Construction of Z-scheme BiOCl/Bi24O31Br10 hierarchical heterostructures with enhanced photocatalytic activity

A novel Z-scheme BiOCl/Bi24O31Br10 heterojunction with hierarchical structure was firstly fabricated, in which BiOCl nanosheets grew in-situ and vertically on the surface of Bi24O31Br10 nanosheets. The obtained BiOCl/Bi24O31Br10 composites exhibited favorable photocatalytic activity for RhB degradation under simulated sunlight irradiation. Especially, BB-0.3 (mass fraction of Bi24O31Br10, 30%) composite performed the best photocatalytic activity, and its degradation rate constant (k) for RhB was nearly 4.1 and 7.7 times higher than that of pure BiOCl and Bi24O31Br10, respectively. Larger specific surface area, wider photo-response range and efficient separation of photogenerated carriers were the main reasons for improving photocatalytic activity, which could be proved by Brunner-Emmett-Teller (BET) analysis, UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence spectra (PL), transient photocurrent response and electrochemical impedance (EIS). Meanwhile, the effects of the catalyst dosage, pollutant concentration, initial solution pH and inorganic ions were discussed. Free radical scavenging experiments and electron spin resonance (ESR) measurement indicated that •O2- and h+ made significant contributions to the photocatalytic degradation of RhB. And recycling tests showed that the BB-0.3 heterojunction had a good stability. The possible photocatalytic mechanism of the Z-scheme heterojunction between BiOCl and Bi24O31Br10 was proposed.