Improved photocatalytic activity of d-FeOOH by using H2O2 as an electron acceptor.

Abstract

In this work, d-FeOOH nanoparticles were synthesized by a simple co-precipitation method and used as a photocatalyst in the presence of H2O2 for the oxidation of Rhodamine B (RhB) dye under artificial light. The d-FeOOH was characterized by powder X-ray diffraction, 57Fe Mössbauer spectroscopy, N2 adsorption/desorption and UV–vis diffuse reflectance measurements. The d-FeOOH nanoparticles have high specific surface area (101 m2 g 1) and optical bandgap energy of 2.02 eV. Under artificial light, only 59% of RhB (100 mL; 20 mg L 1) was photocatalytically degraded by d-FeOOH in 60 min reaction. However, after adding H2O2, the photocatalytic activity of d-FeOOH was significantly improved, reaching 87% of dye removal. Tests using scavengers of reactive species and EPR analysis revealed that h+ and OH are the main species in this system. Based on the experimental results, the mechanism of RhB photodegradation in the presence of d-FeOOH and H2O2 was proposed. By this mechanism, the OH can be formed by direct water oxidation or by H2O2 reduction, as the electron transfer from the conduction band of d-FeOOH to H2O2 is thermodynamically favorable. Moreover, the H2O2 retards the electron-hole recombination in d-FeOOH, thus increasing its photocatalytic activity. Given its high efficiency for degrading RhB in water, d-FeOOH revealed to be a promising photocatalyst to be tested in the oxidation of emerging pollutants for the environmental decontamination.