Structure and Dynamics of Water Confined in Transition Metal Carbide MXenes: Implications for Electrochemical Applications.

Abstract

Two-dimensional transition metal carbides and nitrides (MXenes) are an important family of electrochemically active 2D materials. MXenes combine high conductivity with hydrophilicity, making them attractive materials for many applications, including electrochemical energy storage, sensing, desalination, and others. In order to better understand the role of structure on MXene properties, here, we investigated the vibrational properties and diffusion of water in MXenes with differing layer thicknesses and transition metal compositions using inelastic, quasi-elastic, and small-angle neutron scattering. We found that all of the Mo-containing MXenes studied here exhibited comparable vibrational dynamics and diffusion coefficients to each other and to previously studied Ti₃C₂T _<i>x</i> . However, Ti₂CT _<i>x</i> was distinguished by its faster diffusion and more hydroxyl groups compared to the other MXenes studied. These results can help guide the selection of appropriate MXenes for energy storage and electrochemical water purification applications.