Electrochemical water desalination techniques are an attractive alternative to the conventional technologies, such as reverse osmosis, because of their potential for reduced energy consumption. One such electrochemical desalination technology is capacitive deionization (CDI), a technique that utilizes capacitive carbon-based electrode materials to store salt ions in the electrical double layer. CDI is compelling because it can operate without the use of membranes, but its ability to desalinate water is limited by small salt storage capacities intrinsic to capacitive electrode materials. In response, researchers are exploring faradaic materials to replace capacitive materials. Faradaic materials, such as manganese oxides, differ from purely capacitive materials because they have far higher salt storage capacities due to their abilities to store charge via redox reactions between cations in solution and the oxide crystal structure, in addition to capacitive reactions. Previous research in our group showed that manganese oxide salt storage capacities are strongly influenced by the crystal structure of the oxide. The goal of this study is to optimize the performance of electrochemical desalination with manganese oxide electrodes and to identify parameters that can be used to predict material performance in the future. We systematically characterized the material properties, electrochemical properties, and desalination performance of a suite of manganese oxide powders of varying crystal structures. Initial experiments indicate that layered manganese oxides produce the highest storage capacities, regardless of measured BET surface areas, owing to its ability to readily accommodate ions within the interlayer space.

Electrochemical water desalination: Framework for selecting among manganese oxide electrode materials

2019 Spring National Meeting

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