SnO2 foam grain-shaped nanoparticles: Synthesis, characterization and UVA light induced photocatalysis

• SnO2 NPs photocatalysts were synthesized using a facile sol–gel route.
• As-prepared SnO2 NPs were characterized by XRD, SEM and UV–vis-DRS techniques.
• Noticeably UVA-light photodegradation of Congo red (CR) dye by SnO2 NPs.
• The hydroxyl radical was the primary oxidant in SnO2 NPs photocatalysis.

Cassiterite (tin oxide; SnO2) nanoparticles (NPs), has been successfully synthesized via a sol-gel method. The obtained compounds are subsequently calcined at 80, 450 and 650 °C for 4 h and are assigned as SnO2-80, SnO2-450 NPs and SnO2-650 NPs, respectively. All prepared samples were characterized using thermogravimetric analysis coupled with mass spectroscopy (TG-SM), X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The XRD results confirmed the aggregated cassiterite SnO2 nanoparticles (NPs) with a size ranging from 13 to 23 nm. The absorption edge of the SnO2 NPs samples calcined at higher temperatures showed 25 nm (SnO2-450 NPs) and 10 nm (SnO2-650 NPs) red shifted compared with that of commercial SnO2-com NPs sample. The photodegradation efficiency of SnO2 NPs was investigated using Congo red (CR) dye, as model organic pollutant. The effect of environmental factors (e.g., reaction time and calcination temperature) on the photocatalysis process of CR on SnO2 NPs was investigated in photocatalysis process under UVA light irradiation. We found that the SnO2-650 NPs with 23 nm particle size and about 3.49 eV band gap was higher than that of the SnO2-450 as well as the commercial SnO2-com NPs. Pseudo-first-order kinetic model gave the best fit, with highest correlation coefficients (R2 ≥ 0.95). On the basis of the energy band diagram positions, the enhanced photodegradation efficiency SnO2 NPs catalyst could be proceeded via direct reactions with (O2- and OH), as active oxidative species involved in the photocatalysis process of CR dye under UVA-light irradiation.

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