Effect of surface termination on the balance between friction and failure of Ti3C2Tx MXenes

Abstract

Reactive molecular dynamics simulations of Ti3C2Tx with three different surface terminations were used to understand friction and failure of MXenes during sliding at normal pressures from 2–20 GPa and temperatures from 300–1100 K. The O-terminated MXene had the smallest shear stress at low pressures and temperatures, but failed at more severe conditions due to interlayer bonding and the formation of Ti–O–Ti bridges between MXene layers. Failure was not observed for the OH-terminated MXene or a heterostructure combining O- and OH-terminations. For these, at less severe operating conditions, shear stress was smaller for the OH-terminated MXene, while the opposite was observed at higher temperatures and pressures. These trends were explained in terms of adhesion and the complex effect of hydrogen atoms that can either facilitate or hinder sliding, depending on the termination and conditions. Results show that friction and failure are affected by and potentially tunable via MXene surface termination.

Stepless IR Chromism in Ti3C2Tx MXene Tuned by Interlayer Water Molecules

“…The physisorbed water is weakly bound to the abundant ─OH groups in Ti 3 C 2 T x laminates, forming OH─H 2 O complexes. [43] As expected, the areal fraction of physisorbed water in the XPS spectra on the wet surface (18.2%) was much higher than that on the dry film annealed at 60 °C for 2 h (9.4%). Prior works suggest that the residue water in the dry film (annealed at 60 °C for 2 h) is ascribed to a stabilized state of physisorbed water, which can be removed by annealing at even high temperatures (>200 °C).…”

“…This is due to the decrease in the water adsorption capacity of the Ti 3 C 2 T x membranes caused by the increasing interlayer interactions including the hydrogen bonds and van der Waals force. [ 43 ] In dry Ti 3 C 2 T x membranes with ─OH, ─O─, and ─F terminations, the hydrogen bonds can form between ─OH terminations (donor) of one layer and ─O─ or ─F (acceptor) of the other layer when the free spacing between the two neighboring layers is smaller than 0.3 nm. Moreover, the strength (Δ G formation ) of the hydrogen bond rises exponentially as the free spacing decreases, for example, from −8.4 to −104.7 kJ mol −1 as the distance decreases from 0.3 to 0.245 nm.…”

Synthesis and Characterization of Nanomaterials for Application in Cost-Effective Electrochemical Devices

“…Accordingly, further research has to be conducted to strike a good compromise between high-rate electrochemical performance and high-volume capacitance [196]. The influence of surface termination on the functional characteristics of MXene is poorly understood [197]. The optimization of the MXenes' surface terminations has great promise for controlling their characteristics, but a thorough study is needed to demonstrate the necessary relationships [198].…”

Combining Tailored Ionic Liquids with Ti3C2Tx MXenes for an Enhanced Load‐Carrying Capacity Under Boundary Lubrication

“…[21] However, their layer structure with reduced bonding strength between the layers renders MXenes also interesting for tribological applications. [22] MXenes' interlayer binding energy and, therefore, the friction between the layers are significantly influenced by the surface terminations, [23,24] making it possible to tailor their tribological properties. MXenes have already demonstrated their promising tribological performance on the nanoscale, [25,26] the laboratory scale, [27,28] and even when used for lubricating machine elements.…”