Understanding the behavior of functional materials under realistic operational conditions requires in situ tracking of their non-equilibrium states. Electron microscopy provides valuable insights into atomic movements and chemical dynamics from a microscale perspective. However, in-situ Transmission Electron Microscopy (TEM), despite its atomic-scale resolution, is constrained by limited fields of view, stringent sample preparation requirements, and the need for electron transparency. Additionally, TEM observations often require reducing the system’s chemical potential to decelerate dynamic processes, which can result in an overemphasis on spatial resolution while neglecting essential mesoscale behaviors.
To address these limitations, we employ a modified surface-sensitive SEM equipped with advanced electron optical hardware to enable surface-specific imaging. By introducing a focusing-deflection electron optics system and integrating energy-filtering techniques, our modified SEM achieves heightened sensitivity to surface structures and processes. These enhancements allow for real-time imaging of surface dynamics at the nanoscale under near-ambient pressure and elevated temperature conditions, bridging the "pressure gap" for gas-solid interactions. Compared to conventional SEM and TEM, this approach minimizes electron beam-induced artifacts, allowing for direct, non-destructive observation of complex surfaces and interfaces.
The surface-sensitive SEM complements the localized atomic-scale information obtained via TEM by enabling the study of multiscale behaviors of clusters and materials under higher chemical potentials. This capability facilitates the direct observation of dynamic processes, such as gas-solid reactions, redox transformations, and interfacial phenomena, on realistic catalysts and functional surfaces. The approach also offers rapid, high-throughput screening of experimental parameters, providing an efficient pathway to link atomic-scale mechanisms with macroscopic material behavior.
In summary, surface-sensitive SEM opens new avenues for studying the intrinsic relationships between catalyst structure and function during interactions with gas phases. In this presentation, we demonstrate its application in capturing the dynamic changes of metal catalysts under redox conditions, the spatiotemporal patterning induced by non-equilibrium oscillations, and the chemical vapor deposition of two-dimensional materials on metal surfaces under high-temperature gas atmospheres.