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.
Jian-Wu Xiao,Li-Wang Jiang,Yu-Ma Yang,Yun-Feng Zhu,Fu-An He,Dong-Dong Mai
Superhydrophobic electrospun films for oil–water separation, particularly those with multiple functions such as magnetism, catalysis, and piezoelectricity, have received widespread attention. In this work, a novel electrospun superhydrophobic magnetic CoFe2O4@TiO2/polyvinylidene fluoride (PVDF) composite film was fabricated. Firstly, a CoFe2O4@TiO2 hybrid filler was prepared by a simple and effective solvothermal method, and its structure and magnetism were confirmed by different characterization techniques. Secondly, the electrospun CoFe2O4@TiO2/PVDF composite film was prepared and then modified with trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (HFDS) to form the electrospun HFDS-CoFe2O4@TiO2/PVDF composite film. The resulting HFDS(2 wt%)-CoFe2O4@TiO2(30 wt%)/PVDF composite film was found to be superhydrophobic and could achieve oil–water separation by gravity filtration and direct absorption, with absorption capacities for valorous oils ranging from 7.7 g g−1 to 8.2 g g−1. The crystallinity degree of the polar piezoelectric β- and γ-form crystals of PVDF in the HFDS(2 wt%)-CoFe2O4@TiO2(30 wt%)/PVDF composite film was 25.1%, whereas the corresponding value of the pure PVDF solid film was only 14.3%. In addition, the HFDS(2 wt%)-CoFe2O4@TiO2(30 wt%)/PVDF composite film exhibited a magnetization strength of 0.69 emu g−1 at 20 000 Oe and could catalyze the degradation of Sudan Red dye. The multi-functional CoFe2O4@TiO2/PVDF composite film demonstrates its potential for various applications in oil–water separation and other fields.
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