Isolated manganese sites empower g-C3N4 with remarkable desalination capacity and stability via the effective suppression of H2O2 generation

Graphitic carbon nitride (g-C 3 N 4 ) recently has attracted considerable attention in the field of capacitive deionization (CDI) due to its tunable electronic structure and low synthesis cost. However, the practical application of this material is severely hindered by a critical bottleneck of failure to balance the trade-off between desalination capacity and cycling stability. This bottleneck mainly stems from two key issues, namely insufficient exposed active sites and material corrosion induced by hydrogen peroxide (H 2 O 2 ). In this work, atomically dispersed manganese-doped g-C 3 N 4 material (Mn/g-C 3 N 4 ) was successfully prepared. Mn/g-C 3 N 4 delivers an ultrahigh desalination capacity of 149.86 mg/g and maintains long-term stability with no significant capacity decay (>90%) after 150 cycles at an applied voltage of 1.2 V, which outperforms most g-C 3 N 4 -based materials. Ex-situ characterizations and electrochemical measurements confirm that isolated manganese sites not only act as high-density Na + trapping sites to enhance ion adsorption capacity, but also effectively suppresses H 2 O 2 formation by altering the ORR pathway, thus alleviating the anodic oxidative corrosion. The present work provides a novel perspective to construct CDI electrode of high capacity and stability with integration of desalination and ORR catalytic function.