Analysis of photoelectrochemical systems by impedance spectroscopy

Abstract

The operation of photovoltaic and photoelectrochemical systems based on semiconductors that absorb visible light involves a variety of electronic processes in the semiconductor that are followed by charge extraction and photoelectrochemical reactions at the solid/liquid interface. In recent years, a wide variety of semiconductor systems have been developed, and an increasingly complex structure of the catalyzed surface, nanostructured morphologies, and tandem configurations are being investigated. Here we describe the application of frequency-modulated impedance spectroscopy to provide mechanistic information about the different kinetic steps, as well as the distribution of energetic features as band bending and flat band potentials. The paper is focused on the interpretation of impedance spectroscopy results that contain key information about the photoelectrochemical performances of semiconductor systems. In particular, we investigate the origin of cathodic shift in water oxidation reaction due to different surface treatments, and we distinguish the effects of variation of recombination and charge transfer kinetics based on the equivalent circuit that can be established from impedance spectroscopy measurements.