Preparation Of Carbon Based Composites And Their Applications In Environmental Photocatalysis

As one of the most promising routes for alleviating the environmental pollution and energy crisis,the visible light-driven heterogeneous photocatalysis has attracted extensive attention.To date,numerous semiconducting materials have been reported as possible photocatalysts for environmental remediation.However,many photocatalysts cannot be used to eliminate organic pollutant effectively for their poor visible light utilization efficiency and fast recombination process of photo-generated electrons and holes.The construction of composite photocatalyst was recognized as one of efficient strategies towards improvement of photocatalytic performance.Owing to the outstanding optical and electronic properties,remarkable chemical stability,low cost and facile preparation,the carbon based composite photocatalysts have attracted considerable interest in diverse photocatalytic applications.In this thesis,focusing on the development of highly efficient carbon based composite photocatalyst,the main results are summarized as follows:We investigated the photocatalytic property of the composite of C/CaFe₂O₄nanorods（NRs）in an effort to reveal the influences of carbon modification.It was demonstrated that the photocatalytic degradation activity is significantly dependent on the mass ratio of C to CaFe₂O₄.The optimal carbon content is determined to be 58wt%to yield a methylene blue（MB）degradation rate of 0.0058 min^-1,which is 4.8times higher than that of the pristine CaFe₂O₄ NRs.The decoration of carbon on the surface of CaFe₂O₄ NRs can significantly improve its adsorption capacity of MB dye,which is specifically adsorbed on the surface as monolayer according to the adsorption isotherm analysis.The trapping experiments of the reactive species indicate that the superoxide radicals（·O₂^-）are the main active species responsible for the removal of MB under visible light irradiation.Overall,the unique feature of carbon coating enables the efficient separation and transfer of photogenerated electrons and holes,strengthens the adsorption capacity of MB,and improves the light harvesting capability,hence enhancing the overall photocatalytic degradation of MB.The novel and highly efficient Ag₆Si₂O₇/Carbon composite photocatalysts were successfully synthesized by an in situ-precipitation method.The photocatalytic activities of as-prepared samples were evaluated by the degradation of Rhodamine B（RhB）under visible light irradiation（λ?>?420 nm）.It was found that the Ag₆Si₂O₇content in the composite played a key role in affecting the photocatalytic activity.Among all as-synthesized photocatalysts,the 50 wt%Ag₆Si₂O₇/Carbon exhibits the highest activity for RhB degradation,and the apparent reaction rate constant is 3.0 and5.4 times as high as that of pure Ag₆Si₂O₇ and Carbon,respectively.Moreover,in the photodegradation process of the RhB solution,holes and hydroxyl radicals play an important role,which was analyzed using active species trapping experiments.Finally,the intermediates of RhB in the photocatalytic degradation process were analyzed by high-performance liquid chromatography-mass spectroscopy（HPLC-MS）.A possible photocatalytic degradation pathway of RhB was also proposed.