Comparative Study on Photocatalytic Degradation of Methylene Blue by Degussa P25 Titania: Pulsed Laser Light Versus Continuous Broad Spectrum Lamp Irradiation

While most technologists use lamp light for the evaluation of catalysts synthesized for photocatalytic processes, some researchers prefer laser light. To conform in judgement, a comparative study of photocatalytically degrading methylene blue is reported, using a model catalyst Degussa P25, under different energies of 355 nm pulsed laser and under lamp (visible light and broader lamp light) irradiations. The used amounts of Degussa P25 after each batch of experiments were characterized by X-ray diffractometry, BET surface area analysis, field emission scanning electron microscopy, energy dispersive X-ray spectrometry and diffuse reflectance spectroscopy. The spectral photocatalytic degradation efficiencies, between broad lamp light and UV pulsed laser light, were comparable. Larger and spherical nanoparticles formation and reduction of BET surface area were noticed under pulsed UV laser beam irradiation of Degussa P25, while such trends were not observed under lamp irradiation for similar incident light intensities. The carbon contents on the surface, even after calcination of used samples at 500∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$500\, ^{\circ }$$\end{document}C, and the red shift in absorption spectra, were recorded in Degussa P25 used samples for both pulsed UV laser and lamp photocatalysis. Moreover, no change in the phases of Degussa P25 resulted under either types of irradiations during photocatalysis evaluation.