Synthesis of Different Shapes ZnFe₂O₄–BiOCl Nanocomposites for Photocatalytic Reduction of CO² in Cyclohexanol

Abstract

Nanosheet and hierarchical microsphere nanostructures of ZnFe₂O₄–BiOCl nanocomposites with various ZnFe₂O₄ contents were prepared through hydrothermal deposition method. The morphology and structure of the as-prepared samples were systematically characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, Brunauer-Emmert-Teller method, and photoluminescence spectra. The photocatalytic activities of the two different shapes of ZnFe₂O₄–BiOCl composites have been evaluated by photocatalytic reduction of CO₂ in cyclohexanol under UV light irradiation. The results showed that cyclohexanol was oxidized to cyclohexanone (CH), and CO₂ was reduced and then reacted with cyclohexanol to produce cyclohexyl formate (CF). The ZnFe₂O₄–BiOCl composites with different shapes showed much higher CF and CH yields than those of pristine BiOCl and mechanically mixed samples, respectively. When the ZnFe₂O₄ content in the composites reached 9%, two different shapes of ZnFe₂O–BiOCl composites both achieved the highest photocatalytic activities. In contrast, the activities for photocatalytic reduction of CO₂ in cyclohexanol over hierarchical microsphere ZnFe₂O₄–BiOCl composites were higher than those of nanosheet structure samples. The higher activities over hierarchical microsphere composites could be attributed to its unique hierarchical structure, large illumination area, and low Photoluminescence (PL) emission intensity, which were beneficial for the separation of photogenerated charge carriers. This work provided a novel approach for the design and construction of highly efficient photocatalyst and reaction system for photoreduction of CO₂.

Ferrite Materials for Photoassisted Environmental and Solar Fuels Applications

“…Esterification between these two intermediates would form cyclohexyl formate, while part of the alcohol would be further oxidized to the ketone (Figure 14). This research group has also reported the combination of the zinc ferrite with bismuth oxychloride, BiOCl, for the same reaction [181,182]. Apparently, the same type of heterojunction as in the case of the ZnFe2O4/TiO2 can be formed with the oxychloride instead of titania, leading to improved photocatalytic activity with respect to the separate semiconductors.…”

“…In addition, systems with hierarchical microsphere microstructure showed higher photocatalytic activities, apparently due to a better charge carrier separation, than those with non-hierarchical nanosheet morphology [182]. Furthermore, photocatalytic activity in the ZnFe2O4/BiOCl system is also influenced by the exposed facets of BiOCl.…”

“…Apparently, the same type of heterojunction as in the case of the ZnFe2O4/TiO2 can be formed with the oxychloride instead of titania, leading to improved photocatalytic activity with respect to the separate semiconductors. The preparation method and the resulting morphology of the particles affected the final photocatalytic activity, in such a way that hydrothermally obtained samples displayed a better performance than physical mixtures of the semiconductors, probably due to a more extended interphase contact [182].…”