Ru Single Atoms Anchored on Co₃O₄ Nanorods for Efficient Overall Water Splitting under pH‐Universal Conditions

Abstract Single‐atom catalysts (SACs) show great promise for electrocatalytic water splitting due to their exceptional metal atom utilization efficiency. Herein, it is demonstrated that Ru single atoms (SAs) anchored on Co₃O₄ nanorod arrays (Ru_x‐Co₃O₄, where x is the Ru loading in weight percent) afford outstanding electrocatalytic performance and durability for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting across a wide pH range (0.3–14). Ru_8%‐Co₃O₄ achieves 10 mA cm⁻² at overpotentials of only 214, 286, and 138 mV for OER, and 13, 72, and 59 mV for HER, in 1 m KOH, 0.1 m PBS, and 0.5 m H₂SO₄, respectively, outperforming benchmark RuO₂ and Pt/C catalysts. When Ru_8%‐Co₃O₄ is utilized as the anode and cathode catalysts in an anion exchange membrane water electrolyzer (AEMWE), a cell voltage of only 2.06 V is required to achieve 1 A cm⁻². Chronopotentiometry verified Ru_8%‐Co₃O₄ possesses excellent stability during both OER and HER at 100 mA cm⁻² in acidic, neutral, and alkaline media. Density functional theory (DFT) calculations reveal that the abundant Ru‐O‐Co interfaces in Ru_8%‐Co₃O₄ shift the d‐band center from −1.72 eV (for Ru cluster/Co₃O₄) to −1.58 eV (for Ru SA/Co₃O₄), creating more energetically favorable pathways for OER and HER.