Bi/SnO₂/TiO₂-graphene nanocomposite photocatalyst for solar visible light–induced photodegradation of pentachlorophenol

In this study, for the first time, a TiO₂/graphene (G) heterostructure was synthesized and doped by Bi and SnO₂ nanoparticles through a hydrothermal treatment. The as-synthesized nanocomposite was employed for photocatalytic degradation of pentachlorophenol (PCP) under visible light irradiation. Structural characterizations such as X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectroscopy (XRD) proved the valence band alignment at Bi/SnO₂/TiO₂-G interfaces and crystallinity of the nanocomposite, respectively. The as-developed nanocomposite photocatalyst was able to decompose 84% PCP, thanks to the generation of a large number of active OH^•− and O₂^•− radicals. To achieve this optimum photodegradation efficiency, various parameters such as pH, catalyst dosage, and PCP concentration were optimized. The results showed that the PCP photodegradation process followed the first-order kinetic model and the reaction rate constant rose from 0.007 min⁻¹ (Bi) to 0.0149 min⁻¹ (Bi/SnO₂/TiO₂-G). The PCP photodegradation efficiency did not decrease significantly after 5 cycles, and the nanocomposite photocatalyst still showed a high efficiency of 68% in the last cycle. The excellent photocatalytic activity of Bi/SnO₂/TiO₂-G is ascribed as well as the heterostructure of the nanocomposite photocatalyst.