Twin crystals with highly ordered atomic arrangement can not only promote the transport of free charge carriers (electrons and holes) inside a single crystalline photocatalyst, but also limit the recombination of photoexcited charge carriers owing to their self-building electrostatic field. Hence, the investigations on twin-dependent photocatalytic performances of crystalline micro-/nanostructures have received much attention in recent years. However, there is still no specialized review article on twin engineering of photocatalysts so far. Herein, the existing twinned micro-/nanostructures, mainly including metal sulfides and metal oxides, are overviewed on the basis of the synthesis engineering, transmission electron microscopy (TEM) characterization and twin-dependent photocatalytic mechanism. Some challenging issues and future directions are also discussed. Expectantly, this minireview would serve as a theoretical guidance for people who are now focusing on twin crystals to design and synthesize novel photocatalysts.

中文翻译：

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光触媒的双重工程：综述

具有高度有序原子排列的双晶不仅可以促进单晶光催化剂内自由电荷载流子（电子和空穴）的传输，而且由于其自生静电场，还可以限制光激发电荷载流子的复合。因此，近年来对晶体微/纳米结构的双依赖光催化性能的研究受到了广泛的关注。但是，到目前为止，还没有关于光催化剂双工程的专业评论文章。在此，基于合成工程，透射电子显微镜（TEM）表征和双依赖光催化机理，概述了主要包括金属硫化物和金属氧化物的现有孪生微/纳米结构。还讨论了一些具有挑战性的问题和未来的方向。期望的是，这项小型综述将为那些现在正专注于双晶设计和合成新型光催化剂的人们提供理论指导。