Photocatalytic Degradation Of Volatile Organic Pollutants By G-C₃N₄ Quantum Dots

In recent years,the problem of environmental pollution has become more and more serious with the deepening of industrialization.These environmental problems include air pollution,water pollution,solid waste pollution,and so on.Among them,air pollution has become the focus of research in recent years,and volatile organic compounds?VOCs?have become an important pollutant in air pollution.At this stage,VOCs pose a serious threat to the ecological environment and even human health.In recent years,VOCs had been included in the scope of supervision for the first time in China,which brings new opportunities for the development and promotion of VOCs governance technology.Among the many treatment technologies,catalytic oxidation technology can finally mineralize VOCs into CO₂ and water to achieve the purpose of efficiently removing VOCs.The emerging photocatalytic oxidation technology,using sunlight as energy to convert energy into chemical energy through photocatalyst to decompose VOCs into CO₂ and water,is one of the important methods to solve environmental problems,and is also one of the most promising technologies in catalytic oxidation technology.Among many photocatalysts,g-C₃N₄ QDs have excellent light absorption properties and can be used as photosensitizers in photoelectrochemical reactions.In addition,due to the unique photoluminescence?PL?and upconversion photoluminescence?UCPL?characteristics of g-C₃N₄ QDs,they can be used as spectral converters in photocatalysis,especially UCPL behavior can utilize longer wavelengths near-infrared?NIR?light.Not only g-C₃N₄ QDs are composed of abundant elements carbon and nitrogen on the earth,but also g-C₃N₄ QDs also have good biocompatibility and special quantum effects.Therefore,g-C₃N₄ QDs with excellent optical properties are selected as the research.The object,by summarizing the synthesis,properties and applications of its system,provides a theoretical basis for further research.We combine g-C₃N₄ QDs with the wide-bandgap P25?Titanium dioxide in rutile and anatase phase,about 25 nm in size?to improve the visible light absorption and the photocatalytic performance of P25.Finally,the photocatalytic performance of the prepared catalyst is evaluated by self-designed laboratory gas-solid phase photocatalytic degradation system for VOCs.The specific content of this paper is as follows:In order to better simulate the actual situation of VOCs,a set of laboratory gas-solid phase photocatalytic degradation system for VOCs was designed.Firstly,the stability of the system was verified by blank experiment,and then the practicability of the system was evaluated by the known catalysts.This system can not only provide different concentrations of VOCs,oxygen and mixed gases of different humidity,but also regulate the reaction temperature for impact evaluation experiments.In summary,the results show that this system built by us has good stability and practicability.In order to understand the relevant characteristics of g-C₃N₄ QDs,this paper systematically summarizes various preparation methods,excellent optical properties and various applications in the field of photocatalysis of g-C₃N₄ QDs,Which provide theoretical basis for the subsequent experiments.The g-C₃N₄ QDs are prepared by the low temperature solid phase method using urea as nitrogen source and sodium citrate as carbon source,and g-C₃N₄QDs/P25 complexes are synthesized by hydrothermal method.In addition,g-C₃N₄QDs/P25 complexes with different g-C₃N₄ QDs content can be synthesized in different proportions.Experiments on adsorption-photocatalytic degradation of styrene show that g-C₃N₄QDs/P25 complexes exhibit higher photocatalytic properties,which is mainly due to the extension of g-C₃N₄ QDs as a photosensitizer to the visible region which improves the light response of P25 in the visible region.