| In this paper,nitrogen was doped in titanium dioxide by solvothermal method,obtaining the ability to respond visible light,as the traditional UV-type photocatalyst.The graphitic carbon nitride with mesoporous structure was successfully synthesized through the soft-template process.Herein,heterostructured photocatalysts composed of nitrogen-doped titanium dioxide and mesoporous graphitic carbon nitride were characterized to systematically investigate the photoactivity,crystal structure,morphology and size of composite materials.The separation and transfer efficiency of photo-generated carriers,radicals,the major active species were detected in the photocatalytic reaction through photoelectrochemical measurements and the analysis of photocatalytic mechanism to understand the reasons for enhancing photocatalytic performance and potential mechanism.Therefore,designing and preparing novel photocatalysts with visible-light response,high photocatalytic efficiency and strong redox ability is of great significance for photocatalysis research.This paper would provide some theoretical principles and experimental evidence for further research and development.The influence of the molar ratio of urea to titanium butoxide on structure and the degradation of methylene blue was studied by exploring the preparation process of nitrogen-doped titanium dioxide.Experimental results demonstrated that the suitable nitrogen source was urea and the best molar ratio of urea to titanium butoxide was 3 : 1.The nitrogen-doped titanium dioxide with textured surface,wrinkle and porous structure was prepared under these conditions.The samples were characterized using XRD,SEM,nitrogen adsorption,XPS,UV and PL to study on the modified mechanism of nitrogen.XRD results showed that the anatase phase had been retained without phase change after nitrogen doping.SEM results showed that the samples had the morphology of the sphere,no matter what urea or triethylamine.The photocatalysts with textured surface,wrinkle and porous structure were synthesized when the molar ratio of urea to titanium butoxide was 3 : 1.Nitrogen adsorption results showed that the photocatalysts with mesoporous structures and high specific surface area could be synthesized by adopting the best molar ratio of urea to titanium butoxide.XPS results showed that nitrogen doped into the lattice and changed the chemical environment of the elements,which caused partial electron transfer from the nitrogen to titanium,reducing the binding energy.UV-visible DRS results showed that the doping of nitrogen enhanced the light absorption capacity and decreased the band gap as well as promoted the photocatalytic activity.PL results showed that the fluorescence emission peak was the weakest and the recombination rate of the photo-generated carriers was the lowest when the molar ratio of urea to titanium butoxide was 3 : 1.The influence of the mass ratio of mesoporous graphitic carbon nitride to nitrogen-doped titanium dioxide on the degradation of methylene blue was studied by exploring the preparation process of composite materials.When the best mass ratio of mesoporous graphitic carbon nitride to nitrogen-doped titanium dioxide was 1 : 2,the composites could obtain the highest photocatalytic activity.The samples were characterized using XRD,SEM,TEM,nitrogen adsorption,XPS,FT-IR,UV and PL to study on potential photocatalytic mechanism.SEM results showed that nitrogen-doped titanium dioxide particles were mainly loaded into holes of graphitic carbon nitride.XRD and TEM results showed that the composites were made up of mesoporous graphitic carbon nitride and nitrogen-doped titanium dioxide.Nitrogen adsorption results showed that specific surface area and photocatalytic activity of the composites had been elevated by loading nitrogen-doped titanium dioxide on the surface of mesoporous graphitic carbon nitride.XPS results showed that the density of electron atmosphere on the titanium atom had been weakened and the binding energy had been reduced,because of partial electron transfer from the nitrogen to titanium.FT-IR results showed that there was an interface with strong interaction between mesoporous graphitic carbon nitride and nitrogen-doped titanium dioxide,which accelerated the transfer efficiency of photo-generated carriers and photocatalytic activity.UV-visible DRS results showed that an additional absorption in the region of ca.400–430 nm in the composites.PL results showed that the composites could reduce the recombination rate of the photo-generated carriers.Photoelectrochemical measurements results showed that the composites could obtain higher transfer efficiency of photo-generated carriers and photocatalytic activity,when the best mass ratio of mesoporous graphitic carbon nitride to nitrogen-doped titanium dioxide was 1 : 2.The analysis of photocatalytic mechanism results showed that superoxide redical and hydroxyl redical were major active species which could effectively enhance separation of the charge carriers and redox ability,implying photocatalytic mechanism of composites was accord with Z-scheme heterojunction. |
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