Panta Rhei - tuning silver nanostructure evolution with flow and radiolysis in liquid phase STEM

Liquid phase (scanning) transmission electron microscopy (LP-(S)TEM) enables exploring processes down to the nanoscale. This allows to unravel degradation pathways of electrocatalysts, such as silver nanostructures, which gained attention for CO 2 upconversion. However, the nanoscale resolution in LP-TEM comes at the cost of introducing new effects such as radiolysis, and with the emergence of liquid cell systems with active mass transport, the impact of advection must be considered when evaluating the radiolytic on-site chemistry. We provide proof of a chemical environment control depending on systematically varied liquid flow velocity and dwell time at a constant dose rate. Using AgNO 3 as a probe solution, our findings show a clear dependence of nanosilver evolution on these parameters, ranging from fast growth to dissolution. This implies a change between reductive and oxidative conditions, achieved by independently adjusting volumetric flow rate or dwell time. Kinetic modeling further supports the underlying radiation chemistry. Our results illustrate that a precise understanding of flow-mediated radiation chemistry is crucial in LP-TEM and paves the way for performing controlled operando studies into materials degradation without the electron probe being the driving force. • LP-STEM drives reversible nanosilver growth and etching in an AgNO 3 solution. • Flow and dwell time alone can control beam-induced Ag nanostructure evolution. • Parameter tuning allows precise redox control at a constant dose rate. • Flow and dwell time govern the build-up of secondary radiolysis products. • Experimental trends are verified by kinetic modeling.