Adsorption-degradation synergetic effects on removal of methylene blue over heterostructured TiO₂/Co₄S_4.23Se _3.77 composites

Novel heterostructured TiO₂/Co₄S _4.23Se_3.77 composites were synthesized by a combination of solid-state and sol-gel methods, and were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and photocurrent measurements. The results of photocatalytic degradation of methylene blue over the as-prepared materials indicate that photocatalytic efficiency is closely related to the composition of the materials, and the 30%TiO₂/Co₄S_4.23Se_3.77 catalyst exhibits the best adsorption and photodegradation efficiency under sunlight or visible-light irradiation. The adsorption capacity of 30%TiO₂/Co ₄S_4.23Se_3.77 for methylene blue is 18.59 mg/g calculated based on the Langmuir adsorption model. Adsorption kinetics studies show that the process fits well with a pseudo-second-order rate mechanism. Recycle experiments confirm that the 30%TiO₂/Co₄S _4.23Se_3.77 catalyst is stable. The present work illustrates a new way for the design and syntheses of stable and high-efficiency catalysts applicable for the degradation of organic pollutants.