New insights into the efficient charge transfer by construction of adjustable dominant facet of BiOI/CdS heterojunction for antibiotics degradation and chromium Cr(VI) reduction under visible-light irradiation.

The narrow light-response range and high electron/hole recombination rate greatly restrict the widespread use of photocatalytic technology. The integration of exposing dominant facet of semiconductor and Z-scheme heterostructures designing is expected to break those barriers. Herein，In this work, hydrothermal and ultrasonic stirring methods were used to selectively exposed the (001) and (110) facet of BiOI to construct the BiOI/CdS heterostructures. The obtained BiOI(001)/CdS material shown the maximum degradation for tetracycline-based antibiotics (Oxytetracycline, Tetracycline and Doxycycline), and excellent reduction of hexavalent chromium. Combining the electron spin resonance and scavenger experiments, the superior photocatalytic capacity was attributed to the generation of superoxide and hydroxyl radicals. DFT calculation results shown BiOI(001)/CdS performed high binding energy and adsorption energy for hexavalent chromium, and the different work function between BiOI(001) and CdS confirmed the building of internal electric field, thereby increased the charge separation. Finally, the Gaussian 09 and HPLC-MS program investigated the attack sites of free radicals and degradation pathways in the degradation of antibiotics. This study not only provides a potential photocatalyst, also gives an in-depth understanding of the photocatalytic properties of heterojunctions constructed by different exposed crystal facets.