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Nano Research

Article Title

Pseudocapacitive desalination via valence engineering with spindle- like manganese oxide/carbon composites

Authors

Yingsheng Xu, Department of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China; Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China
Shuhong Xiang, Department of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China; Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China
Hengjian Mao, Department of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China; Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China
Hongjian Zhou, Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China
Guozhong Wang, Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China
Haimin Zhang, Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China
Huijun Zhao, Key Laboratory of Materials Physics Centre for Environmental and Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031 China; Centre for Clean Environment and Energy Griffith University Gold Coast Campus QLD 4222 Australia

Keywords

capacitive deionization, manganese oxides, Faradic electrode, desalination, valence engineering

Abstract

Manganese tetravalent oxide (MnO2), a superstar Faradic electrode material, has been investigated extensively for capacitive desalination, enabling higher salt adsorption capacity compared to the great majority of carbonous electrodes. However, few works paid attention on the relationship between the valences of manganese oxide and their desalination performance. For the first time, we prepared the spindle-like manganese oxides/carbon composites with divalent (MnO@C), trivalent (Mn2O3@C) and divalent/ trivalent (Mn3O4@C) manganese by pyrolysis of manganese carbonate precursor under different condition, respectively. The electrochemical behavior in three-electrode system and electrosorption performance obtained in hybrid membrane capacitive deionization (HMCDI) cells assembled with capacitive carbon electrodes were systematically evaluated, respectively. High salt adsorption capacity (as large as 31.3, 22.2, and 18.9 mg·g–1) and corresponding average salt adsorption rates (0.83, 0.53, and 1.71 mg·g–1·min–1) were achieved in 500 mg·L–1 NaCl solution for MnO@C, Mn2O3@C, and Mn3O4@C, respectively. During fifteen electrosorption-desorption cycles, ex-situ water contact angle and morphology comparison analysis demonstrated the superior cycling durability of the manganese oxide electrodes and subtle difference between their surface redox. Furthermore, density functional theory (DFT) was also conducted to elaborate the disparity among the valence states of manganese (+2, +3 and +2/+3) for in-depth understanding. This work introduced manganese oxide with various valences to blaze new trails for developing novel Faradic electrode materials with high-efficiency desalination performance by valence engineering.

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