Effect of the microwave-assisted hydrothermal synthesis conditions on the photocatalytic properties of BiNbO4 and silver nanocomposites

Developing new photocatalysts based on metal oxide semiconductors for dye degradation under sunlight irradiation is an expanding area of research. These studies mainly focus on efficiency enhancement by controlling the morphology and crystalline structures, lowering the bandgap energy, and adding co-catalysts. Here we describe the microwave-assisted hydrothermal synthesis of bismuth niobate nanostructures (BiNbO4) and its decoration with silver nanoparticles through an in situ microwave-assisted reflux synthesis. The resultant catalyst was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance, zeta power and electrochemistry. Furthermore, the photocatalytic activity was evaluated by quantifying hydroxyl and superoxide radicals generated by holes and electrons photogenerated on the catalyst surface, respectively, and through the degradation of Rhodamine B. The studies revealed that the crystalline structure strongly depends on the irradiation conditions, forming a mixture of triclinic and orthorhombic BiNbO4. Also, the decoration method results in the formation of metallic Ag, AgO and Ag2O. As a result, the catalyst formed by BiNbO4 synthesized at 150 °C and 550 W irradiation power, decorated with silver nanoparticles, showed the highest photocatalytic activity (32.6%).