Polarization-induced space charge separation revealed by Dalian Chemicals promotes total photocatalysis
Recently, the Chinese Academy of Sciences Dalian Institute of Chemical Physics State Key Laboratory of Catalysis Basics, Chinese Academy of Sciences Li Can, Researcher Li Rengui, etc., and the Chinese Academy of Semiconductors Researcher Yan Jianchang team, made new progress in the research of artificial photosynthesis system photogenerated charge separation: discovery of polarity induction The surface electric field effectively promotes the spatial separation of photo-generated charges and greatly improves the activity of photocatalytic total decomposition of water. In addition to the crystal morphology and crystal planes that can be used to control the separation of photogenerated charges, for most semiconductor materials, surface polarity characteristics are an extremely common and common material intrinsic property, however, for semiconductor materials, intrinsic polarity The rational design and regulation of the system and its effect on the separation of photogenerated charges are still unclear. In this work, the researchers selected a representative semiconductor gallium nitride (GaN) as a model, and prepared a metal-organic vapor deposition method to prepare a gallium nitride nanorod array structure with clear surface polarity characteristics, and the array structure respectively exposed the polarity of the top Surface and vertical non-polar surface, the study found that the polar and non-polar surface of the GaN nanoarray structure showed obvious photo-generated charge separation characteristics, and the photo-generated electrons were selectively concentrated on the non-polar surface of the nanorod , And the photo-generated holes are concentrated on the polar surface. This is because the dipole moments of the polar and non-polar surfaces are different, which induces the formation of different surface electric fields, thereby driving the selective migration of photogenerated electrons and holes, and the effective separation of photogenerated charges. Further characterization by photoelectrochemical and photocatalytic reactions revealed that the photogenerated charge separation efficiency of GaN nanorods with polar and non-polar faces exceeds 80%, which is more than ten times higher than the charge separation efficiency of GaN thin films, which is reported by similar materials. The highest value of charge separation efficiency. At the same time, based on the photo-generated charge separation effect between polar and non-polar surfaces, the redox dual cocatalysts were constructed on polar and non-polar surfaces, respectively, and the quantum efficiency of photocatalytic complete water decomposition can be increased from 0.9% to 6.9%. This work proposes a universal new photo-separation strategy for photo-generated charge, which lays a theoretical foundation for constructing an efficient artificial photo-synthesis system. At the same time, it also provides new ideas for further understanding and understanding of the essential driving force of photo-generated charge separation. Artificial photosynthesis is a "holy grail" scientific subject in the international scientific field. Photo-generated charge separation is the core scientific issue of artificial photo-synthesis of solar fuel. Designing and developing an efficient photo-generated charge separation strategy to promote the separation and transmission of photo-generated charge has always been a hot topic in this research field. difficulty. The team of Li Can has long been devoted to the cutting-edge scientific problems of artificial photosynthesis of solar fuel, and has made a series of progress. He has successively proposed the mechanism of charge separation of heterogeneous junctions (Angew. Chem. Int. Ed., 2008; ), Found the effect of photo-generated charge separation between crystal planes (Nat. Commun. 2013), developed the photo-generated charge separation strategy of highly symmetric semiconductor materials (Energy Environ. Sci. 2016), and independently developed new technologies for photo-generated charge imaging ( Angew. Chem. Int. Ed., 2015; Nat. Energy, 2018), which has received extensive attention from academia. The research result "Surface polarity-induced spatial charge separation boosting photocatalytic overall water splitting on GaN nanorod arrays" was published online in "German Applied Chemistry" in the form of Full Article. The research work was supported by the Clean Energy Leading Science and Technology Project of the Chinese Academy of Sciences, major research projects of the Chinese Academy of Sciences and the National Natural Science Foundation of China.
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