Urea-assisted synthesis of carbon-doped BiNbO4 with oxygen vacancies and visible light photocatalytic applications

Abstract

Although carbon doping in simple metal oxides like TiO₂ and ZnO has been proven to increase photocatalytic dye degradation in visible light, it's unclear if carbon doping in complex BiNbO₄ would have the same effect. For the first time, carbon doped BiNbO₄ (U-BiNbO₄) has been synthesized with urea as the carbon source utilizing a simple sol–gel process. The creation of oxygen vacancies and their energy levels in BiNbO₄'s electronic band structure are controlled by the decomposition of urea. X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and carrier scavenging tests verified the presence of surface oxygen vacancies and carbon doping. Both pure BiNbO₄ and U-BiNbO₄ are multi-crystalline structures with orthorhombic and triclinic phases. When compared to pure BiNbO₄, U-BiNbO₄ degraded cationic methylene blue (MB, 75.7 ± 3.5%) and brilliant green dyes (BG, 86.3 3.5%) more efficiently. The creation of carbon modulated oxygen vacancies and the lowering of the bandgap (from 3.19 eV to 2.95 eV for BiNbO₄ and U-BiNbO₄) were also postulated as dye degradation mechanisms. By employing a synthesis method of alternate low- and high-oxygen partial pressures, this novel process might be exploited to construct high-performance Bi-based photocatalysts.