Alternating Current Techniques for a Better Understanding of Photoelectrocatalysts

Several spectroscopic and electroanalytical techniques are in use when it comes to the investigation of interfaces in photoelectrocatalysis (PEC). Among them, AC techniques are the least used ones except for electrochemical impedance analysis despite having several advantages over DC electroanalytical techniques. Though AC electrolysis of water was known in the early years of the 20th century, it was not given significant attention either. In this Perspective, we discuss how these barely used yet powerful AC techniques, namely, (1) Mott–Schottky in impedance and photoelectrochemical impedance analyses (equivalent circuit analysis, capacitance spectroscopy), (2) intensity-modulated photocurrent spectroscopy (IMPS), (3) FS-HA-FT-AC voltammetry, and (4) paired electrolysis, can lead us ahead in the way of further fathoming interfaces in PEC with highlights on prospects of these AC techniques for energy conversion reactions.