Investigation of the photocatalytic potential enhancement of silica monolith decorated tin oxide nanoparticles through experimental and theoretical studies

Abstract

Photodegradation of organic pollutants is considered to be the most suitable and cheaper technique to counter decontamination issues. Metal nanoparticles are considered the most effective heterogeneous photocatalysts for photodegradation of organic pollutants, but neat nanoparticles agglomerate in the reaction medium and display less photocatalytic efficiency. Herein, silica monolith particles (SiO₂) were synthesized and utilized as a support medium for the synthesis of SnO₂ nanoparticles to retard their agglomeration. Silica-supported tin oxide nanoparticles (SnO₂/SiO₂ NPs) and neat tin oxide nanoparticles (SnO₂ NPs) were prepared through chemical reduction method and characterized by AFM, SEM, TEM, EDX and mapping, XRD, FTIR and zeta sizer. Morphological and mapping analyses revealed that SiO₂ increases the surface area of SnO₂ NPs and magnificently enhances their photocatalytic activity. The neat SnO₂ NPs are highly agglomerated and hence show less photocatalytic activity. XRD and FTIR analyses confirm the synthesis of SnO₂ NPs. The neat SnO₂ NPs have a PDI of 0.51, which reveal much variation in the particles’ size and have a surface charge of −11.2 ± 0.87 mV, which is not enough for the NPs’ repulsion in suspended form and hence are agglomerated. The SnO₂/SiO₂ NPs degraded about 94.58% and 93.73% orange II (O II) dye while SnO₂ NPs degraded 65.93% and 46.11% dye within 30 min irradiation under UV and visible light respectively. The enhanced photocatalytic activity of SnO₂/SiO₂ NPs is due to the synergistic effect of rapid adsorption followed by drastic photodegradation of dye. The SnO₂/SiO₂ NPs are much more sustainable than SnO₂ NPs due to easy recycling and washing and the recovered SnO₂/SiO₂ NPs degraded about 83.38% of dye while SnO₂ degraded 21.91% within 30 min. In addition, the density functional theory (DFT) calculations show that the SnO₂/SiO₂ NPs have greater adsorption capacity then pristine SiO₂ and SnO₂ surfaces, having shorter binding distances, a larger E_ads value (4.29 eV) and a larger reduction in band gap.