121st General Meeting of the KCS

Type Symposium
Area Advanced Electrochemical Analysis
Room No. Room 202A
Time FRI 10:40-:
Code ELEC2-5
Subject Short Diffusion Length in Semiconductor Electrode and Fourier-transform Electrochemical Impedance Spectroscopy
Authors TAEK DONG CHUNG
Department of Chemistry, Seoul National University, Korea
Abstract Semiconductor materials convert the photons into the electron-hole pairs, which drive an electrochemical reaction in the solution. If the diffusion length of the semiconductor is short enough, the photoelectrochemical reaction occurs exclusively at the spot where the light is illuminated. This unique characteristic of the semiconductor enables us to introduce a variable electrode on the semiconductor anywhere we want simply by manipulating the features of the light; size, position and shape. We introduce some applications based on this new electrochemistry including mask-free patterning of Ni-Mo, hydrogen evolution reaction catalyst, on a-Si using a digital micromirror device. Such electrolytic behavior comes from the characteristic interface between the semiconductor electrode and aqueous electrolyte, which can be represented by its equivalent circuit determined by conventional electrochemical impedance spectroscopy (EIS). The components in the equivalent circuit provide clues to find out what causes the electrochemistry in the given system, while the continuous EIS cannot allow us to see its time-dependent transition. Fourier-transform electrochemical impedance spectroscopy (FT-EIS) employing a small step function for perturbation has been one of the powerful techniques for real-time impedance analysis of transient electrochemical systems. However, its application to low current (~ nA) condition such as at ultramicroelectrodes(UME) has been hindered due to insufficient signal gain of current conversion. In this talk, we discuss low current FT-EIS equipped with handmade high-speed potentiostat circuit with high voltage gain and potential application for photoelectrochemical system analysis.
E-mail tdchung@snu.ac.kr