skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization

Abstract

We report that hybrid capacitive deionization (HCDI), which combines a capacitive carbon electrode and a redox active electrode in a single device, has emerged as a promising method for water desalination, enabling higher ion removal capacity than devices containing two carbon electrodes. However, to date, the desalination performance of few redox active materials has been reported. For the first time, we present the electrochemical behavior of manganese oxide nanowires with four different tunnel crystal structures as faradaic electrodes in HCDI cells. Two of these phases are square tunnel structured manganese oxides, α-MnO2 and todorokite-MnO2. The other two phases have novel structures that cross-sectional scanning transmission electron microscopy analysis revealed to have ordered and disordered combinations of structural tunnels with different dimensions. The ion removal performance of the nanowires was evaluated not only in NaCl solution, which is traditionally used in laboratory experiments, but also in KCl and MgCl2 solutions, providing better understanding of the behavior of these materials for desalination of brackish water that contains multiple cation species. High ion removal capacities (as large as 27.8 mg g-1, 44.4 mg g-1, and 43.1 mg g-1 in NaCl, KCl, and MgCl2 solutions, respectively) and high ion removal rates (as large asmore » 0.112 mg g-1 s-1, 0.165 mg g-1 s-1, and 0.164 mg g-1 s-1 in NaCl, KCl, and MgCl2 solutions, respectively) were achieved. By comparing ion removal capacity to structural tunnel size, it was found that smaller tunnels do not favor the removal of cations with larger hydrated radii, and more efficient removal of larger hydrated cations can be achieved by utilizing manganese oxides with larger structural tunnels. Extended HCDI cycling and ex situ X-ray diffraction analysis revealed the excellent stability of the manganese oxide electrodes in repeated ion removal/ion release cycles, and compositional analysis of the electrodes indicated that ion removal is achieved through both surface redox reactions and intercalation of ions into the structural tunnels. In conclusion, this work contributes to the understanding of the behavior of faradaic materials in electrochemical water desalination and elucidates the relationship between the electrode material crystal structure and the ion removal capacity/ion removal rate in various salt solutions.« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3];  [1]
  1. Drexel Univ., Philadelphia, PA (United States). Department of Materials Science and Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1422591
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Nano Energy
Additional Journal Information:
Journal Volume: 44; Journal Issue: C; Journal ID: ISSN 2211-2855
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; Hybrid capacitive deionization; Manganese oxides; Electrochemical water desalination; Tunnel crystal structures

Citation Formats

Byles, Bryan W., Cullen, David A., More, Karren Leslie, and Pomerantseva, Ekaterina. Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization. United States: N. p., 2017. Web. doi:10.1016/j.nanoen.2017.12.015.
Byles, Bryan W., Cullen, David A., More, Karren Leslie, & Pomerantseva, Ekaterina. Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization. United States. doi:10.1016/j.nanoen.2017.12.015.
Byles, Bryan W., Cullen, David A., More, Karren Leslie, and Pomerantseva, Ekaterina. Mon . "Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization". United States. doi:10.1016/j.nanoen.2017.12.015. https://www.osti.gov/servlets/purl/1422591.
@article{osti_1422591,
title = {Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization},
author = {Byles, Bryan W. and Cullen, David A. and More, Karren Leslie and Pomerantseva, Ekaterina},
abstractNote = {We report that hybrid capacitive deionization (HCDI), which combines a capacitive carbon electrode and a redox active electrode in a single device, has emerged as a promising method for water desalination, enabling higher ion removal capacity than devices containing two carbon electrodes. However, to date, the desalination performance of few redox active materials has been reported. For the first time, we present the electrochemical behavior of manganese oxide nanowires with four different tunnel crystal structures as faradaic electrodes in HCDI cells. Two of these phases are square tunnel structured manganese oxides, α-MnO2 and todorokite-MnO2. The other two phases have novel structures that cross-sectional scanning transmission electron microscopy analysis revealed to have ordered and disordered combinations of structural tunnels with different dimensions. The ion removal performance of the nanowires was evaluated not only in NaCl solution, which is traditionally used in laboratory experiments, but also in KCl and MgCl2 solutions, providing better understanding of the behavior of these materials for desalination of brackish water that contains multiple cation species. High ion removal capacities (as large as 27.8 mg g-1, 44.4 mg g-1, and 43.1 mg g-1 in NaCl, KCl, and MgCl2 solutions, respectively) and high ion removal rates (as large as 0.112 mg g-1 s-1, 0.165 mg g-1 s-1, and 0.164 mg g-1 s-1 in NaCl, KCl, and MgCl2 solutions, respectively) were achieved. By comparing ion removal capacity to structural tunnel size, it was found that smaller tunnels do not favor the removal of cations with larger hydrated radii, and more efficient removal of larger hydrated cations can be achieved by utilizing manganese oxides with larger structural tunnels. Extended HCDI cycling and ex situ X-ray diffraction analysis revealed the excellent stability of the manganese oxide electrodes in repeated ion removal/ion release cycles, and compositional analysis of the electrodes indicated that ion removal is achieved through both surface redox reactions and intercalation of ions into the structural tunnels. In conclusion, this work contributes to the understanding of the behavior of faradaic materials in electrochemical water desalination and elucidates the relationship between the electrode material crystal structure and the ion removal capacity/ion removal rate in various salt solutions.},
doi = {10.1016/j.nanoen.2017.12.015},
journal = {Nano Energy},
number = C,
volume = 44,
place = {United States},
year = {2017},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 18 works
Citation information provided by
Web of Science

Figures / Tables:

Figure 1 Figure 1: Schematic illustration of ion removal from water via a hybrid capacitive deionization (HCDI) cell. As brackish water is flown into cell, an electric potential is applied across two electrodes. In the carbon electrode, ions are adsorbed on the surface of the activated carbon. In the manganese oxide nanowiremore » electrode, ions chemically react with the surface or intercalate into the structure of the TuMO nanowires, as is shown on the right. The tunnel size is defined by the number of MnO6 octahedra on perpendicular sides of the rectangular tunnels (“X” octahedra x “Y” octahedra). The ionic radius (RI) and hydrated radius (RH) are shown for Cl-, K+, Mg2+, and Na+ ions. A coordination of VI is assumed for ionic radii.« less

Save / Share:

Works referencing / citing this record:

Faradaic reactions in capacitive deionization for desalination and ion separation
journal, January 2019

  • Yu, Fei; Wang, Lei; Wang, Ying
  • Journal of Materials Chemistry A, Vol. 7, Issue 27
  • DOI: 10.1039/c9ta01264h

Faradaic reactions in capacitive deionization for desalination and ion separation
journal, January 2019

  • Yu, Fei; Wang, Lei; Wang, Ying
  • Journal of Materials Chemistry A, Vol. 7, Issue 27
  • DOI: 10.1039/c9ta01264h

    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.