Heteroatom-Mediated Interactions between Ruthenium Single Atoms and an MXene Support for Efficient Hydrogen Evolution

A titanium carbide (Ti₃ C₂ T_x ) MXene is employed as an efficient solid support to host a nitrogen (N) and sulfur (S) coordinated ruthenium single atom (Ru_SA ) catalyst, which displays superior activity toward the hydrogen evolution reaction (HER). X-ray absorption fine structure spectroscopy and aberration corrected scanning transmission electron microscopy reveal the atomic dispersion of Ru on the Ti₃ C₂ T_x MXene support and the successful coordination of Ru_SA with the N and S species on the Ti₃ C₂ T_x MXene. The resultant Ru_SA -N-S-Ti₃ C₂ T_x catalyst exhibits a low overpotential of 76 mV to achieve the current density of 10 mA cm^-2 . Furthermore, it is shown that integrating the Ru_SA -N-S-Ti₃ C₂ T_x catalyst on n⁺ np⁺ -Si photocathode enables photoelectrochemical hydrogen production with exceptionally high photocurrent density of 37.6 mA cm^-2 that is higher than the reported precious Pt and other noble metals catalysts coupled to Si photocathodes. Density functional theory calculations suggest that Ru_SA coordinated with N and S sites on the Ti₃ C₂ T_x MXene support is the origin of this enhanced HER activity. This work would extend the possibility of using the MXene family as a solid support for the rational design of various single atom catalysts.