Ruthenium Engineered A₂B₂O₆-Hybrid Columbite Ferrite for Bifunctional pH-Universal Water Splitting

Single-atomic catalysts based on ruthenium have a balanced efficiency for water splitting, but it is necessary to control their activity and durability. In this work, a binder-free Fe_2-xRu_xNb₂O₆ (FRNO) hybrid catalyst is rationally designed through a facile hydrogel-crosslinking route. The as-prepared FRNO catalyst exhibits high electrocatalytic activity and stability when operating under acidic (0.5 m H₂SO₄) and alkaline (1 m KOH) media. Operando X-ray adsorption and density functional theory calculations show that FRNO/CC, with its high intrinsic conductivity, promotes the adsorption and dissociation of water on its surface by regulating the charge distribution via charge transfer to the coordinated surface oxygen. This facilitates the oxygen evolution reaction (OER) performance by stabilizing *OOH adsorption on Ru and Fe. The FRNO/carbon cloth (CC) hybrid catalyst also delivers excellent activity and stability for both hydrogen evolution reaction (HER) and OER in pH-universal electrolytes with low overpotentials of 30 mV per 82 mV for HER and 200 mV per 260 mV for OER at a current density of 10 mA cm^-2 in acidic/basic medium. Ultimately, the FRNO/CC hybrid catalyst shows good water-splitting performance, and it is expected to help contribute to the creation of various hybrid electrocatalysts.