FeWO4/g-C3N4 heterostructures decorated with N-doped graphene quantum dots prepared under various sonication conditions for efficient removal of noxious vapors

Abstract

Herein, N-doped graphene quantum dots (NGQDs) were prepared in an environmentally friendly manner using different sonication conditions by varying two important operating parameters: ultrasonic amplitude and sonication duration. In addition, they were decorated onto FeWO4/g-C3N4 heterostructures to afford a NGQD/FeWO4/g-C3N4 ternary-nanocomposites (NGQD/FWO/CN), which were tested for the photocatalytic removal of noxious vapors. The surface properties of the NGQDs varied with the sonication duration and the ultrasonic amplitude, and the photocatalytic capability of NGQD/FWO/CN varied with the type of decorated NGQDs, which were defined based on the sonication conditions. Moreover, the photocatalytic capability of FeWO4/g-C3N4 heterostructures decorated with sonication-treated NGQDs was higher than that of those decorated with NGQDs prepared without a sonication process. NGQD/FWO/CN also exhibited higher photocatalytic efficiency compared with selected photocatalyst counterparts, most likely due to the upconversion photoluminescence properties of NGQDs and the charge-separation abilities promoted by the electron-affinitive NGQDs and by the Z-scheme carrier-transport progress at the interfaces between the g-C3N4 and FeWO4. Specifically, the average removal efficiencies of vaporous 2-butoxy ethanol and ethyl benzene over a representative NGQD/FWO/CN sample under specified operational conditions were 97.3% (±0.7%) and 55.1% (±0.6%), respectively. Moreover, the pollutant removal capabilities of the photocatalysts were in accordance with their photocurrent measurements. The ternary nanocomposite also revealed excellent photocatalytic stability after successive uses for the decomposition of the model contaminants. Overall, this study highlights the promising role of nanocomposites decorated with sonication-processed NGQDs as photocatalysts for the efficient removal of noxious vapors.