Synthesis of core/shell cobalt-doped rutile TiO2 nanorods for MB degradation under visible light

Although TiO2 has been widely applied in many fields, the design and preparation of one-dimensional rutile TiO2 nanomaterials for high-efficiency photocatalysis under visible light remain challenging. Herein, uniform Co-doped rutile TiO2 nanorods with selective adsorption and photocatalytic activity for methylene blue (MB) have been developed via a one-pot molten salt flux method. Compared to pure rutile TiO2 nanorods, the Co-doped rutile TiO2 nanorods exhibited an obvious core/shell structure with smaller inner crystal face spacing (d001 = 0.20 nm) and a larger rough surface (the BET specific surface area is 25 m2 g−1). Furthermore, different dyes were employed to investigate the adsorption ability of Co-doped rutile TiO2 nanorods. The density functional theory (DFT) calculations determined that both the electrostatic potential and molecular structure could influence the adsorption behavior on the photocatalyst surface. The results indicated that the Co-doped TiO2 nanorods possessed a high selective adsorption capacity for MB (134.54 mg g−1 in neutral solution). The degradation of MB using Co-doped rutile TiO2 nanorods was conducted under visible light irradiation, yielding with an apparent rate constant of 0.301 min−1 at pH = 7. The degradation mechanism was further explored through electron spin resonance (ESR) experiments, which identified the formation of superoxide anions (·O2−) and hydroxyl radicals (·OH) in the system. This study provides a new strategy for preparing novel rutile TiO2 photocatalysts for the degradation of organic dyes under visible light.