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

Ramalingam, Vinoth; Varadhan, Purushothaman; Fu, Hui-Chun; Kim, Hyunho; Zhang, Daliang; Chen, Shuangming; Song, Li; Ma, Ding et al. · Adv Mater · 2019

basic_science · Level V

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Abstract

A titanium carbide (Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> ) MXene is employed as an efficient solid support to host a nitrogen (N) and sulfur (S) coordinated ruthenium single atom (Ru<sub>SA</sub> ) 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 Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> MXene support and the successful coordination of Ru<sub>SA</sub> with the N and S species on the Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> MXene. The resultant Ru<sub>SA</sub> -N-S-Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> catalyst exhibits a low overpotential of 76 mV to achieve the current density of 10 mA cm<sup>-2</sup> . Furthermore, it is shown that integrating the Ru<sub>SA</sub> -N-S-Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> catalyst on n<sup>+</sup> np<sup>+</sup> -Si photocathode enables photoelectrochemical hydrogen production with exceptionally high photocurrent density of 37.6 mA cm<sup>-2</sup> that is higher than the reported precious Pt and other noble metals catalysts coupled to Si photocathodes. Density functional theory calculations suggest that Ru<sub>SA</sub> coordinated with N and S sites on the Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> 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.