Construction Of Z-scheme Graphitic Carbon Nitride-Based Composite Photocatalyst And Photocatalytic Performance Research

Environmental pollution and energy dilemma have always been major problems that plague mankind to achieve green and sustainable development.Therefore,the conversion of clean solar energy into renewable energy has become a research hotspot for scientists.In recent years,the emergence of semiconductor photocatalysis technology has made it possible to develop and efficiently use solar energy,achieve green management of environmental pollution,and the renewable utilization of clean energy.However,due to the limitations of the photocatalyst itself,the conversion rate of solar energy is still low,and certain screening,doping and even restructuring of the photocatalyst are required.Among them,graphitic carbon nitride(g-C₃N₄)has become one of the most potential photocatalysts due to its unique layered structure,adjustable electronic band position,excellent visible light response and chemical stability.Even so,g-C₃N₄ still has shortcomings such as high photogenerated carrier recombination rate,low interfacial charge mobility,and small light absorption range.Therefore,this article modified the g-C₃N₄ material,prepared a series of new photocatalysts by doping and constructing new heterostructures,and explored the separation of photogenerated carriers,interface charge mobility and optical properties of ternary composites.The photocatalytic activity of the ternary composite material is explored,and the synthesized samples are characterized to determine the optimal conditions and clarify the relevant mechanism.Finally,the photocatalytic performance of ternary composites was evaluated from the degradation of dye and antibiotic wastewater and the photocatalytic H₂O₂ production.The main research contents and conclusions are as follows:1.Construction of Z-scheme heterojunction Bi VO₄/C-dots/g-C₃N₄ photocatalysts with C-dots as the photoelectron transfer media for degradation of minocycline hydrochloride and Rh BIn this work,a novel and efficient Z-scheme heterojunction Bi VO₄/C-dots/g-C₃N₄photocatalysts with C-dots as the photoelectron transfer center were designed.As a solid-state electron medium of composite photocatalysts,carbon dots(C-dots)increase the transition process of photogenerated carriers and inhibit their rapid recombination.FTIR,HRTEM,TEM,XRD and PL were used to investigate the physical and chemical properties of the photocatalysts.Due to the up-conversion photoluminescence characteristics of the C-dots,the Bi VO₄/C-dots/g-C₃N₄ photocatalysts exhibit significant interfacial charge transfer capability and a broader visible absorption range.In addition,the photocatalytic activity of the photocatalysts was improved by changing the doping amount and optimizing the synthesis conditions.As a result,the Bi VO₄/C-dots/g-C₃N₄composites showed remarkable degradation efficiency of minocycline hydrochloride(Mino-HCl)and Rhodamine B(Rh B)under near-visible LED light.Furthermore,the photodegradation efficiency of the Bi VO₄/C-dots/g-C₃N₄-40 photocatalyst was conspicuously improved over those of pure Bi VO₄,g-C₃N₄ and the composites with other content ratios.The comparative experiment also proved that the introduction of carbon dots can enhance the performance of the photocatalyst.Finally,the possible catalytic mechanism was explored via a free radical capture experiment for the active substances,and the excellent photostability and reusability of the Bi VO₄/C-dots/g-C₃N₄ composites were proved through three cycles of experiments.2.Schottky functionalized Z-scheme heterojunction photocatalyst Ti₃C₂/g-C₃N₄/BiOCl for efficient photocatalytic H₂O₂ production via two-channel pathwayUsing solar energy to realize photocatalytic H₂O₂ production is a promising clean energy technology,and the construction of new and efficient photocatalyst is one of the important ways to improve the yield of H₂O₂.In this study,a Schottky-functionalized Z-scheme heterojunction photocatalyst Ti₃C₂/g-C₃N₄/BiOCl(TC/g-CN/BOC)was synthesized by a simple hydrothermal method,which synergistically promoted the formation of H₂O₂ from the conduction band and the valence band,respectively.As a layered material with good conductivity,Ti₃C₂ can form a Schottky junction with N-type semiconductors,capture photocarriers in the conduction band,and promote semiconductor photogenerated electron-hole separation.g-C₃N₄ can construct a Z-scheme heterojunction with BiOCl,which can adjust the position of the energy band,so that the valence band has a stronger oxidation ability,and assists the production of H₂O₂.The physicochemical and optical properties of the photocatalyst were characterized by FT-IR,TEM,XRD,DRS,PL spectroscopy.As the optimal sample,1%TC/g-CN/BOC displayed the highest photocatalytic activity,and the yield of H₂O₂ reached 1275?M within 60 min.The enhanced photocatalytic activity can be attributed to the combined effect of the Schottky junction and the Z-scheme mechanism,which can increase the photocatalytic reaction rate.In addition,the PEC response test and EIS verified the enhanced interfacial charge transfer capability of 1%TC/g-CN/BOC,and combine with the results of free radicals trapping experiments revealed the mechanism of photocatalytic H₂O₂ production.This work provides new ideas for constructing composite photocatalytic materials and further insights into the low-cost production of H₂O₂.