SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 94: Poster Session VII: Poster to Mini-Symposium: Electrified solid-liquid interfaces II

O 94.8: Poster

Donnerstag, 4. März 2021, 10:30–12:30, P

Doping of Free-standing Graphene Measured with Kelvin Probe Force Microscopy under Electrochemical Reaction Conditions — •Salma Khatun, Sidney Cohen, Irit Goldian, and Baran Eren — Weizmann Institute of Science, Rehovot, Israel

Solid-liquid interfaces play a central role in electrochemistry, electrolysis, and catalysis. The electrical double layer (EDL) which forms at the solid-electrolyte interface, plays a key role in moderating these processes. Due to the difficulty in probing this thin layer, very few experimental mechanistic studies under realistic reaction conditions have been reported. We know, free-standing single layer graphene (SLG) is transparent to both electrons and photons. When used as the solid interface in an electrochemical environment, a variety of microscopic and surface-sensitive spectroscopic techniques can be used to probe that interface from the upper side. Our study examines some of the fundamental issues in such a set-up. We have built an electrochemical micro-reactor cell enclosed by a SLG membrane. The double layer thickness is varied controllably by changing the pH of the aqueous NaOH solution. Since our SLG is not doped via any support or contaminants, the changes occur only due to doping from applied electric field. KPFM measurements are used to monitor the shift of Fermi-energy. Due to cleanliness of our technique, the result can be described fairly well by a model considering the applied electrochemical potential, modified by the capacitative drop in the EDL. Differences between experimental values and those predicted by the model can be explained by electrochemical doping during the evolution of O2 and H2.