Computational evaluation of structural and chemical possibilities exposed by Ti2CTx nanoribbons and 2D-nanoparticles†

Abstract

MXenes are a rapidly expanding family of 2D materials known for their unique tunability, yet studies of their edges remain sparse compared to their better-characterized basal planes. Herein, we use density functional theory (DFT) to computationally investigate the structural and chemical properties of Ti₂CT_x nanoribbons and 2D-nanoparticles. Our findings reveal that under-coordinated edge atoms exhibit stability and reactivity distinct from that forming the basal planes, driven by edge symmetry and environmental chemical potentials. Specifically, the constructed stability diagrams and Wulff constructions illustrate how 2D-nanoparticle morphologies and edge terminations evolve under different hydrogen chemical potentials. Reducing conditions favor fluorine terminations, while oxidizing environments stabilize oxygen-terminated edges. Hydrogen adsorption analysis highlights unique edge-specific chemistries, with certain terminations achieving hydrogen evolution reaction (HER) overpotentials comparable to those of the previously identified basal planes of Mo₂C MXene. Notably, our study identifies the {010} and {110} edges as highly active catalytic sites under specific conditions, emphasizing the role of edge under-coordination in dictating catalytic behavior. These results underscore the potential of MXene edges for tailoring properties beyond the basal plane, providing pathways for designing next-generation materials for catalysis, energy, and environmental applications.