(21d) Derivative Peak Fitting of Differential Diffuse Reflectance for Compositional Analysis of Multiphase Semiconductor, P25 TiO2

The ability to characterize changes in polymorph composition and analyze the compositional of variations of multi-phase semiconductors thoroughly and quickly is important to catalyst manufacturers and users alike. Diffuse-reflectance UV-Visible spectroscopy derivative peak fitting (DPR) is a technique that can measure both concentration of a multi-phase semiconductor as well as the band gap energies of each semiconductor in the material. Degussa P25 TiO₂ is a widely-used semiconductor catalyst in both industry and academia. As-received P25 samples were subjected to grinding, sieving, and calcination treatment, and a combination of these operations. As-received and as-prepared samples were analyzed via DPR, X-ray Diffraction (XRD), and Raman Spectroscopy to quantify the percentage of anatase and rutile polymorphs present in the sample. Compositional measurements from DPR were consistent with XRD and Raman analysis. The effect of treatment conditions on the phase composition of P25 was measured. The onset of rutilization upon calcination of as-received P25 was 873 K. However, grinding and sieving (between 53 μm and 45 μm) P25 lowered the onset of rutilization during calcination, and had a three-fold increase in rutilization when calcined at 773 K as compared to as-received P25, as determined via in situ diffuse-reflectance UV-visible spectroscopy during calcination.