Prediction of band edge potentials and reaction products in photocatalytic copper and iron sulfides

The prediction of band edge potentials in photocatalytic materials is an important but challenging task. In contrast, bandgaps can be easily determined through absorption spectra. Here, we present two simple theoretical approaches for the determination of band edge potentials which are based on the electron negativity and work function of each constituent atom. We use these approaches to determine band edge potentials in semiconducting metallic oxides and sulfides, such as titanium dioxide (TiO₂), chalcopyrite (CuFeS₂), pyrite (FeS₂), covellite (CuS), and chalcocite (Cu₂S) with respect to an absolute scale (eV) and an electrochemical scale (V). Until now, there is little information on iron and copper sulfides referring to these thermodynamic parameters. TiO₂ (Titania p25) was used as reference semiconductor to validate the calculation procedures using experimental values by X-ray diffraction analysis (XRD), diffuse reflectance spectrometry (DRS), and electron paramagnetic resonance spectroscopy (EPR). The production of key chemical species such as reactive oxygen species (ROS) and reactive sulfur species (RSS) has been theoretically and experimentally determined by EPR.