Techniques to Characterize the Photoactivity of Semiconductor Materials Defining Performance in Advanced Oxidation Processes and Fuel Generation

Semiconductor materials have received a renowned interest in materials science resulting from the emergence of photocatalysis. These phases possess exclusive capacity to separate the electron and hole charge carriers during a light absorption stage, which relies upon the occurrence of numerous processes involving adsorption of species, photon absorption, photoejection, charge separation, and charge transfer reactions occurring at various interfaces. Overall, this determines the photoactivity of a catalyst whence it constitutes a great challenge. Additionally, most oxidative photocatalytic reactions have been developed using powders or particles in suspension of the reaction medium, which complicates the characterization of the direct activity of the materials. Under this idea, this study critically reviews spectroscopic techniques (e.g. Raman, X-ray photoelectron spectroscopy, UV–Vis spectroscopy, Fourier-transform infrared spectroscopy, Electron paramagnetic resonance), electrochemical techniques (voltammetry, chronoamperometry, chronopotentiometry, electrochemical impedance spectroscopy, Mott-Schottky), among others, and their constitutive equations to characterize the photoactivity of semiconductor materials concerning oxidation reactions (i.e. hole involvement). Likewise, the impregnation and deposition methods for powders and particles are revisited to conduct some of the aforementioned physicochemical characterizations.