The effect and mechanism of different pore structure distribution on electrosorption selectivity of anions during capacitive deionization

Capacitive deionization (CDI) has been widely studied as a new and energy-efficient technology, and the ion selectivity has often been focused. In this article, the effect of different pore structure distributions of carbon-based electrodes on the adsorption selectivity of four anions is discussed. The results show that PAC with multistage pore structure and the highest mesoporous rate has higher specific capacitance and the strongest desalting performance than other materials. The competitive adsorption of four anions shows that AC has obvious differences in selectivity for the four anions, while PAC with activated pore structure as well as CF and PCF with narrow pore size distribution doesn’t show such selectivity discrepancy. This discrepancy is determined by the ion mass transfer resistance jointly limited by pore structure and ionic hydration energy. This study reveals an important role of pore structure distribution in ion selectivity, providing a potential direction for selective regulation.