AbstractThe urgent development of effective electrocatalysts for hydrogen evolution and hydrogen oxidation reaction (HER/HOR) is needed due to the sluggish alkaline hydrogen electrocatalysis. Here, an unusual face‐centered cubic (fcc) Ru nanocrystal with favorable HER/HOR performance is offered. Guided by the lower calculated surface energy of fcc Ru than that of hcp Ru in NH₃, the carbon‐supported fcc Ru electrocatalyst is facilely synthesized in the NH₃ reducing atmosphere. The specific HOR kinetic current density of fcc Ru can reach 23.4 mA cm_PGM⁻², which is around 20 and 21 times greater than that of hexagonal close‐packed (hcp) Ru and Pt/C, respectively. Additionally, the HER specific activity is enhanced more than six times in fcc Ru electrocatalyst when compared to Pt/C. Experimental and theoretical analysis indicate that the phase transition from hcp Ru to fcc Ru can negatively shift the d band center, weaken the interaction between catalysts and key intermediates and therefore enhances the HER/HOR kinetics.