arXiv 2602.004332026-02cond-mat.mtrl-sci

反应条件下的氨催化剂演变揭示于环境和多模式电子显微镜

In situ Gas-Cell Electron Microscopy Reveals Pressure-Selected Restructuring Pathways in AuRu Ammonia Catalysts

Stanford University（斯坦福大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）

Amy S. McKeown-Green, Parivash Moradifar, Zisheng Zhang, Cedric Lim, Andrew Barnum, Lin Yuan, Robert Sinclair, Frank Abild-Pedersen, Colin Ophus, Jennifer A. Dionne

备注：: First two authors contributed equally to this work. First two and final author are corresponding authors. This work was conducted at Stanford University

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AI总结：

通过环境和多模式电子显微镜研究，揭示了AuRu催化剂在反应条件下的结构演变机制，揭示了氢驱动的纳米空洞形成及压力对重构的影响。

摘要：

双金属催化剂为可持续氨合成提供了新途径，但其在真实条件下的结构动态控制性能仍不明确。在此，我们结合原位气体池和多模式电子显微镜，解析了AuRu催化剂在温度、压力和化学条件下的重构，揭示了仅在大气压下可获得的路径。作为合成的AuRu纳米催化剂是多晶面心立方合金，具有Au/Ru互混，随着温度升高（>450°C）相分离为Au-rich和Ru-rich区域。增加压力（~1 atm在3:1氢气:氮气中）解锁了显著的晶面形成和内部纳米空洞形成，系统气体化学变化识别为氢驱动。基于密度泛函理论的原子间势能显示，氢可以放大Au/Ru扩散不对称性，通过气体介导的Kirkendall机制促进纳米空洞形成。这些结果弥合了传统原位电子显微镜与台式氨反应器之间的压力差距，使多组分系统中不同重构刺激的解析成为可能。

英文摘要：

Bimetallic catalysts provide new routes toward sustainable ammonia synthesis, but the nanoscale structural dynamics under reaction-relevant conditions remain poorly understood. Here, we combine in situ gas-cell and multimodal electron microscopy to determine how temperature, gas pressure, and chemistry select among distinct restructuring pathways in AuRu nanocrystal catalysts. Initially, the AuRu nanocrystals form polycrystalline face-centered cubic (FCC) alloys with Au/Ru intermixing. Elevated temperature ($\geq 350~^\circ$C) induces intraparticle phase segregation into distinct Au-rich (FCC) and Ru-rich hexagonal close-packed (HCP) domains that exhibit localized plasmonic modes. Atmospheric-pressure 3:1 H$_2$:N$_2$ gas unlocks a distinct restructuring regime absent at lower pressures, characterized by pronounced faceting and nanovoid formation. Systematic gas variation identifies hydrogen as the dominant driver. Density functional theory-trained machine-learning interatomic potentials and grand-canonical Monte Carlo simulations reveal that H-Ru interactions enhance the Au/Ru diffusivity mismatch, promoting vacancy accumulation and nanovoid formation. Together, these results show that, rather than simply accelerating the thermally driven phase segregation observed at lower pressures, atmospheric-pressure H$_2$:N$_2$ gas redirects restructuring toward faceting and nanovoid formation through a gas-mediated Kirkendall-type mechanism.

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