Quantifying Aqueous Radiolytic Products in Liquid Phase Electron Microscopy

Liquid phase electron microscopy (LPEM) is rapidly gainingimportancefor in situ studies of chemical processes. However, radiolysis dueto interactions between the liquid medium and the electron beam resultsin the formation of highly reactive species that influence the studiedprocesses. Our understanding of LPEM radiolysis is currently basedon simulations that rely on data collected from measurements at lowelectron flux intensities, requiring extrapolation by several ordersof magnitude to match the intensities utilized in LPEM. We demonstratedirect electrochemical measurements of radiolytic products duringin situ LPEM, which allows us to directly assess the high flux accuracyof low-flux radiolysis models. Using a specially designed liquid cellfor electrochemical detection, we quantify the primary expected stableradiolysis products H-2 and H2O2 ina scanning electron microscope. We find H-2 production israpid and in reasonable agreement with predictions, but H2O2 levels are lower than expected from the low-flux extrapolatedradiolysis models. This study demonstrates a new approach to experimentallyvalidate simulations and indicates that the chemical environment maybe far more reducing than predicted from current models.