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First Author: Chen Yuhui

Corresponding Authors: Jiang Ying, Wang Yong

Corresponding Institution: Zhejiang University Electron Microscopy Center & Zhejiang University School of Materials Science and Engineering

https://doi.org/10.1002/anie.202504686

CHIPNOVA Transmission Electron Microscope Double-Tilt Heating In Situ System

In the in situ analysis, this paper utilizes CHIPNOVA transmission double-tilt heating in situ system and CHIPNOVA in situ heating chip ， The prepared Pd / TiO₂ catalyst dispersed on the sample chip is loaded into the ETEM through the double-tilt heating sample holder for observation.

1. Full Text Overview

Wang Yong's research group at Zhejiang University used environmental transmission electron microscopy technology ( ETEM) discovered that under specific redox conditions, the SMSI coating layer on the Pd / TiO₂ catalyst surface exhibits oscillatory behavior. This oscillation causes the SMSI coating layer to act as a dynamic temporary reservoir for Ti, capable of capturing reduced Ti from the support and driving epitaxial growth of the TiO₂ support. This finding expands the understanding of the dynamic behavior of SMSI under reaction conditions and material transport in supports, providing a new mechanism for solid-state growth of nanostructures. The above research results were published in Angew! In this groundbreaking experiment, the CHIPNOVA (CHIPNOVA) transmission electron microscope double-tilt heating in situ system provided key technical support for the study. 。

2. Background Introduction

Metal nanoparticles hold an indispensable position in modern catalytic science due to their high efficiency, multifunctionality, and tunability. The interaction mechanism between metal nanoparticles and oxide supports has always been a core research topic. Among them, metal -support strong interaction (SMSI) has attracted much attention due to its unique interfacial characteristics. However, the experimental construction and configuration control of the SMSI coating layer highly depend on the chemical environment. The dynamic behavior of SMSI under redox conditions remains unclear, and there is still a significant lack of understanding of its atomic-scale evolution mechanism. To address these issues, Wang Yong's research group conducted in-depth studies using the latest ETEM and CHIPNOVA in situ system to observe the mass transfer processes related to SMSI changes and the dynamic response of the support at the atomic scale. CHIPNOVA transmission electron microscope double-tilt heating in situ system provided key technical support for the experiment. Its unique double-tilt function and high-precision temperature control ( ≤0.01℃ stability) enabled atomic-scale dynamic observation of materials at precise temperatures. 3. Research Highlights

1. In situ observation and mechanism revelation: Through

ETEM real-time tracking, it was found that the oscillation originates from the competition of redox conditions, causing the TiOₓ coating layer to switch between single and double layers, and Pd nanoparticles rotate under stress. 2. Atomic-scale analysis: Precisely identified the double-layer structural features of 3.0Å/3.4Å.

4. Illustration and Explanation

Figure

1: Quasi in situ observation of Pd/TiO₂ under different atmospheres: SMSI coating layers form in pure O₂, H₂, and 5:1 O₂/H₂ mixed atmospheres, but the coating layer is partially damaged under redox conditions, and support protrusions appear at the interface. 2: In situ ETEM tracking of structural evolution under mixed atmosphere: The SMSI double-layer coating oscillates at the interface, accompanied by atomic layer addition of support protrusions, supporting protrusion growth into nanowires.

1: Quasi in situ observation of Pd/TiO₂ under different atmospheres: SMSI coating layers form in pure O₂, H₂, and 5:1 O₂/H₂ mixed atmospheres, but the coating layer is partially damaged under redox conditions, and support protrusions appear at the interface. 3: In situ characterization under pure O₂ conditions: The SMSI coating layer expands, pushing Pd particles away from the support, and the support protrusions grow into nanowires. EELS confirms the coating layer contains Ti³⁺.

1: Quasi in situ observation of Pd/TiO₂ under different atmospheres: SMSI coating layers form in pure O₂, H₂, and 5:1 O₂/H₂ mixed atmospheres, but the coating layer is partially damaged under redox conditions, and support protrusions appear at the interface. 4: Observation of oscillatory behavior along the TiO₂[001] axis: The number of SMSI coating layers positively correlates with the number of atomic layers in the support protrusions, and Pd particle rotation relates to the interface topology.

1: Quasi in situ observation of Pd/TiO₂ under different atmospheres: SMSI coating layers form in pure O₂, H₂, and 5:1 O₂/H₂ mixed atmospheres, but the coating layer is partially damaged under redox conditions, and support protrusions appear at the interface. 5. Summary and Expectations

Research Conclusions

1. For the first time, the SMSI oscillation phenomenon of Pd/TiO₂ under redox conditions was revealed, with the coating layer acting as a dynamic Ti reservoir, driving the tip growth of support protrusions.

• The oscillation mechanism does not depend on the epitaxial relationship between Pd and TiO₂ but is dominated by Ti migration regulated by redox balance.
• Scientific Significance This result expands the understanding of the dynamic behavior of SMSI under reaction conditions and provides a new perspective for understanding the relationship between catalytic performance and SMSI.

2. The study proposed an SMSI-mediated nanowire growth mechanism, offering new ideas for the synthesis of one-dimensional nanomaterials.

• Future Directions Explore the specific effects of SMSI oscillations on catalytic reactions (such as CO₂ hydrogenation and oxidation reactions).
• Study the dynamic behavior of SMSI under redox conditions in other metal -support systems (such as Pt/CeO₂, Ni/TiO₂).

3. 未来方向

• 探索 SMSI 振荡对催化反应（如 CO₂加氢、氧化反应）性能的具体影响。
• 研究其他金属-载体体系（如 Pt/CeO₂、Ni/TiO₂）在氧化还原条件下的 SMSI 动态行为。