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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. [ABSTRACT FROM AUTHOR]

Uniform black TiO2 nanothorns/graphene/black TiO2 nanothorns sandwichlike nanosheets (denoted as G@BTN) are fabricated through facile solvothermal approach and subsequent surface hydrogenation, in which the black TiO2 nanothorns vertically grow on the surface of two sides of graphene and form the sandwichlike structure. The rational control of hydrolysis and condensation of Ti precursors results in a uniform coating of amorphous TiO2 seeds, which then vertically grow in TiO2 nanothorns. After surface hydrogenation, the resultant G@BTN materials, with uniform sandwichlike configuration and narrow band gap of approximately 2.81 eV, can extend the photoresponse from the ultraviolet to the visible-light region and exhibit an excellent solar-driven photocatalytic performance for the degradation of the highly toxic pesticide atrazine (99 %). The first-order rate constant ( k) of G@BTN (0.863 h−1) is about three times as high as that of black TiO2 nanothorns (0.287 h−1), which implies the significant role of the introduction of graphene for improving the photocatalytic performance. The high solar-driven photocatalytic performance is ascribed to the formed Ti3+ in frameworks and surface disorders enhancing the absorption of solar light, and the sandwichlike structure favoring the separation and transportation of photogenerated charge carriers. [ABSTRACT FROM AUTHOR]

Graphical abstract Defect-engineered γ-Fe 2 O 3 /mesoporous black TiO 2 hollow sphere heterojunctions are fabricated by metal-ion intervened hydrothermal technology and high-temperature hydrogenation reduction, which exhibit efficient charge separation and boosting solar-driven photocatalytic degradation performance of biotoxic tetracycline due to ultrathin γ-Fe 2 O 3 nanosheets with narrow bandgap offering more surface active sites, the hollow structure and the defect engineering enhancing solar-light-harvesting and spatial separation of photogenerated charge carriers. Highlights • Defect-engineered γ-Fe 2 O 3 /mesoporous black TiO 2 hollow sphere heterojunctions are prepared. • Defect engineering extends the photoresponse to visible light and near infrared region. • The ultrathin γ-Fe 2 O 3 nanosheets favor the transport of charge carriers. • It shows excellent solar-driven photocatalytic performance and good magnetic separation. • The possible photocatalytic mechanism of biotoxic tetracycline degradation is proposed. Abstract Defect-engineered magnetic γ-Fe 2 O 3 ultrathin nanosheets/mesoporous black TiO 2 hollow sphere heterojunctions (γ-Fe 2 O 3 /b-TiO 2) are fabricated by a metal-ion intervened hydrothermal technique and high-temperature hydrogenation, which exhibit wide-spectrum response and magnetic separation. The specific surface area, pore size and pore volume of the resultant γ-Fe 2 O 3 /b-TiO 2 with hollow structure are ∼63 m2 g−1, 10.5 nm and 0.14 cm3 g−1, respectively. After surface hydrogenation, α-Fe 2 O 3 nanosheets are converted to γ-Fe 2 O 3 ultrathin nanosheets (∼6 nm) combined with the formation of surface defects. The ultrathin nanosheet structure facilitates the surface engineering and also favors the diffusion and transportation of photogenerated charge carriers. The apparent rate constant (k) of defect-engineered γ-Fe 2 O 3 /b-TiO 2 photocatalytic degradation biotoxic tetracycline is ∼3 times higher than that of α-Fe 2 O 3 /b-TiO 2 under AM 1.5 irradiation. The enhancement is attributed to the introduction of narrow bandgap unit-cell-thick γ-Fe 2 O 3 nanosheets, the hollow structure and the defect engineering, which are beneficial to solar-light-harvesting and rapid electron transport, and spatial separation of photogenerated charge carriers. The photocatalytic degradation mechanism is also proposed. The novel magnetic γ-Fe 2 O 3 /b-TiO 2 heterojunction is a promising photocatalyst for recovering the domestic sewage in environment. [ABSTRACT FROM AUTHOR]

Ag nanoparticle-decorated self-floating porous black TiO 2 foams (Ag-FBTFs) are fabricated by facile wet-impregnation and high-temperature surface hydrogenation strategy, utilizing self-floating porous black TiO 2 foams (FBTFs) with 3D macro-mesoporous architectures as hosts. The composites are evidently investigated by X-ray diffraction (XRD), Raman, N 2 adsorption, diffuse reflectance spectroscopy (DRS), transmission electron microscope (TEM), scanning electron microscopy (SEM), scanning Kelvin Probe (SKP), surface photovoltage spectroscopy (SPS) and photoluminescence (PL). The results show that the small Ag nanoparticles with diameter of 3–4 nm are decorated on the surface of FBTFs uniformly, which extend the photoresponse to visible-light region and show obvious surface plasmon resonance (SPR). The Ag-FBTFs exhibit excellent solar-driven photocatalytic performance for complete mineralization of some high-toxic organic contaminants. The enhancement can be attributed to the 3D macro-mesoporous networks facilitating the diffusion of reactants and products, the floating feature and small Ag nanoparticle-decoration favoring light-harvesting and spatial separation of photogenerated electron-hole pairs due to SPR effect. This novel SPR-enhanced solar-driven floating photocatalyst will have potential application in fields of natural environment. [ABSTRACT FROM AUTHOR]

The recycle and light-harvesting of powder photocatalysts in suspended system are bottlenecks for practical applications in photocatalysis. Herein, we demonstrate the facile synthesis of self-floating amphiphilic black TiO 2 foams with 3D macro-mesoporous architectures through freeze-drying method combined with cast molding technology and subsequent high-temperature surface hydrogenation. Ethylenediamine plays bifunctional roles on acid-base equilibrium and “concrete effect” on stabilizing the 3D macro-mesoporous networks against collapsing, which also inhibit the phase transformation from anatase-to-rutile and undesirable grain growth during hydrogenation at 600 °C. The resultant black TiO 2 foams, which can float on the water, extend the photoresponse from UV to visible-light region and exhibit excellent solar-driven photocatalytic activity and long-term stability for complete mineralization of floating insoluble hexadecane and some typical pesticides. Especially for floating contaminant hexadecane, the photocatalytic reaction apparent rate constant k is ∼7 times higher than that of commercial Degussa P25 under AM 1.5 irradiation. This enhancement is attributed to the 3D macro-mesoporous networks facilitating mass transport, the super amphiphilicity benefiting rapid adsorption, the floating feature and Ti 3+ in frameworks favoring light-harvesting and spatial separation of photogenerated electron-hole pairs. The novel self-floating photocatalyst will have real practical applications for mineralizing floating contaminants in natural environment. [ABSTRACT FROM AUTHOR]