High Photocatalytic Activity of Transparent Films Composed of ZnO Nanosheets

Abstract

Nanometric thin films were prepared by dip-coating and inkjet printing ZnO nanosheets on glass plates. The side-by-side alignment of the ZnO nanosheets on the substrate resulted in thin, transparent, oriented ZnO surfaces with the high-energy {001} facets exposed. The method of nanosheet deposition affected the film morphology; the dip-coated films were very smooth and nonporous, while the inkjet-printed films were rough and porous with the estimated void volume approximately 60-70% of the total film volume. The first-order rate constants for the photocatalytic degradation of 4-chlorophenol on the nanosheet-based films were approximately 2 times larger than those on nanocolumnar ZnO films or ZnO films prepared by the sol-gel technique. We attribute the high photocatalytic activity of the ZnO nanosheets to the fact that their {001} facets were predominantly exposed to the oxidized substrate. This surface arrangement and the simplicity of fabricating the ZnO nanosheet-based films make them promising for the construction of optical devices and dye-sensitized solar cells.

Immobilized rGO/TiO2 Photocatalyst for Decontamination of Water

“…The restored OH radical can either further oxidize the primary ring opening product or attack another molecule of 4-chlorophenol. These DFT results were in good agreement with the photocatalytic degradation experiments conducted using both ZnO and TiO 2 photocatalysts [23,27]. According to the parallel mechanism, the products of 4-chlorophenol degradation are the experimentally identified aromatics hydroquinone and benzoquinone, as well as various ring-opening compounds formed under the restoration of OH radicals (Figure 4a).…”

“…To explain the mechanism of 4-chlorophenol photocatalytic degradation, in our previous studies, we employed experimental and theoretical, using density function theory (DFT), approaches. Our results therein showed that the hydroxylation and opening of the aromatic ring can occur in parallel with the release of the hydroperoxyl and hydroxyl radicals [23,27]. The restored OH radical can either further oxidize the primary ring opening product or attack another molecule of 4-chlorophenol.…”

“…This mechanism dominated the performance of the composite while the degradation due to the direct charge transfer mechanism was smaller. The present study, together with our previous ones [21,[23][24][25][26][27][28][29], form the basis for extensive and complex research into the photocatalytic performance of composites containing different allotropes of TiO 2 and carbonaceous dopants, including fullerene, carbon nanotubes, reduced graphene oxide, and graphene itself.…”

“…European Union (EU) legislation has also addressed this issue, setting a maximum allowed phenol concentration of 0.5 µg L −1 in tap water. Our previous studies showed that this toxic compound can be efficiently degraded by photocatalysis [21,[23][24][25][26][27][28][29].…”

Sprayed Pyrolyzed ZnO Films with Nanoflake and Nanorod Morphologies and Their Photocatalytic Activity

“…In fact, this ratio shows a direct correlation with the trend followed by app , indicating again that the nanoflake morphology is more photoactive because a greater number of active facets are exposed to the dye molecules and to the UV light. Other authors have found similar results, in which nanoplatelets, nanosheets, or crystals with a large (100)/(002) XRD planes intensity ratio have higher photocatalytic activity than the nanorod morphology [44][45][46], and attributed this behavior to the presence of a major proportion of polar faces. Analyzing deeper the surface-to-volume ratio of the nanorod structures, it is possible to observe that as the dimensions of the rod decrease (length and radius), the surface-to-volume ratio increases, while for larger dimensions this ratio rapidly decreases.…”