High-capacity and high-stability capacitive desalination with dual redox-active MnCo2S4/g-C3N4 heterojunction electrode
Yingsheng Xu, Rongxia Quan, Jianguo Zhou, Hengjian Mao, Chen Li, Siyao Ma, Junteng Mou, Hongjian Zhou
Abstract
Capacitive deionization (CDI) utilizing dual redox-active electrodes has shown significant promise in desalinating low-concentration brackish waters, which is crucial for addressing global freshwater shortages. However, improvements in salt adsorption capacity and long-term operational stability are still required. In this study, we introduce, for the first time, a binary metal sulfide MnCo 2 S 4 /g-C 3 N 4 (MCS-CN) heterojunction as a CDI electrode. The innovative integration of dual redox-active centers and heterojunction structures in the MCS-CN composite electrodes underscores their potential for achieving both high capacity and stability in capacitive desalination applications. The microscopic morphology, crystal structure, pore structure , and surface valence properties of the MCS-CN heterojunction composite materials were extensively characterized using various analytical techniques. In-situ X-ray diffraction, refined ex-situ X-ray photoelectron spectroscopy, three-electrode electrochemical analysis , and theoretical calculations were employed to elucidate the electrosorption and desorption mechanisms of sodium ions with the MCS-CN electrodes and to clarify the enhanced desalination performance of the binary metal sulfide-based heterojunction structure. As a result, the optimal MCS-CN-40 electrode exhibited the highest salt removal capacity of 71.64 mg g −1 and maintained stable desalination performance over 100 cycles in a 500 mg L −1 NaCl solution. This innovative approach provides a noval perspective for developing heterojunction electrodes with high redox activity and efficient desalination performance.