Hanaoka M., Iwado S., Nozawa K., Aoyama M., Ohhashi S., Fujita N., Kameoka S. . Creation of novel Pd single-atom catalysts using complex intermetallic compound Al13Fe4 . Applied Materi2025 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Applied Materials Today In recent years, single-atom catalysts have attracted attention as new catalytic materials because they exhibit unique catalytic properties. We focused on the crystallographically non-equivalent atomic sites present in the complex intermetallic compound Al<inf>13</inf>Fe<inf>4</inf> and found that Pd atoms can be selectively substituted at specific sites by simply doping with Pd atoms, and Pd single-atom catalysts can be easily prepared. The single-atom dispersion state of Pd atoms in Al<inf>13</inf>Fe<inf>4</inf> was characterized by X-ray diffraction (XRD) and hard X-ray photoelectron spectroscopy (HAXPES), and the preferred substitution sites were further predicted using density functional theory calculations. By XRD measurements, a change in the crystal phase of Al<inf>13</inf>Fe<inf>4</inf> with increasing Pd doping was observed (monoclinic phase (0, 0.2 at% Pd) → orthorhombic phase (1, 3, 4, 5 at% Pd) epsilon phase (10 at% Pd)). The Pd-doped Al<inf>13</inf>Fe<inf>4</inf> (Al<inf>13</inf>Fe<inf>4</inf>-Pd) prepared here was found to exhibit very high catalytic properties for the semi-hydrogenation of C<inf>2</inf>H<inf>2</inf> (C<inf>2</inf>H<inf>2</inf> + H<inf>2</inf> → C<inf>2</inf>H<inf>4</inf>). The catalytic activity increased with increasing Pd doping, but the activity decreased at 10 at% Pd. In contrast, the C<inf>2</inf>H<inf>4</inf> selectivity of each sample showed almost the same behavior (selectivity over 80 % at 200 °C). These excellent C<inf>2</inf>H<inf>2</inf> semi-hydrogenation properties are presumably induced by the formation of monoatomic dispersed Pd sites. Using intermetallic compounds as a platform to substitute specific lattice sites with small amounts (a few atomic percent) of catalytic elements (e.g., Pd, Pt, and Rh) is a promising approach to prepare novel single-atom catalytic materials. DOI： 10.1016/j.apmt.2025.102878 Scopus
Iwamura K., Otani Y., Takahashi Y., Ishii Y., Nozawa K. . First-Principles Study of Adsorption of Atomic Oxygen on PdZn(111) Surface . MATERIALS TRANSACTIONS65 ( 92024 · 担当区分： 最終著者, 責任著者 記述言語： 英語 出版者・発行元： 公益社団法人 日本金属学会 The adsorption structure of atomic oxygen on the PdZn(111) surface is studied using the first-principles calculation. At lower coverages up to 0.5 ML, oxygen atoms prefer to adsorb at threefold hollow sites surrounded by two Zn atoms and a Pd atom. Surface Zn atoms bonded with adsorbed oxygen atoms move toward the vacuum region, and the maximum displacement has reached 0.1 nm at 0.375 ML. At higher coverages from 0.625 ML to 1.0 ML, some oxygen atoms intruded into the surface layer and formed bonds with the Zn atoms in the second layer. At 0.75 ML, we observed the formation of the Zn-O hexagonal rings on the surface layer. It seems that the formation of the hexagonal rings largely contributes to the stability of the surface layer. However, the surface DOS and H2O adsorption indicate no essential difference owing to the hexagonal Zn-O rings, and the hexagonal Zn-O rings disappeared at higher coverages. We discussed the relation of the adsorption energy, coverage, and the number of atoms located in the vicinity of the adsorbed oxygen atoms. [doi:10.2320/matertrans.MT-M2024060] DOI： 10.2320/matertrans.mt-m2024060 Scopus CiNii Research その他リンク： https://doi.org/10.2320/matertrans.MT-M2024060
M. Sato, T. Hiroto, Y. Matsushita, K. Nozawa . Accuracy of Cluster Model Calculations for Quasicrystal Surface . Materials Transactions62 ( 3 ) 3502020 · 担当区分： 最終著者, 責任著者 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： 公益社団法人 日本金属学会 <p>Accuracy of the adsorption energy on a quasicrystal surface calculated with the density functional theory and cluster models were discussed. Two types of cluster models of various sizes were tested to represent a fivefold surface of the Ag–In–Yb quasicrystal. Some cylindrical clusters caused unnaturally rippled potential energy surfaces regardless of the cluster thickness. However, it was confirmed that the ripples are disappeared with a cluster radius of 1.4 nm or larger. A similar trend was observed even in the hemispherical clusters, and also confirmed in their root mean square errors. It was concluded that both cluster models with a certain size are expected to give relative adsorption energy within an error of 0.15 eV.</p> DOI： 10.2320/matertrans.MT-MB2020015 Scopus CiNii Research
