Synthesis Of Silver Nanoparticles Plasmonic Composite Photocatalysts With Photocatalystic Performance

In recent years,plasmonic photocatalysts(referred that composite photocatalysts composed of nanoparticles with surface plasmon(SPR)resonance effects(such as Ag,Au,Pt,etc.NPs)and semiconductors or other carriers)have become novel visible-light photocatalysts.The plasmonic photocatalysts not only enhance the visible light absorption performance,but also promote the separation of the photo-induced carriers,for facilitating the improvement of the photocatalytic efficiency.To achieve degradation of dye and tetracycline wastewater efficiently,solve the problems of Ag-based compounds as photocatalyst with unstable,small specific surface area,and high recombination rate of photo-induced electron and hole(photo-induced carriers).The study focus on leverage the surface plasmon resonance effect of silver nanoparticles and characteristics of composite photocatalytic materials to develop new visible light photocatalysts,improving photoabsorption and the separation efficiency of the photo-induced carriers over silver-based semiconductor photocatalysts(silver vanadate(Ag3VO4)and silver iodide(AgI)),and then the photocatalytic activity enhanced,moreover,the photocatalytic mechanism was discussed.The main contents are as follows:A facile co-precipitation method was applied to synthesize Ag2MoO4/Ag3VO4 composites with different molar ratios,metal Ag was formed during the initial phase of photocatalysis,resulted in plasmonic Z-scheme Ag2MoO4/Ag/Ag3VO4 photocatalysts,and the crystalline morphology,crystal phase,surface chemical states,photo-absorption property and separation effciency of photo-induced carriers were characterized.The photocatalytic performance of Ag2MoO4/Ag3VO4 composite photocatalysts under visible light irradiation(?>420nm)was evaluated by rhodamine B(Rh B)removal rate.The 5%Ag2MoO4/Ag3VO4 composite photocatalysts(Ag2MoO4/Ag3VO4 molar ratio of 0.05)displayed the highest photocatalytic activity among all samples,higher than Ag2MoO4 and Ag3VO4,Rh B removal rate of 93%within 6 min and the photocatalytic rate is 0.47977min-1,which 2.92 and 66.82 times than that of precurs Ag3VO4 and Ag2MoO4,respectively.After four recycle experiments,the pure Ag3VO4 for the degradation of RhB decreases to 36.8%,while 5%Ag2MoO4/Ag3VO4 composite still keep around 85%,effectively restrain Ag3VO4 photocorrosion.The introduction of Ag2MoO4 could change the crystal size of Ag2MoO4/Ag3VO4,the agglomeration of Ag3VO4 particles were increased,and the SPR effect of Ag and it act as the Z-scheme charge transmission bridge,the separation of photo-induced carriers were promoted,high redox ability of photo-induced electrons and holes were remained,thereby enhancing the photocatalytic activity and stability of Ag2MoO4/Ag/Ag3VO4.The superoxide radical(·O2-),photogenerated holes(h+)and superoxide radical(·OH)were the main active species that promoted Rh B degradation in the photocatalytic system,in which h+ had the greatest effect to Rh B degradation.The plasmonic photocatalysts of visible-light-driven Ag@AgI/CdWO4(AICW)were synthesized via in-precipitation and photoreduction methods,and the crystalline morphology,crystal phase,surface chemical states,specific surface area,photo-absorption property and separation effciency of photo-induced carriers were characterized.The photocatalytic performance of Ag@AgI/CdWO4 photocatalysts towards rhodamine B(Rh B)and tetracycline(TC)degradation under visible light irradiation(?>420nm)was evaluated.AICW-3(the optimal proportion)displayed the highest photocatalytic activity among all samples,higher than Ag@AgI(AI)and CdWO4(CW).Under the optimal experimental conditions(the catalyst concentration was 0.2 g/L,and the initial contaminant concentration was 20 mg/L),Rh B removal rate of AICW-3 was 99.3%after 24 min light irradiation and the photocatalytic rate is 0.1675min-1,which 2.43 and 139.58 times than that of precurs AI and CW,respectively;TC removal rate of AICW-3 was 77.0%after 20 min light irradiation and the photocatalytic rate is 0.1077min-1,which 2.61 and 538.50 times than that of precurs AI and CW,respectively.After five recycle experiments,AICW-3 had high photocatalytic activity,the removal rate of Rh B and TC were 90.2%and 67.6%,respectively.The appropriate band-matching structure between AgI and CdWO4 reduced the bandgap value of the composites,enhanced light absorption and promoted the separation and transfer of photo-induced carriers,and with the SPR effect of Ag assisted,thereby enhancing the photocatalytic activity and stability of Ag@AgI/CdWO4.The superoxide radical(·O2-),photogenerated holes(h+),superoxide radical(·OH)and iodine atom(I0)were the main active species that promoted the degradation of Rh B and TC in the photocatalytic system,in which O2-had the greatest effect to the degradation of Rh B and TC.