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O: Fachverband Oberflächenphysik
O 120: Focus Session: Nonequilibrium Electron Transfer Across Interfaces in Real Time
O 120.5: Vortrag
Freitag, 20. März 2020, 12:00–12:15, TRE Ma
Charge transfer and the hydrogen evolution reaction on Pt: bridging timescales from femto- to milliseconds by ultrafast electrochemical and optical measurements — •Gregor Zwaschka1, Yujin Tong1,2, Martin Wolf1, and Kramer Campen1,2 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin — 2Universität Duisburg-Essen, Fakultät für Physik, Lotharstr. 1, 47057 Duisburg
Despite decades of study, the mechanism of the hydrogen evolution reaction (HER) on the best available catalyst, Pt, remains controversial. At least in part, understanding is complicated by the necessity to describe processes with timescales ranging from femtoseconds (interfacial charge transfer) to milliseconds (mass transport). We approach this problem by performing perturbation experiments with ultrashort laser pulses that drive the HER close to its reversible potential and induce charge transfer along the Pt-H bond in the underpotential deposition region. We disentangle the involved timescales by performing both i) time averaged electrochemical measurements under femtosecond laser irradiation and ii) time resolved sum frequency generation spectroscopy (SFS) of Pt-H after laser excitation. Ultrafast charge transfer is found to be a function of interfacial structure (electrode and electrolyte). Trends on single crystals and a microelectrode correlate with HER activity and allow insight into the reactions rate determining step. SFS provides information on Pt-H as a function of potential, electrolyte composition and temporal evolution during and after ultrafast charge transfer. Implications for the HER are discussed.