Preparation of Light-Driven Spinel Nanoparticles CoAl2O4, MgFe2O4 and CoFe2O4 and Their Photocatalytic Reduction of Carbon Dioxide

Visible-light response CoAl₂O₄, MgFe₂O₄ and CoFe₂O₄ spinel nanoparticles were prepared by the inorganic salt sol-gel method, and characterized by using XRD, SEM and UV-Vis. The characterization show that the three photocatalysts were in spinel-type structure with the spherical-like particle size in the range of 3~20 nm. The absorbing wavelengths of the three photocatalysts were larger than 800 nm. Their calculated band gaps were less than 1.55 eV. CO₂ was photocatalytically reduced to form HCOOH by CoAl₂O₄, MgFe₂O₄ and CoFe₂O₄ nanoparticles under the irradiation of the simulated daylight lamp. The investigation shows that the three photocatalysts all have better activity. Methanoic acid yield may achieve 4988.11 μmol/g-Cat when irradiation time is five hours, and the activity of CoFe₂O₄ had best.