Construction of novel MWCNTs/Bi4O5I2 nanosheets with enhanced adsorption and photocatalytic performance for the degradation of tetracycline: Efficiency, mechanism and regeneration

Bismuth oxyhalide-based photocatalysts with anisotropic sandwiched-structure present excellent photoactivity in water purification. However, rapid recombination of photogenerated charge carriers and regeneration are two significant challenges of bismuth-based photocatalyst. Herein, a novel multiwalled carbon nanotubes (MWCNTs)/Bi4O5I2 heterostructure with narrow band-gap and high reactive species (RSs) production capacity were firstly designed via interfacial amidation linkage. Photoelectrochemical analysis confirmed that the interfacial amidation linkage significantly boosted the surface charge effective transfer (45 times vs Bi4O5I2) and broadened the visible light adsorption (555 nm), resulting in the enhanced photocatalytic activity. As expected, the optimized MWCNTs/Bi4O5I2 photocatalyst exhibited remarkable adsorption and photocatalytic performance for Tetracycline (TC) degradation under visible light with respect to that of Bi4O5I2 (2.32 times). Radical trapping experiments and Electron spin resonance (ESR) results clarified that h+ and center dot O2- contributed 34.48% and 93.97% of TC photodegradation, respectively. Density Functional Theory (DFT) calculation including frontier electron densities (FEDs) and Fukui methods further revealed the possible attack sites of RSs for TC. More insights for the decrease of stability showed that main adsorption sites and iodine dissolution were considered to be the key parameters for application of MWCNTs/Bi4O5I2 photocatalyst. Afterwards, we firstly proposed a facile regeneration strategy to solve the deactivation of bismuth oxyhalide-based photocatalysts. This study provided a potential approach to design novel bismuth oxyhalide-based photocatalysts with the high efficiency and possibility of regeneration.