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.