 2641, Yamazaki, Noda, Chiba 278-8510
⁸ JEOL, 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan
⁹ NMR Station, National Institute for Materials Science (NIMS), 3-13 Sakura, Tsukuba, Ibaraki, 305-0003, Japan
¹⁰ Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, 980-8577, Japan
¹¹ Titan Kogyo, Ltd., 1978-25 Ohaza Kogushi, Ube, Yamaguchi 755-8567, Japan
¹² Department of Applied Physics, School of Advanced Engineering, Kogakuin University, Tokyo 192-0015, Japan
¹³ PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012, Japan

[Published in Applied Materials Today, Vol. 44 (2025), 102710]

https://doi.org/10.1016/j.apmt.2025.102710
E-mail: hideki-h[at]cc.kogakuin.ac.jp
Key Words: amorphous materials, oxides, nuclear magnetic resonance, high-energy X-ray diffraction, catalysts

Pentacoordinated aluminum (Al^V) sites, which are infrequently observed in crystals, have been shown to enhance material properties such as catalytic and mechanical performances. We synthesized porous amorphous alumina particles using a straightforward precipitation method and demonstrated the catalytic benefits of Al^V sites. While the sample contained trace amounts of hydroxyl groups and physisorbed water, it was entirely amorphous, consisting primarily of AlO₄, AlO₅, and AlO₆ units, with AlO₅ as the dominant component. This material exhibited catalytic activity in the dehydrogenation of propane. When paired with a molecular complex that facilitates electrocatalytic hydrogen generation, it resulted in an increased catalytic current and a reduction in overpotential. The Al^V sites are believed to play a crucial role in these enhancements. With its abundant Al^V sites throughout both the interior and surface, amorphous alumina serves as an ideal material for advancing the "chemistry of pentacoordinated aluminum."