报告人：王竹君 教授 (上海科技大学)
报告题目：Environmental Scanning Electron Microscopy (ESEM) is leveraged to elucidate the underlying mechanisms governing gas-solid interface interactions
时 间：2024年3月25日（周一）下午15:30
地 点：科研楼三层阶梯教室
邀请人：裘晓辉 研究员
报告人简介：
王竹君于2016年12月于马普学会弗利茨·哈伯研究所获理学博士学位。博士期间主要从事扫描电子显微镜在近常压气氛下对于低维纳米材料的原位成像方法开发工作。针对在极端条件下（高温、近常压小分子与腐蚀性气氛）样品表面原子级敏感实空间实时成像这一难题，致力于设计开发新型电子显微镜物镜差分光阑与极化电子探测器。通过自主改装的原位电子显微镜，国际上首次在真实化学气相沉积条件下观测到液态铜表面上的单原子层石墨烯/六方硼氮的生长行为并揭示其机理，发展了独具特色的原位实空间观测系统。目前该观测手段仍然保持着对表层面内（in-plane）原子层敏感度实空间成像的最高温度记录。于2017年1月在马普学会弗利茨·哈伯研究所开始博士后阶段工作。期间工作重心为设计发展适用于气-固催化界面的近常压气氛实空间成像方法并探索催化剂工况下动态行为与机理。针对如何获得工况下单层气体分子吸附在催化剂表面衬度信息的难题，提出了在极化探测器上加装电子能量过滤器的设计策略，获得了单层二氧化氮气体分子吸附在铂表面的二次电子衬度信号。在此基础上系统深入研究了近常压气氛下气-固催化界面非线性振荡行为，并成功地获得了催化界面处非平衡态下的反应速率与时空斑（spatiotemporal patterns）行为之间的构效关系。该研究成果在国际上首次证明了电子束扫描成像方案具有在近常压气氛下对表面原子级敏感度的识别，为表面科学与材料科学领域的仪器开发奠定了理论与应用基础。于2018年7月博士后出站，并于同年8月就任苏黎世联邦理工学院显微镜中心senior scientist职位。期间利用仿生学的“多目视场角三维形貌重构理论”开创性的发展了多重三维空间视场的拼接极化探测器，实现了对工况下金属催化剂表面真实三维形貌信息的实时追踪方案，并成功的将该技术应用于高温单晶合金晶畴定向生长领域中。该研究成果已临近产业化，将为全新的低维材料与异质催化的研究奠定理论和应用基础。2020年10月加入上海科技大学物质学院，从事新一代原位在线表面敏感扫描电子显微镜的研制。截至目前，以第一作者或通讯作者发在Nature、Nature Materials、Nature Catalysis、Nature Communications、PRL、Nano letters、ACS Nano等期刊。2020获得欧洲电子显微镜学会（European Microscopy Society）杰出论文奖（Outstanding Paper Award）， 发明的表面敏感成像技术 “Surface Sensitive Imaging”目前正在被美国Thermofisher公司在位于捷克Brno厂区商业化并应用于下一代电子显微镜。
报告摘要：
In order to fully comprehend the behavior of functional materials under real operational states, tracking their non-equilibrium state in situ is essential. Electron microscopy offers a window into atomic movements and chemical dynamics from an electron microscopical perspective. However, in-situ Transmission Electron Microscopy (TEM) is often limited by the field of view and stringent transmission requirements of the electron beam, imposing strict constraints on the sample's morphology and preparation. Moreover, the detailed atomic dynamics can only be captured when the system's temporal resolution aligns with the atomic-scale processes. During gas-solid interface interactions, it's common to reduce the chemical potential to decelerate the dynamics for in-situ TEM observation, which has led to an overemphasis on spatial resolution at the cost of neglecting the versatile Environmental Scanning Electron Microscopy (ESEM) approach that allows meso to nanoscale real-time observations.
In-situ ESEM complements the localized information obtained through TEM by revealing the multiscale behavior of atomic clusters. Compared to TEM, ESEM is less restrictive in terms of sample size and morphology. This opens possibilities to bridge the gap between simplified models and complex real-world systems. Additionally, ESEM's capability to track cluster dynamics enables real-time observation of non-equilibrium processes under higher chemical potentials, thus closing the"pressure gap"in situ observation. Using lower electron radiation dose rates and energies in ESEM minimizes electron beam-induced artifacts commonly encountered in TEM. Hence, in-situ ESEM allows for rapid, efficient high-throughput screening of experimental parameters, facilitating more effective use of in-situ TEM facilities.
In summary, employing in-situ ESEM provides essential insights into the intrinsic correlations between catalyst structure and function in the interactions between gas phases and metal catalysts. In this presentation I will showcase the dynamic changes of metal catalysts under redox conditions and the spatiotemporal patterning induced by interfacial non-equilibrium oscillations. It will also detail the chemical vapor deposition of two-dimensional materials on metal surfaces under high-temperature gas atmospheres.
