Preparation of fully coated PEDOT: PSS film on MXene for high reliability capacitive deionization

Abstract

MXene (Ti₃C₂T_x) is a promising CDI electrode material with two-dimensional (2D) layer, which performs excellent capacitance, conductivity, interlayer reversibility and plentiful active sites. However, Ti layer of MXene is easily oxidized to TiO₂ by dissolved oxygen in water, which causes structural instability and affects its desalting performance. In this paper, the sandwich PEDOT:PSS@MXene film electrode was prepared by uniformly coating PEDOT:PSS film on the surface of MXene through template-assisted polymerization. The film improves the stability of the composite by protecting the Ti layer. The specific capacitance of PEDOT:PSS@MXene performs 185.5 F g⁻¹ at 5 mV s⁻¹. The desalination capacity of hybrid AC//PEDOT:PSS@MXene cell in 500 mg L⁻¹ NaCl solution is 35.8 mg g⁻¹. After 40 desalting cycles, the cell performs better retention rate than AC//MXene cell (82.5 %), which keeps 97.2 %. The morphology and structure of composite show no exists of TiO₂ after 40 desalting cycles, indicating that PEDOT:PSS as a coating film can achieve high reliability capacitive deionization of MXene.