Ligand-confined two-dimensional rhodium hydride boosts hydrogen evolution

Transition metal hydrides hold great potential as high-efficiency cat-alysts for hydrogen-involving reactions, benefiting from finely mod-ulable electronic states and reaction paths by interstitial hydrogen. But their severe thermodynamic instability brings challenges for their preparation and utilization under ambient conditions. Herein, we report a ligand confinement effect to break thermodynamic re-striction and for the first time realize the construction of ambient -stable two-dimensional (2D) rhodium hydride (RhH) nanosheets. By using electron-attracting n-butylamino ligands to enhance the interaction between Rh and interstitial hydrogen, the formation of 2D RhH becomes thermodynamically permissible. It exhibits a supe-rior hydrogen evolution reaction (HER) activity with a lower overpo-tential and 3.1 times and 1.4 times higher mass activity than 2D Rh catalyst and commercial Pt/C catalyst, respectively. Theoretical calculations reveal the significant effect of interstitial H atoms and surface ligands in boosting the HER activity of Rh, by moderately weakening hydrogen adsorption and accelerating H2 desorption via a ligand-mediated H-transfer mechanism.