Preparation And Photocatalytic Performance Of Silver-based Plasmonic Photocatalyst

Loading noble metal nanoparticles on semiconductor materials can enhance photocatalytic activity via surface plasmon resonance(SPR).Herein,the noble metal Ag was combined with AgCl and ZnO semiconductor materials,to obtain two kinds of plasmonic photocatalyst-Ag@AgCl and Ag-ZnO composites.In this dissertation,the reaction mechanisms of material preparation process were interpreted,the photocatalytic activities of the prepared samples were evaluated by the degradation of organic pollutants(including various dyes and phenol),and the possible mechanisms of photocatalysis over the plasmonic photocatalyst were conjectured.The main contents are as follows:(1)A stable magnetic separable plasmonic photocatalyst was successfully fabricated by grafting silver@silver chloride(Ag@AgCl)and ferroferric oxide(Fe3O4)nanoparticles on graphene sheets(denoted as(Ag@AgCl)-Fe3O4/RGO).The composite exhibited high activity degrading methylene blue(MB)and rhodamine B(RB)under visible light irradiation:decomposition 97.4%of MB in 100 minutes and 97.9%of RB in120 minutes.The enhanced photocatalytic activities can be attributed to synergistic effect between Ag@AgCl and graphene:the effective charge transfer from Ag@AgCl to graphene promotes the separation of electron-hole pairs.Moreover,the excellent magnetic property gives a more convenient way to recycle the photocatalysts.(2)The most popular magnetic material Fe3O4 is an important half-metallic material,which exhibits much lower electrical conductivity than that of pure metals.As a result,Fe3O4 particles in photocatalysts may hinder charge transfer process which is essential in photocatalysis.Here we report a new visible light active,stable and magnetically separable plasmonic photocatalyst by anchoring urchin-like Ni and Ag@AgCl nanoparticles(NPs)on the reduced graphite oxide(denoted as(Ag@AgCl)-Ni/RGO).Under visible light irradiation,the photocatalytic performance of(Ag@AgCl)-Ni/RGO in degrading MB(cationic dyes)was better than that of(Ag@AgCl)-Fe3O4/RGO,little worse than that of(Ag@AgCl)/RGO;the photocatalytic performance of(Ag@AgCl)-Ni/RGO in degrading methyl orange(MO,anionic dye)was much better than that of(Ag@AgCl)-Fe3O4/RGO,even better than that of(Ag@AgCl)/RGO.The incorporation of Ni in the photocatalyst rendered strong magnetism thus allowing the catalyst to be conveniently recovered from reaction system.Simultaneously,possession of large specific surface area,good electrical conductivity and strong magnetism makes the Ni/RGO an effective and enhancing carrier for photocatalysts.(3)This dissertation proposed to prepare Ag-ZnO composite derived from Ag-Zn(NO3)2(N2H4)3 energetic material via "detonation deposition" method,which combined annealing and vapour deposition process simultaneously.The molecular structure of ZIF-8 was destroyed by Ag+ to form[Ag,Zna(MeIm)b](x+2a-b)+ polymeric complex via competitive coordination.This immobilization of Zn2+ and Ag+ in the polymeric complex favors the formation of Ag-Zn(NO3)2(N2H4)3 composite after the addition of N2H4·H2O.The Ag-Zn(NO3)2(N2H4)3 composite would self-assemble to form hexagonal prisms structure by oriented attachment under strong centrifugal force.(4)A new energetic material system composed of energetic Ag-Zn(NO3)2(N2H4)3 composite buried in ZIF-8(zeolitic imidazolate framework-8)particles was developed to prepare Ag-ZnO photocatalyst via "detonation deposition" method.Ag-Zn(NO3)2(N2H4)3 composite served as explosive source and zinc source in detonation process.Because of the excellent thermal conductivity,Ag nanoparticles embedded in Zn(NO3)2(N2H4)3 would increase the homogeneity of the whole detonation system.Meanwhile,the surrounding ZIF-8 particles were another zinc source,ensuring the safety and controllability of the whole detonation process.The detonation process introduced a lot of defects in ZnO,which were confirmed by PL(photoluminescence spectrophotometer)spectra.These defects would form multiple defect-related levels in the band gap,which contributed to the excellent photocatalytic performance with the concerted effects from Ag nanoparticles.When Ag-ZnO nanocomposite was used as the photocatalyst,the degradation reaction of MB and phenol could finish within 30 min and 90 min,respectively.