Z-scheme B-g-C3N4/MoO3 modified by hollow CoSx polyhedral for degradation of mixed pollutants

There are various dye molecules in dye wastewater, making the degradation treatment of mixed dyes more practical. This work used ZIF-67 as a sacrificial template to prepare hollow CoS_x polyhedral as a co-catalyst to modify and improve B-doped g-C₃N₄/MoO₃ (BCM) photocatalysts for efficient degradation of MO + MB + RhB mixed dyes (the concentrations of MO and MB were both 10 mg/L and RhB was 20 mg/L). In the evaluation of the catalytic performance of mixed pollutants (100 mL) with a catalyst content of 20 mg under a simulated light source with a power of 300 W, the best degradation performance was achieved by a photocatalyst (CBCM-60) with a mass ratio of BCM to ZIF-67 of 60:1. It completely degraded MO within 20 min and degraded 87 % MB and 37 % RhB, respectively, within 200 min. In sharp contrast, the time for complete degradation of MO by BCM without CoS_x modification was extended to 40 min, and at 200 min, only 62 % of MB and 17 % of RhB could be degraded. The enhancement of the catalytic performance of CBCM is closely related to the hollow structure of CoS_x polyhedral. Firstly, the cavity structure captures incident light and undergoes multiple reflections/scattering, significantly enhancing light absorption. Secondly, the modification of CoS_x increased the specific surface area of the material, overcoming the insufficient reduction in BCM specific surface area caused by B doping. Finally, CoS_x can serve as a “high-speed channel” for electron transfer, further improving the carrier separation efficiency on the basis of Z-type heterojunctions. Therefore, the hollow CoS_x polyhedral modified B-doped g-C₃N₄/MoO₃ photocatalyst is expected to be suitable for practical industrial wastewater purification, which is also of great significance for studying how to remove mixed pollutants with two or three different molecular structures in photocatalysis.