Morphological Characterization of Selected Natural and Calcined TiO2 Photocatalysts Using SEM, XRD and BET

Abstract

The present work characterized commercial TiO2 powder photo-catalysts (P25, AV01, S7001, PC100 & PC500) using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Brauner, Emmer and Teller (BET) techniques to determine crystalline size(nm), particle size(nm) and specific surface area(m2/g) of natural and calcined TiO2 catalyst particles. TiO2 particulate layers were prepared by deposition from aqueous TiO2suspensions c=10g.L-1 on degreased microscopic glass of dimensions 75mm í— 25mm calcined at 300°C for 2hrs. The calcined layers were scanned to obtain cross-sectional images and reveal particle size and catalyst morphology. The results indicate a crystalline/surface area ratio as follows; [(P25=28nm/50m2/g); (AV01=169nm/10m2/g); (S7001=9nm/250m2/g) ;(PC100=198nm/79.5m2/g) ;(PC500=173.6nm/91.3m2/g)]. Particle size of AV01 powder catalyst (100-150 nm) was larger compared to the other catalysts., catalyst P25, PC100, PC500 and S7001 appear to have almost similar particle sizes of between (50-100 nm). Comparing the observed particle sizes using the SEM technique with those calculated using XRD, it can be concluded that these values are very similar. X-Ray Diffraction patterns indicated that the crystalline structure AV01, S7001, PC100 and PC500 comprises of pure anatase phase. Catalyst P25 catalyst powder consisted of a crystal structure 74% anatase and 26% rutile content. Crystalline sizes were calculated by Scherer formula using a special programme Analytical X`pert.PRO + high score plus. It can be concluded that smaller crystalline size favours increased surface areas. An optimum balance between surface area and crystallinity is desirable to obtain maximum semi-conductor properties since the predominant electron/hole recombination depends on relative particle size/surface area ratios.