Ligand-confined two-dimensional rhodium hydride boosts hydrogen evolution

Summary

Transition metal hydrides hold great potential as high-efficiency catalysts for hydrogen-involving reactions, benefiting from finely modulable 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 restriction 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 superior hydrogen evolution reaction (HER) activity with a lower overpotential 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.