Ag2CO3@AgBr复合光催化剂的制备、表征及其可见光催化性能

Synthesis and characterization of core-shell like Ag2CO3@AgBr composite photocatalyst and its high visible light photocatalytic performance

  • 摘要: 采用连续沉淀法合成了类似核/壳结构的Ag2CO3@AgBr复合光催化剂.利用氮气物理吸附、X射线粉末衍射、扫描电镜、透射电镜、光电子能谱、紫外-可见漫反射和光电流等测试手段对所制备的AgBr、Ag2CO3和Ag2CO3@AgBr进行了系列表征,考察了AgBr壳对Ag2CO3的组织结构、光吸收、光电流响应性能和光催化性能的影响.结果表明,在Ag2CO3晶体表面的复合AgBr纳米颗粒,能显著增强催化剂在可见光区的吸光性能、增大催化剂的比表面积和增强光电流响应强度.在可见光下(400 nm<λ<660 nm),催化降解甲基橙测试表明,Ag2CO3@AgBr表现出优异的光催化性能,其降解速率常数分别是纯Ag2CO3和AgBr的11倍和10倍,同时其稳定性也得到大幅度提高.在核/壳界面中,形成了具有能级匹配的Ag2CO3@AgBr异质相结,这种异质相结提高了光生电子和空穴的分离效率,同时壳层AgBr可以阻止主体光催化剂Ag2CO3在水溶液中的溶解,提高其稳定性.

     

    Abstract: Core-shell like Ag2CO3@AgBr composite photocatalyst was fabricated by the successive precipitation method. The obtained AgBr, Ag2CO3, Ag2CO3@AgBr samples were well characterized by N2 physical adsorption, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectra, and photocurrent test. The effects of AgBr shell on the texture, light absorption, photocurrent response and photocatalytic performance for main Ag2CO3 photocatalyst were investigated. The results showed that Ag2CO3@AgBr composite displayed much stronger and broader visible light absorption than pure AgBr and Ag2CO3. A distinct increase in both surface area and photocurrent density for Ag2CO3@AgBr was observed. Under visible light (400 nm < λ < 660 nm) irradiation, the photocatalytic activity test in degradation of methyl orange (MO) dye showed that Ag2CO3@AgBr showed excellent photocatalytic activity and the degradation rate constant over Ag2CO3@AgBr (0.209 min-1) was 14 times higher than that of Ag2CO3 (0.0136 min-1), 10 times faster than that of AgBr (0.0180 min-1). Moreover, in recycling photoactivity tests, AgBr and Ag2CO3 fast lost the activity, but high stabilty was obtained over Ag2CO3@AgBr. Between the AgBr shell and Ag2CO3 core, the produced intimate Ag2CO3/AgBr interface with matched band-gap structure largely promoted the transfer of photogenerated electrons and holes. Moreover, the AgBr shell could effectively inhibit the dissolution of Ag2CO3 in aqueous solution, resulting in extremely high stability.

     

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