|Abstract: ||本研究以電化學阻抗譜(Electrochemical Impedance Spectroscopy)分析光化學於光反應與暗反應之行為，藉由擬合(fitting)以及電路圖了解光電化學反應系統，|
;In this study, we analyzed the photochemical behavior of light and dark reaction on Electrochemical Impedance Spectroscopy, by fitting (fitting) and circuit diagram to understand photoelectric chemical reaction system.
The mott-schottky equation was used to understand the parameters of photoanode.The materials are mainly CIS, CZIS series and BiVO4, which are divided into two electrochemical mechanisms: dark reaction and light reaction. Randles cirsuit equivalent circuit model is used for dark reaction.
For the light reaction, an equivalent circuit model dominated by surface state transfer charge is selected after the comparison of fitting.
Mott-schottky plot was plotted by using Mott-schottky equation to calculate slope and intercept, and then the horizontal band potential and carrier concentration of the experimental materials were obtained, and the values were cross-confirmed by hall measurement.
By Observing equivalent circuit element of light and dark reation, Rct,trap (surface charge transfer impedance interface) value has fallen dramatically which compared with dark reaction.
Confirmed that the recombination rate of electrons and holes is very low under illumination. The trop of Rct reflects the holes are more likely to be in contact with the electrolyte, and transfers charge, then produces oxygen.
The curve of charge transfer impedance and surface state capacitance change, combined with the flat band potential of mott-schottky plot, indicated that when the bias voltage was near the flat band potential, the surface state had a large amount of charge accumulation and the capacitance reached the maximum value, the charge was not easy to be transferred from the electric field, and the surface state charge transfer impedance also reached the highest level.
However, when the bias voltage is increased, the hole is easier to reach the electrolyte and combine with the anions on the interface to produce oxygen, so the charge accumulation situation decreases, and the surface state capacitance and charge transfer impedance also decrease correspondingly.