Sub-nanometric High-Entropy Alloy Cluster: Hydrogen Spillover Driven Synthesis on CeO2 and Structural Reversibility

High-entropy alloy (HEA) nanoparticles (NPs) have attracted significant attention as promising catalysts owing to the various unique synergistic effects originating from the nanometer-scale, near-equimolar mixing of five or more components to produce single-phase solid solutions. However, the study of sub-nanometer HEA clusters having sizes of less than 1 nm remains incomplete despite the possibility of novel functions related to borderline molecular states with discrete quantum energy levels. The present work demonstrates the synthesis of CeO2 nanorods (CeO2-NRs) on which sub-nanometer CoNiCuZnPd HEA clusters were formed with the aid of a pronounced hydrogen spillover effect on readily reducible CeO2 (110) facets. The CoNiCuZnPd HEA sub-nanoclusters exhibited higher activity during the reduction of NO by H2 even at low temperatures compared with the corresponding monometallic catalysts. These clusters also showed a unique structural reversibility in response to repeated exposure to oxidative/reductive conditions, based on the sacrificial oxidation of the non-noble metals. Both experimental and theoretical analyses established that multielement mixing in quantum-sized regions endowed the HEA clusters with entirely novel catalytic properties.Hashimoto N., Mori K., Matsuzaki S., et al. Sub-nanometric High-Entropy Alloy Cluster: Hydrogen Spillover Driven Synthesis on CeO2 and Structural Reversibility. JACS Au , (2023); https://doi.org/10.1021/jacsau.3c0021

金属酸化物担持貴金属触媒のナノ構造と触媒活性に関する研究

京都大学0048新制・課程博士博士(工学)甲第15389号工博第3268号新制||工||1492(附属図書館)27867京都大学大学院工学研究科物質エネルギー化学専攻(主査)教授 江口 浩一, 教授 井上 正志, 教授 垣内 隆学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDA

SO₂共存下におけるPt–Li₂O/TiO₂–Al₂O₃触媒のNO吸蔵還元特性

The NO storage-reduction properties of 1 wt% Pt–10 wt% Li2O/TiO2–Al2O3 catalysts prepared by the impregnation and sol-gel methods were investigated in the presence and absence of SO2. The surface area and NO storage amount of catalysts were smaller for the Pt–Li2O/TiO2–Al2O3 catalyst than for the Pt–Li2O/Al2O3 catalyst. However, the Pt–Li2O/TiO2–Al2O3 sample with mixed oxide support achieved high NO removal efficiency for a long period, although the reduction of NO sorption amount by sulfur poisoning was comparable for all catalysts. These results revealed that the mixed oxide support in the catalyst is a key component for continuous NO removal. The preparation method affected the NO storage amount and the crystalline phases of catalysts. The strong diffraction peak of Li2TiO3 phase was observed in the XRD pattern of sample prepared by the impregnation method. The formation of Li2TiO3 weakened the basicity of the catalyst, resulting in decreased NO storage capacity under a SO2-free atmosphere and the enhancement of tolerance to sulfur poisoning