Enhanced photocatalytic degradation of tetracycline by constructing a controllable Cu2O–TiO2 heterojunction with specific crystal facets

Abstract

A heterojunction photocatalytic system has been widely called for to solve tetracycline (TC) water pollution problems. However, the pollutant degradation mechanism with a Z-scheme or double-charge transfer photocatalyst has remained ambiguous. In this work, we successfully constructed a controllable heterojunction between TiO₂ and Cu₂O by adjusting the exposed facets of Cu₂O without additional surfactant. XPS, FT-IR, EIS, PL, EPR, LC-MS, photocurrent curves and scavenger experiments, as well as XRD characterization before and after photocatalysis, demonstrate that the heterojunction with double-charge transfer mechanism exists between TiO₂ and cubic Cu₂O exposed {100} facets (100Cu₂O), where electrons diverted from 100Cu₂O to TiO₂ by O atoms to enhance the TC photocatalytic degradation rate. However, the complete decomposition of TC intermediate products was attenuated as the TC degradation reaction was drifted on the more positive conduction band of TiO₂. Instead, Z-scheme heterojunction between TiO₂ and octahedral Cu₂O exposed {111} facets, (111Cu₂O) was formed where electrons moved from the conduction band of TiO₂ to the valence band of 111Cu₂O by Cu atoms. Thereby, TC degradation occurred at the conduction band of 111Cu₂O, which enhanced the TC photo-degradation rate and the profound decomposition of TC intermediate simultaneously. We expect that this work can contribute to the prospective application of heterojunction for the photocatalytic degradation of antibiotics.