(376g) Highly Porous Ti3C2Tx Mxene-Based Fibers Via Interfacial Complexation

Two-dimensional titanium carbide MXene (Ti₃C₂T_x, T = OH, O, F), has found great promises in electrochemical and environmental applications due to the combination of abundant hydrophilic surface-active sites, electro conductivity, and mechanical properties. However, for each specific application, taking full advantage of the inherent properties of MXene nanosheets relies highly on the components' hierarchical assemblies from nano to macro scales. The presence of liquid crystalline phases in the dispersion of MXene nanosheets, due to the strong repulsion among them as well as the thin 2D geometry, provides the opportunity to design macroscopically aligned assemblies in the form of fibers. Different studies were focused on designing MXene fibers through the common wet-spinning processes in the coagulation bath. In this processing method, the necessity of a high enough concentration of MXene suspension drives the high packing density of flakes in the final fibers. In this work, the highly porous MXene fibers were designed by making a sleeve of positively charged polyelectrolyte solution around the suspension of negatively charged MXene. Ti₃C₂T_x MXene was synthesized from its MAX precursor Ti₃AlC₂ through a minimally intensive layer delamination method to reach single-layer nanosheets with high aspect ratio and minimal in-plane defects. To make MXene fibers, a tweezer was used to draw the coagulated MXene phase formed at the interface of MXene and polyelectrolyte droplets. In fact, by the diffusion of polymer chains into the MXene phase and their concurrent adsorption on MXene surfaces, patchy nanosheets with positive and negative sites resulted, which could be connected and drawn in the form of fibers. The increase in the inlet mass flux of polymer chains, controlled by increasing the concentration of polyelectrolyte droplets in the range of 28 to 450 mg/ml, enhanced the cross-sectional porosity of fibers. Besides, increasing the concentration of the MXene phase from 28 to 50 mg/ml increased the density of fibers while preserved the morphology. This flexible and purely thermodynamic assembly process can open a new way toward designing electro conductive MXene fibers with tunable accessible surface area for electrochemical performance.