In situ construction of WO3 nanoparticles decorated Bi2MoO6 microspheres for boosting photocatalytic degradation of refractory pollutants.

Visible-light-driven (VLD) heterojunction photocatalysts for refractory contaminant degradation have aroused huge interest because of their outstanding photocatalytic performance. From the aspect of practical application, it is important to develop a highly efficient, durable, eco-friendly and inexpensive VLD photocatalyst. Herein, we report a novel VLD WO3/Bi2MoO6 heterojunction photocatalyst with remarkable photocatalytic activity, which was fabricated via an electrospinning-calcination-solvothermal route. The phase, composition, morphologies, and optical properties of WO3/Bi2MoO6 heterojunctions were comprehensively characterized. The photocatalytic performance of WO3/Bi2MoO6 heterojunctions was assessed by the removal of rhodamine (RhB) and tetracycline hydrochloride (TC) under visible light (VL). WO3/Bi2MoO6 heterojunctions displayed superior photocatalytic activities compared to Bi2MoO6, WO3, or the mechanical mixture of WO3 and Bi2MoO6. In particular, the heterojunction material (0.4WB, theoretical molar ratio of WO3/Bi2MoO6 is 0.4/1.0) exhibited the best degradation efficiency (100%) and mineralization rate (52.3%) in 90 min, both of which exceeded the observed rates for Bi2MoO6 by 5.3 and 6.4 times, respectively. Moreover, 0.4WB showed a good durability in eight runs. The optimized photocatalytic property of WO3/Bi2MoO6 can be attributed to enhanced VL absorption and reduced recombination efficiency of carriers owing to the synergistic effects between Bi2MoO6 and WO3. The necessity of direct contact between WO3/Bi2MoO6 and contaminants was experimentally verified. The study on photocatalytic mechanism demonstrates that superoxide free radicals (O2-) and photo-generated hole (h+) are dominantly responsible for the pollutant degradation, as demonstrated by the trapping experiments and electron spin resonance (ESR) analysis. Therefore, the WO3/Bi2MoO6 heterojunction holds huge potential to be utilized as a durable and highly active photocatalyst for wastewater treatment.