A possible formation mechanism and photocatalytic properties of CoFe2O4/PVA-SiO2 nanocomposites

Abstract

The paper presents the synthesis of CoFe2O4 nanocrystallites embedded in PVA-SiO2 hybrid matrix by a modified sol-gel method. The paper is focused on two aspects: (1) formation of cobalt and iron carboxylate-type precursors (oxalate, lactate, malonate and succinate) in the presence of tetraethylorthosilicate, polyvinylalcohol (PVA) and different diols: 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and (2) possible decomposition mechanism of carboxylate-type precursors into CoFe2O4 within the pores of PVA-SiO2 hybrid matrix. The formation and decomposition of carboxylate-type precursors was studied by thermal analysis coupled with mass spectrometry, while the formation of CoFe2O4/PVA-SiO2 nanocomposites (NCs) was investigated by X-ray diffraction and Fourier transformed infrared spectroscopy. The particle size and shape were studied by transmission electron microscopy. At 1000 °C, well-crystallized CoFe2O4 was evidenced as single phase in G1,2ED and G1,4BD and together with Co2SiO4 in G1,2 PD and G1,3 PD. Based on UV–vis absorption spectra, the band gaps of the NCs were evaluated. The photocatalytic activities of the NCs were evaluated by degrading Rhodamine B under UV–vis light irradiation. The reactive radical species produced at the solid-liquid interface were evidenced using electron spin resonance coupled with spin trapping.