Study On G-C₃N₄ Photocatalytic Performance Of Transition Metals?Cu,Co,Ni?under Coordination Effect

Energy and the environment have been very attractive topics in the field of chemistry and chemical engineering.In recent years,the rapid development of photocatalytic technology,so that more and more people pay attention to this clean,efficient chemical means.Photocatalytic technology has been used in air purification,water purification and the elimination of hazardous waste.Therefore,it is very important to develop photocatalysts that are responsive to visible light and have high electron transport efficiency.The triazine ring structure of graphite-phase carbon nitride?g-C₃N₄?is coordinable,it has good chemical stability and response under visible light irradiation and other advantages,so it has been widely used in photocatalytic technology.In this paper,g-C₃N₄ is mainly used as modified material to improve its photocatalytic activity in view of its disadvantages such as small specific surface area,less active reaction sites and high photoelectron-hole recombination rate.The g-C₃N₄ electron configuration is regulated by the p-orbital coordination between the transition metal d orbital and g-C₃N₄,so as to eliminate defects and enhance photocatalytic performance.The main research contents and results of this paper are as follows:?1?Cu-doped g-C₃N₄?Cu/C₃N₄?was synthesized by a simple thermal polymerization method.By adjusting the amount of transition metal doping,the photocatalytic activity was measured and compared to determine the optimal amount of doping.A series of characterization analysis,including XRD,SEM,EPR active oxygen substance detection,DFT calculation,XPS,UV-Vis,EIS and so on,proved that Cu was successfully doped into the g-C₃N₄ lattice,and Cu filled the vacancy of triazine ring structure as the best coordination electron configuration.Experiments show that Cu/C₃N₄photocatalytic composites have solved the disadvantages of low electron transport efficiency and small specific surface area of g-C₃N₄ with the addition of Cu atoms.Through the detection of reactive oxygen species,Cu/C₃N₄ can efficiently produce·O₂^-and H₂O₂ with good oxidation properties.The production efficiency of reactive oxygen species?·O₂^-and H₂O₂?of optimal sample Cu/C₃N₄-3 greatly exceeds that of g-C₃N₄,which is 4 times and 2.75 times respectively.As can be seen from the experimental results of formaldehyde elimination,modified Cu/C₃N₄ photocatalytic materials have a good performance of photocatalytic elimination of formaldehyde,g-C₃N₄ formaldehyde removal efficiency is only 26%,and Cu/C₃N₄ samples of formaldehyde removal efficiency as high as 85%,a significant improvement.In addition,Cu/C₃N₄ still maintains good chemical stability after five cycles of NO elimination.At the same time,potential photocatalytic reaction mechanism of Cu/C₃N₄ was also proposed.?2?The photocatalytic activity of methyl orange was improved by introducing Co₃O₄into g-C₃N₄?Co₃O₄-CN?via the coordination modification of photocatalyst between d orbital of transition metal and g-C₃N₄ N p orbital.XRD,SEM,UV-Vis,photocurrent and other characterization methods were used to analyze the photocatalytic materials of Co₃O₄-CN.The results showed that the introduction of Co₃O₄ increased the reactive sites of the composite material Co₃O₄-CN,enhanced the electron migration rate,and increased the absorption capacity of the sample to visible light.The results of photocatalytic degradation of methyl orange showed that the photocatalytic activity of Co₃O₄-CN was significantly better than that of g-C₃N₄,and the degradation efficiency was up to 70%,which was 2.15 times higher than that of g-C₃N₄.According to the analysis of photocatalytic results,it is not the case that the more Co₃O₄ is introduced,the better the photocatalytic performance of the sample material is;on the contrary,the photocatalytic degradation performance of 0.1%Co₃O₄-CN is the best,and the composite of photogenerated electron-hole pair can be effectively inhibited.?3?The photocatalytic performance was enhanced by introducing catalyst Ni?OH?₂into g-C₃N₄?Ni?OH?₂-CN?.A series of characterization methods including XRD,SEM,uv-vis and EIS were used to analyze the photocatalytic material.The results showed that the coordination of Ni?OH?₂ to g-C₃N₄ could effectively increase the specific surface area of the composite material,and at the same time have a wider photocatalytic response region.With the introduction of Ni?OH?₂,the photocatalytic performance of composite Ni?OH?₂-CN was greatly improved.The modified material makes up for the shortcomings of g-C₃N₄,reduces the recombination rate of photogenerated electron-hole pairs,and has a good performance and stability of photocatalytic reduction of UO₂²⁺.Among them,the reduction efficiency of 0.5%Ni?OH?₂-CN sample for UO₂²⁺can reach80%within 70 min,which is 3.3 times higher than that of g-C₃N₄.After four cycles,it still maintains good chemical stability.