Magnetic Fe2O3/mesoporous black TiO2 hollow sphere heterojunctions with wide-spectrum response and magnetic separation

The solar-light-harvesting and separation of nanostructured photocatalysts in slurry systems are key issues in fields of photocatalysis. Herein, magnetic Fe 2 O 3 /mesoporous black TiO 2 hollow sphere heterojunctions (M-Fe 2 O 3 /b-TiO 2 ) are fabricated through wet-impregnation and surface hydrogenation strategy, which show wide-spectrum response and magnetic separation. The decreased specific surfaces, pore sizes and pore volumes from ∼80 to 67   m 2   g −1 , ∼12 to 10.3   nm, and ∼0.20 to 0.16   cm 3   g −1 , respectively, all confirm the efficient loading of magnetic Fe 2 O 3 . The M-Fe 2 O 3 /b-TiO 2 with narrow bandgap of ∼2.41   eV extends the photoresponse from UV to near infrared region and exhibits excellent solar-driven photocatalytic degradation performance and long-term stability for complete mineralization methyl orange and high-toxic herbicide metribuzin. The photocatalytic reaction apparent rate constant k for metribuzin is   ∼   9 times higher than that of pristine TiO 2 under AM 1.5 irradiation. Especially for single-wavelength of 950   nm, the degradation ratio is up to 4%. The enhancement is attributed to Ti 3+ and magnetic Fe 2 O 3 with narrow bandgap facilitating solar-light-harvesting, the hollow structure benefiting mass transport, and the heterojunctions favoring the spatial separation of photogenerated electron-hole pairs. The magnetic separation is conducive to recycle of photocatalysts, which favors practical applications in environment.