Effect of the surface termination on the electrochemical properties of the Ti(3-x)MoxC2Tz (Tz = O, S) MXenes

Double transition metal (DTM) MXenes are a family of two-dimensional composite nanomaterials with excellent potential when applied as electrodes for energy storage devices; Ti(3-x)MoxC2Tz DTM MXenes are promising electrode materials for energy storage devices. Yet, we currently lack an understanding of the possible chemical configurations of Ti/Mo-based DTM MXenes and the effect of surface terminations on their capacity to function as reliable electrodes. In this study, we demonstrate the thermodynamic stability, in addition to the structural and electrochemical properties, of Ti(3-x)MoxC2Tz (Tz = O, S) DTM MXenes using first-principles DFT-based methods. A solid understanding of their chemical composition and material properties gives insights into their electrode performance in energy storage devices, focusing on Li-ion batteries. A defect formation energy formalism was employed to study the thermodynamic stabilities of the compositional variations of the Ti(3-x)MoxC2 pristine MXenes. The most stable configuration was selected as the base for placing surface terminations. The surface terminations (O, S) were placed in 3 high-symmetry sites on the DTM MXene, and the most stable systems were chosen to study the lithiation process. Electrochemical characterization was carried out employing Open Circuit Voltage (OCV) curves. Our results show a potential Janus-like structure that induces changes in the Ti(3-x)MoxC2 MXene’s ability to allow the surface transport and intercalation of lithium ions, possibly paving the way for enhanced energy storage devices. 

We thank DGAPA-UNAM projects IA100624 and IN101523 for the financial support. Calculations were performed in the DGCTIC-UNAM Supercomputing Center, project LANCAD-UNAM-DGTIC-422 and  LANCAD-UNAM-DGTIC-150.