Preparation And The Photocatalytic Properties Of Cobalt-based Nanocomposites With Metal Organic Framework Template

Co-based photocatalysts and photocatalytic processes have attracted much attention recently.Compared with TiO2 investigated mostly,Co-based photocatalysts are an intriguing semiconductor,the narrow band gap of Co-based oxides or sulfides could reduce the excitation energy of electron-hole pairs separating,while the high electron mobility is benefit for photocatalytic activity improvement.Unfortunately,it is generally accepted that the fast recombination of photogenerated electron-hole pairs is still a significant challenge.The construction of composites with metal-organic framework precursors has been paid close attention for application of versatile functionalities.Such materials usually have controlled morphology,higher surface area and porosity.Many methods have been developed and applied to improve photocatalytic performance,such as heterojunction and noble metal load.In this study,cobalt oxide heteronanostructures with well-controlled morphology are fabricated by means of topotactic transformation of metal-organic frameworks.The morphology of as-prepared samples were performed by Scanning electron microscopy(SEM)and Transmission electron microscopy(TEM),as well as the specific surface area were detected by BET N2 adsorption-desorption isotherms.The crystalline phase and chemical composition analysis of composite materials were carried out by the X-ray diffractometer(XRD),X-ray photoelectron spectroscopy(XPS)and thermogravimetric analysis(TG).The converted C doping hybrid nanocomposite with large specific area has advantage in charge transfer and charge-separation efficiency,and then is evaluated by degrading methylene blue(MB)under visible light irradiation(? > 400 nm).The degradation efficiency of ZnO/Co3O4/C reached 95 %,8.4 times that of ZnO/C,and the degradation effect of ZnS/CoS2/C achieved 85 %,3.2 times than ZnS/C.the way of deposition of noble metals was adopted for Ag50-Co3O4/CNTs,the degradation of MB was up to 90 %,which was 4.6 times that of Co3O4/C.The experiment demonstrates the catalytic performance of the hybrid nanocomposite with controlled microstructure is much higher than simplex substance.Importantly,the in-situ synthesized composites show noteworthy stability and recyclability,even after five runs.A possible photocatalytic mechanism also is mentioned,the results illustrate that synergistic effect of coupled semiconductor system with C doping dramatically suppresses the recombination of photogenerated electron-hole pairs,and it is concluded that which active substance plays an important role in the process of photocatalytic degradation.This work exhibits an effective method for the design of other nonmetal doping sound heterojunctions with well-controlled morphology that significantly enhance photocatalytic behavior.