In-situ generation Bi12O15Cl6/BiOI core-shell photocatalyst with efficient LED light-driven degradation and antibacterial properties: Factors, degradation pathway and mechanism

Abstract

• New core/shell Bi 12 O 15 Cl 6 /BiOI hybrid junction was prepared by a facile in-situ generation method. • Bi 12 O 15 Cl 6 /BiOI can effectively remove MO, TC and E.coli under LED light. • h + , •O 2 - and •OH are all active substances in photocatalytic reactions and possible degradation pathway of TC was proposed. • Fermi level reached new equilibrium between p-type BiOI and n-type Bi 12 O 15 Cl 6 . • The core-shell structure and n-p junction effectively promote the separation and migration of photogenic carriers. The construction of composite photocatalytic materials with compact heterojunction is of great significance for improving the properties of materials. To achieve this goal, novel core/shell Bi 12 O 15 Cl 6 /BiOI photocatalyst, with n-p junction heterojunction, was prepared by using p-type BiOI nanosheet coating with lamellar n-type Bi 12 O 15 Cl 6 . A series of techniques including XRD, TEM, HRTEM and BET confirmed the structure of Bi 12 O 15 Cl 6 /BiOI. As expected, methyl orange (MO), tetracycline (TC) and E. coli can be effectively removed by the novel photocatalyst under LED light illumination. The optimal sample Bi 12 O 15 Cl 6 /BiOI can degrade 90.3% MO in 90 min, degrade 75.5% TC in 180 min, and completely destroy E. coli in 40 min. Photocurrent and electrochemical impedance analysis (EIS) show that the separation efficiency of photo-excited electron-hole pairs in the composite material is significantly improved. Between n-type Bi 12 O 15 Cl 6 and p-type BiOI semiconductor, a Fermi level movement produced a more negative conduction band position and a more positive valence band position, which is conducive to the production of active species and the photocatalytic redox reaction. Moreover, the effects of catalyst dosage and pollutant concentration on the degradation of MO and TC were systematically investigated. The capture experiment proved that the superoxide anion radicals (•O 2 − ) and holes (h + ) are main active species in photocatalytic reaction. The intermediates were identified by mass spectrometry analysis (MS), and the possible photocatalytic degradation pathway of TC was proposed.