Activating the Basal Planes of TiC MXene for Accelerated Ammonia Electrosynthesis: Role of Surface Terminations.

Altering the edge sites of 2D MXenes for electrochemical dinitrogen reduction reaction (ENRR) is widely reported, whereas activation of its relatively inert basal planes is neglected. Herein, the activation and the optimization of the basal planes of TiCT (T = *F, *O, and *OH) MXenes toward enhanced ENRR to ammonia is reported. The balanced surface functionalization in TiCT regulates the ENRR kinetics by regulating the potential of zero charge (E) and the electrochemical work function ( ). Specifically, the altered E and enhances electric field localization and potential screening at the TiCT/water interface stabilizing the transition state and reducing ENRR activation energy (ΔE). Hydrodynamic voltammetry, in situ Raman, and post-ENRR X-ray spectroscopy suggest faster ENRR kinetics, via an associative distal pathway, with *OH and *F terminated Ti as the dominant active sites over TiCT surface. TiCT achieves an ammonia yield of 35.2  at Faradaic efficiency of 5.9% in 0.05 m HSO, which further improves to 49% in 0.5 m NaBF. The strategy concurrently modulates the ENRR interface via, proton-repelling functional groups (*F) on the electrode surface and weak proton donor electrolytes (NaBF). This suppresses HER kinetics, minimizes competition for active sites, and promotes selective nitrogen activation, thereby boosting ENRR efficiency.