N/P co-doped modified porous carbon for high-efficiency membrane capacitance deionization in seawater desalination

Nowadays, membrane capacitive deionization technology, as an emerging method for seawater desalination, has attracted increasing attention and research efforts due to its ability to mitigate the co-ion effect and redox reactions associated with capacitive deionization, thereby significantly enhancing desalination adsorption capacity. In this study, N/P co-doped biomass carbon with a porous structure was synthesized using a one-step calcination method from sugarcane bagasse. The material exhibits excellent electrochemical and desalination performance, with a high specific surface area providing abundant active sites and enhancing ion transport efficiency. Appropriate N/P doping improved the electrochemical performance of the material, thereby enhancing the desalination performance in the MCDI process. The NP-ABS electrode demonstrated a high specific capacitance of 430.48F g^-1 at a current density of 1 A g^-1. In the MCDI experiment, a high adsorption capacity of 35.79 mg g^-1 for Na⁺ was observed. During the adsorption of different ions, the adsorption capacity for Cr³⁺ reached as high as 46.61 mg g^-1.After 50 adsorption–desorption cycles, the material retained 88.2 % of its initial capacity.DFT calculations revealed that NP doping significantly enhanced the adsorption performance of the material. Combined with the MCDI mechanism, the study highlighted the crucial role of hydration energy in MCDI. This material exhibits great potential for applications in seawater desalination.