Decoupling the electrochemical behavior of associated manganese oxide (MnO2) and the capacitive property of microporous carbonaceous support allows one to have deep insight in a capacitive deionization (CDI) process. A series of electrodes with different MnO2/carbon weight ratios were thus fabricated in this study and their CDI performances were evaluated by operating at different applied potentials in three consecutive charging/discharging circles. Interestingly, it was noted that the capacitance of the electrodes decreased proportionally with increasing MnO2/carbon weight ratio. However, high CDI performances were often observed at electrodes associated with certain amount of MnO2, which was of particularly significant when applied potential exceeded -1.2 VRHE. It is therefore proposed that salt removal at low operation potential is mainly attributed to the electric double layer (EDL) capacitance arisen by microporous carbonaceous materials. By contrary, operation under high applied potential led high CDI performance, presumably through faradaic or electrochemical charge induced by established electric field. Our results furthermore suggested that CDI efficiency enhancement can be achieved by increasing either the capacitance when operated under low applied potential or the faradaic or electrochemical charge if high potential is applied.

Interplay between manganese oxide and microporous carbonaceous support in capacitive deionization

2019 Fall National Meeting

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