Surface Termination Engineering for Simultaneously Optimizing Friction and Conductivity in MXene-Based Sliding Contacts.

The trade-off between low friction and high electrical conductivity represents a long-standing bottleneck in optimizing sliding electrical contacts. Two-dimensional layered MXenes offer a solution due to their excellent electrical properties and potential for superlubricity. Here, we investigate how surface terminations (O, S, Se, F, Cl, Br) regulate the interfacial tribological and electronic properties of Ti2CT2 MXenes and their graphene heterostructures. The sliding barriers of Ti2CT2 homojunctions generally decrease with increasing terminal atomic number within the same group. Constructing incommensurate Ti2CT2/graphene interfaces further reduces the barriers by one to 2 orders of magnitude while preserving the low-corrugation sliding state under the investigated electric fields. Electronic transport is primarily governed by termination-dependent orbital coupling at the Cu/MXene interface. Chalcogen terminations promote pronounced hybridization between terminal-atom p orbitals and Cu-d states, enhancing electron transmission near the Fermi level and reducing the effective interfacial tunneling barrier. Among all configurations, the Cu-Ti2CS2-Gr-Cu device delivers the highest current (23.8 nA at 1 mV bias), approximately 20-fold higher than that of halogen-terminated devices. These findings establish a dual interface-design strategy in which structural incommensurability suppresses sliding resistance, while termination-controlled orbital hybridization enhances charge transport.