Green Synthesis Of Efficient Graphitic Carbon Nitride And Their Photocatalytic Activities In Degradation For Organic Pollutants

The global crisis of energy shortage and environmental issues are becoming serious threats to the sustainable development of human society.Semiconductor-based photocatalysis,in which the inexhaustible and clean solar energy can be harvested and utilized as a feasible technology,has gained considerable interdisciplinary attention for its diverse potential in energy and environmental applications.It’s the key factor to design and fabricate highly efficient and enough robust photocatalysts to carry out numerous catalytic reactions.Since the pioneering work in 2009 for visible-light photocatalytic water splitting,graphitic carbon nitride（g-C₃N₄）has been considered as the next generation photocatalyst and also a step to achieve sustainability for artificial photosynthesis and environmental remediation.However,practical applications of g-C₃N₄ are still hindered by several obstacles and shortcomings of common bulk g-C₃N₄ prepared by direct polycondensation from nitrogen-rich precursors,especially the low specific surface area,the limited active sites,the poor adsorption ability of light,the poor dispersion in water and the serious aggregation during the photocatalytic process.In this dissertation,it is the emphasis to design facile,green and efficient strategies and prepare high-efficency and stable modified g-C₃N₄ materials for environmental applications.The main studies were as follows:First of all,we introduced pyrolysis-generated self-producing atmosphere in the preparation of g-C₃N₄ by controlling the entrance of N₂.The experiment results have demonstrated the self-producing atmosphere can create a well-distributed condition and induce the process of condensation.Under the self-producing atmosphere and without any other additives,we fabricated porous g-C₃N₄ nanosheets with more uncondensed amino groups,higher surface area and more homogeneous morphology.Enhanced photocatalytic activity is seen as well from a drastic increase in the degradation of rhodamine B（RhB）.This work provides a simple and efficient strategy for fabricating porous texture and realizing the tunable structure of g-C₃N₄ to enhance its photocatalytic activity.Secondly,based on the conception of self-producing atmosphere,we further developed different modified g-C₃N₄ materials from different precursors.A variety of characterization methods were conducted to analysis chemical and physical properties of the different materials.The adsorption capabilities and photocatalysis activities of different materials were assessed by removal of rhodamine B（RhB）and tetracycline hydrochloride（TC-HCl）.The results indicated that the urea-derived g-C₃N₄ exhibited the strongest adsorption capability and highest photocatalysis activity.We also proposed the possible mechanism of the excellent degradation of pollutants.This work provides a novel modifed g-C₃N₄ material with excellent activity,and meanwhile provides new insights into fabrication of bifunctional catalyst which could be employed for the adsorption and subsequent degradation of harmful organic pollutants.At last,we have successfully prepared a series of carbon-doping petal-like carbon nitride materials using melamine（MA）,cyanuric acid（CA）and2,4,6-triaminopyrimidine（TAP）as raw materials.Compared to the common bulk g-C₃N₄,the texture of modified carbon nitride was optimized to possess high surface area,homogeneous petal-like morphology and porous structure.The prepared materials showed significant enhancement in activity in degradation of rhodamine B（RhB）and tetracycline hydrochloride（TC-HCl）.This work demonstrates a facile and green preparation strategy that simultaneously integrates copolymerization,non-metal doping and molecular self-assembly.And meanwhile,the new as-prepared photocatalyst 0.03TAP-CN demonstrates excellent photocatalytic performance and hold great promise in environmental remediation.