Controllable synthesis of the defect-enriched MoO3−x nanosheets as an effective visible-light photocatalyst for the degradation of organic dyes

Abstract

Transition metal oxides (TMOs) are emerging as a promising class of photocatalysts for pollutants' treatment. In this report, by integrating anti-solvent crystallization and thermal treatments, we have developed a facile and environmental approach for the synthesis of MoO_3−x nanosheets in the presence of hexadecyl-trimethyl ammonium bromide (CTAB). The thickness of MoO_3−x nanosheets varies from 20 nm to 40 nm. CTAB promotes the formation of nanosheet morphology and Mo⁵⁺ defects. Combining experimental results and density functional theory (DFT) calculations, we demonstrate that the Mo⁵⁺ defect state in MoO_3−x nanosheets can enhance visible light harvest and promote the separation of photo-generated electron–hole pairs. Hence, MoO_3−x-8, the optimal photocatalyst, shows the highest concentration of surface Mo⁵⁺ defect (18.7%) and the best photocatalytic activity toward rhodamine B (RhB) photodegradation. About 95.9% RhB is degraded within 15 min under visible-light irradiation (λ > 420 nm). The kinetic rate of MoO_3−x-8 reaches 117 times that of commercial MoO₃. It was proved by the total organic carbon (TOC) measurements that about 43.3% of RhB molecules were degraded to CO₂ and H₂O. Overall, this work provides an effective pathway for the nanomaterial design and potential applications in the photocatalytic oxidation of organic pollutants.