3D-2D-3D BiOI/porous g-C3N4/graphene hydrogel composite photocatalyst with synergy of adsorption-photocatalysis in static and flow systems

Abstract

Abstract A novel 3D-2D-3D BiOI/porous g-C3N4/graphene hydrogel (BPG) composite photocatalyst was synthesized via a two-step hydrothermal method and shows a synergy of adsorption and photocatalysis. In comparison with bulk g-C3N4, 2D porous g-C3N4 (pCN) exhibited not only shortened diffusion distance for photogenerated carrier transport but also large contact area for rapid interfacial charge separation. Nevertheless, the photocatalytic performance was far from satisfactory due to the poor light harvesting. Incorporating 3D flower-like BiOI with 2D pCN to form a heterojunction was found to be an efficiency way for improving light harvesting, while charge separation efficiency was also enhanced. 3D graphene hydrogel, in which the effective photocatalyst 3D-2D BiOI/pCN heterojunction was homogenously distributed, not only revealed excellent adsorption capability and bulk electron transfer but also provided simplicity of separation and recovery. Consequently, in static system, the degradation efficiency of methylene blue (MB) and the typical antibiotic levofloxacin hydrochloride (LVF) was 7.2 and 2.7 times as high as that for BiOI. In flow system, the pollutants could be constantly degraded without separation with the removal rates about 1.54 and 1.67 times higher than those of BiOI, which kept unchanged for 30\u202fh. The construction of 3D-2D-3D BPG composite combined the excellent adsorption capacity of GH with the photocatalytic activity of BiOI/pCN heterojunction, resulting in a high removal efficiency towards pollutants. This work provided deep insight into design and fabrication of 3D hydrogel composites with excellent synergy of adsorption and photocatalytic properties.