Intercalation behavior of MXenes from ab initio molecular dynamics*

MXenes are a large family of two-dimensional materials, primarily transition metal carbides and highly conductive, displaying exceptional performance for supercapacitors, batteries, and water purification. MXenes can host a wide range of species between their layers. Predictions and understanding are complicated by the presence of surface functional groups, such as O, OH, and F. Intercalation with aqueous ions such as Li, K, or Mg results in distinct structural and electrochemical responses. Here we present density functional ab intio molecular dynamics calculations for the behavior of ions confined in wetted MXene Ti₃C₂ layers. In this confined aqueous environment, ions display distinct behavior relating to their size, preferred solvation shell, and interaction with the surface groups, consistent with recent scanning probe microscopy data. This suggests that, besides the choice of electrolyte, careful selection of the surface groups and choice of MXene surface metal atoms are routes to optimize supercapacitor and sensing performance.