Highly efficient and recyclable triple-shelled Ag@Fe3O4@SiO2@TiO2 photocatalysts for degradation of organic pollutants and reduction of hexavalent chromium ions

Abstract

Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2 (P25), pure TiO2 microspheres, Fe3O4@SiO2@TiO2 and annealed Ag@Fe3O4@SiO2@TiO2 nanocomposites, the as-obtained amorphous triple-shelled Ag@Fe3O4@SiO2@TiO2 hierarchical nanospheres exhibit a markedly enhanced visible light or sunlight photocatalytic activity towards the photodegradation of methylene blue and photoreduction of hexavalent chromium ions in wastewater. The outstanding photocatalytic activities of the plasmonic photocatalyst are mainly due to the enhanced light harvesting, reduced transport paths for both mass and charge transport, reduced recombination probability of photogenerated electrons/holes, near field electromagnetic enhancement and efficient scattering from the plasmonic nanostructure, increased surface-to-volume ratio and active sites in three dimensional (3D) hierarchical porous nanostructures, and improved photo/chemical stability. More importantly, the hierarchical nanostructured Ag@Fe3O4@SiO2@TiO2 photocatalysts could be easily collected and separated by applying an external magnetic field and reused at least five times without any appreciable reduction in photocatalytic efficiency. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, make these multifunctional nanostructures promising candidates to remediate aquatic contaminants and meet the demands of future environmental issues.

TiO2 hybrid photocatalytic systems: impact of adsorption and photocatalytic performance

“…The experimental results indicated that the shortening of the duration of the heat treatment not only significantly lowers the extent of the interaction between Fe 3 O 4 core and TiO 2 coatings but also limits the extent of the oxidation of the Fe 3 O 4 core. Therefore, several groups worked on improving the photocatalytic activity of magnetic photocatalysts by depositing TiO 2 /Fe 3 O 4 hybrids with silver, platinum, or nitrogen (Xu et al 2005, Su et al 2014b. Some studies also introduced SiO 2 as an inert substance between TiO 2 procedure via charge separation.…”

Nanostructuring of a GNS-V2O5–TiO2 core–shell photocatalyst for water remediation applications under sun-light irradiation

“…[1][2] The interactions between the core and shell material can drastically improve the overall performance of the core/shell nanostructure system and even create advantageous synergetic effects, which may bring a series of opportunities for their potential applications such as chemical sensors, light-emitting diodes, photocatalysis. [6][7][8] This simple method to fabricate hierarchical core/shell nanoarchitecture is highly desirable now as well as in the near future for energy and environment cleaning applications. It can efficiently generate charge separation and the large aspect ratio can increase the active sites and wide range of light absorption.…”

Polyacrylamide exotemplate-assisted synthesis of hierarchically porous nanostructured TiO2macrobeads for efficient photodegradation of organic dyes and microbes

“…28 In the same way, the direct interaction of chemically reactive Ag with TiO 2 may oxidize Ag into AgO at the TiO 2 -Ag junction. In order to avoid these problems, the iron oxide and Ag cores were coated by the non-toxic and hydrophilic inorganic or organic materials including SiO 2 …”

“…6). Aer subtracting MB removal in the dark, the reaction rate constant values of PAM, PAM-TiO 2 NC and porous TiO 2 Table S-1 †) 28 because of their comparatively greater affinity for water and MB, higher probability to directly contact MB, hierarchical porosity, higher surface area, narrower bandgap (see Fig. S-1 †), and orderly crystalline anatase phase (known to be more photoactive).…”