Lifting the Fog: Graphene Gas Cell for <i>In Situ</i> (Scanning) Transmission Electron Microscopy with Robust Single-Atom Sensitivity

Capturing the dynamic behavior of heterogeneous catalysts under realistic reaction environments is essential for understanding their structure-property relationships and advancing catalyst design. Although conventional silicon nitride-based gas cells allow atomic-resolution imaging at ambient pressure, the 30-50 nm windows on each side make images appear "foggy", hindering reliable detection of single-atom species and complicating chemical analysis. Here, we present a graphene-based gas cell by integrating mechanically exfoliated multilayer graphene (<i>e.g.</i>, 1-3 nm) onto micropatterned MEMS chips, offering greatly reduced adverse diffuse-scattering background together with excellent gas tightness, which could maintain gas tightness at at least 101.3 kPa (1 atm) pressure and operational stability at temperature as high as 800 °C. This graphene gas cell effectively "lifts the fog" for <i>in situ</i> electron microscopy at high gas pressure, demonstrating robust single-atom sensitivity with both high (<i>e.g.</i>, 200 keV) and low (<i>e.g.</i>, 80 keV) energy electrons. It also enabled significantly improved signal-to-background ratios in electron energy loss spectroscopy (EELS) analysis under a gaseous environment. This ultrathin, robust graphene gas cell architecture opens opportunities for better probing of gas-solid interactions with robust single-atom sensitivity and atomic resolution.