Key Words:Iron compounds;Electrolytic reduction - Heterojunctions - Image enhancement - Oxygen - Oxygen reduction reaction - Photocatalysis - Photocatalytic activity - Rate constants - TiO2 nanoparticles - Titanium dioxide

Abstract:The improved photocatalytic activity of TiO<inf>2</inf> with the addition of spinel CoFe<inf>2</inf>O<inf>4</inf> as an effective catalyst for O<inf>2</inf> reduction reaction (ORR) is studied and proved in this study. CoFe<inf>2</inf>O<inf>4</inf>-TiO<inf>2</inf> heterostructure nanoparticles are prepared by a reflux condensation and two-step hydrolysis-hydrothermal method. The addition of trace CoFe<inf>2</inf>O<inf>4</inf> onto TiO<inf>2</inf> can improve its affinity to O<inf>2</inf>, generate a faster transportation of photo-induced carriers, but hardly affect band structure. With an appropriate amount of CoFe<inf>2</inf>O<inf>4</inf> to TiO<inf>2</inf>, a remarkable acceleration occurs in photocatalytic decolorization of dye wastewater, and the calculated apparent kinetic constant (k<inf>app</inf>) of the composite (0.020 min⁻¹) is 2.4 and 5.6 times of pure TiO<inf>2</inf> (0.0085 min⁻¹) and CoFe<inf>2</inf>O<inf>4</inf> (0.0036 min⁻¹), respectively. Quenching experiments with different radical scavengers show that O<inf>2</inf>^–∙ is the key oxidative radical in all photocatalytical reactions. Meanwhile, the rapid growth of O<inf>2</inf>^–∙ production by CoFe<inf>2</inf>O<inf>4</inf>-TiO<inf>2</inf> is proved to be a major cause for photocatalytic performance improvement. Furthermore, an improved electrochemical ORR catalytic ability by CoFe<inf>2</inf>O<inf>4</inf>-TiO<inf>2</inf> is verified and the 2-plus-2 electron route generates the same product (H<inf>2</inf>O<inf>2</inf>) as the photocatalytic process. Therefore, the synergistic operation of photocatalytic and catalytic ORR process by CoFe<inf>2</inf>O<inf>4</inf>-TiO<inf>2</inf> resulted in a rapid degradation of dye wastewater.<br/> © 2020 Elsevier B.V.

Volume:516

Issue:wu

Translation or Not:no