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Physical Chemistry Seminar 228: Franz Geiger

Physical Chemistry Seminar

November 6, 2023 4:00 pm - 5:00 pm
Mani L. Bhaumik Centennial Collaboratory
607 Charles E. Young Dr., East
Los Angeles, CA 90095 United States
Speaker Professor Franz Geiger


Geiger Flyer

Title: Photonic Electrochemistry

Abstract: Water’s oxygen is the electron source in the industrially important oxygen evolution reaction, but how water interacts with an electrode remains enigmatic. While much microscopic insight into the Stern layer comes from atomistic simulations or joint theory-experiment approaches, water’s strong absorber problem has clouded our view of how water aligns in response to applied potentials. Here, we employ nonlinear optics with a non-resonant pulse triplet at Ni:NiOx electrodes during cyclic voltammetry at pH 13 to quantify š¯’©waterā†“, the Stern layer water molecules pointing their oxygen atoms towards the electrode, and Ftot, the total interfacial potential. š¯’©waterā†“ varies sigmoidally with applied potential, U, but linearly with Ftot. While there is no net alignment at U=0.4 V, 3/4 of a water monolayer align at U=0.6 V and Eflip, the energy associated with water flipping, matches liquid water’s cohesive energy. At U=0.8 V, all Stern layer water molecules (1 x 10^15 cm^-2) align and Eflip matches the cohesive energy of ice. The current density is exponentially sensitive to š¯’©waterā†“ and Eflip. Our experiments provide new benchmarks for electrical double layer models and a diagnostic tool for molecular electrochemistry.

Professor Franz Geiger

Physical Chemistry Seminar

Ā Department of Chemistry

Northwestern University