| Based on urbanization and industrialization,environmental pollution and energy shortage have become urgent global problems.Photocatalysis has become a hot topic in the field of environmental remediation.In order to enhance the photocatalytic activity for the removal of environmental pollutants,a large number of strategies have been adopted to fabricate novel photocatalysts.In recent years,graphite carbon nitride(9-C3N4)attest extensive concern in the field of photocatalysis due to large specific surface area,stability and excellent electrical conductivity.Considering persistent organic pollutants and heavy metals in water,various g-C3N4-based composites had been synthesized via hydrothermal route,calcination method.Then,the as-obtained materials had been characterized via a variety of techniques for analyzing morphology,structure and physical-chemical property.Finally,the photocatalysts were applied to remove persistent organic pollutants from water under the ultraviolet,visible light,near-infrared light exposure,and the mechanisms were also proposed.This dissertation is mainly composed of the following two sections.In the first section,a novel g-C3N4/NiTiO3 composite was fabricated by one-step calcination method using dicyandiamide,tetrabutyl titanate and nickel acetate as the precursors.The samples were characterized by different characterization techniques,and indicated that the hybrids owned a large surface area,mesoporous structure and improved visible light absorption.As the carrier of semiconductor,g-C3N4 improve the performance of photocatalytic NiTiO3 effectively.The optimal g-C3N4 content in the g-C3N4/NiTiO3 composite was 18.4 wt%,and the corresponding visible-light removal rate for nitrobenzene was 0.0132 min-1,about 1.6 times higher than that of pure NiTi03.The enhanced photocatalytic activity may be attributed to the large surface area,stronger absorption in the visible region and efficient electron-hole separation.Cycling experiment also indicated the reusability and stability of g-C3N4/NiTiO3 photocatalysts for pollutant removal.In the second section,a novel Sb2S3/ultrathin g-C3N4 sheets heterostructures embedded with g-C3N4 quantum dots(CNS)was successfully fabricated via a facile hydrothermal process where ultrathin g-C3N4(utg-C3N4)acted as the supporter for solving the problem of no near-infrared response of g-C3N4.From the results of different characterization,it was indicated that loading utg-C3N4 into the Sb2S3 extended the absorption from ultraviolet-visible to near-infrared region.Moreover,the CNS composite exhibits a significant photoelectric conversion property in near-infrared(NIR)wavelength range.The photocatalytic activities of the samples were evaluated by the degradation of methyl orange(MO)upon NIR irradiation.The photodegradation rate of the optimal CNS for MO was 0.0103 min-1,about 2.6 times higher than that of pure Sb2S3.The improved NIR photocatalytic activity may base on the improved absorption in the NIR region,efficient electron-hole separation and the up-converted PL property of g-C3N4 quantum dots. |
