Cation Vacancies Anchored Transition Metal Dopants Based on a Few-Layer Ti3C2Tx Catalyst for Enhanced Hydrogen Evolution

This study addresses the efficiency and cost challenges of hydrogen evolution reaction (HER) catalysts in the context of carbon neutrality strategies by employing a synergistic approach that combines cation vacancy anchoring and transition metal doping on two-dimensional (2D) MXenes. Using an in situ LiF/HCl etching process, the aluminum layers in Ti3AlC2were precisely removed, resulting in a few-layer Ti3C2TxMXene with an increased interlayer spacing of 12.3 Å. Doping with the transition metals Fe, Co, Ni, and Cu demonstrated that Fe@Ti3C2provided the optimal HER performance, characterized by an overpotential (η10) of 81 mV at 10 mA cm−2, a low Tafel slope of 33.03 mV dec−1, and the lowest charge transfer resistance (Rct= 5.6 Ω cm2). Mechanistic investigations revealed that Fe’s 3d6electrons induce an upward shift in the d-band center of MXene, improving hydrogen adsorption free energy and reducing lattice distortion. This research lays a solid foundation for the design of non-precious metal catalysts using MXenes and highlights future avenues in bimetallic synergy and scalability.