II-VI族硫化物堆垛层错结构的可控制备及电荷分离特性

The roles of crystal defects during the separation and migration of phtogenerated electrons and holes in photocatalytic reactions are still not clear up to now, especially there are no research works focused on the influences of planar defects. As known, stacking faults, planar defects which are quite different from point defects, are always resulted by the changes of atomic stacking sequences with no affect on the lattice integrity. Thus stacking faults may play different roles in photocatalysis compared to those of point defects. Investigations on the crucial roles of stacking faults during photocatalytic process is of great scientific and theoretical importances. II-VI group sulphide semiconductors have been extensively reported to exist in many polytypes consisting of periodically arranged zinc-blende and wurtzite layers induced by stacking faults. The self-polarization of hexagonal structure causes the formation of internal fields with oppsite directions in the neighbouring hexagonal and cubic segments, leading to a significant difference in electrostatic potential around the structure interface.Thus, the photogenerated electrons and holes migrate towards different directions, resulting in the anomalous photovoltaic effect. Obviously, the stacking faults in II-VI sulphide semiconductors are very likely to be benificial for the photocatalytic reactions.Therefore, the goal of this proposal is to investigate the influences of stacking faults on the photocatalytic activities of semiconductors, in order to provide important scientific reference for future works on the design of novel photocatalytic materials. We will try to develop novel synthesis methods for controllable introducing repetitive stacking faults into II-VI sulphide semiconductors in this project, and investigate the influences of planar defects on photocatalytic reactions, finally demonstrate the crucial roles of stacking faults in the separation and migration processes of photogenerated electrons and holes.

晶体缺陷在光催化过程中具体作用的相关研究仍处于起步阶段，特别是特殊面缺陷结构对半导体材料光催化性能的影响尚未见文献报道。II-VI族硫化物半导体材料因其自身结构特点极易形成堆垛层错结构。该结构是典型的面缺陷结构，由晶体内部原子排列次序改变所形成，不改变晶体内部点阵完整性。文献报道II-VI族堆垛层错结构会导致晶体内部形成内建电场并影响光生电荷的空间分布，最终引起光电压叠加，产生反常光伏效应。显然，光生电荷的分离和迁移极有可能受到该结构的重要影响，聚焦于II-VI族硫化物堆垛层错在光催化过程关键作用的研究将具有重要的科学意义。因此，本研究将选择II-VI族硫化物为研究对象，设计向该类半导体材料中引入堆垛层错结构的新型制备方法，以探明堆垛层错对其光催化性能的具体影响，揭示其在光生载流子分离和迁移过程中的关键作用，期望能够为半导体光催化材料研究提供重要的科学依据和研究基础。

晶体缺陷在光催化过程中具体作用的相关研究仍处于起步阶段，特别是特殊面缺陷结构对半导体材料光催化性能的影响尚未见文献报道。II-VI族硫化物半导体材料因其自身结构特点极易形成堆垛层错面缺陷，会导致晶体内部形成内建电场，对光生电荷的分离和迁移有显著的影响。因而，聚焦于II-VI族硫化物堆垛层错面缺陷在光催化过程中关键作用的研究将具有重要的科学意义。本项目以研究II-VI族硫化物半导体材料中面缺陷即堆垛层错结构的存在对其光生载流子分离性能的影响为目的，在堆垛层错结构光催化剂可控制备以及堆垛层错结构强化电荷分离的基本原理揭示方面开展了系统的研究工作。我们利用取向附生生长机制，设计了溶剂热处理超声共沉淀所得硫化物纳米晶的新型制备手段，成功获得了具有较高堆垛层错密度的Cd1-xZnxS固溶体光催化剂，并证明其高效光催化分解水制氢性能与堆垛层错结构的存在密切相关；构建了与堆垛层错结构相对应的闪锌矿-纤锌矿超晶格材料结构模型，采用第一性原理理论模拟手段对其内部的电势变化和载流子分布进行了系统研究，发现纤锌矿结构内部的自发极化效应导致的超晶格结构内部的锯齿形电势分布能够使光生电子和空穴自发地空间分离，是材料在光催化分解水制氢方面显示出优异性能的根本原因；提出了具备闪锌矿-纤锌矿超晶格结构的一维纳米半导体材料是极为理想的能够高效分离、利用光生电荷的光催化剂材料之一，在光催化分解水制氢领域有巨大的应用潜力，并围绕该思想开展了该类特殊一维纳米材料的可控制备工作，取得了较好的研究进展。本项目的相关科学发现拓展了高效半导体光解水制氢材料的设计理念，亦将为原子尺度下晶态纳米材料微观结构的精细调控及其光生载流子行为的实验和理论研究提供重要科学参考。