Study On Controllable Preparation Of Carbon Nitride Nanotubes And Their Photocatalytic Degradation Of Pollutants Simultaneous With Hydrogen Production

In the first half of the 21st century,developing and utilizing new clean energy has become the consensus of human society.Photocatalytic technology,which is driven by solar energy and appropriate semiconductor as photocatalyst,is considered as an effective way to convert solar energy directly into chemical energy.At the same time,photocatalytic technology plays a great role in the field of environmental protection,such as the degradation of pollutants,reduction of heavy metal,self-cleaning and other aspects.Graphite carbon nitride?g-C₃N₄?has attracted great attention since it was used in the field of photocatalysis.However,the photocatalytic performance is greatly affected by its large volume,small specific surface area,low separation efficiency of photo-generated carrier and slow charge transport process.For this,this thesis combined hydrothermal method/supramolecular self-assembly/ionic solvothermal method with high-temperature calcination and prepared a series of carbon nitride nanotubes.The experiments of dye removal and hydrogen production were carried out,and the synergistic hydrogen production performance of photocatalytic degradation was also explored.The specific research contents are as follows:?1?The synthesis of"red"carbon-rich carbon nitride nanotubes?R-CN?and its degradation synergistic hydrogen production.Carbon nitride nanotubes were synthesized by hydrothermal hybrid precursor and then controlled calcination atmosphere?Air,N₂,Ar?.It is proved by degradation experiments on different pollutants that R-CN calcined under air atmosphere have more excellent photocatalytic activity.After 3 hours of light exposure,the photocatalytic degradation of Rhodamine B?RhB?by R-CN reached 60%,which was about 3 times higher than bulk g-C₃N₄.R-CN can also degrade bisphenol A?BPA?at different concentrations,and the degradation rate of 10 ppm BPA was more than 90%.Through ESR capture experiments,it was known that the holes can oxidize OH^-to produce·OH to degrade target pollutants,efficiently.?2?The synthesis of nitrogen-rich carbon nitrogen nanotubes?CNNTs?and its degradation synergistic hydrogen production.The band and morphology of bulk g-C₃N₄ were further optimized by supramolecular self-assembly method.The constructed tubular structure enhanced separation/migration performance of photogenerated carrier,accelerated the surface interface reaction and enhanced the photocatalytic performance.In the experiment of hydrogen production,using triethanolamine as sacrificial agent and Pt as cocatalyst,the hydrogen evolution rate of CNNTs was 903.11?mol?5 hours of light irradiation?;and the apparent quantum yield?AQY?was 12.54%??=420 nm?.Under the same conditions,in photocatalytic degradation and synergistic hydrogen production experiment,the BPA degradation rate of CNNTs was 92%and simultaneously 13.63?mol hydrogen was produced,which effectively realized the conversion of hydrogen energy.?3?The synthesis of surface cyano-modified carbon nitride nanotubes?IL-CNX?and its degradation synergistic hydrogen production.The prismatic tubular structure carbon nitride was synthesized by using acid ionic liquid as a green template through assisted thermal-calcination method.The results showed that the ionic liquid carbon nitride nanotubes?IL-CN3?whose addition amount is 14.4 mmol have good tubular morphology and the best photocatalytic performance.In the co-production of hydrogen by degradation of BPA,the degradation rate of IL-CN3 for 10 ppm BPA was over 90%,for 20 ppm and 30 ppm BPA were 58%and 54%,respectively;Meanwhile,the synergistic hydrogen production at three concentrations was 1.65,3.87 and 8.34?mol.With the increase of BPA concentration,its degradation rate and hydrogen production increased regularly,thus IL-CN3 can effectively degrade different concentrations BPA and produce hydrogen.The results of mass spectrometry?LC-MS?showed that BPA in this system was completely degraded into small molecules CO₂ and H₂O,and the win-win purpose between pollutant degradation and hydrogen energy conversion was achieved.