O-termination-induced electronic modulation in MXene-based heterostructures toward sustainable hydrogen evolution

MXenes, a rapidly expanding family of two-dimensional (2D) materials derived from MAX phase ceramics, have emerged as transformative candidates for electrocatalysis. However, the inherent heterogeneity of surface terminations (e.g., –F, –O, –OH) inherited from synthesis often limits their potential for the hydrogen evolution reaction (HER). Herein, we report a facile surface engineering strategy to precisely modulate the surface chemistry of Ti₃C₂T_x by selectively converting detrimental –F terminations into catalytically advantageous –O groups via n-butyllithium treatment. By systematically tuning the –O/–F ratios, we demonstrate a significant enhancement in HER activity for both Pt/Ti₃C₂T_x and MoS₂/Ti₃C₂T_x heterostructures. Our findings reveal that the optimized O-rich catalysts Pt/Ti₃C₂T_x-9 (121 vs. 179 mV) and MoS₂/Ti₃C₂T_x-9 (179 vs. 209 mV) achieve dramatically reduced overpotentials compared to the parental F-rich analogs. Density functional theory (DFT) calculations combined with experimental characterizations unravel different enhancing mechanisms: enriched –O groups facilitate electron depletion from Pt nanoparticles to enhance H* adsorption while conversely inducing electron accumulation on Mo sites to alleviate excessive H* binding. This work establishes a scalable methodology for tailoring the surface chemistry of MXene-based functional ceramics and provides profound insights into interfacial electronic modulation for highly efficient hydrogen production.