Fabrication of a novel Z-scheme Bi2MoO6/GQDs/MoS2 hierarchical nanocomposite for the photo-oxidation of ofloxacin and photoreduction of Cr(VI) as aqueous pollutants

Abstract

In this study, a novel MoS2/Bi2MoO6 composite photocatalyst, which was further sensitized using graphene quantum dots (GQDs), was developed to realize multiple photocatalytic applications in antibiotic remediation and Cr(VI) reduction. A simple chemical mixing procedure was used to prepare the GQD-MoS2/BMO composite photocatalyst, which was comprehensively characterized to confirm the structural purity, morphology, and distribution of GQDs on the MoS2/BMO catalyst. The enhanced charge separation and channeling of fast electron migration were confirmed by photocurrent and impedance measurements obtained for the 5 GQD-30 MoS2/BMO ternary catalyst system. The photoefficiency observed for the degradation of ofloxacin and reduction of Cr(VI) was 99.5% and 97.2% after 100 and 30 min, respectively, of photochemical reaction under visible-light irradiation. The reaction rate with 5 GQD-30 MoS2/BMO was 14.3- and 1.8-fold higher than that using pristine Bi2MoO6 and 30 MoS2/BMO photocatalysts, respectively. Persulfate (3 mM) improved the photo-oxidation of ofloxacin, with > 80% degradation occurring in the first 20 min. The excellent photocatalytic performance is attributed to the improved light absorption owing to the GQDs and the promotion of charge transfer between Bi2MoO6 and MoS2 via GQDs through a Z-scheme mechanism and the electron-attracting properties of the GQDs.