Hydrothermal synthesis of h-MoO3 catalyst for Rhodamine B degradation under visible light

Abstract

In the work, hexagonal molybdenum trioxide (h-MoO₃) was synthesized via the hydrothermal reaction between ammonium heptamolybdate tetrahydrate (AHM) and concentrated nitric acid, and different technologies, such as XRD, FESEM, UV–vis DRS, PL, BET method and laser particle size analyzer, were adopted to characterize the experimental data. The results revealed that, when the reaction time was in the range of 8–14 h, single‑phase h-MoO₃ with the hexagonal-shaped morphology was synthesized; however, when the reaction time increased to 16 h, orthorhombic molybdenum trioxide (α-MoO₃) with the platelet-shaped morphology would form. The photocatalytic experiment results demonstrated that, with the increase of initial Rhodamine B (RhB) concentration, the degradation efficiency was gradually decreased; however, with the increase of h-MoO₃ dosage, the degradation efficiency showed a trend of first increase and then decrease. Due to the higher BET specific surface area (2.1801 m²/g), smaller particle size (1.06 μm), and lower recombination rate of photo-generated electron–hole pairs, h-MoO₃ micro-rods synthesized at 160℃ for 14 h exhibited a more excellent photocatalytic performance, with the degradation efficiency up to 98.28%. Additionally, the possible degradation mechanism was proposed.