The acidic oxygen evolution reaction (OER) is essential for many renewable energy conversion and storage technologies. However, the high energy required to break the strong covalent O-H bond of H₂O in acidic media results in sluggish OER kinetics. Here, we report the critical role of iron in a new family of iron-containing yttrium ruthenate (Y_2-xFe_xRu₂O_7-δ) electrocatalysts in highly increasing the electrophilicity of surface oxygen, leading to a significant reduction of the kinetics barrier by 33%, thus an exceptional OER mass activity of 1,021 A· up to 12.4 and 7.7 times that of Y₂Ru₂O_7-δ and RuO₂, respectively. Introducing iron reduces the Mulliken atomic charge on the O sites in the generated Ru-O-Fe structure, thereby facilitating the acid-base nucleophilic assault from H₂O and reducing the free energy on the rate-determining step of OER. This work provides an effective strategy to reduce the kinetics barrier to achieve highly efficient and economic OER in acidic conditions.