Table shows the catalytic performance, surface area (SBET), apparent activation energy ( app Ea), and reaction orders of N2 (α), H2 (β), and NH3 (γ) of Ru/CaH2-2xOx, where x is 0.14, 0.25, and 0.44. The surface area of the catalysts did not change so much as the oxygen content changed. Among the three, the reaction rate was the maximum value (Figure ), and app Ea showed the minimum (59 kJ mol -1 ) in Ru/H1.50O0.25. NH3 order (γ) was unchanged even as oxygen increased. On the other hand, H2 order (β) increased as the oxygen amount was raised. It means the oxygen suppressed the hydrogen poisoning over Ru and enhanced the activity.