0.09 wt.% Ru Enables Robust Bifunctional Water Splitting on Co‐N ₄ Sites

Abstract The development of high‐performance bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is crucial for efficient and cost‐effective water splitting in sustainable hydrogen production. A significant challenge in this area is engineering active sites that maintain robust stability and high activity under the varying electrochemical conditions encountered in both alkaline and acidic media. This study presents Co 80 Ru 1 ‐NCNFs, an advanced bifunctional electrocatalyst that showcases a self‐supported carbon nanofiber membrane with uniformly dispersed Ru‐modified Co‐N 4 active sites, excelling in both OER and HER. The trace incorporation of Ru (0.09 wt%) significantly enhances catalytic activity and stability through synergistic Co/Ru interactions. Co 80 Ru 1 ‐NCNFs demonstrate promising OER performance in 1.0 m KOH, along with remarkable HER activity in both alkaline and acidic conditions. Density functional theory (DFT) calculations reveal that Ru incorporation optimizes the adsorption energies of reaction intermediates on the Co‐N 4 active sites, thereby improving reaction kinetics. This work provides critical insights for the design and development of efficient and stable bifunctional electrocatalysts for sustainable energy conversion.