(337g) Synthesis of ZnFe2O4-TiO2 Nanobelts Heterostructure for Photocatalytic Reduction of Carbon Dioxide in Cyclohexanol

The concentration of carbon dioxide (CO₂) in the atmosphere has been increased due to the burning of fossil fuels, which has become a global environmental problem. Many researchers are focusing on search reliable strategies to mitigate CO₂ emissions. Among them, the ideas of imitating the nature photosynthesis to convert CO₂ into clean energy fuels such as methanol or methane can solve the energy crisis and environmental problems. In this work, TiO₂ nanobelts were synthesized by simple hydrothermal method using NaOH solution as morphology directing agent. And ZnFe₂O₄-TiO₂ nanocomposite were fabricated with different ZnFe₂O₄ content by hydrothermal deposition technique. The photocatalysts were characterized by SEM, XRD, TEM, XPS, and UV-vis DRS techniques. The photocatalytic activities of the ZnFe₂O₄-TiO₂ nanocomposites were tested by photocatalytic reduction of CO₂ using cyclohexanol as solvent and hole sacrificial agent under UV light irradiation. The results showed that ZnFe₂O₄ nanoparticles grew on the TiO₂ nanobelts, and the obtained nanocomposites have ordered nanobelt structure with a high crystallinity. Cyclohexanol was oxidized to cyclohexanone (CH) and produced H⁺ at the same time on the valence band (VB) of the catalyst, and CO₂ was reduced and then esterification reaction with cyclohexanol in the liquid phase to produce cyclohexyl  formate (CF) on the conduction band (CB). The obtained ZnFe₂O₄-TiO₂ nanocomposites showed much higher photocatalytic performance than pure TiO₂ nanobelts and ZnFe₂O₄ nanoparticles. And the yields of the expected products of cyclohexanone and cyclohexyl formate increased alone with the reaction time and showed a near linear relationship; When the content of ZnFe₂O₄ reached at 9.78% in the heterostructure, the composite had the highest photocatalytic activity. The reason for the decrease of catalyst activity was that excessive ZnFe₂O₄ assembled on the surface of the TiO₂ nanobelts and blocked light.