Sulfur vacancy-rich (α/β-CdS)/SiO2 photocatalysts for enhanced visible-light-driven photocatalytic degradation of rhodamine B

Abstract

The development of highly efficient photocatalysts for visible-light-driven degradation of organic pollution is of great interest for wastewater purification. In this work, a sulfur vacancy-rich (α/β-CdS)/SiO2 (α: hexagonal &β: cubic) photocatalyst with a high catalytic activity was novelly synthesized on a nano-SiO2 carrier by the reaction of Cd2+ with a CS2 storage material (CS2SM) as sulfur source and crystalline modifiers. The dispersion of α/β-CdS on the nano-SiO2 carrier significantly enhanced the visible-light-driven catalytic activity of (α/β-CdS)/SiO2 photocatalyst, and 93.37 % rhodamine B (RhB) conversion was determined over 50 mg (α/β-CdS)/SiO2 photocatalyst for 30 mL 400 mg/L RhB solution at light intensity of 150 mW/cm2 and 298.15 K. After five cycle tests, the (α/β-CdS)/SiO2 photocatalyst still owned excellent visible-light-driven catalytic degradation stability (>90 %). The characterizations of morphology, functional groups, and photo-electrochemistry of (α/β-CdS)/SiO2 photocatalyst demonstrated that nano-SiO2 as a carrier played meaningful role in dispersing α/β-CdS and reducing agglomeration, thus increasing the active site of photocatalytic degradation reaction, and the presence of α/β hetero-phase junctions and sulfur vacancies allows the rapid separation of photo-generated carriers and inhibits photo-generated electron-holes recombination. Meanwhile, the electron paramagnetic resonance (EPR) and free radical masking test have also proved that the main active species is ·O2− for the oxidation of RhB. Therefore, the work is providing a new reference to the visible-light-driven degradation of wastewater with high RhB concentration at room temperature.