Studies On Synthesis And Photocatalytic Properties Of Carbon Nitride And Its Composites

The increasing challenges in environmental pollution concerns and energy shortage issues leads to the considerable progress of semiconductor photocatalysis.Semiconductor photocatalysis has attracted extensive attention in the field of environmental protection,especially in the degradation of organic water pollutants due to the advantages of environment friendly,efficient,energy saving and clean.However,the traditional semiconductor photocatalysts have low photocatalytic efficiency and low photocarrier separation efficiency,which restricts their development in the field of photocatalysis.In this paper,a facile and rapid route is presented for synthesis ultra-thin g-C3N4 nanosheets.Meanwhile,the novel ?-C3N4?CuO and ?-C3N4?Cu2O heterojunction are successfully fabricated via a facile reflux method followed by a thermal process for the first time.The physicochemical properties such as the surface morphology,grain size and micro structure of the samples are systematically studied by various characterization methods.The photocatalytic degradation of MB is used as a model reaction to investigate the activity of the prepared sanples.This work provides an experimental basis for the design and preparation of high-efficiency,high catalytic activity carbon nitride photocatalysts.The main achievements are listed as follows:(1)A rapid and efficien method for the preparation of g-C3N4 nano sheets is developed.The stripping time is only about 1 minute and and yield up to about 30%.Compared with the traditional method,the method does not need to be filtered and repeatedly washed to remove residual acid,and has the advantages of simple operation,high efficiency and reliability.The modified g-C3N4 has an ultra-thin two-dimensional nano sheet structure with an average lateral size of about 75 nm and a minimum thickness of about 4 nm.The apparent reaction-rate constant for the MB degradation of g-C 3 N4 nano sheets is 3.1 times over that of bulk g-C3N4,and has a good stability.This can be attributed to the synergistic effect between the two-dimensional nano flakes and the unique photophysical properties.(2)Novel ?-C3N4?CuO composites are successfully fabricated via a facile reflux method followed by a thermal process.The surface morphology and composition of ?-C3N4?CuO composites can be controlled by regulating the volume water in the mixed precursors.The photocatalytic properties and the growth mechanism of the ?-C3N4 @ CuO nano sheets are systematically investigated.Meanwhile.the trapping experiment is conducted to investigate the role of the active species in the photocatalytic process.The photocatalytic activity for the MB degradation with a?3.4 and 1.9 fold increase in efficiency over that of pure g-C3N4 and commercial P25,respectively.This can be attributed to the combined effects of morphology,structural advantages and heterojunction structure.Based on the solid band theory,the photocatalytic reaction principle of ?-C3N4?CuO nanosheets is explored.(3)Based on a facile reflux method followed by a thermal process,a novel ?-C3N4?Cu2O composite with excellent photocatalytic activity is synthesized.The cupric chloride has a significant effect on crystal morphology and growth of as-prepared samples.When the molar mass ratio of cupric chloride and urea is 1:1,?-C3N4?Cu2O nanowire structure is synthesized with a diameter of about 30 nm.The morphology and photocatalytic properties of the as-prepared samples are investigated.The photocatalytic activity for the MB degradation with a?5.4 fold increase in efficiency over that of pure g-C3N4.To investigate the main active species in the photocatalytic process and reveal the photocatalytic mechanisms over ?-C3N4?Cu2O nano flakes.