Changes in Polymorph Composition in P25-TiO2 during Pretreatment Analyzed by Differential Diffuse Reflectance Spectral Analysis

Elucidating structural and compositional polymorph changes of multiphase semiconductors in a quick and quantitative manner is important for their manufacturing and applications in catalysis alike. Derivative peak fitting of diffuse reflectance UV–visible spectra (DPR) is presented as an inexpensive, fast, and quantitative method to estimate both the composition of a multiphase semiconductor sample as well as the band gap energies of each component semiconductor in the mixture. Degussa P25 TiO2, a widely used catalyst support and semiconductor photocatalyst, is a mixture of anatase and rutile polymorphs. The as-received P25 samples were subjected to grinding, sieving, and calcination or a combination of these operations. Samples were analyzed via DPR, X-ray diffraction (XRD), and Raman spectroscopy to quantify the percentage of anatase and rutile polymorphs present in each sample. Compositional measurements from DPR were in good quantitative agreement with XRD and Raman analysis. The application of in situ...