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

[Display omitted] •Heterostructured CoFe2O4-TiO2 nanoparticles show an excellent photocatalytic property.•CoFe2O4-TiO2 is also proved to be an efficient catalyst for O2 reduction reaction (ORR).•The rapid growth of O2–∙ by CoFe2O4-TiO2 results in photocatalytic activity improvement.•Synergistic operation of photocatalysis and catalytic ORR is conducted by CoFe2O4-TiO2. The improved photocatalytic activity of TiO2 with the addition of spinel CoFe2O4 as an effective catalyst for O2 reduction reaction (ORR) is studied and proved in this study. CoFe2O4-TiO2 heterostructure nanoparticles are prepared by a reflux condensation and two-step hydrolysis-hydrothermal method. The addition of trace CoFe2O4 onto TiO2 can improve its affinity to O2, generate a faster transportation of photo-induced carriers, but hardly affect band structure. With an appropriate amount of CoFe2O4 to TiO2, a remarkable acceleration occurs in photocatalytic decolorization of dye wastewater, and the calculated apparent kinetic constant (kapp) of the composite (0.020 min−1) is 2.4 and 5.6 times of pure TiO2 (0.0085 min−1) and CoFe2O4 (0.0036 min−1), respectively. Quenching experiments with different radical scavengers show that O2–∙ is the key oxidative radical in all photocatalytical reactions. Meanwhile, the rapid growth of O2–∙ production by CoFe2O4-TiO2 is proved to be a major cause for photocatalytic performance improvement. Furthermore, an improved electrochemical ORR catalytic ability by CoFe2O4-TiO2 is verified and the 2-plus-2 electron route generates the same product (H2O2) as the photocatalytic process. Therefore, the synergistic operation of photocatalytic and catalytic ORR process by CoFe2O4-TiO2 resulted in a rapid degradation of dye wastewater.