Surface Reconstruction of Decalcified CaMnO 3 Perovskites for Low‐Temperature NO Oxidation

Effective oxide‐based catalysts with the potential to replace noble metal catalysts remain elusive for NO‐to‐NO 2 oxidation, which is essential for low‐temperature NO x abatement. Herein, we report a time‐controlled selective decalcification strategy to reconstruct dense CaMnO 3 perovskite into Mn‐rich porous oxides for NO oxidation. Acid etching progressively removed Ca from the CaOMn framework, forming MnO 2 ‐like porous structures with well‐defined [MnO 6 ] units and MnOMn bridges. The optimized catalyst, denoted as CMO‐24 h, decreased the temperature required for 50% NO conversion from 378 to 181 °C and increased the maximum NO conversion from 54% to 92%. The promoted activity arose from an optimized MnOMn lattice‐oxygen microenvironment within the reconstructed porous framework. Mn enrichment and pore formation increased the accessibility of Mn‐rich surface domains, while the connected MnOMn network facilitated Mn redox cycling among Mn 2+ /Mn 3+ /Mn 4+ at low temperatures. Meanwhile, enriched surface‐accessible lattice oxygen and an expanded surface/subsurface lattice‐oxygen reservoir provided reactive oxygen for the oxidation of adsorbed NO‐derived species. Temperature‐programed desorption and in situ diffuse reflectance infrared Fourier transform spectroscopy (with NO or NO + O 2 as probes) further revealed that CMO‐24 h enhanced NO x adsorption/desorption and accelerated the evolution of nitrosyl/nitrite‐type species toward nitrate‐ and NO 2 ‐related species.