High-Performance Water Desalination of Heteroatom Nitrogen- and Sulfur- Codoped Open Hollow Tubular Porous Carbon Electrodes via Capacitive Deionization

Capacitive deionization (CDI) was a competent technique for water desalination on account of its low energy consumption, easy operation and environmental friendliness. In this work, the heteroatom nitrogen- and sulfur- codoped open hollow tubular porous carbon (N, S-HTPC) with hierarchical porous tube wall and high specific surface area (1412 m2 g-1) has been successfully fabricated via a facile MnO2-nanorods template method, in which LB agar coupled with β-cyclodextrin hydrogel (LB agar@β-CD hydrogel) was employed as carbon, nitrogen and sulfur sources. The obtained N, S-HTPC possessed a unique open hollow tubular structure with micropores-mesopores distributed in the tube wall and excellent N, S doping property. The open hollow tubular structure of N, S-HTPC electrodes could guarantee unimpeded ion diffusion inside the carbon tubes and micro-/meso- pores in the tube wall provided sufficient diffusion pathways and more adsorption sites for ion transport and capture. In addition, the incorporation of N and S in the carbon matrix resulted in excellent charge and ion transportation ability, excellent conductivity and hydrophilicity. Compared with open hollow tubular porous carbon (HTPC) and N, S co-doped porous carbon (N, S-PC), N, S-HTPC displayed a remarkable capacitive deionization behavior with high electrosorption capacity (12.05 mg g-1) at 1.2 V in a NaCl solution of 25 mg L-1. The heteroatom co-doped hierarchical porous carbon with unique channels, low energy consumption and stable regeneration performance has provided great potential for the development of high-performance CDI.