Highly Efficient Capacitive Deionization Enabled by NiCo4MnO8.5 Electrodes

The shortage of fresh water resources is one of the major challenges facing this planet. Capacitive deionization (CDI) techniques that are deemed to be highly efficient and require low capital cost have attracted widespread attention in the last few decades. In this work, the cubic ternary metal oxides NiCo4MnO8.5 (Ni-Co-Mn-O) are synthesized by facile hydrothermal method for enhanced symmetrical CDI. Electrochemical measurements illustrate that the Ni-Co-Mn-O possesses low internal resistance and ion diffusion impedance. As a result, the salt removal capacity of the Ni-Co-Mn-O electrode increases from 26.84 to 65.61 mg g(-1) by varying the voltage from 0.8 to 1.4 V in 1.0 x 10(-2) m NaCl solution, while the charge efficiency stabilizes at approximate to 80%. After 20 cycles, the capacitance retained is 64.27%, which is due to the irreversibility of Co2+/Co3+ and Mn2+/Mn3+ and the release of Ni3+ from the Ni-Co-Mn-O electrode after long desalination/salination cycles.

Automated summary

In this study, cubic ternary metal oxides NiCo4MnO8.5 were synthesized by a facile hydrothermal method for enhanced symmetrical capacitive deionization. Electrochemical measurements showed that the Ni-Co-Mn-O electrode had low internal resistance and ion diffusion impedance, leading to improved salt removal capacity and stable charge efficiency. After 20 cycles, the capacitance retention was 64.27%, attributed to the irreversible changes in metal oxidation states and the release of Ni3+ ions from the electrode.