In this paper, we discuss the importance of distinguishing the contributions of photolysis, adsorption, sensitization, degradation and mineralization processes to the photocatalytic activity of a visible-light active semiconductor: Bi₂O₃. Based on this case study, we propose a follow-up work plan to obtain the relevant information and achieve proper interpretation of reported data to adequately infer the photocatalytic activity of the Bi₂O₃ material. To do so, we compared the changes in the theoretical and experimental absorbance spectra of three different dyes during the photodegradation process: rhodamine-B (RhB), acid blue 113 (AB) and indigo carmine (IC). Photocatalytic degradation of these dyes using the same semiconductor material (Bi₂O₃) was performed using the standard spectrocolorimetric method while taking care to appropriately consider the competing processes mentioned above. Furthermore, the degree of mineralization achieved due to the photocatalytic degradation of the dyes was obtained using the total organic carbon (TOC) analysis. The commonly used evaluation of the results suggests that a certain degree of photodegradation and mineralization was achieved. However, careful analysis indicates that this was mainly due to a decrease in the relative concentration of the dye molecules in the solution because of their adsorption on the surface of the semiconductor and not to complete degradation.

TiO₂ nanoparticles containing 0.0, 1.0, 5.0, and 10.0 wt.% Mo were prepared by a reverse micelle template assisted sol–gel method allowing the dispersion of Mo atoms in the TiO₂ matrix. Their textural and surface properties were characterized by means of X-ray powder diffraction, micro-Raman spectroscopy, N₂ adsorption/desorption isotherms at −196 °C, energy dispersive X-ray analysis coupled to field emission scanning electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV–Vis spectroscopy, and ζ-potential measurement. The photocatalytic degradation of Rhodamine B (under visible light and low irradiance) in water was used as a test reaction as well. The ensemble of the obtained experimental results was analyzed in order to discover the actual state of Mo in the final materials, showing the occurrence of both bulk doping and Mo surface species, with progressive segregation of MoO_x species occurring only at a higher Mo content.

Bi ₂ O ₃ /nylon multilayered nanocomposite membrane was fabricated by electrospinning and effectively used to degrade organic dye pollutants and pathogens through ROS produced by photocatalysis.