Hydrochloric acid‐mediated synthesis of ZnFe_(2)O_(4) small particle decorated one‐dimensional Perylene Diimide S‐scheme heterojunction with excellent photocatalytic ability

盐酸介导策略合成的具有优异光催化能力的ZnFe_(2)O_(4)小颗粒点缀一维苝二酰亚胺S型异质结

The recyclable and stable ZnFe_(2)O_(4) small particle decorated one‐dimensional perylene diimide(PDI)S‐scheme heterojunction(1D PDI/ZnFe_(2)O_(4))is prepared by the hydrochloric acid‐mediated(HCl‐mediated)strategy,interestingly,the morphology of the 1D PDI/ZnFe_(2)O_(4) can also be effectively regulated by HCl‐mediated process,the existence of HCl can regulate PDI into a uniform rod structure,while the co‐existence of HCl and PDI can limit ZnFe_(2)O_(4) to become the uniform small particles.More importantly,based on the 1D rod structure of PDI and the small size effect of ZnFe_(2)O_(4),carriers can migrate to the surface more easily,which can improve the photocatalytic activity.Meanwhile,due to the appropriate energy level structure,the S‐scheme heterojunction structure is formed between PDI and ZnFe_(2)O_(4),which eliminates meaningless photo‐generated charge carriers through recombination and introduces strong redox to further enhance the photodegradation effect,thereby,1D PDI/ZnFe_(2)O_(4) exhibits excellent photocatalytic ability,under the visible light irradiation,the degradation rate of tetracycline(TC)with 1D PDI/ZnFe_(2)O_(4)(66.67%)is 9.18 times that with PDI(7.26%)and 9.73 times that with ZnFe_(2)O_(4)(6.85%).This work proposes new ideas for the assembly of magnetic organic‐inorganic S‐scheme heterojunction photocatalysts.

由于有机材料的结构多样性,越来越多的研究者选择有机材料作为光催化剂.典型的n型有机半导体苝二酰亚胺(PDI)不仅在可见光照射下有较强的光响应能力,而且有合适的带隙和负导带,使得光激发电子具有较强的还原能力.半导体光催化剂的适用性受到光生载流子复合的限制,而构建S型异质结可有效保证电荷分离,也可保证空穴和电子的强氧化能力和强还原能力.此外,由于普通光催化剂分离回收困难,可以将PDI与磁性半导体ZnFe_(2)O_(4)相结合来构建复合光催化剂,该复合光催化剂可以通过外加磁场进行回收以降低成本,在提高复合光催化剂性能的基础上保证回收率,并且具有较好的光化学稳定性.然而,不同方法制得不同粒径和形貌的PDI或ZnFe_(2)O_(4)的光催化性能也不同.因此控制PDI和ZnFe_(2)O_(4)的形貌对增强光催化活性起着至关重要的作用.本文采用盐酸-介导策略制备了ZnFe_(2)O_(4)小颗粒点缀的一维PDI的S型异质结(1D PDI/ZnFe_(2)O_(4)).实验发现,用盐酸介导策略调控二者的形貌可以使其具有更好的光催化能力.采用透射电镜(TEM)、X射线衍射、X射线光电子能谱等对1D PDI/ZnFe_(2)O_(4)进行表征,通过光降解四环素溶液评价1D PDI/ZnFe_(2)O_(4)的光催化能力和稳定性,并利用DFT理论计算和ESR方法等对1D PDI/ZnFe_(2)O_(4)的光催化机理进行深入的探讨.扫描电子显微镜和TEM结果表明,盐酸介导可有效调控1D PDI/ZnFe_(2)O_(4)的形貌,经过盐酸介导,PDI变成均匀的棒状结构,ZnFe_(2)O_(4)变成均匀的小颗粒,并点缀在PDI上;而未引入盐酸的PDI仍呈不规则块状,其ZnFe_(2)O_(4)仍为小颗粒团聚的大球状结构.XPS结合能的偏移及DFT理论计算结果表明,材料间形成了内部电场.当PDI和ZnFe_(2)O_(4)接触时,为了使PDI和ZnFe_(2)O_(4)的费米能级相同,PDI中的e^(-)通过界面转移到ZnFe_(2)O_(4)中,导致界面处产生了内部电场.同时,由于e^(-)的流失,PDI的带边向上弯曲,而ZnFe_(2)O_(4)的带边向下弯曲.在光照射下,PDI和ZnFe_(2)O_(4)的e^(-)从VB激发到CB.内电场、带边弯曲和库仑相互作用加速了PDI CB上e^(-)和ZnFe_(2)O_(4) VB上h^(+)的复合,也抑制了PDI CB上e^(-)和VB上h^(+)的复合.综上,1D PDI/ZnFe_(2)O_(4)的电子传递机理与S型异质结光催化反应机理一致.光催化剂催化四环素溶液降解性能结果表明,1D PDI/ZnFe_(2)O_(4)催化四环素溶液的降解率分别是PDI和ZnFe_(2)O_(4)的9.18倍和9.73倍.说明通过盐酸介导策略可以有效地调控1D PDI/ZnFe_(2)O_(4)的形貌,使其具有良好的光催化性能和回收再利用性.本文为磁性有机-无机S型异质结光催化剂的组装提供了新思路.