The Dalian Institute of Chemicals, Chinese Academy of Sciences, developed a new technology to inhibit the reverse reaction of photocatalytic water splitting of water to hydrogen production

The cover image was produced by the Science Visualization Center of China Science Daily

Recently, Academician Li Can, academician Li Can, postdoctoral fellow Li Zheng and Li Rengui, State Key Laboratory of Basic Catalysis and Solar Energy Research Department, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, have made new progress in the research of the reverse reaction of nanoparticle photocatalytic complete decomposition of water to hydrogen (the reaction of hydrogen and oxygen combined to form water), confirmed that the photocatalytic complete water splitting reverse reaction occurs at the low coordination active site, and uses atomic layer deposition technology to accurately modify the inverse reaction, thereby significantly improving the performance of photocatalytic complete water splitting.

On January 12, 2023, the research results were published in Nature Catalysis under the title “Blocking the reverse reactions of overall water splitting on a Rh/GaN–ZnO photocatalyst modified with Al2O3”. The co-first authors of the work are Li Zheng and Li Rengui.

Solar photocatalysis to completely split water to produce hydrogen not only has an important application background, but also is a frontier topic in the field of basic science. Among them, the hydrogen-oxygen reverse reaction on the surface of the cocatalyst in the photocatalytic complete decomposition of water system is an important problem in this field for a long time. The existence of the reverse reaction makes the efficiency of the photocatalytic system for complete water decomposition very low, and even the water splitting reaction cannot be realized, which is the “last mile” of photocatalysis to completely split water. Li Can’s team has long been committed to the research on the catalytic action of cocatalysts and their surfaces in photocatalytic decomposition water, and has made a series of important progress: the concept of double cocatalysts was proposed and developed earlier in the world (J. Catal.,2009;Catal. Lett.,2010;Acc. Chem. Res.,2013;Energy Environ. Sci., 2016), and developed a mononuclear manganese water oxidation catalyst with an activity comparable to the oxygen-producing activity of natural water oxidation catalysts (Nat. Catal., 2018), which has received extensive attention from the academic community.

This work focuses on the hydrogen-oxygen reverse reaction of the cocatalyst surface in the photocatalytic complete water splitting system, and takes the typical catalyst Rh/GaN-ZnO of the visible photocatalytic complete water splitting as the research object, and deposits alumina (Al2O3) to the photocatalyst reaction center by atomic layer deposition (ALD), which can significantly improve the activity of photocatalytic total water splitting. It was found that ALD deposition of Al2O3 could reduce the inverse reaction on Rh/GaN-ZnO by 90%, and further proved through spectral characterization combined with theoretical simulation that Al2O3 was mainly deposited on the low coordination site on the surface of Rh nanoparticles, revealing that the low coordination site on the Rh surface was the main reaction site of the hydrogen-oxygen reverse reaction. The team selectively deposited Al2O3 on the low coordination site on the Rh surface through ALD, effectively blocking the occurrence of hydrogen-oxygen reverse reaction, thereby increasing the quantum efficiency of visible photocatalytic complete water splitting on Rh/GaN-ZnO from 0.3% to 7.1%. In addition, this work also found that the strategy of selective deposition of oxides by ALD can also be applied to other noble metal cocatalysts, proving the universality of this strategy. This work clarifies the active site and mechanism of the reverse reaction of hydrogen-oxygen in photocatalytic complete decomposition of water, which provides a new universal strategy for solving this challenging problem.

The theoretical simulation part of this work was mainly completed with the team of Xiao Jianping, a researcher in the research group of the Theoretical Catalysis Innovation Special Zone Research Group of the State Key Laboratory of Fundamentals of Catalysis. The above work has been supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China “Artificial Photosynthesis” Basic Science Center and other projects. (Source: Science Network)

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