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DTSTART;TZID=America/Los_Angeles:20231106T160000
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DTSTAMP:20260614T120048
CREATED:20230816T015405Z
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UID:30833-1699286400-1699290000@www.chemistry.ucla.edu
SUMMARY:Physical Chemistry Seminar 228: Franz Geiger
DESCRIPTION:Geiger Flyer \nTitle: Photonic Electrochemistry \nAbstract: 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 𝒩water↓\, the Stern layer water molecules pointing their oxygen atoms towards the electrode\, and Ftot\, the total interfacial potential. 𝒩water↓ 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 𝒩water↓ and Eflip. Our experiments provide new benchmarks for electrical double layer models and a diagnostic tool for molecular electrochemistry.
URL:https://www.chemistry.ucla.edu/events/physical-chemistry-seminar-228-franz-geiger/
LOCATION:Mani L. Bhaumik Centennial Collaboratory\, 607 Charles E. Young Dr.\, East\, Los Angeles\, CA\, 90095\, United States
CATEGORIES:Physical Chemistry Seminar
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