Controllable Synthesis And Properties Of Hierarchical Structure Ag/ZnO

In this paper,the precursors for Ag/ZnO have been prepared via a solution phase method at 90 ? by using zinc acetate and silver nitrate as salt sources ?Ag/ZnO hierarchical structures with remained structures and morphologies were successfully obtained by calcining the precursors at 300 ?.The preparation of Ag/ZnO assemblies with controlled morphologies and structure can be realized by adjusting the type and/or concentration of precipitants and complexing agent.The crystal phase and morphologies of the samples were characterized using XRD and SEM.The optical properties of Ag/ZnO were characterized by UV-vis DRS spectra and PL spectra.The electrochemical properties such as EIS spectra and Mott-Schottky curves have also been measured.The performances of Ag/ZnO samples in adsorption and photocatalytic decomposition of organic dyes in water and photocatalytic hydrogen evolution have been investigated.The research results are summarized as follows:(1)Porous Ag/ZnO hierarchical structures assembled with nanosheets were synthesized by using urea asprecipitants and sodium potassium tartrate as complexing agent.The as-prepared porous Ag/ZnO composites were evaluated as photocatalysts in photocatalytic hydrogen evolution and 4-nitrophenol(4-NP)decomposition in aqueous solution under visible light irradiation.The results demonstrate that the photocatalytic activities of the composites were strongly influenced by the loading dosage of silver.UV-vis diffuse reflection spectroscopy and the Mott-Schottky technique were carried out to investigate the influence factors of the enhanced photocatalytic activity.The reactive radicals involved in the photocatalytic process were examined in detail via active species trapping experiments.The possible mechanism of high photocatalytic activities was also discussed.The improved photocatalytic activities can be attributed to the synergetic effect between ZnO nanosheets and sliver nanospecies,whichbenefits the migration of photo-induced charge carriers and enhances the redox activity.(2)Ultra long Ag/ZnO nanowire bundles with different Ag loading have been successfully synthesized when much higher concentration of potassium sodium tartrate was added.The experiment results show that the Ag nanoparticles were successfully loaded on the surface of ultralong ZnO nanowires.It was found that the ultralong Ag/ZnO nanowire bundles show excellent photocatalytic activity for decomposition of Methylene blue(MB)dyes in aqueous solution at room temperature.The Ag/ZnO nanowire bundles with 1% Ag have the highest photocatalytic activities.The possible growth mechanism for Ag/ZnO nanowire bundles was discussed.(3)Ag/ZnO hierarchical structures assembled with nanobelts were synthesized with both HMT and urea as precipitants in the absence of a ligand.The photocatalytic properties of as-prepared samples have been investigated,such as photocatalytic decomposition of organic dyes,photocatalytic hydrogen evolution,and other photoelectrochemical properties.The results show that urea dosages have great influence on the photocatalytic activity of the as-prepared samples.The sample prepared by using 1 g urea has the highest photocatalytic activity for dyes decomposition and hydrogen evolution,due to its higher light harvesting efficiency and faster charge carrier separation.The generation of ·OH radical was confirmed by the coumarin fluorescent method.Furthermore,possible photocatalytic reaction mechanism was discussed.