Study On Doping Graphitic Carbon Nitride And Its Photocatalytic Properties

With the development of society,environmental pollution and energy crisis have become the two most serious problems in today's society.Graphitic carbon nitride?g-C₃N₄?has been widely used in photocatalytic cracking water for H₂ and O₂production,photocatalytic reduction of CO₂,pollutant degradation and other related fields due to its many advantages.It has great potential in solving environmental pollution and new energy development.However,the practical application of g-C₃N₄is limited by the defects of itself,so the researchers focus on morphology regulation,element doping,semiconductor recombination,modification of g-C₃N₄ by copolymer and surface photosensitization to improve its photocatalytic activity.The water pollution is a particularly prominent problem in environmental fields,in order to further improve the degradation efficiency of g-C₃N₄ in the degradation of pollutants,we take method of doping elements to modified and to improve its photocatalytic degradation activity,the specific research contents are as follows:Firstly,g-C₃N₄ was modified by doping phosphorus element with melamine,sodium phosphate and ammonium phosphate as raw materials and the optimum preparation conditions were determined.The results showed that the addition of the phosphorus element could inhibit the growth of the catalyst grain,widen the range of the visible light response of the sample,and improve the utilization rate of the visible light,the width of bandgap is obviously reduced,and the photogenerated electron-hole recombination is effectively restrained,and the photocatalytic performance of the sample is improved significantly.And the photocatalytic activity of P-CN?1:8?was the highest,and its rate constant of photocatalytic degrading RhodamineB was 38 times that of pure g-C₃N₄.Secondly,g-C₃N₄ was modified by doping boron element with melamine,borax,boric acid and boron oxide as raw materials and the optimum doping preparation conditions were determined.The results showed that the addition of boron element inhibited the growth of catalyst grains,but did not change the graphitic structure of the catalyst.At the same time,the response range of the sample to visible light is widened,the utilization ratio of visible light is increased,the width of bandgap is reduced,and the photogenerated electron-hole recombination is effectively restrained.The photocatalytic activity of B-CN?1:6?in the samples with different boron content is the highest.Its rate constant of degrading RhodamineB is 3.1 times that of pure g-C₃N₄.Lastly,g-C₃N₄ was modified by co-doping of P element and B element with melamine,sodium phosphate and boron oxide as raw materials and the optimal doping treatment method was determined.The results showed that the co-doping of P and B element could inhibit the grain growth of g-C₃N₄,and the crystal defects and crystallinity of the samples were balanced.At the same time,the samples doped with P and B element have wider range of response to visible light and larger absorption intensity of light.The efficiency of visible light is higher,the energy band width is smaller,and the photogenerated electron-hole recombination is restrained more effectively.Therefore,the photocatalytic activity of the sample doped with P and B element,that is P-B-CN,is significantly higher than that of pure g-C₃N₄,and its rate constant of degrading RhodamineB is 59.2 times that of pure g-C₃N₄.