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Recently, Prof. Wei Shiqiang and Prof. Yao Tao of the National Synchrotron Radiation Laboratory of the University of Science and Technology of China have used the Synchrotron X-ray Absorption Spectroscopy (XAFS) technology to accurately design single-site cobalt-based catalysts to achieve solar-driven spontaneous water decomposition. China made important progress. The relevant research results were published in the journal "German Applied Chemistry" (Angew. Chem. Int. Ed. 2017, 56, 9312). The editors were selected as the current hot article "Hot Paper" and at the same time as "Frontispiece." "Report on highlights. The co-first authors of the dissertation are doctoral student Liu Wei and graduate student Cao Linlin.
"Artificial photosynthesis", which uses sunlight to drive water decomposition, is an ideal way to achieve clean, renewable hydrogen production from solar energy, and it is also an ideal way to solve future energy and environmental crises. However, at present, most photocatalysts are difficult to achieve sunlight-driven water decomposition without sacrificing agents, and their efficiency is far from the actual application requirements. The photolysis water process involves complex multi-electron, multi-step reactions. The requirements for the catalyst materials are very high. Not only must the appropriate energy level structure absorb enough visible light, but the key is to effectively separate and transmit the photogenerated electrons. Holes, but also have highly efficient and stable hydrogen production and oxygen production active sites. Therefore, the search for a new, highly efficient, stable, and inexpensive photocatalyst still faces great challenges.
The research group proposed to separate the photoelectron and hole pairs by designing and constructing a single active site structure, and as a co-catalyst to achieve efficient full water repellency (see the figure above). The atomic-scale dispersed structural sites were synthesized by the nano-carbon nitride nano-space confinement effect. Synchrotron radiation X-ray absorption spectroscopy and high-angle annular dark field images clearly formed the single-site Co1-P4 configuration, thereby obtaining a single-site cobalt-based load. Phosphorus doped carbon nitride composite photocatalyst. The composite structure forms a special intermediate state in the electronic energy band structure, which not only greatly improves the visible light absorption of the material, but also effectively suppresses the photoelectron-hole pair recombination, and successfully increases the lifetime of the photogenerated carriers by about 20 times. The photocatalysts they designed achieved a full solution hydrogen production rate of 410.3 μmol h-1 g-1 under simulated sunlight, without sacrificing agents and precious metals, with a quantum efficiency of 2.2% at 500 nm. The single-site composite photocatalyst will provide a new design idea and method for further improving the water decomposition performance of the existing photocatalyst, and at the same time, it provides a new and effective way to explore the catalytic active center and reaction mechanism from the atomic scale.
The study was funded by the National Key R&D Program, the National Natural Science Foundation, and the Hefei University Science Center Fund.
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