Accelerated generation of hydroxyl radical through surface polarization on BiVO4 microtubes for efficient chlortetracycline degradation

Photocatalysis is generally considered as a promising candidate to treat antibiotics in wastewater. The weak adsorption of target molecule makes the degradation largely depend on the dissociative hydroxyl radical oxidation pathway. In this work, porous BiVO4 microtubes were co-modified with H3PO4 and H3BO3 by using glycerol as a bridge to increase their surface polarity which was supposed to accelerate the generation rate of hydroxyl radical in chlortetracycline degradation. Our results show that the co-modified BiVO4 microtubes showed obviously enhanced efficiency in chlortetracycline degradation, its reaction rate is 2.0 and 3.8 times of solely modified with H3PO4 and pristine BiVO4 microtubes. We attributed this enhancement to the accelerated generation of free hydroxyl radicals by the ionization of hydroxyl groups in modifying inorganic acid, which increases the intensity of surface electric field. The surface electric field will result in tendentious migration of holes to the surface of BiVO4 microtubes to take catalytic reactions, and thus improve the separation rate of photogenerated charges. The degradation pathway of chlortetracycline was analyzed to reveal the mechanism underlying the enhanced catalytic activity. This work provides a feasible strategy to improve the catalytic degradation efficiency of photocatalysts to weak-adsorbed organic pollutant through surface polarization.