One-dimensional Ti3C2Tx MXene nanofiber anchored ultrafine iridium nanocrystals for alkaline hydrogen evolution

The development of cost-effective hydrogen evolution reaction (HER) catalysts is crucial for the large-scale production of green hydrogen through water electrolysis. Herein, we present a strategy for fabricating a highly efficient HER catalyst where iridium (Ir) nanocrystals (NCs) are dispersed on one-dimensional MXene nanofibers (Ir@NF 550). The MXene nanofiber (MXene-NF) is reconstructed from the MXene nanosheet accompanying the formation and extension of cracks, which avoids the self-stacking of MXene and stimulates the dispersion of Ir metal catalysts. The existence of electron transfer and the strong electrostatic interaction between the Ir species and the conductive MXene substrate endows the as-prepared catalyst with superior HER activity in the alkaline media, with an ultralow overpotential of 15.8 mV to reach a current density of 10 mA cm^-2, remarkably high mass activity about 4.8-fold greater than the commercial Ir/C catalyst, and an excellent long-term stability. As evidenced by the density functional theory calculations, MXene-NF supported Ir NCs exhibit a hydrogen adsorption for free energy (ΔG_H* = -0.35 eV) closer to thermodynamic neutrality, significantly boosting the catalytic kinetics. This work introduces a facile strategy on design of highly active MXene-based catalysts with a low noble-metal loading.