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A High-Efficiency Hematite Photoanode with Enhanced Bonding Energy Around Fe Atoms
Authors:Dr. Yangchun Lan  Dr. Shuai Kang  Dr. Dehu Cui  Zhuofeng Hu
Affiliation:1. School of Microelectronics, Southern University of Science, and Technology, Shenzhen, 518055 P. R. China

These authors contributed equally to this work.;2. Micro-nano Manufacturing and System Integration Center, Chongqing Institute of Green and Intelligent Technology (CIGIT), Chinese Academy of Sciences, Chongqing, 400714 P. R. China

These authors contributed equally to this work.;3. School of Microelectronics, Southern University of Science, and Technology, Shenzhen, 518055 P. R. China;4. School of Environmental Science and Engineering, Guangdong, Provincial Key Laboratory of, Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275 P. R. China

Abstract:Hematite nanoarrays are important photoanode materials. However, they suffer from serious problems of charge transfer and surface states; in particular, the surface states hinder the increase in photocurrent. A previous strategy to suppress the surface state is the deposition of an Fe-free metal oxide overlayer. Herein, from the viewpoint of atomic bonding energy, it is found that the strength of bonding around Fe atoms in the hematite is the key to suppressing the surface states. By treating the surface of hematite with Se and NaBH4, the Fe2O3 transforms to a double-layer nanostructure. In the outer layer, the Fe−O bonding is reinforced and the Fe−Se bonding is even stronger. Therefore, the surface states are inhibited and the increase in the photocurrent density becomes much faster. Besides, the treatment constructs a nanoscale p–n junction to promote the charge transfer. Improvements are achieved in onset potential (0.25 V shift) and in photocurrent density (5.8 times). This work pinpoints the key to suppressing the surface states and preparing a high-efficiency hematite nanoarray, and deepens our understanding of hematite photoanodes.
Keywords:bonding energy  electrochemistry  hematite  photoelectrochemistry  surface state
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