The development of efficient carbon-based materials is crucial for overcoming the performance limitations of traditional electrodes in capacitive deionization (CDI). However, the practical performance of heteroatom-doped carbon electrodes for desalination in complex multi-ion water matrices remains largely unexplored. In this work, we studied the ion selectivity toward Li+ and the removal efficiency of nitrogen‑sulfur co-doped and boron-doped carbon electrodes in brackish water, using multi-salt cation solutions containing monovalent (Li+, Na+, K+) and divalent (Ca2+, Mg2+) ions. These modifications enhanced charge distribution, wettability, and ion diffusion within the electrodes. As a result, the N,S-AC electrode exhibited pronounced lithium selectivity in brackish water, while the B-AC electrode delivered higher adsorption capacity. The B-AC electrode achieved both high capacity and enhanced lithium selectivity even under strong competition from Na+, Mg2+, and Ca2+. These findings demonstrate the distinct and complementary roles of N,S-co-doping and B-doping, offering valuable insights into how heteroatom engineering can advance CDI performance.
Desalination , 2026, 634 120232.