N, O-codoped carbon aerogel electrode improves capacitive deionization performance.

Capacitive deionization (CDI) using porous carbon materials provides an environmentally friendly and sustainable solution to produce affordable fresh water. However, low salt adsorption rates significantly limit its practical application. In this study, N, O-codoped carbon aerogel (NOCA) was prepared by a simple sol-gel method using agar as the carbon framework, NaCl as the template, NHHCO as the nitrogen source and self-blowing agent. The electrochemical and electrosorption properties of the NOCA electrode were significantly better than compared to commercial activated carbon (CAC) electrodes. The NOCA material had the following characteristics: (i) During the rapid freeze-drying process, NaCl crystals provide a three-dimensional network structure for effective dispersion of agar, reducing the agglomeration of particles. The volatile gas generated during the thermal decomposition of NHHCO reduces the plugging of pores. (ii) The fluffy interconnecting network structure of the material enhances its electrical conductivity, providing sufficient channels and adsorption sites for the entry and exit of salt ions. (iii) The abundant hydroxyl and ether groups in the agar enhance the hydrophilicity of the material, whereas N doping further improves the electrical conductivity and reduces the ion transport resistance. The electrosorption capacity and adsorption rate of the NOCA material in 500 mg/L NaCl solution were 22.1 mg/g and 4.4 mg/(g·min), respectively. These values correspond to low energy consumption and high energy recovery efficiency in the electrosorption process. The adsorption capacity remained at 95.5 % after 50 adsorption/desorption cycles. These findings show that NOCA is a novel and potential electrode material for CDI applications.