Honeycomb Nb2O5/RGO wrapped on MoO3 nanorods for visible light-driven degradation of sulfasalazine and ciprofloxacin in water

Abstract

Successful engineering of heterojunction photocatalysts remains one of the most promising routes towards fabricating materials with improved photocatalytic properties. Herein, novel Nb2O5RGO/MoO3 ternary nanocomposites with varying MoO3 loadings (5, 10 and 15 wt%) were carefully prepared via a two-step method involving hydrothermal synthesis and ultrasonication assisted assembly. The fabricated photocatalysts were studied using FESEM, HRTEM, XRD, UV-Vis DRS, PL, EIS and XPS to reveal their morphology, phase composition, optical response, electrochemical behaviour and chemical composition and states. As anticipated, the ternary nanostructures showed improved photocatalytic activity towards ciprofloxacin (CIP) and sulfasalazine (SSZ) compared to the single or binary nanocomposites. Specifically, the highest activity was attained at 10 wt%MoO3 (Nb2O5-RGO/10 wt%MoO3), which reached 85.4% and 88.2% for CIP and SSZ removal in just 60 min, respectively. This corresponds to CIP and SSZ degradation rates that were 3.6 and 2.3 times, and 4.2 and 3.4 times higher than those over Nb2O5 and Nb2O5-RGO, respectively. The incorporated RGO functioned as a charge transfer bridge between Nb2O5 and MoO3, thereby ensuring efficient migration and separation of the charge carriers, which was confirmed by EIS, and PL. Radical scavenging tests revealed that the •OH radicals were the predominant active species, and this was further confirmed using the terephthalic acid test. Finally, a plausible charge transfer pathway was proposed, and the possible SSZ degradation route was detailed based on HPLC-MS studies. This work provides a rational design of a novel material with promising environmental applications towards pharmaceutical pollution mitigation.