Synthesis and properties of Bi2WO6 coupled with SnO2 nano-microspheres for improved photocatalytic reduction of Cr6+ under visible light irradiation

Abstract Bi2WO6 coupled with SnO2 nano-microspheres (nSnO2/BWO) with excellent photocatalytic activity for Cr6+ reduction was successfully synthesized via a facile solvothermal-calcining route. The results showed that the coupling of SnO2 to Bi2WO6 caused the shape of the catalyst to have a regular microsphere structure and increased surface adsorption sites, narrowed the band gap, and enhanced the electrical conductivity of the as-prepared composites. The surface structure of the as-prepared composites accelerated carriers' migration, improved the separation and transfer of photogenerated carriers, and enhanced the response of the composite to visible light. The optimal mass ratio of SnO2 to Bi2WO6 was determined to be 7%. The 7SnO2/BWO sample exhibited a high Cr6+ photoreduction rate of 98.2% in 50 min; this is 47.5% higher than that of pure Bi2WO6. Moreover, the photocatalytic oxidation capacity of the as-prepared composites was evaluated to further explain its photocatalytic mechanism, and the maximum degradation rates of tetracycline and rhodamine were found to be 85.9% in 120 min and 94.4% in 40 min, respectively. Thus, this work presents a simple and high-yield method for the synthesis of Bi2WO6 coupled with SnO2 photocatalysts. Given their enhanced photocatalytic activity, the as-prepared composites are promising candidates for Cr6+ reduction and for meeting the requirements of future photocatalytic materials.