Photocatalytic Activity of Reduced Graphene Oxide-Bi2WO6 for Environmental Purification

(De Gruyter) – In the recent years, more attention has been paid to solving the various widespread pollution of effluents from urban and agricultural industries including biorecalcitrant and organic pollutants. Environmental purification has focused on the use of photocatalysts for photodegradation particularly in the areas of air purification, water disinfection, hazardous waste degradation, and sewage treatment and purification.

Because of good chemical stability, high oxidized activity, visible light excitation, and low price, Bi2WO6 (BWO) has been the popular photocatalyst for environmental purification. However, the band gap of BWO is large, and it can only be excited by a small fraction of visible light. Rapid recombination of the photogenerated electron-hole pairs in BWO is responsible for the low efficiency of solar energy utilization hampering application of BWO. Generation of a smaller band gap and the suppression of recombination of electron-hole pairs are the key for the improvement of photocatalytic activity.

Graphene oxide (GO)-BWO hybrid materials have recently attracted a lot of attention because combining GO and BWO can potentially mitigate electron-hole pair recombination. GO is composed of graphite nanosheets with oxygen-containing functional groups such as hydroxyl, epoxide groups, and carboxyl groups covalently bonded to the edge of the nanosheets. These oxygen-containing functional groups allow transmission of cations and provide reactive sites for nucleation and growth of the nanoplates. In addition, the incorporation of reduced graphene oxide (rGO) nanosheets into BWO benefits the transfer and separation of photogenerated carriers because conversion of GO to rGO suppresses charge recombination effectively.

The authors studied the visible-light-driven rGO-BWO samples synthesized by a hydrothermal method, and the photocatalytic activity was evaluated. With increasing contribution of rGO photocatalytic activity of the rGO-BWO samples were enhanced compared to pure BWO. The good electrical conductivity and effective charge separation of rGO introduced to BWO lead to red-shifts in the absorption wavelength, the larger specific surface area, and smaller band gap affecting the photocatalytic activity.

The enhanced photocatalytic activities of rGO-BWO samples were interpreted to be the result of three factors: (1) the morphology of the unbroken microsphere can provide the greater light-harvesting capacities by multiple scattering of the light and more possible reaction sites for the photocatalytic reaction; (2) the smaller band gap reduces the electron energy from the valence band transition to the conduction band; (3) the appropriate GO content may effectively suppress electron-hole pair recombination by the migration of photoinduced carriers.

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Nanotechnol Reviews. 6(6), 2017, 505–516.

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