Symmetry Breaking in RhPb ₂ Nanocubes Induced Hydrogen Spillover for Enhanced Hydrogen Oxidation and Evolution

Exposing distinct facets on an intermetallic nanocrystal can leverage their synergistic effect to tune the adsorption behavior of intermediates. Additionally, the interface between the facets can facilitate the intermediates transfer, thus accelerating the reaction kinetics. However, current methods normally yield intermetallic nanocrystals with high symmetry, for example, quasi‐spherical particles exposing facets with the lowest surface energy or nanocrystals with equivalent facets. The simultaneous exposure of two distinct facets on a single intermetallic nanocrystal has not been achieved. Herein, we synthesize RhPb 2 nanocubes (NCs) that simultaneously expose {001} and {110} facets, breaking the high symmetry of conventional NCs enclosed by equivalent {001} facets. The NCs demonstrate high catalytic performance in alkaline hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER). The kinetic current density and exchange current density for HOR are 2.12 and 0.96 A mg −1 , respectively. In HER, these NCs require an overpotential of 18 mV to reach 10 mA cm −2 . Theoretical calculations suggest that the synergy of the facets reduces the energy barriers of HOR and HER, and that the hydrogen spillover between the facets further enhances reaction kinetics. These findings provide new insights into facet control in intermetallics and induce hydrogen spillover for enhancing electrocatalytic performance.