Preparation And Performance Study Of Ag/NaCNN/NiFe-LDH Photocatalys

In recent years,global concerns about resource scarcity and environmental pollution have been increasing,and semiconductor photocatalysts,as an environmentally friendly technology,provide new solutions to the above problems.Among them,layered double hydroxides have potential research value in the field of photocatalysis because of their special layered structure,high specific surface area and highly dispersed metal composition.This topic deals with the preparation and performance of nickel-iron layered double hydroxides(NiFe-LDH)-based photocatalysts.The Fenton-like reaction of NiFe-LDH gives it an advantage in degrading pollutants,but the single NiFe-LDH-based material has the problems of high photogenerated charge complexation and low transfer rate.Therefore,in this work,we load C3N4 and Ag NPs on NiFe-LDH to construct a Z-scheme heterojunction system,to improve the separation and transfer of photogenerated charges.Ag/NaCNN/NiFe-LDH shows great improvement in both photocatalytic degradation of pollutants and hydrogen production.This topic is discussed in the following aspects:(1)NiFe-LDH in the form of flower spheres is prepared by a simple hydrothermal method,and then Ag/NiFe-LDH is prepared by depositing Ag NPs on NiFe-LDH by in situ deposition.Ag/NiFe-LDH exhibits excellent photocatalytic activity under visible light,and the flower sphere structure exposes a large number of surface active sites that allow multiple reflections and refractions of sunlight within the sphere,thus improving the utilization of light.The degradation efficiency of Ag/NiFe-LDH for 4-NPs and BPA could reach 60.7 and 70.5%,both of which are higher than that of single NiFe-LDH material.The improved photocatalytic performance is attributed to the photocatalyticFenton-like coupling system that generates highly reactive·OH involved in the degradation of pollutants,and the SPR effect that accelerates the transfer of photogenerated carriers and broadens the photoresponse range of the material,and the synergy of these two effects can effectively improve the photocatalytic performance of the composites.(2)Alkali metal Na-doped and N vacancy C3N4 nanosheets(NaCNN)are prepared by calcination and ion thermal methods,and ternary composite photocatalysts Ag/NaCNN/NiFe-LDH are prepared by loading NaCNN and Ag NPs onto NiFe-LDH blobs.The introduction of doping and defects can change the electronic structure and band gap structure,which can increase the specific surface area and active site density and accelerate the transfer kinetics of photogenerated carriers.The Z-scheme heterojunction constructed in Ag/NaCNN/NiFe-LDH can make it difficult for electrons and holes to compound,thus enhancing the charge separation efficiency,improving the redox ability in photocatalytic reactions and enhancing the absorption of light.The Ag/NaCNN/NiFe-LDH degradation efficiencies of 98.9 and 99.1%are achieved for both 4-NPs and BPA,and the hydrogen precipitation rate is 0.543 mmol h-1,indicating the excellent photocatalytic performance of the composite samples.