Mn, N co-doped carbon nanospheres for efficient capture of uranium (VI) via capacitive deionization

Heteroatom doping, involving the introduction of atoms with distinct electronegativity into carbon materials, has emerged as an effective approach to optimize their charge distribution. In this study, we designed a strategy to synthesize in-situ Mn, N co-doped carbon nanospheres (Mn-NC) through the polycondensation of 2,6-diaminopyridine and formaldehyde in synchronization with Mn²⁺ chelation to form Mn-polytriazine precursor, followed by calcination to form carbonaceous solid. Then Mn-NC was fabricated into a capacitive deionization (CDI) electrode for the selective removal of uranium ions (U (VI)), which is commonly found in radioactive water. Interestingly, Mn-NC exhibited good selectivity for UO₂²⁺ capture with a demonstrated adsorption capacity of approximately 194 mg/g @1.8 V. The systematic analysis of the adsorption mechanism of UO₂²⁺ revealed that N dopants within Mn-NC can coordinate with the U (VI) ions, thereby facilitating the removal process. Our study presents a straightforward and convenient strategy for removing UO₂²⁺ ions by harnessing the coordination effect, eliminating the requirement for pore size control.