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.