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 mV vs. 179 mV) and MoS₂/Ti₃C₂T_x-9 (179 mV vs. 209 mV) achieve dramatically reduced overpotentials as compared to the parental F-rich analogues. 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.