Highly Dispersed Ru Nanoparticles on Boron-Doped Ti₃C₂T_x (MXene) Nanosheets for Synergistic Enhancement of Electrocatalytic Hydrogen Evolution

2D-layered materials have attracted increasing attention as low-cost supports for developing active catalysts for the hydrogen evolution reaction (HER). In addition, atomically thin Ti₃C₂T_x (MXene) nanosheets have surface termination groups (T_x: -F, -O, and -OH), which are active sites for effective functionalization. In this work, heteroatom (boron)-doped Ti₃C₂T_x (MXene) nanosheets are developed as an efficient solid support to host ultrasmall ruthenium (Ru) nanoparticles for electrocatalytic HER. The quantum-mechanical first-principles calculations and electrochemical tests reveal that the B-doping onto 2D MXene nanosheets can largely improve the intermediate H* adsorption kinetics and reduce the charge-transfer resistance toward the HER, leading to increased reactivity of active sites and favorable electrode kinetics. Importantly, the newly designed electrocatalyst based on Ru nanoparticles supported on B-doped MXene (Ru@B–Ti₃C₂T_x) nanosheets shows a remarkable catalytic activity with low overpotentials of 62.9 and 276.9 mV to drive 10 and 100 mA cm⁻², respectively, for the HER, while exhibiting excellent cycling stabilities. Moreover, according to the theoretical calculations, Ru@B–Ti₃C₂T_x exhibits a near-zero value of Gibbs free energy (ΔG_H* = 0.002 eV) for the HER. This work introduces a facile strategy to functionalize MXene for use as a solid support for efficient electrocatalysts.