Revealing the Crystal Phase‐Activity Relationship on NiRu Alloy Nanoparticles Encapsulated in N‐Doped Carbon towards Efficient Hydrogen Evolution Reaction

Abstract Adjusting the crystal phase of a metal alloy is an important method to optimize catalytic performance. However, detailed understanding about the phase‐property relationship for the hydrogen evolution reaction (HER) is still limited. In this work, the crystal phase‐activity relationship of NiRu nanoparticles is studied employing N‐doped carbon shell coated NiRu nanoparticles with different phase contents. It is found that the NiRu@NC (mix) with both face‐centred cubic (fcc) and thermodynamically unstable hexagonal close‐packed (hcp) phase NiRu give the best HER performance. Further activity studies demonstrate that hcp NiRu has better HER performance, and NiRu@NC (mix) with rich (∼70 %) hcp phase presented outstanding performance with an overpotential of only 27 mV @ 10 mA ⋅ cm −2 . The high HER activity of NiRu@NC (mix) is attributed to the formation of hcp phase. This finding indicates that the regulation of crystal structure can provide a new strategy for optimizing HER activity.