Deep understanding of particularly in the surface behaviors of redox sensitive additives is important in further efficiency enhancement of capacitive deionization (CDI) technique. In this study, effect of surface ionization on the CDI efficiency of Fe, Co, and Ni doped α-MnO2 as a model system is studied. It was found that the CDI efficiency of dopedα-MnO2 increases with increasing positive surface charge, which is realized as a result of reduced chloride electroadsorption capacity when surface is negatively charged. This further accounts the observations that the CDI efficiency increases with increasing pKa1 and pKa2 of doped α-MnO2 as a low degree of surface ionization is in favor of CDI efficiency. Moreover, reduced structural stress induced by doped elements is noted to possess higher pKa1 and pKa2, suggesting that adjusting the structural stress of α-MnO2 would be a promising strategy in further CDI efficiency enhancement.

Correlation between the degree of surface ionization and the capacitive deionization efficiency of doped MnO2 electrodes

256th National Meeting (2018)

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