The effect of electrode thickness and electrode/electrolyte interface on the capacitive deionization behavior of the Ti₃C₂T_x MXene electrodes

2D MXene sheets have been regarded as promising capacitive deionization (CDI) electrodes owing to their high conductivity, hydrophilic surface, excellent adsorption capacity, and reversible intercalation of metal cations. The 2D structure characteristic enables MXene sheets to provide massive spaces to catch Na⁺ and Cl^- ions during the CDI process. In this work, the CDI behavior of Ti₃C₂T_x MXene has been comprehensively investigated by constructing a symmetrical device. The effect of electrode thickness and electrode/electrolyte on the CDI behavior of the Ti₃C₂T_x MXene electrodes is deeply investigated. The thin electrode could facilitate the electrolyte (NaCl solution) penetration in the electrode, provide more electrode/electrolyte interface contact, and shorten the ion diffusion pathway from the electrolyte to the internal electrode, leading to faster ion diffusion and better desalination capacity. The optimized MXene‖MXene CDI device with an electrode thickness of 18.41 µm exhibits a high salt removal capacity of 100.9 mg g⁻¹ in NaCl solution at 1.2 V.