Accelerating directional charge separation via built-in interfacial electric fields originating from work-function differences  

源于功函数差异的界面内建电场调控载流子定向分离的作用机制研究

作　　者：Chao Xue Hua An Guosheng Shao Guidong Yang 薛超;安华;邵国胜;杨贵东(郑州大学材料科学与工程学院,国家低碳环保材料智能设计国际联合研究中心,河南郑州450001;西安交通大学化学工程与技术学院,西安交通大学-牛津大学催化国际联合实验室,陕西西安710049)

机构地区：[1]State Centre for International Cooperation on Designer Low-carbon and Environmental Materials(CDLCEM),School of Materials Science and Engineering,Zhengzhou University,Zhengzhou 450001,Henan,China [2]XJTU-Oxford International Joint Laboratory for Catalysis,School of Chemical Engineering and Technology,Xi'an Jiaotong University,Xi'an 710049,Shaanxi,China

出　　处：《Chinese Journal of Catalysis》2021年第4期583-594,共12页催化学报（英文）

基　　金：国家自然科学基金(U1862105);河南省重点研发与推广专项(科技攻关)(202102210053);中国博士后科学基金(2019M662515);王宽诚教育基金.

摘　　要：In this work,a hierarchical porous SnS_(2)/rGO/TiO_(2)hollow sphere heterojunction that allows highly-efficient light utilization and shortening distance of charge transformation is rationally designed and synthesized.More importantly,an rGO interlayer is successfully embedded between the TiO_(2)hollow sphere shells and outermost SnS_(2)nanosheets.This interlayer functions as a bridge to connect the two light-harvesting semiconductors and acts as a hole injection layer in the tandem heterojunction.The induced built-in electric fields on both sides of the interface precisely regulate the spatial separation and directional migration of the photo-generated holes from the light-harvesting semiconductor to the rGO hole injection interlayer.These synergistic effects greatly prolong the lifetime of the photo-induced charge carriers.The optimized tandem heterojunction with a 2 wt%rGO loading demonstrate enhanced visible-light-driven photocatalytic activity for Rhodamine B(RhB)dye degradation(removal rate:97.3%)and Cr(VI)reduction(removal rate:97.09%).This work reveals a new strategy for the rational design and assembly of hollow-structured photocatalytic materials with spatially separated reduction and oxidation surfaces to achieve excellent photocatalytic performance.近年来,由有机污染物和重金属引起的水污染对人类健康、生态系统和社会可持续发展构成了严重威胁.而光催化技术以其高效、低成本、节能、无二次污染等优点成为解决日益严重的环境污染问题的一个极具吸引力的策略.众所周知,宽光谱吸收、高效载流子分离和快速的表面反应动力学是高性能光催化剂所必备的基本条件.而多孔TiO_(2)空心球具有以下结构优势:(1)成本低、无毒、氧化还原电位适中、物理化学性质稳定;(2)中空结构有利于入射光多重散射,而且大表面积可以暴露更多的活性位点;(3)多孔结构有利于传质过程.但是,窄光谱吸收和低的光生载流子分离效率严重阻碍了空心结构TiO_(2)的实际应用.因此,通过耦合窄带隙半导体构建异质结光催化剂可以有效提高光吸收和促进光生电荷的分离.窄带隙(Eg=2.18–2.44 eV)半导体材料SnS_(2)具有无毒、化学性质稳定、低成本和宽谱响应等诸多优点.若将超薄SnS_(2)纳米片锚定生长在多孔TiO_(2)空心球表面,将对异质结的光催化性能产生显著的影响.一方面,分级结构的空心球具有高可见光捕获率;另一方面,超薄SnS_(2)纳米片具有更短的载流子扩散距离,从而有效地抑制光生载流子在催化剂体相内部复合.然而,由于其能带结构的限制,二元TiO_(2)/SnS_(2)复合材料很容易形成嵌入式I型异质结,在很大程度上降低了光催化氧化还原能力.此外,在光催化剂表面聚集的光生电子和空穴容易发生随机性复合.因此,迫切需要通过引入界面驱动力来调节表面载流子的分离和转移.众多研究表明,通过化学功能化可以实现对还原氧化石墨烯(rGO)的能带结构、功函数、电导率、亲水性和光学性质的调控.功能化的rGO可以作为优良的空穴提取材料,在rGO两侧分别耦合不同能级结构的半导体光催化材料,通过异质界面能级和功函数差异带来的界面

关 键 词：SnS_(2)/rGO/TiO_(2) Hollow sphere PHOTOCATALYST Hole injection layer Cr(VI)reduction 

分 类 号：O643.36[理学—物理化学] O644.1[理学—化学] X703[环境科学与工程—环境工程]