Research PaperSelf-floating amphiphilic black TiO2 foams with 3D macro-mesoporous architectures as efficient solar-driven photocatalysts

•Self-floating amphiphilic macro-mesoporous black TiO2 foam prepared by freeze-drying.•With exceptional visible light photocatalytic activity and long-term stability.•Super amphiphilic character favors the rapid adsorption and photocatalysis.•Complete mineralization of floating insoluble hexadecane.•Favoring solar-light-harvesting directly and recycling easily.

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 TiO2 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 TiO2 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 Ti3+ 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.

Graphical abstractDownload high-res image (169KB)Download full-size imageSelf-floating amphiphilic macro-mesoporous black TiO2 foams are prepared via freeze-dried method combined with molding technology and hydrogenation, which extend photoresponse to visible-light region and exhibit excellent solar-driven photocatalytic activity due to the 3D amphiphilic macro-mesoporous networks facilitating mass transport and adsorption, the floating feature and Ti3+ favoring light-harvesting and the separation of photogenerated electron-hole pairs.