Boron enriched edge-nitrogen defective carbon network toward high-capacity capacitive deionization

Abstract

Nitrogen doping is an effective strategy to enhance the salt adsorption capacity (SAC) of carbon electrodes for capacitive deionization (CDI) via generating abundant active adsorption sites. However, the uncontrolled interior doping and the undesired defective sites usually restrict the further enhancement in SAC. Herein, the additional boron element is introduced into the carbon matrix to not only create the porous architectures but also modulate the types of doping species. It is observed that the introduction of B selectively converts the inert graphitic N into active pyrrolic N species with enhanced adsorption capacity in the carbon skeleton. Specifically, the optimized B enriched edge-N defective carbon network (ENC-X) exhibits a high edged N doping content of 85.8 %. Benefitting from the integrative modulation in surface functionalities, the optimized samples demonstrate a significantly higher SAC value of 84.6 mg g−1 in 500 mg L−1 NaCl solution at 1.2 V, comparable to that of the most carbonaceous materials reported so far. Additionally, density functional theory calculations uncover the synergistic effect between B and N doping, further facilitating the capacitive adsorption of sodium ions. Overall, this study highlights the advantages of regulating heteroatom species and co-doping, offering a new perspective for the application of heteroatom-doped carbon in CDI field.