Microscopic Dimensional Control And Modification Of G-C₃N₄ Photocatalyst

With the development of the times and the improvement of people's living standard,the energy crisis and environmental problems are becoming more and more serious.Solar energy as an inexhaustible source of clean,renewable energy,efficient and rational use of it is our common goal.In recent years,graphite-like carbon nitride?g-C₃N₄?has been widely studied due to its ability to photocatalytic water for hydrogen production under visible light,carbon nitride is rich in simple elements,has good stability against acid and alkali corrosion,and is cheap and easy to prepare.But it is limited by the small specific surface area and high recombination rate of charge carriers.In order to solve these problems,we can modify them through microscopic morphology control and element doping.This dissertation mainly regulates the micro-dimension of g-C₃N₄ to increase the specific surface area of the material and further modify it to effectively inhibit the recombination of photo-generated carriers.Photocatalytic hydrogen production and photocatalytic degradation were used to characterize the changes of the photocatalytic activity of the materials,and the modification mechanism of the materials was studied.Using dicyandiamide as a precursor,bulk g-C₃N₄ was prepared by thermal polycondensation method,and an ultra-thin two-dimensional g-C₃N₄ nanosheet was further prepared by a simple wet mechanical grinding method.Compared to bulk g-C₃N₄,the hydrogen production capacity of the ultrathin two-dimensional g-C₃N₄ nanosheets is increased by 3.2 times.At the same time,90%degradation of rhodamine B can be achieved within 20 minutes,and the material has a good stability.Photoelectrochemical tests were used to investigate the reasons for the improvement in photocatalytic performance of the series of samples.The results show that the mechanical milling process reduces the thickness of the layered structure of g-C₃N₄.The presence of quantum confinement effects broadens the bandgap of the material.The present results indicated that the oxidation capacity of photogenerated holes and electrons mobility on the horizontal plane were increased after exfoliation,thus improving the photocatalysis performance.Bulk g-C₃N₄ prepared from thermal condensation of dicyandiamide and glucose mixture was used as raw materials,further obtain C modified g-C₃N₄ nanosheets through a simple secondary heat treatment.The test results show that the C element was embedded into the g-C₃N₄ structure by replacing the bridge N atom with a C atom,which broadens the light absorption range of the material.At the same time,the formation of delocalization of large?bond accelerates the migration rate of photogenerated carriers,thous improving the photocatalysis performance of the material.