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Ion Transport and Competition Effects on NaTi2(PO4)3 and Na4Mn9O18 Selective Insertion Electrode Performance
S Shanbhag1, Y Bootwala1, J F Whitacre1
1Department of Civil and Environmental Engineering, ‡Department of Materials Science and Engineering, §Department of Engineering and Public Policy, and ∥The Scott Institute for Energy Innovation, Carnegie Mellon University , 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 14, 2017
Summary
Electrochemically reversible insertion electrodes show promise for targeted ion removal. Performance depends heavily on electrolyte composition and ion concentration, impacting efficiency and capacity.
Area of Science:
- Electrochemistry
- Materials Science
- Environmental Engineering
Background:
- Insertion electrodes offer potential for selective ion removal from aqueous solutions.
- Understanding electrode material chemistry and electrolyte effects is crucial for optimizing performance.
Purpose of the Study:
- To evaluate the efficiency and capacity of sodium insertion electrodes for targeted ion removal.
- To compare the performance of NaTi₂(PO₄)₃ and Na₄Mn₉O₁₈ in various electrolyte environments.
- To gain mechanistic insight into how solution composition affects electrode performance.
Main Methods:
- Experimental evaluation of two sodium insertion materials (NaTi₂(PO₄)₃ and Na₄Mn₉O₁₈).
- Testing across diverse aqueous solution compositions with varying sodium and non-inserting ion concentrations.
- Analysis of overpotential losses and round trip Coulombic efficiency.
Main Results:
- In dilute solutions, ion transport limitations at the electrode interface reduce removal rates and efficiency.
- Water electrolysis causes parasitic charge loss, especially for electrodes with high redox potentials.
- High concentrations of non-inserting ions impede inserting ion flux, lowering capacity and efficiency.
Conclusions:
- Electrode performance in ion removal is significantly influenced by electrolyte concentration and composition.
- Optimizing insertion electrode design and operating conditions is necessary to overcome transport limitations and enhance efficiency.