Construction of a Z-scheme g-C3N4/NBGO/BiVO4 heterostructure with visible-light driven photocatalytic degradation of tetracycline: efficiency, reaction pathway and mechanism

Abstract

In this study, an aminated graphene-like biochar (NGBO) was used as a solid-state electron mediator at a g-C₃N₄/BiVO₄ interface to construct a hybrid Z-scheme system (g-C₃N₄/NBGO/BiVO₄) for the photocatalytic degradation of tetracycline (TC) from aqueous solutions. The construction of the Z-scheme heterojunction led to the consumption of a photogenerated hole (h⁺). This promotes charge carrier transfer (e⁻) of g-C₃N₄, which ensures that the g-C₃N₄ is exposed with active sites, and shows a high efficiency for TC degradation. Among the composites of various ratios, the prepared g-C₃N₄/NBGO/BiVO₄-0.5 presented the best degradation of TC when compared to other heterojunctions prepared under the same conditions, and the photocatalytic degradation rate constants of TC were enhanced significantly, being approximately 10.85 times and 2.70 times greater than that of pure g-C₃N₄ and g-C₃N₄/BiVO₄, respectively. The response surface design methodology (RSM) was also used to optimize the parameters of the degradation of TC. The ESR measurement and radical quenching experiments indicated that the h⁺ and ˙O₂⁻ were mainly responsible for the TC degradation. The plausible mechanisms of the photoinduced electron transfer pathways and photocatalytic reaction degradation pathway of TC were investigated by experimental analysis. It is expected that the formation of graphene-like biochar-based Z-scheme heterojunctions would be promising candidate photocatalysts for environmental applications.