The Preparation And Photocatalytic Performance Of Ca₂Fe₂O₅/Graphene Composites

Semiconductor photocatalytic technology has advantages of low cost and no secondary pollution,so it has been widely used in environmental governance.Hence,it is of great significance to prepare photocatalyst with stable chemical properties,high catalytic efficiency and wide range of visible light absorption.As a typical semiconductor with narrow band gap,Ca₂Fe₂O₅ has attracted extensive attentions mainly duo to its high catalytic activity,low cost and environmental friendly.However,the high recombination of photogenerated electrons and holes limits the practical application of Ca₂Fe₂O₅ materials.Therefore,the graphene material was introduced to reduce the high recombination of photogenerated electrons and holes in the Ca₂Fe₂O₅.Graphene,two-dimensional semiconductor,was discovered and synthesized in recent years.The zero energy gap of the graphene is favorable for the electronic transmission on the surface of the composite materials.Thus,graphene can lead to an effective restrain of the electrons and holes recombination in the compound and the larger surface area can provide more active sites.With these in mind,the main purpose of the paper is to prepare Ca₂Fe₂O₅/graphene composites,making Ca₂Fe₂O₅ material photoproduction electrons and holes effectively separated,so as to achieve the aim of improving Ca₂Fe₂O₅ photocatalytic activity.The main work is as follows:?1?Graphite oxide was prepared by improved Hummers method and layered structure grapheme was synthesized via reduced the graphite oxide by hydrothermal method in this artical.The crystal structure and morphological properties of the products were characterized by XRD,SEM,FT-IR and Raman.?2?In the paper,Ca₂Fe₂O₅ materials were prepared by two methods at low temperature.Firstly,the Ca₂Fe₂O₅ porous nanofibers were synthesized via a facile electrostatic spinning combined with sol-gel.Meanwhile,the best synthesis process was explored and studied.The results showed that the Ca₂Fe₂O₅ characteristic diffraction peaks were very obvious when the calcination temperature at 600?,proved that the Ca₂Fe₂O₅ nanofibers had been successfully prepared.At the same time,the uniform spherical Ca₂Fe₂O₅ particles were fabricated by hydrothermal method without any template agent.The influence of the structure and morphology were disscussed by controlling the concentration of NaOH,reaction time,reaction temperation and calcination temperature of the experimental parameter and determined the best experimental conditions.Finally,photocatalytic activity was evaluated by the degradation of methylene blue?MB?under visible light irradiation and the highest photocatalytic activity was observed for the nanofibers calcinated at 600?.?3?Ca₂Fe₂O₅/graphene composites were prepared by hydrothermal method,with the reduction of graphene and the crystallization of Ca₂Fe₂O₅ happened in one step.The Ca₂Fe₂O₅/graphene composites with different quality of graphene were characterized by XRD,SEM,FT-IR and EDS.In this study,the influence of graphene quality on the photocatalytic properties were explored via EIS and though the photocatalytic degradation of methylene blue solution to determine the optimal quality of graphene.The results showed that Ca₂Fe₂O₅/graphene composites had the best photocatalytic activity when the quality of graphene was 5wt %.Finally,the formation process and photocatalytic mechanism of composite materials were put forward.The results show that the enhanced photocatalytic activity of composites may be contribute to the synergistic effect of Ca₂Fe₂O₅ and graphene materials.On one hand,the graphene can effectively restrain the growth of the Ca₂Fe₂O₅ grain.At the same time the graphene has excellent electrical conductivity,as electron transmission channel,making photogenerated carriers efficient separated.On the other hand,the uniform perovskite particles distribute evenly on the sheets of graphene,keeping the layered structure of graphene by increasing the graphene interlayer spacing,which make for the absorption of dye molecules.Therefore,the research work has a certain reference for photocatalytic activity enhancement of other perovskite materials.