Radiation damage of liquid electrolyte during focused X-ray beam photoelectron spectroscopy

Abstract

Ambient pressure X-ray photoelectron spectroscopy (APXPS) has evolved into an effective tool to analyze the chemical states of interfaces relevant to realistic environments and operating conditions. Herein we employ a graphene-capped microvolume arrays sample platform for scanning photoelectron spectro-microscopy (SPEM) of electrified liquid-solid electrochemical interfaces. By using highly electron and X-ray transparent graphene membrane as a working electrode, we probed the electronic structure of a model electrochemical system under operando conditions within the first few nanometers of the electrode/liquid electrolyte interface. We report the conditions when highly focused X-ray irradiation affects the chemistry at the liquid–solid interface due to solvent radiolysis by primary radiation, photoelectrons as well as secondary electrons. We recorded radiolytic products by photoemission spectroscopy and characterized their impact on the chemical speciation at the electrified solid-liquid interface. Three different exposure regimes were tested to elucidate the onset and dependence of XPS radiolytic signatures of the dose rate. The observed effects highlight the need for careful consideration of radiolytic processes for artifact-free liquid phase XPS measurements and data interpretation.