The Controllable Synthesis And Properties Of Ag@AgX (X= Cl, Br) Photocatalysts

Semiconductor photocatalytic materials indicate a promising future in which emerging global issues such as environmental pollution,energy crisis,and global warming could be solved by the means of photocatalysis by utilization of solar energy.In recent years,water pollution has attracted increased attention due to our enhanced awareness of the need for environmental protection.Photocatalysis is considered one of the most promising methods for waste water treatment due to its high-efficient,eco-friendly and low-cost properties.Photocatalysis is considered one of the most promising methods for waste water treatment due to its high-efficient,eco-friendly and low-cost properties.Using solar energy as driving force is an important feature which makes up a primary advantage over fossil energy.As we know,a large portion of solar spectrum is visible light.To take full use of the sunlight,more and more researchers focus on the visible-light-driven photocatalysts.Therefore,development of new structures or new materials with high visible-light performance is the main direction people are continuously pursuing.Noble metal nanoparticles（NPs）such as Au,Ag and Pt NPs have gained wide attention owing to since their high absorption of visible light resulting from the surface plasmon resonance（SPR）effect.Silver halides are an interesting family of visible-driven photocatalysts because of their high initial visible light catalytic activity[1].Since they were firstly proved to be high efficient photocatalysts for the decolorization of organic dyes,silver halides have been widely studied.In this paper,the controllable synthesis of silver halide was studied systematically,and the relationship between the enhanced catalytic activity of silver halides and the morphology design and cocatalyst modification was discussed systematically.Research shows that the well-controlled morphology of silver halide catalysts and the modification of appropriate cocatalyst can greatly improve the photocatalytic activity and stability.This work provides ideas for the extension of silver halide in the practical application and the synthesis of similar photocatalysts.The main research points and conclusions are listed as follows:（1）In order to obtain high visible light active photocatalysts with large surface area and more active sites,a novel polyhedral shell Ag@AgCl photocatalyst was prepared with a facile template-assisted route at room temperature.The polyhedral shell Ag@AgCl photocatalyst showed excellent visible light performance for the degradation of rhodamine b（RhB）and phenol due to its SPR effects and large specific surface area.The novel polyhedron shell Ag@AgCl plasmonic photocatalyst can completely degrade10 mg/L solution of RhB in 150 s.A possible mechanism for the decomposition process of polyhedral shell Ag@AgCl photocatalyst was proposed.It helps insight into the transfer process of photogenerated electrons.（2）In order to obtain highly visible active photocatalysts with large surface area,more active sites and high stability,Cu（II）cocatalyst was modified on 3D structure Ag@AgCl photocatalyst by a simple impregnation method.The modification of Cu（II）cocatalyst significantly enhanced visible light catalysis activity and stability of Ag@AgCl.It was proposed that Cu（II）cocatalyst worked as a reduction active site.Electrons were transferred from valence band of AgCl to the surface of Cu（II）cocatalyst and reacted with oxygen efficiently.（3）On the basis of ensuring large surface area and multiple active sites,highly controllable photocatalysts with high visible light activity are expected through low-cost and simple synthesis method.Stable and highly active hollow porous tetrahedron-shaped Ag@AgBr photocatalysts were prepared via a facile template-assisted method at room temperature,and the amount of the Ag NPs produced in situ could be precisely controlled by adjusting the amount of AgNO₃.The Ag@AgBr tetrahedrons showed remarkable photocatalytic performance under visible light irradiation,and·O₂^-and·OH were confirmed as effective radicals to decompose the RhB molecules into CO₂ and H₂O.