The favourable synergistic operation of photocatalysis and catalytic oxygen reduction reaction by a novel heterogeneous CoFe2O4-TiO2 nanocomposite

The improved photocatalytic activity of TiO 2 with the addition of spinel CoFe 2 O 4 as an effective catalyst for O 2 reduction reaction (ORR) is studied and proved in this study. CoFe 2 O 4 -TiO 2 heterostructure nanoparticles are prepared by a reflux condensation and two-step hydrolysis-hydrothermal method. The addition of trace CoFe 2 O 4 onto TiO 2 can improve its affinity to O 2 , generate a faster transportation of photo-induced carriers, but hardly affect band structure. With an appropriate amount of CoFe 2 O 4 to TiO 2 , a remarkable acceleration occurs in photocatalytic decolorization of dye wastewater, and the calculated apparent kinetic constant ( k app ) of the composite (0.020 min −1 ) is 2.4 and 5.6 times of pure TiO 2 (0.0085 min −1 ) and CoFe 2 O 4 (0.0036 min −1 ), respectively. Quenching experiments with different radical scavengers show that O 2 –∙ is the key oxidative radical in all photocatalytical reactions. Meanwhile, the rapid growth of O 2 –∙ production by CoFe 2 O 4 -TiO 2 is proved to be a major cause for photocatalytic performance improvement. Furthermore, an improved electrochemical ORR catalytic ability by CoFe 2 O 4 -TiO 2 is verified and the 2-plus-2 electron route generates the same product (H 2 O 2 ) as the photocatalytic process. Therefore, the synergistic operation of photocatalytic and catalytic ORR process by CoFe 2 O 4 -TiO 2 resulted in a rapid degradation of dye wastewater.