Photocatalytic performance of binary and ternary Pt–Cu₂O–BiVO₄ catalysts under visible-light irradiation

Various Pt–Cu₂O–BiVO₄ ternary and binary hybrid composite catalysts were synthesized using in-situ methods. Cuprous oxide and platinum were obtained by chemical reduction of copper sulfate and hexachloroplatinic acid, respectively, while BiVO₄ was synthetized by ultrasonic spray pyrolysis. All the synthesis routes allowed the formation of ternary and binary catalysts without the presence of impurities. The materials were structurally characterized using X-ray diffraction, morphologically by scanning electron microscopy and transmission electron microscopy, optically with UV–vis diffuse reflectance spectroscopy, and photocatalytically during the degradation of methyl orange (MO) under visible-light irradiation. TEM images confirmed the formation of heterojunctions and the deposition of metallic particles on the semiconductor surfaces. A similar performance was displayed by Cu₂O/Pt–BiVO₄, Pt-(Cu₂O/BiVO₄), Pt–BiVO₄ and Cu₂O/BiVO₄ photocatalysts showing ca. 90% of MO degradation, which could indicate a competitive mechanism between Pt and Cu₂O as co-catalysts of ternary composites. A significant content of Cu₂O in the photocatalysts generated an important dye absorption, like in Cu₂O and Pt–Cu₂O catalysts. Cu₂O/Pt–BiVO₄ exhibited the highest production of hydroxyl radicals, indicating the important role of Pt deposition to increase the photocatalytic performance of the semiconductors via the electron sink effect.