Catalysts on the left wing of this plot have too low U OH for the optimal condition due to the excessive stabilization of OH*. Under this condition, k 2 ≫ k 5 , k -5 , and thus, the reaction is limited by the OH* removal reaction (5) (j ≃ j limit k 5 ). On the other hand, catalysts on the right wing are limited by the HO 2 * formation reaction (2) (j ≃ j limit k 1 , k 5 ≫ k 2 , k -5 ).