D.B. Hernández-Uresti

Regular ArticleDirect evidence of the photocatalytic generation of reactive oxygen species (ROS) in a Bi2W2O9 layered-structure

In the present work, the Bi2W2O9 photocatalyst has been prepared by an easy and prompt co-precipitation route. From the structural characterization, we have stated that the formation of the Bi2W2O9 is accompanied by a small amount of the Bi2WO6 oxide, which gradually decreases by increasing the calcination temperature. The conduction and valence band edges of the Bi2W2O9 semiconductor were experimentally estimated for the first time using the X-ray photoelectron (XPS) and diffuse reflectance (DRS) spectroscopies. The best photocatalytic performance was attained for the sample calcined at 700°C, which showed the highest production of hydroxyl radicals, superoxide ions as well as the highest photodegradation of the ciprofloxacin drug. In addition, by means of photoluminescence spectroscopy we propose that the effective separation of the photogenerated charge carriers in the sample calcined at 700°C produces a higher production of reactive oxygen species and thus a higher photoactivity under solar-like irradiation conditions.

Direct evidence of the photocatalytic generation of reactive oxygen species (ROS) in a Bi2W2O9 layered-structure

In the present work, the Bi2W2O9 photocatalyst has been prepared by an easy and prompt co-precipitation route. From the structural characterization, we have stated that the formation of the Bi2W2O9 is accompanied by a small amount of the Bi2WO6 oxide, which gradually decreases by increasing the calcination temperature. The conduction and valence band edges of the Bi2W2O9 semiconductor were experimentally estimated for the first time using the X-ray photoelectron (XPS) and diffuse reflectance (DRS) spectroscopies. The best photocatalytic performance was attained for the sample calcined at 700°C, which showed the highest production of hydroxyl radicals, superoxide ions as well as the highest photodegradation of the ciprofloxacin drug. In addition, by means of photoluminescence spectroscopy we propose that the effective separation of the photogenerated charge carriers in the sample calcined at 700°C produces a higher production of reactive oxygen species and thus a higher photoactivity under solar-like irradiation conditions.

Photocatalytic Degradation of RhB with Microwave Prepared PbMoO4

Abstract Synthesized PbMoO4 from H2MoO4 and Pb(NO3)2 with microwaves was compared, in terms of its photocatalytic activity as catalyzer for decomposing rhodamine B (RhB), against samples prepared by hydrothermal and sonochemical methods from the same precursors. Microwave synthesis lasted 20 minutes; hydrothermal, 10 minutes and sonochemical method, 1 hour. X-rays diffraction patterns show that PbMoO4 prepared by these three routes is compounded by the same phase. It is found that microwave synthesized PbMoO4 particles are rounder, in an intermediate size (250 nm), compared to sonochemical (100 nm) and hydrothermal (500 nm) routes; microwave particles also exhibit higher photocatalytic activity for degradation of RhB under a xenon lamp. This difference is not explicable in terms of surface area measurements, but could be explained by UV light scattering by the rounder particles produced by means of the microwave processing, which are about one half size compared to the wavelength.