In Situ Characterization of Bipolar Electrodes by using Vibrational Stark Spectroscopy and Surface‐Enhanced Raman Spectroelectrochemistry. Issue 3 (30th September 2015) - Sanghapi, Axline
Abstract: We report on the use of Raman spectroscopy to interrogate the electrical double layer near Au bipolar electrodes. Well‐characterized adsorbed molecules are used as local spectroscopic probes that report on the state of the electrode–electrolyte interface. We discuss two applications of in situ Raman scattering to characterize the electrode–electrolyte interface in bipolar electrochemical systems: vibrational Stark spectroscopy and surface‐enhanced Raman (SER) spectroelectrochemistry. From Stark spectroscopy on CN − /Au, we estimate an upper limit of about 7 MV cm −1 for the electric field at the cathodic pole of an Au bipolar electrode (BPE), consistent with measurements on unipolar electrodes. Through the SER spectroelectrochemistry of an adsorbed redox‐active molecule [2‐(ethylthio)‐9, 10‐dihydroxyanthracene], we were able to directly measure the linear variation of the interfacial potential along the principle axis of an Au BPE near the cathodic pole. Abstract : Yes, SER ! Surface‐enhanced Raman (SER) microscopy is employed to determine the distance dependence of the interfacial potential difference along the principle axis of a bipolar electrode, using 2‐(ethylthio)‐9, 10‐dihydroxyanthracene (2‐H2 A) as the Raman probe. The SER spectrum provides information about the ratio of the surface concentrations of the oxidized and reduced forms of 2‐H2 A, and thus reports on the local interfacial potential difference.