| Affiliation: | (1) Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106-7078, USA;(2) Global Science Center, Duracell, Berkshire Corporate Park, Bethel, CT 06801, USA;(3) ICET Inc., 916 Pleasant Street, Unit 12, Norwood, MA 02062, USA;(4) De Amertek Corporation Inc., 300 Windsor Drive, Oak Brook, IL 60523, USA |
| Abstract: | Changes in the state of charge of a high-area RuOx electrode in an operating RuOx|Nafion|IrOx supercapacitor were monitored in situ by time-resolved, transmission Ru K-edge X-ray absorption spectroscopy (XAS). Linear and reversible variations in the intensity of the transmitted X-ray beam as a function of time were found by fixing the energy of the incident X-ray beam, Ei, at judiciously selected values within the Ru K-edge X-ray near edge structure (XANES), while the supercapacitor was charged and discharged at constant current. The sign of the slope of these temporal signals was found to vary, depending on the value of Ei. This behavior could be rationalized based on the spectral differences between the Ru K-edge XANES of RuOx in the fully oxidized and fully reduced states, recorded in situ from films of the material electrodeposited on a gold substrate in the fluorescence mode.This paper is dedicated to Prof. Wolf Vielstich on the occasion of his 80th birthday for his outstanding contributions to electrochemistry |
