Strategic design and fabrication of MXenes-Ti3CNCl2@CoS2 core-shell nanostructure for high-efficiency hydrogen evolution

CoS 2 is considered to be a promising electrocatalyst for hydrogen evolution reaction (HER). However, its further widespread applications are hampered by the unsatisfactory activity due to relatively high chemisorption energy for hydrogen atom. Herein, theoretical predictions of first-principles calculations reveal that the introduction of a Cl-terminated MXenes-Ti 3 CNCl 2 can significantly reduce the HER potential of CoS 2 -based materials and the Ti 3 CNCl 2 @CoS 2 core-shell nanostructure has Gibbs free energy of hydrogen adsorption (∣ΔG H ∣) close to zero, much lower than that of the pristine CoS 2 and Ti 3 CNCl 2 . Inspired by the theoretical predictions, we have successfully fabricated a unique Ti 3 CNCl 2 @CoS 2 core-shell nanostructure by ingeniously coupling CoS 2 with a Cl-terminated MXenes-Ti 3 CNCl 2 . Interface-charge transfer between CoS 2 and Ti 3 CNCl 2 results in a higher degree of electronic localization and a formation of chemical bonding. Thus, the Ti 3 CNCl 2 @CoS 2 core-shell nanostructure achieves a significant enhancement in HER activity compared to pristine CoS 2 and Ti 3 CNCl 2 . Theoretical calculations further confirm that the partial density of states of CoS 2 after hybridization becomes more non-localized, and easier to interact with hydrogen ions, thus boosting HER performance. In this work, the success of oriented experimental fabrication of high-efficiency Ti 3 CNCl 2 @CoS 2 electrocatalysts guided by theoretical predictions provides a powerful lead for the further strategic design and fabrication of efficient HER electrocatalysts.