In Situ Studies of Surface Electric Field on Cobalt Oxide Electrode Surfaces with Second Harmonic Generation (SHG)
Cobalt compounds are proven to be efficient electrochemical (EC) catalysts, and the surface electric field may partly explain the efficiency. Surface electric field indicates electron/hole separation, and accumulation in the space charge layer, which can be probed in situ by electric field-induced second harmonic generation (EFISH). However, the EFISH technique remains underdeveloped for catalyst systems beyond TiO₂. This work focuses on the development of the EFISH method for detecting the surface electric field of Co-based electrocatalyst thin films. An optical electrochemistry cell, and an SHG setup were built, and EFISH response on Co/Co (hydr)oxide/solution sample was collected, with different EC methods applied simultaneously. Electrochemical impedance measurement (EIS), in situ Raman, and chronoamperometry were also applied to the sample, for the explanation of electrochemical and physical properties. This work provides new methods for calculating the surface electric field, and proposes new assumptions for EFISH signal generation, both of which contribute to the further development of EFISH theory.
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