Steam‐Activated Lattice Oxygen Enhances Interfacial Redox Stability for Low‐Temperature N ₂ O Decomposition over Rh/CeO ₂

Abstract Activation of surface lattice oxygen is crucial for enabling low‐temperature catalytic oxidation reactions. While earlier studies have hinted that steam treatment could enhance the activity of lattice oxygen in CeO 2 supported catalysts, the mechanistic understanding remains superficial. Here, we unravel the origin and role of steam‐activated lattice oxygen in promoting low‐temperature N 2 O decomposition. Using a combination of isotope‐labeled steam (H 2 18 O), in situ ambient‐pressure X‐ray photoelectron spectroscopy (AP‐XPS), and in situ X‐ray absorption spectroscopy (XAS), we provide direct evidence that high‐temperature steam induces lattice oxygen activation at the Rh–CeO 2 interface. These activated oxygen species facilitate oxygen desorption and enhance the redox cycling stability of Rh and Ce species, dramatically improving catalytic activity at low temperatures. Our findings reveal a previously overlooked pathway for surface lattice oxygen activation and offer mechanistic insights to guide the rational design of efficient low‐temperature redox catalysts.