Insight from the synergistic effect of dopant and defect interplay in carbons for high-performance capacitive deionization

Abstract

Carbon-based materials with heteroatoms doping and structural defects have been regarded as effective alternatives to boost capacitive deionization (CDI) performance. However, the underlying interaction between doping and defects cannot be clearly clarified. Especially, there is still a lack of comprehensive research of the underlying interplay on CDI applications. Herein, a series of porous carbons with different degrees of dopants and vacancy defects have been precisely designed and prepared to further explore their capacitive properties. Density functional theory simulations combined with the electrochemical results elucidate that the doping-defect underlying can further optimize the distribution of charge density and structural characteristics to enhance the capability of ion adsorption and diffusion, thereby maximizing pore and heteroatom utilization. For another, N dopants can be transformed into the effective N configurations as active sites to remarkably facilitate the intrinsic affinity of ions, benefiting to the ion-adsorption ability. As a result, the optimized carbon sample (NC-P) exhibits a salt removal capacity of 23.6 mg g−1 in 500 mg L-1 NaCl at 1.2 V. Also, in different ionic solutions, NC-P still shows superior ion-adsorption capability. This work not only provides a deep new insight to the critical role of the doping-defect interplay on carbon-based CDI applications, but also will inspire further work to reasonably design of carbons for prominent CDI performance.