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 hexachlomplatinic 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.