(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.