Internal electric field promoted NCDs/BiOBr/AgBr Z-scheme heterojunction with rich oxygen vacancies for efficient photocatalytic degradation of tetracycline and reduction of Cr (VI)

It is important to prepare efficient photocatalysts for the degradation of antibiotics and heavy metals. In this study, NCDs/BiOBr/AgBr Z-scheme heterojunction photocatalysts with excellent performance were constructed. NCDs/BiOBr/AgBr form a Z-type heterojunction system with pyrrole nitrogen-doped carbon quantum dots (NCDs) as charge transfer channels. The internal electric field formed in NCDs/BiOBr/AgBr greatly facilitated electron transfer. The more easily broken Bi-O bonds were utilized in the synthesis to introduce rich oxygen vacancies (OVs) into NCDs/BiOBr/AgBr to promote molecular oxygen activation. Meanwhile, silver nanorods were reduced in the synthesis to enhance the photodegradation performance. The photocatalytic degradation of tetracycline (TC) and reduction of Cr (VI) were enhanced by about 4 and 6 times. The factors affecting the removal effects of TC and Cr (VI) were analyzed. The catalysts were also tested to have good stability and potential for application in real wastewater. The reactive oxygen species (ROS), which play a dominant role in the photodegradation of TC and Cr (VI) by NCDs/BiOBr/AgBr, were tested, and a possible photocatalytic mechanism was proposed.