Synergistic effects in simultaneous photocatalytic removal of Cr(VI) and tetracycline hydrochloride by Z-scheme Co3O4/Ag/Bi2WO6 heterojunction

Promoting the efficient full utilization of photogenerated electrons and holes for dual-function photocatalytic pollutants removal has become a research hot spot. Herein, a well-designed Z-Scheme Co3O4/Ag/Bi2WO6 nanocomposite was fabricated through a multi-step synthesis and applied for removing heavy metal ions Cr(VI) and antibiotic tetracycline hydrochloride (TCH) simultaneously under visible light irradiation for the first time. Compared to the half-reactions, the photocatalytic efficiency of Co3O4/Ag/Bi2WO6 in removal of Cr(VI)-TCH coexistence system was found to be 6.86(Cr(VI)) and 2.58(TCH) times higher than that in its single system due to synergistic effects of photocatalytic reduction and oxidation with better utilization of electrons and holes. Meanwhile, The photocatalytic performance of Co3O4/Ag/Bi2WO6 in simultaneous degradation of Cr(VI) and TCH is about 7.89 and 5.65 times higher than that of pure Bi2WO6, respectively. And ternary Co3O4/Ag/Bi2WO6 photocatalyst exhibited much better photocatalytic activity compared with single Bi2WO6, Ag/Bi2WO6 and Co3O4/Bi2WO6 heterojunctions owing to the wide spectral response, more efficient photogenerated charge separation and utilization and strong redox capacity. Besides, the Z-Scheme photocatalytic enhanced mechanism of Co3O4/Ag/Bi2WO6 heterojunction was proved based on the photoluminescence (PL), photoelectrochemical and electron spin resonance (ESR) measurements, band structure characterizations and corresponding theoretical analyses.