BiPO₄ Nanorod/Graphene Composite Heterojunctions for Photocatalytic Degradation of Tetracycline Hydrochloride

Precisely manipulating the built-in electric fields of heterojunctions is an effective way to promote photogenerated charge separation. In this work, BiPO4 nanorods/graphene (GA) hydrogels were prepared by hydrothermal methods. The BiPO4 nanorods were evenly embedded in the graphene hydrogel, forming a stable three-dimensional (3D) network structure. The 70% BiPO4/GA hydrogel shows the highest tetracycline hydrochloride degradation activity, which is 3.2 times that of pure BiPO4. The formation of the built-in electric field of the BiPO4/GA hydrogel is demonstrated by experimental investigation (especially in situ atomic force microscopy (AFM) surface potential investigation) and theoretical calculation. The reasons for the enhanced photocatalytic activity are the optimal built-in electric field of the interface induced by precisely manipulating the interfacial contact of the BiPO4/GA hydrogel, as well as the synergistic effect of in situ photocatalytic degradation and adsorption enrichment induced by the 3D network structure. This work provides technical approach and research ideas for the photocatalytic degradation of antibiotics through the manipulation of interlaminar built-in electric field and heterojunction.